Hi all,
I've just sent the pandoc stuff to Lotte, and here is the draft in its
current state (which I have called 14c) just for your information. Not a
huge amount of difference between from v13. Also, the changes section lies,
because it doesn't yet address Justin's review, but obviously the final
version 14 will :)
Kind regards,
Vicky.
Mobile Ad hoc Networks Working Group C. Perkins
Internet-Draft Futurewei
Intended status: Standards Track S. Ratliff
Expires: September 5, 2016 Idirect
J. Dowdell
Airbus Defence and Space
L. Steenbrink
HAW Hamburg, Dept. Informatik
V. Mercieca
Airbus Defence and Space
March 4, 2016
Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing
draft-ietf-manet-aodvv2-14
Abstract
The Ad Hoc On-demand Distance Vector Version 2 (AODVv2) routing
protocol is intended for use by mobile routers in wireless, multihop
networks. AODVv2 determines unicast routes among AODVv2 routers
within the network in an on-demand fashion.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 5, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 8
4. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 10
4.1. Interface List . . . . . . . . . . . . . . . . . . . . . 10
4.2. Router Client Table . . . . . . . . . . . . . . . . . . . 10
4.3. Neighbor Table . . . . . . . . . . . . . . . . . . . . . 11
4.4. Sequence Numbers . . . . . . . . . . . . . . . . . . . . 11
4.5. Local Route Set . . . . . . . . . . . . . . . . . . . . . 12
4.6. Multicast Route Message Table . . . . . . . . . . . . . . 14
5. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6. AODVv2 Protocol Operations . . . . . . . . . . . . . . . . . 18
6.1. Initialization . . . . . . . . . . . . . . . . . . . . . 18
6.2. Next Hop Monitoring . . . . . . . . . . . . . . . . . . . 19
6.3. Neighbor Table Update . . . . . . . . . . . . . . . . . . 20
6.4. Interaction with the Forwarding Plane . . . . . . . . . . 21
6.5. Message Transmission . . . . . . . . . . . . . . . . . . 23
6.6. Route Discovery, Retries and Buffering . . . . . . . . . 24
6.7. Processing Received Route Information . . . . . . . . . . 25
6.7.1. Evaluating Route Information . . . . . . . . . . . . 26
6.7.2. Applying Route Updates . . . . . . . . . . . . . . . 28
6.8. Suppressing Redundant Messages Using the Multicast Route
Message Table . . . . . . . . . . . . . . . . . . . . . . 30
6.9. Local Route Set Maintenance . . . . . . . . . . . . . . . 32
6.9.1. LocalRoute State Changes . . . . . . . . . . . . . . 32
6.9.2. Reporting Invalid Routes . . . . . . . . . . . . . . 35
7. AODVv2 Protocol Messages . . . . . . . . . . . . . . . . . . 35
7.1. Route Request (RREQ) Message . . . . . . . . . . . . . . 35
7.1.1. RREQ Generation . . . . . . . . . . . . . . . . . . . 37
7.1.2. RREQ Reception . . . . . . . . . . . . . . . . . . . 38
7.1.3. RREQ Regeneration . . . . . . . . . . . . . . . . . . 39
7.2. Route Reply (RREP) Message . . . . . . . . . . . . . . . 40
7.2.1. RREP Generation . . . . . . . . . . . . . . . . . . . 41
7.2.2. RREP Reception . . . . . . . . . . . . . . . . . . . 43
7.2.3. RREP Regeneration . . . . . . . . . . . . . . . . . . 44
7.3. Route Reply Acknowledgement (RREP_Ack) Message . . . . . 45
7.3.1. RREP_Ack Generation . . . . . . . . . . . . . . . . . 45
7.3.2. RREP_Ack Reception . . . . . . . . . . . . . . . . . 46
7.4. Route Error (RERR) Message . . . . . . . . . . . . . . . 46
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7.4.1. RERR Generation . . . . . . . . . . . . . . . . . . . 47
7.4.2. RERR Reception . . . . . . . . . . . . . . . . . . . 49
7.4.3. RERR Regeneration . . . . . . . . . . . . . . . . . . 50
8. RFC 5444 Representation . . . . . . . . . . . . . . . . . . . 51
8.1. Route Request Message Representation . . . . . . . . . . 52
8.1.1. Message Header . . . . . . . . . . . . . . . . . . . 52
8.1.2. Message TLV Block . . . . . . . . . . . . . . . . . . 52
8.1.3. Address Block . . . . . . . . . . . . . . . . . . . . 52
8.1.4. Address Block TLV Block . . . . . . . . . . . . . . . 52
8.2. Route Reply Message Representation . . . . . . . . . . . 53
8.2.1. Message Header . . . . . . . . . . . . . . . . . . . 53
8.2.2. Message TLV Block . . . . . . . . . . . . . . . . . . 53
8.2.3. Address Block . . . . . . . . . . . . . . . . . . . . 54
8.2.4. Address Block TLV Block . . . . . . . . . . . . . . . 54
8.3. Route Reply Acknowledgement Message Representation . . . 55
8.3.1. Message Header . . . . . . . . . . . . . . . . . . . 55
8.3.2. Message TLV Block . . . . . . . . . . . . . . . . . . 55
8.3.3. Address Block . . . . . . . . . . . . . . . . . . . . 55
8.3.4. Address Block TLV Block . . . . . . . . . . . . . . . 56
8.4. Route Error Message Representation . . . . . . . . . . . 56
8.4.1. Message Header . . . . . . . . . . . . . . . . . . . 56
8.4.2. Message TLV Block . . . . . . . . . . . . . . . . . . 56
8.4.3. Address Block . . . . . . . . . . . . . . . . . . . . 56
8.4.4. Address Block TLV Block . . . . . . . . . . . . . . . 57
9. Simple External Network Attachment . . . . . . . . . . . . . 57
10. Optional Features . . . . . . . . . . . . . . . . . . . . . . 58
10.1. Expanding Rings Multicast . . . . . . . . . . . . . . . 59
10.2. Precursor Lists . . . . . . . . . . . . . . . . . . . . 59
10.3. Intermediate RREP . . . . . . . . . . . . . . . . . . . 60
10.4. Message Aggregation Delay . . . . . . . . . . . . . . . 60
11. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 60
11.1. Timers . . . . . . . . . . . . . . . . . . . . . . . . . 61
11.2. Protocol Constants . . . . . . . . . . . . . . . . . . . 62
11.3. Local Settings . . . . . . . . . . . . . . . . . . . . . 63
11.4. Network-Wide Settings . . . . . . . . . . . . . . . . . 63
11.5. Optional Feature Settings . . . . . . . . . . . . . . . 63
11.6. MetricType Allocation . . . . . . . . . . . . . . . . . 64
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 64
12.1. RFC 5444 Message Types . . . . . . . . . . . . . . . . . 64
12.2. RFC 5444 Address Block TLV Types . . . . . . . . . . . . 65
12.3. ADDRESS_TYPE TLV Values . . . . . . . . . . . . . . . . 65
13. Security Considerations . . . . . . . . . . . . . . . . . . . 66
14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 68
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 69
15.1. Normative References . . . . . . . . . . . . . . . . . . 69
15.2. Informative References . . . . . . . . . . . . . . . . . 70
Appendix A. AODVv2 Draft Updates . . . . . . . . . . . . . . . . 71
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 71
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1. Overview
The Ad Hoc On-demand Distance Vector Version 2 (AODVv2) routing
protocol (formerly named DYMO) enables on-demand, multihop unicast
routing among AODVv2 routers in mobile ad hoc networks (MANETs)
[RFC2501].
Although AODVv2 is closely related to AODV [RFC3561], and shares some
features of DSR [RFC4728], AODVv2 is not interoperable with either of
those protocols. Compared to AODV, AODVv2 makes some features
optional, notably intermediate route replies, expanding ring search,
and precursor lists. Hello messages and local repair have been
removed. AODVv2 provides a mechanism for the use of multiple metric
types. Message formats have been updated and made compliant with
[RFC5444].
AODVv2 control messages are defined as sets of data, which are mapped
to messages using the Generalized MANET Packet/Message Format defined
in [RFC5444] and sent using the parameters in [RFC5498].
The basic operations of the AODVv2 protocol are route discovery and
route maintenance.
An AODVv2 router is configured to perform route discovery on behalf
of a configured set of IP addresses known as Router Clients. Route
discovery is performed when an AODVv2 router needs to forward an IP
packet from one of its Router Clients, but does not have a valid
route to the packet's destination. AODVv2 routers use Route Request
(RREQ) and Route Reply (RREP) messages to carry route information
between the originator of the route discovery and the router
responsible for the target, establishing a route to both endpoints on
all intermediate routers. A metric value is included to represent
the cost of the route contained within the message. AODVv2 uses
sequence numbers to identify stale routing information, and compares
route metric values to determine if advertised routes could form
loops.
Route maintenance includes confirming bidirectionality of links to
next hop AODVv2 routers before considering discovered routes to be
valid, issuing Route Error (RERR) messages if link failures
invalidate routes, reacting to received Route Error messages, and
extending and enforcing route timeouts.
To enable the on-demand nature of AODVv2, signals are required to be
exchanged between AODVv2 and the forwarding plane, to indicate when a
packet is to be forwarded, in order to initiate route discovery, when
packet forwarding fails, in order to initiate route error reporting,
and when a packet is successfully forwarded, for route maintenance.
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Security for authentication of AODVv2 routers and encryption of
control messages is accomplished using the TIMESTAMP and ICV TLVs
defined in [RFC7182].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. In addition, this document uses terminology from
[RFC5444], and defines the following terms:
AddressList
A list of IP addresses as used in AODVv2 messages.
AckReq
Used in a Route Reply message to indicate the IP address of the
router from which a Route Reply Acknowledgement is expected.
AdvRte
A route advertised in an incoming route message.
AODVv2 Router
An IP addressable device in the ad hoc network that performs the
AODVv2 protocol operations specified in this document.
CurrentTime
The current time as maintained by the AODVv2 router.
ENAR (External Network Access Router)
An AODVv2 router with an interface to an external, non-AODVv2
network.
Invalid route
A route that cannot be used for forwarding but still contains
useful sequence number information.
LocalRoute
An entry in the Local Route Set.
MANET
A Mobile Ad Hoc Network as defined in [RFC2501].
MetricType
The metric type for a metric value included in a message.
MetricTypeList
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A list of metric types associated with the addresses in the
AddressList of a Route Error message.
Neighbor
An AODVv2 router from which an RREQ or RREP message has been
received. Neighbors exchange routing information and verify
bidirectionality of the link to a neighbor before installing a
route via that neighbor into the Local Route Set.
OrigAddr
The source IP address of the IP packet triggering route discovery.
OrigMetric
The metric value associated with the route to OrigAddr (and any
other addresses included in the given prefix length).
OrigPrefixLen
The prefix length, in bits, configured in the Router Client entry
which includes OrigAddr.
OrigSeqNum
The sequence number of the AODVv2 router which originated the
Route Request on behalf of OrigAddr.
PktSource
The source address of the IP packet which triggered a Route Error
message.
PrefixLengthList
A list of routing prefix lengths associated with the addresses in
the AddressList of a message.
Reactive
Performed only in reaction to specific events. In AODVv2, routes
are requested only when data packets need to be forwarded. In
this document, "reactive" is synonymous with "on-demand".
RERR (Route Error)
The AODVv2 message type used to indicate that an AODVv2 router
does not have a valid LocalRoute toward one or more particular
destinations.
RERR_Gen (RERR Generating Router)
The AODVv2 router generating a Route Error message.
Routable Unicast IP Address
A routable unicast IP address is a unicast IP address that is
scoped sufficiently to be forwarded by a router. Globally-scoped
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unicast IP addresses and Unique Local Addresses (ULAs) [RFC4193]
are examples of routable unicast IP addresses.
Router Client
An address or address range configured on an AODVv2 router, on
behalf of which that router will initiate and respond to route
discoveries, so that devices configured to use these addresses can
send and receive IP traffic to and from remote destinations.
These addresses may be used by the AODVv2 router itself or by non-
routing devices that are reachable without traversing another
AODVv2 router.
RREP (Route Reply)
The AODVv2 message type used to reply to a Route Request message.
RREP_Gen (RREP Generating Router)
The AODVv2 router that generates the Route Reply message, i.e.,
the router configured with TargAddr as a Router Client.
RREQ (Route Request)
The AODVv2 message type used to discover a route to TargAddr and
distribute information about a route to OrigAddr.
RREQ_Gen (RREQ Generating Router)
The AODVv2 router that generates the Route Request message, i.e.,
the router configured with OrigAddr as a Router Client.
RteMsg (Route Message)
A Route Request (RREQ) or Route Reply (RREP) message.
SeqNum
The sequence number maintained by an AODVv2 router to indicate
freshness of route information.
SeqNumList
A list of sequence numbers associated with the addresses in the
AddressList of a message.
TargAddr
The target address of a route request, i.e., the destination
address of the IP packet triggering route discovery.
TargMetric
The metric value associated with the route to TargAddr (and any
other addresses included in the given prefix length).
TargPrefixLen
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The prefix length, in bits, configured in the Router Client entry
which includes TargAddr.
TargSeqNum
The sequence number of the AODVv2 router which originated the
Route Reply on behalf of TargAddr.
Valid route
A route that can be used for forwarding, which has been confirmed
as having a bidirectional link to the next hop, and has not timed
out or been made invalid by a route error.
Unreachable Address
An address reported in a Route Error message, either the address
on a LocalRoute which became Invalid, or the destination address
of an IP packet that could not be forwarded because a valid
LocalRoute to the destination is not known, and will not be
requested.
Upstream
In the direction from destination to source (from TargAddr to
OrigAddr).
ValidityTime
The length of time the route described by the message is offered.
This document uses the notational conventions in Table 1 to simplify
the text.
+-----------------------+------------------------------------+
| Notation | Meaning |
+-----------------------+------------------------------------+
| Route[Address] | A route toward Address |
| Route[Address].Field | A field in a route toward Address |
| RteMsg.Field | A field in either RREQ or RREP |
+-----------------------+------------------------------------+
Table 1: Notational Conventions
3. Applicability Statement
The AODVv2 routing protocol is a reactive routing protocol. While
proactive routing protocols send frequent messages and determine
routes in advance of them being used, a reactive protocol only sends
messages to discover a route when there is data to send on that
route. Therefore, a reactive routing protocol requires certain
interactions with the forwarding plane, for example, to indicate when
a packet is to be forwarded, in order to initiate route discovery,
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route error reporting, or route maintenance. The set of signals
exchanged between AODVv2 and the forwarding plane are discussed in
Section 6.4.
AODVv2 is designed for stub or disconnected mobile ad hoc networks,
i.e., non-transit networks or those not connected to the internet.
AODVv2 can, however, be configured to perform gateway functions when
attached to external networks, as discussed in Section 9.
AODVv2 handles a wide variety of mobility and traffic patterns by
determining routes on-demand. In networks with a large number of
routers, AODVv2 is best suited for relatively sparse traffic
scenarios where each router forwards IP packets to a small percentage
of other AODVv2 routers in the network. In this case fewer routes
are needed, and therefore less control traffic is produced.
Providing security for a reactive routing protocol can be difficult.
AODVv2 provides for message integrity and security against replay
attacks by using integrity check values, timestamps and sequence
numbers, as described in Section 13. If security associations can be
established, encryption can be used for AODVv2 messages to ensure
that only trusted routers participate in routing operations.
Since the route discovery process aims for a route to be established
in both directions along the same path, uni-directional links are not
suitable. AODVv2 will detect and exclude those links from route
discovery. The route discovered is optimised for the requesting
router, and the return path may not be the optimal route.
AODVv2 is applicable to memory constrained devices, since only a
little routing state is maintained in each AODVv2 router. In
contrast to proactive routing protocols, which maintain routing
information for all destinations within the MANET, AODVv2 routes that
are not needed for forwarding data do not need to be maintained. On
routers unable to store persistent AODVv2 state, recovery can impose
a performance penalty (e.g., in case of AODVv2 router reboot), since
if a router loses its sequence number, there is a delay before the
router can resume full operations. This is described in Section 6.1.
AODVv2 supports routers with multiple interfaces and multiple IP
addresses per interface. A router may also use the same IP address
on multiple interfaces. AODVv2 requires only that each interface
configured for AODVv2 has at least one unicast IP address. Address
assignment procedures are out of scope for AODVv2.
AODVv2 supports Router Clients with multiple interfaces, as long as
each interface is configured with its own unicast IP address. Multi-
homing of a Router Client IP address is not supported by AODVv2, and
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therefore an IP address SHOULD NOT be configured as a Router Client
on more than one AODVv2 router at any one time.
The routing algorithm in AODVv2 MAY be operated at layers other than
the network layer, using layer-appropriate addresses.
4. Data Structures
4.1. Interface List
If multiple interfaces of the AODVv2 router are configured for use by
AODVv2, a list of the interfaces MUST be configured in the
AODVv2_INTERFACES list.
4.2. Router Client Table
An AODVv2 router provides route discovery services for its own local
applications and for other non-routing devices that are reachable
without traversing another AODVv2 router. The addresses used by
these devices, and the AODVv2 router itself, are configured in the
Router Client Table. An AODVv2 router will only originate Route
Request and Route Reply messages on behalf of configured Router
Client addresses.
Router Client Table entries MUST contain:
RouterClient.IPAddress
An IP address or the start of an address range that requires route
discovery services from the AODVv2 router.
RouterClient.PrefixLength
The length, in bits, of the routing prefix associated with the
RouterClient.IPAddress. If a prefix length is included, the
AODVv2 router MUST provide connectivity for all addresses within
that prefix.
RouterClient.Cost
The cost associated with reaching this address or address range.
The Router Client Table for an AODVv2 router is never empty, since an
AODVv2 router's interface addresses are always configured in Router
Client entries.
In the initial state, an AODVv2 router is not required to have
information about the Router Clients of any other AODVv2 router.
A Router Client address MUST NOT be served by more than one AODVv2
router at any one time. To shift responsibility for a Router Client
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to a different AODVv2 router, correct AODVv2 routing behavior MUST be
observed. The AODVv2 router adding the Router Client MUST wait for
any existing routing information about this Router Client to be
purged from the network, i.e., at least MAX_SEQNUM_LIFETIME since the
last SeqNum update on the router which is removing this Router
Client.
4.3. Neighbor Table
A Neighbor Table MUST be maintained with information about
neighboring AODVv2 routers. Neighbor Table entries are stored when
AODVv2 messages are received. If the Neighbor is chosen as a next
hop on an installed route, the link to the Neighbor MUST be tested
for bidirectionality and the result stored in this table. A route
will only be considered valid when the link is confirmed to be
bidirectional.
Neighbor Table entries MUST contain:
Neighbor.IPAddress
An IP address of the neighboring router, learned from the source
IP address of a received route message.
Neighbor.State
Indicates whether the link to the neighbor is bidirectional.
There are three possible states: Confirmed, Unknown, and
Blacklisted. Unknown is the initial state. Confirmed indicates
that the link to the neighbor has been confirmed as bidirectional.
Blacklisted indicates that the link to the neighbor is uni-
directional. Section 6.2 discusses how to monitor link
bidirectionality.
Neighbor.ResetTime
When the value of Neighbor.State is Blacklisted, this indicates
the time at which the value of Neighbor.State will revert to
Unknown. By default this value is calculated at the time the
router is blacklisted and is equal to CurrentTime +
MAX_BLACKLIST_TIME. When the value of Neighbor.State is not
Blacklisted, this time is set to INFINITY_TIME.
4.4. Sequence Numbers
Sequence numbers enable AODVv2 routers to determine the temporal
order of route discovery messages, identifying stale routing
information so that it can be discarded. The sequence number
fulfills the same roles as the "Destination Sequence Number" of DSDV
[Perkins94], and the AODV Sequence Number in [RFC3561].
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Each AODVv2 router in the network MUST maintain its own sequence
number. All RREQ and RREP messages created by an AODVv2 router
include the router's sequence number, reported as a 16-bit unsigned
integer. Each AODVv2 router MUST ensure that its sequence number is
strictly increasing, and that it is incremented by one (1) whenever
an RREQ or RREP is created, except when the sequence number is 65,535
(the maximum value of a 16-bit unsigned integer), in which case it
MUST be reset to one (1). The value zero (0) is reserved to indicate
that the sequence number is unknown.
An AODVv2 router MUST only attach its own sequence number to
information about a route to one of its configured Router Clients.
All route messages regenerated by other routers retain the
originator's sequence number. Therefore, when two pieces of
information about a route are received, they both contain a sequence
number from the originating router. Comparing the sequence number
will identify which information is stale. The previously stored
sequence number is subtracted from the incoming sequence number. The
result of the subtraction is to be interpreted as a signed 16-bit
integer, and if less than zero, the information in the new AODVv2
message is stale and MUST be discarded.
This, along with the processes in Section 6.7.1, ensures loop
freedom.
An AODVv2 router SHOULD maintain its sequence number in persistent
storage. If the sequence number is lost, the router MUST follow the
procedure in Section 6.1 to safely resume routing operations with a
new sequence number.
4.5. Local Route Set
All AODVv2 routers MUST maintain a Local Route Set, containing
information about routes learned from AODVv2 route messages. The
Local Route Set is stored separately from the Routing Information
Base, and the Routing Information Base is updated using information
from the Local Route Set. Alternatively, implementations MAY choose
to modify the Routing Information Base directly.
Routes learned from AODVv2 route messages are referred to in this
document as LocalRoutes, and MUST contain the following information:
LocalRoute.Address
An address, which, when combined with LocalRoute.PrefixLength,
describes the set of destination addresses this route includes.
LocalRoute.PrefixLength
The prefix length, in bits, associated with LocalRoute.Address.
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LocalRoute.SeqNum
The sequence number associated with LocalRoute.Address, obtained
from the last route message that successfully updated this entry.
LocalRoute.NextHop
The source IP address of the IP packet containing the AODVv2
message advertising the route to LocalRoute.Address, i.e. an IP
address of the AODVv2 router used for the next hop on the path
toward LocalRoute.Address.
LocalRoute.NextHopInterface
The interface used to send IP packets toward LocalRoute.Address.
LocalRoute.LastUsed
If this route is installed in the Routing Information Base, the
time it was last used to forward an IP packet.
LocalRoute.LastSeqNumUpdate
The time LocalRoute.SeqNum was last updated.
LocalRoute.ExpirationTime
The time at which this LocalRoute MUST be marked as Invalid. An
AODVv2 router MAY be offered a route for a limited time. In this
case, the route is referred to as a timed route. If a route is
not timed, LocalRoute.ExpirationTime is INFINITY_TIME.
LocalRoute.MetricType
The type of metric associated with this route.
LocalRoute.Metric
The cost of the route toward LocalRoute.Address expressed in units
consistent with LocalRoute.MetricType.
LocalRoute.State
The last known state (Unconfirmed, Idle, Active, or Invalid) of
the route.
LocalRoute.Precursors (optional feature)
A list of upstream neighbors using the route (see Section 10.2).
There are four possible states for a LocalRoute:
Unconfirmed
A route learned from a Route Request message, which has not yet
been confirmed as bidirectional. It MUST NOT be used for
forwarding IP packets, and therefore it is not referred to as a
valid route.
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Idle
A route which has been learned from a route message, and has also
been confirmed, but has not been used in the last ACTIVE_INTERVAL.
It is able to be used for forwarding IP packets, and therefore it
is referred to as a valid route.
Active
A route which has been learned from a route message, and has also
been confirmed, and has been used in the last ACTIVE_INTERVAL. It
is able to be used for forwarding IP packets, and therefore it is
referred to as a valid route.
Invalid
A route which has expired or been lost. It MUST NOT be used for
forwarding IP packets, and therefore it is not referred to as a
valid route. Invalid routes contain sequence number information
which allows incoming information to be assessed for freshness.
When the Local Route Set is stored separately from the Routing
Information Base, routes are added to the Routing Information Base
when LocalRoute.State is valid (set to Active or Idle), and removed
from the Routing Information Base LocalRoute.State becomes Invalid.
Changes to LocalRoute state are detailed in Section 6.9.1.
Note that multiple entries for the same address, prefix length and
metric type may exist in the Local Route Set, but only one will be a
valid entry. Any others will be Unconfirmed, but may offer
improvement to the existing valid route, if they can be confirmed as
valid routes (see Section 6.2).
Multiple valid routes for the same address and prefix length but for
different metric types may exist in the Local Route Set, but the
decision of which of these routes to install in the Routing
Information Base to use for forwarding is outside the scope of
AODVv2.
4.6. Multicast Route Message Table
A route message (RteMsg) is either a Route Request or Route Reply
message. RREQ messages are multicast by default and regenerated
multiple times, and RREP messages may be multicast when the link to
the next router is not known to be bidirectional. Multiple similar
route messages might be received by any one router during one route
discovery attempt. The AODVv2 router does not need to regenerate or
respond to every one of these messages.
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The Multicast Route Message Table is a conceptual table which
contains information about previously received multicast route
messages, so that incoming route messages can be compared with
previously received messages to determine if the incoming information
is redundant, and the router can avoid sending redundant control
traffic.
Multicast Route Message Table entries MUST contain the following
information:
RteMsg.MessageType
Either RREQ or RREP.
RteMsg.OrigAddr
The source address of the IP packet triggering the route request.
RteMsg.OrigPrefixLen
The prefix length associated with RteMsg.OrigAddr, originally from
the Router Client entry on RREQ_Gen which includes
RteMsg.OrigAddr.
RteMsg.TargAddr
The destination address of the IP packet triggering the route
request.
RteMsg.TargPrefixLen
The prefix length associated with RteMsg.TargAddr, originally from
the Router Client entry on RREP_Gen which includes
RteMsg.TargAddr.
RteMsg.OrigSeqNum
The sequence number associated with the route to OrigAddr, if
RteMsg is an RREQ.
RteMsg.TargSeqNum
The sequence number associated with the route to TargAddr, if
present in the RteMsg.
RteMsg.MetricType
The metric type of the route requested.
RteMsg.Metric
The metric value received in the RteMsg.
RteMsg.Timestamp
The last time this Multicast Route Message Table entry was
updated.
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RteMsg.RemoveTime
The time at which this entry MUST be removed from the Multicast
Route Message Table. This is set to CurrentTime +
MAX_SEQNUM_LIFETIME, whenever the sequence number of this entry
(RteMsg.OrigSeqNum for an RREQ, or RteMsg.TargSeqNum for an RREP)
is updated.
The Multicast Route Message Table is maintained so that no two
entries have the same MessageType, OrigAddr, TargAddr, and
MetricType. See Section 6.8 for details about updating this table.
5. Metrics
Metrics measure a cost or quality associated with a route or a link,
e.g., latency, delay, financial cost, energy, etc. Metric values are
reported in Route Request and Route Reply messages.
In Route Request messages, the metric describes the cost of the route
from OrigAddr (and any other addresses included in the prefix length
of RREQ_Gen's Router Client entry for OrigAddr) to the router sending
the Route Request. For RREQ_Gen, this is the cost associated with
the Router Client entry which includes OrigAddr. For routers which
regenerate the RREQ, this is the cost from OrigAddr to the
regenerating router, combining the metric value from the received
RREQ message with knowledge of the link cost from the sender to the
receiver, i.e., the incoming link cost. This updated route cost is
included when regenerating the Route Request message, and used to
install a route back toward OrigAddr.
Similarly, in Route Reply messages, the metric reflects the cost of
the route from TargAddr (and any other addresses included in the
prefix length of RREP_Gen's Router Client entry for TargAddr) to the
router sending the Route Reply. For RREP_Gen, this is the cost
associated with the Router Client entry which includes TargAddr. For
routers which regenerate the RREP, this is the cost from TargAddr to
the regenerating router, combining the metric value from the received
RREP message with knowledge of the link cost from the sender to the
receiver, i.e., the incoming link cost. This updated route cost is
included when regenerating the Route Reply message, and used to
install a route back toward TargAddr.
Assuming link metrics are symmetric, the cost of the routes installed
in the Local Route Set at each router will be correct. The route
discovered is optimised for the requesting router, and the return
path may not be the optimal route.
AODVv2 enables the use of multiple metric types. Each route
discovery attempt indicates the metric type which is requested for
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the route. Only one metric type MUST be used in each route discovery
attempt. However, routes to a single destination might be requested
and created in the Local Route Set for multiple metric types. The
decision of which of these routes to install in the Routing
Information Base to use for forwarding is outside the scope of
AODVv2.
For each MetricType, AODVv2 requires:
o A MetricType number, to indicate the metric type of a route.
MetricType numbers allocated are detailed in Section 11.6.
o A maximum value, denoted MAX_METRIC[MetricType]. This MUST always
be the maximum expressible metric value of type MetricType. Field
lengths associated with metric values are found in Section 11.6.
If the cost of a route exceeds MAX_METRIC[MetricType], the route
is ignored.
o A function for incoming link cost, denoted Cost(L). Using
incoming link costs means that the route learned has a path
optimized for the direction from OrigAddr to TargAddr.
o A function for route cost, denoted Cost(R).
o A function to analyze routes for potential loops based on metric
information, denoted LoopFree(R1, R2). LoopFree verifies that a
route R2 is not a sub-section of another route R1. An AODVv2
router invokes LoopFree() as part of the process in Section 6.7.1,
when an advertised route (R1) and an existing LocalRoute (R2) have
the same destination address, metric type, and sequence number.
LoopFree returns FALSE to indicate that an advertised route is not
to be used to update a stored LocalRoute, as it may cause a
routing loop. In the case where the existing LocalRoute is
Invalid, it is possible that the advertised route includes the
existing LocalRoute and came from a router which did not yet
receive notification of the route becoming Invalid, so the
advertised route should not be used to update the Local Route Set,
in case it forms a loop to a broken route.
AODVv2 currently supports cost metrics where Cost(R) is strictly
increasing, by defining:
o Cost(R) := Sum of Cost(L) of each link in the route
o LoopFree(R1, R2) := ( Cost(R1) <= Cost(R2) )
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Implementers MAY consider other metric types, but the definitions of
Cost and LoopFree functions for such types are undefined, and
interoperability issues need to be considered.
6. AODVv2 Protocol Operations
The AODVv2 protocol's operations include managing sequence numbers,
monitoring next hop AODVv2 routers on discovered routes and updating
the Neighbor Table, performing route discovery and dealing with
requests from other routers, processing incoming route information
and updating the Local Route Set, updating the Multicast Route
Message Table and suppressing redundant messages, and reporting
broken routes. These processes are discussed in detail in the
following sections.
6.1. Initialization
During initialization where an AODVv2 router does not have
information about its previous sequence number, or if its sequence
number is lost at any point, the router resets its sequence number to
one (1). However, other AODVv2 routers may still hold sequence
number information that this router previously issued. Since
sequence number information is removed if there has been no update to
the sequence number in MAX_SEQNUM_LIFETIME, the initializing router
MUST wait for MAX_SEQNUM_LIFETIME before it creates any messages
containing its new sequence number. It can then be sure that the
information it sends will not be considered stale.
Until MAX_SEQNUM_LIFETIME after its sequence number is reset, the
router SHOULD NOT create RREQ or RREP messages.
During this wait period, the router is permitted to do the following:
o Process information in a received RREQ or RREP message to learn a
route to the originator or target of that route discovery
o Regenerate a received RREQ or RREP
o Send an RREP_Ack
o Maintain valid routes in the Local Route Set
o Create, process and regenerate RERR messages
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6.2. Next Hop Monitoring
AODVv2 routers MUST NOT establish routes over uni-directional links.
Consider the following. An RREQ is forwarded toward TargAddr, and
intermediate routers create a LocalRoute corresponding to OrigAddr.
An RREP arrives to be forwarded toward OrigAddr, but the link to the
next hop toward OrigAddr is uni-directional. The RREP sent toward
OrigAddr using this link would not reach the next hop, and would
therefore never reach RREQ_Gen. End-to-end route establishment will
fail. If the route discovery is retried by RREQ_Gen, the same will
happen. Further, if an intermediate router used the route toward
OrigAddr to forward data traffic, the data packets would be lost.
AODVv2 provides a mechanism for testing bidirectional connectivity
during route discovery, and blacklisting routers where bidirectional
connectivity is not available. If a route discovery is retried by
RREQ_Gen, the blacklisted routers can be excluded from the process,
and a different route can be discovered. Further, a route is not to
be used for forwarding until the bidirectionality of the link to the
next hop is confirmed. AODVv2 routers do not need to monitor
bidirectionality for links to neighboring routers which are not used
as next hops on routes in the Local Route Set.
o For the next hop router on the route toward OrigAddr, the approach
for testing bidirectional connectivity is to request
acknowledgement of Route Reply messages. Receipt of an
acknowledgement proves that bidirectional connectivity exists.
All AODVv2 routers MUST support this process, which is explained
in Section 7.2 and Section 7.3. A link to a neighbor is
determined to be unidirectional if a requested acknowledgement is
not received within RREP_Ack_SENT_TIMEOUT, or bidirectional if the
acknowledgement is received within the timeout.
o For the next hop router on the route toward TargAddr, receipt of
the Route Reply message containing the route to TargAddr is
confirmation of bidirectionality, since a Route Reply message is a
reply to a Route Request message which previously crossed the link
in the opposite direction.
To assist with next hop monitoring, a Neighbor Table (Section 4.3) is
maintained. When an RREQ or RREP is received from an IP address
which does not already have an entry in the Neighbor Table, a new
entry is created as described in Section 6.3. While the value of
Neighbor.State is Unknown, acknowledgement of RREP messages sent to
that neighbor MUST be requested. If an acknowledgement is not
received within the timeout period, the neighbor MUST have
Neighbor.State set to Blacklisted. If an acknowledgement is received
within the timeout period, Neighbor.State is set to Confirmed. While
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the value of Neighbor.State is Confirmed, the request for an
acknowledgement of any other RREP message is unnecessary.
When routers perform other operations such as those from the list
below, these MAY be used as additional indications of connectivity:
o NHDP HELLO Messages [RFC6130]
o Route timeout
o Lower layer triggers, e.g. message reception or link status
notifications
o TCP timeouts
o Promiscuous listening
o Other monitoring mechanisms or heuristics
If such an external process signals that the link to a neighbor is
bidirectional, the AODVv2 router MAY update the matching Neighbor
Table entry by changing the value of Neighbor.State to Confirmed. If
an external process signals that a link is not bidirectional, the
value of Neighbor.State MAY be changed to Blacklisted. If an
external process signals that the link might not be bidirectional,
and the value of Neighbor.State is currently Confirmed, it MAY be set
to Unknown.
For example, receipt of a Neighborhood Discovery Protocol HELLO
message with the receiving router listed as a neighbor is a signal of
bidirectional connectivity. The AODVv2 router MAY update the
matching Neighbor Table entry by changing the value of Neighbor.State
to Confirmed.
Similarly, if AODVv2 receives notification of a timeout, for example,
from TCP or some other protocol, this may be due to a disconnection.
The AODVv2 router MAY update the matching Neighbor Table entry by
setting the value of Neighbor.State to Unknown.
6.3. Neighbor Table Update
On receipt of an RREQ or RREP message, the Neighbor Table MUST be
checked for an entry with Neighbor.IPAddress which matches the source
IP address of the message. If no matching entry is found, a new
entry is created.
A new Neighbor Table entry is created as follows:
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o Neighbor.IPAddress := Source IP address of the received route
message
o Neighbor.State := Unknown
o Neighbor.ResetTime := INFINITY_TIME
If the message is an RREP which answers a recently sent RREQ, or an
RREP_Ack which answers a recently sent RREP, the link to the neighbor
is bidirectional and the Neighbor Table entry is updated as follows:
o Neighbor.State := Confirmed
o Neighbor.ResetTime := INFINITY_TIME
If an RREP_Ack is not received within the expected time, the link is
considered to be uni-directional and the Neighbor Table entry is
updated as follows:
o Neighbor.State := Blacklisted
o Neighbor.ResetTime := CurrentTime + MAX_BLACKLIST_TIME
When the Neighbor.ResetTime is reached, the Neighbor Table entry is
updated as follows:
o Neighbor.State := Unknown
When a link to a neighbor is determined to be broken, the Neighbor
Table entry SHOULD be removed.
Route requests from neighbors with Neighbor.State set to Blacklisted
are ignored to avoid persistent IP packet loss or protocol failures.
However, Neighbor.ResetTime allows the neighbor to again be allowed
to participate in route discoveries after MAX_BLACKLIST_TIME, in case
the link between the routers has become bidirectional.
6.4. Interaction with the Forwarding Plane
A reactive routing protocol only reacts when a route is needed, i.e.,
when an application tries to send a packet and the forwarding plane
has no route to the destination of the packet.
AODVv2 requires signals from the forwarding plane:
o A packet cannot be forwarded because a route is unavailable:
AODVv2 needs to know the source and destination IP addresses of
the packet, to determine if the source of the packet is configured
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as a Router Client, in which case the router should initiate route
discovery. If it is not a Router Client, the router should create
a Route Error message.
o A packet is to be forwarded: AODVv2 needs to check the state of
the route to deal with timeouts to ensure the route is still
valid.
o Packet forwarding succeeds: AODVv2 needs to update the record of
when a route was last used to forward a packet.
o Packet forwarding failure occurs: AODVv2 needs to create a Route
Error message.
AODVv2 needs to send signals to the forwarding plane:
o A route discovery is in progress: buffering might be configured
for packets requiring a route, while route discovery is attempted.
o A route discovery failed: any buffered packets requiring that
route should be discarded, and the source of the packet should be
notified that the destination is unreachable (using an ICMP
Destination Unreachable message). Route discovery fails if an
RREQ cannot be generated because the control message generation
limit has been reached, or if an RREP is not received within the
expected time.
o A route discovery is not permitted: any buffered packets requiring
that route should be discarded. A route discovery will not be
attempted if the source address of the packet needing a route is
not configured as a Router Client.
o A route discovery succeeded: install a corresponding route into
the Routing Information Base and begin transmitting any buffered
packets.
o A route has been made invalid: remove the corresponding route from
the Routing Information Base.
o A route has been updated: update the corresponding route in the
Routing Information Base.
These are conceptual signals, and can be implemented in various ways.
Conformant implementations of AODVv2 are not mandated to implement
the forwarding plane separately from the control plane or data plane;
these signals and interactions are identified simply as assistance
for implementers who may find them useful.
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6.5. Message Transmission
AODVv2 sends [RFC5444] formatted messages using the parameters for
port number and IP protocol specified in [RFC5498]. Mapping of
AODVv2 data to [RFC5444] messages is detailed in Section 8. AODVv2
multicast messages are sent to the link-local multicast address LL-
MANET-Routers [RFC5498]. All AODVv2 routers MUST subscribe to LL-
MANET-Routers on all AODVv2 interfaces [RFC5498] to receive AODVv2
messages. Note that multicast messages MAY be sent via unicast. For
example, this may occur for certain link-types (non-broadcast media),
for manually configured router adjacencies, or in order to improve
robustness.
When multiple interfaces are available, an AODVv2 router transmitting
a multicast message to LL-MANET-Routers MUST send the message on all
interfaces that have been configured for AODVv2 operation, as given
in the AODVv2_INTERFACES list (Section 4.1).
To avoid congestion, each AODVv2 router's rate of message generation
SHOULD be limited (CONTROL_TRAFFIC_LIMIT) and administratively
configurable. To prioritize transmission of AODVv2 control messages
in order to respect the CONTROL_TRAFFIC_LIMIT:
o Highest priority SHOULD be given to RREP_Ack messages. This
allows links between routers to be confirmed as bidirectional and
avoids undesirable blacklisting of next hop routers.
o Second priority SHOULD be given to RERR messages for undeliverable
IP packets, so that broken routes that are still in use by other
AODVv2 routers can be reported to those routers, to avoid IP data
packets being repeatedly forwarded to AODVv2 routers which cannot
forward them to their destination.
o Third priority SHOULD be given to RREP messages in order that
RREQs do not time out.
o RREQ messages SHOULD be given priority over RERR messages for
newly invalidated routes, since the invalidated routes may not
still be in use, and if there is an attempt to use the route, a
new RERR message will be generated.
o Lowest priority SHOULD be given to RERR messages generated in
response to RREP messages which cannot be regenerated. In this
case the route request will be retried at a later point.
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6.6. Route Discovery, Retries and Buffering
AODVv2's RREQ and RREP messages are used for route discovery. RREQ
messages are multicast to solicit an RREP, whereas RREP is unicast
where possible. The constants used in this section are defined in
Section 11.
When an AODVv2 router needs to forward an IP packet (with source
address OrigAddr and destination address TargAddr) from one of its
Router Clients, it needs a route to TargAddr in its Routing
Information Base. If no route exists, the AODVv2 router generates
and multicasts a Route Request message (RREQ) containing OrigAddr and
TargAddr. The procedure for this is described in Section 7.1.1.
Each generated RREQ results in an increment to the router's sequence
number. The AODVv2 router generating an RREQ is referred to as
RREQ_Gen.
Buffering might be configured for IP packets awaiting a route for
forwarding by RREQ_Gen, if sufficient memory is available. Buffering
of IP packets might have both positive and negative effects. Real-
time traffic, voice, and scheduled delivery may suffer if packets are
buffered and subjected to delays, but TCP connection establishment
will benefit if packets are queued while route discovery is performed
[Koodli01]. If packets are not queued, no notification should be
sent to the source. Determining which packets to discard first when
the buffer is full is a matter of policy at each AODVv2 router.
RREQ_Gen awaits reception of a Route Reply message (RREP) containing
a route toward TargAddr. If a valid route to TargAddr is not learned
within RREQ_WAIT_TIME, RREQ_Gen will retry the route discovery. To
reduce congestion in a network, repeated attempts at route discovery
for a particular target address utilize a binary exponential backoff:
for each additional attempt, the time to wait for receipt of the RREP
is multiplied by 2. If the requested route is not learned within the
wait period, another RREQ is sent, up to a total of
DISCOVERY_ATTEMPTS_MAX. This is the same technique used in AODV
[RFC3561].
The RREQ is received by neighboring AODVv2 routers, and processed and
regenerated as described in Section 7.1. Routers learn a potential
route to OrigAddr (and other addresses as indicated by OrigPrefixLen)
from the RREQ and store it in the Local Route Set. The router
responsible for TargAddr responds by generating a Route Reply message
(RREP) and sends it back toward RREQ_Gen via the next hop on the
potential route to OrigAddr. Each intermediate router learns the
route to TargAddr (and other addresses as indicated by
TargPrefixLen), regenerates the RREP and sends toward OrigAddr.
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Links which are not bidirectional cause problems. If a link is
unavailable in the direction toward OrigAddr, an RREP is not received
at the next hop, so cannot be regenerated, and it will never reach
RREQ_Gen. However, since routers monitor bidirectionality to next
hops (Section 6.2), the loss of the RREP will cause the last router
which regenerated the RREP to blacklist the router which did not
receive it. Later, a timeout occurs at RREQ_Gen, and a new RREQ is
generated. If the new RREQ arrives via the blacklisted router, it
will be ignored, enabling the RREQ, if also received from a different
neighbor, to discover a different path toward TargAddr.
Route discovery is considered to have failed after
DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for an RREP
response to the final RREQ. After the attempted route discovery has
failed, RREQ_Gen waits at least RREQ_HOLDDOWN_TIME before attempting
another route discovery to the same destination, in order to avoid
repeatedly generating control traffic that is unlikely to discover a
route. Any IP packets buffered for TargAddr are also dropped and a
Destination Unreachable ICMP message (Type 3) with a code of 1 (Host
Unreachable Error) is delivered to the source of the packet, so that
the application knows about the failure. The source might be an
application on RREQ_Gen itself, or on a difference device.
If RREQ_Gen does receive a route message containing a route to
TargAddr within the timeout, it processes the message according to
Section 7. When a valid LocalRoute entry is created in the Local
Route Set, the route is also installed in the Routing Information
Base, and the router will begin sending the buffered IP packets. Any
retry timers for the corresponding RREQ are then cancelled.
During route discovery, all routers on the path learn a route to both
OrigAddr and TargAddr, so that routes are constructed in both
directions. The route is optimized for the forward route.
6.7. Processing Received Route Information
All AODVv2 route messages contain a route. A Route Request (RREQ)
contains a route toward OrigAddr (and other addresses as indicated by
OrigPrefixLen), and a Route Reply (RREP) contains a route toward
TargAddr (and other addresses as indicated by TargPrefixLen). All
AODVv2 routers that receive a route message are able to store the
route contained within it in their Local Route Set. Incoming
information is first checked to verify that it is both safe to use
and offers an improvement to existing information, as explained in
Section 6.7.1. The Local Route Set MAY then be updated according to
Section 6.7.2.
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In the processes below, RteMsg is used to denote the route message,
AdvRte is used to denote the route contained within it, and
LocalRoute denotes an existing entry in the Local Route Set which
matches AdvRte on address, prefix length, and metric type.
AdvRte has the following properties:
o AdvRte.Address := network address given by combining
RteMsg.OrigAddr and RteMsg.OrigPrefixLen (in RREQ) or
RteMsg.TargAddr and RteMsg.TargPrefixLen (in RREP)
o AdvRte.PrefixLength := RteMsg.OrigPrefixLen (in RREQ) or
RteMsg.TargPrefixLen (in RREP). If no prefix length was included
in RteMsg, prefix length is the address length, in bits, of
RteMsg.OrigAddr (in RREQ) or RteMsg.TargAddr (in RREP)
o AdvRte.SeqNum := RteMsg.OrigSeqNum (in RREQ) or RteMsg.TargSeqNum
(in RREP)
o AdvRte.NextHop := RteMsg.IPSourceAddress (an address of the router
from which the RteMsg was received)
o AdvRte.MetricType := RteMsg.MetricType
o AdvRte.Metric := RteMsg.Metric
o AdvRte.Cost := Cost(R) using the cost function associated with the
route's metric type, i.e. Cost(R) = AdvRte.Metric + Cost(L), as
described in Section 5, where L is the link from the advertising
router
o AdvRte.ValidityTime := RteMsg.ValidityTime, if included
6.7.1. Evaluating Route Information
An incoming advertised route (AdvRte) is compared to existing
LocalRoutes to determine whether the advertised route is to be used
to update the AODVv2 Local Route Set. The incoming route information
MUST be processed as follows:
1. Search for LocalRoutes in the Local Route Set matching AdvRte's
address, prefix length and metric type
* If no matching LocalRoute exists, AdvRte MUST be used to
update the Local Route Set.
* If matching LocalRoutes are found, continue to Step 2.
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2. Compare sequence numbers using the technique described in
Section 4.4
* If AdvRte is more recent than all matching LocalRoutes, AdvRte
MUST be used to update the Local Route Set.
* If AdvRte is stale, AdvRte MUST NOT be used to update the
Local Route Set.
* If the sequence numbers are equal, continue to Step 3.
3. Check that AdvRte is safe against routing loops compared to all
matching LocalRoutes (see Section 5)
* If LoopFree(AdvRte, LocalRoute) returns FALSE, AdvRte MUST NOT
be used to update the Local Route Set because using the
incoming information might cause a routing loop.
* If LoopFree(AdvRte, LocalRoute) returns TRUE, continue to Step
4.
4. Compare route costs
* If AdvRte is better than all matching LocalRoutes, it SHOULD
be used to update the Local Route Set because it offers
improvement. If it is not used to update the Local Route Set,
the existing non-optimal LocalRoute will continue to be used,
causing data traffic to use a non-optimal route.
* If AdvRte is equal in cost and LocalRoute is valid, AdvRte
SHOULD NOT be used to update the Local Route Set because it
will offer no improvement.
* If AdvRte is worse and LocalRoute is valid, AdvRte MUST NOT be
used to update the Local Route Set because it does not offer
any improvement.
* If AdvRte is not better (i.e., it is worse or equal) but
LocalRoute is Invalid, AdvRte SHOULD be used to update the
Local Route Set because it can safely repair the existing
Invalid LocalRoute.
If the advertised route is to be used to update the Local Route Set,
the procedure in Section 6.7.2 MUST be followed. If not, non-optimal
routes will remain in the Local Route Set.
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6.7.2. Applying Route Updates
After determining that AdvRte is to be used to update the Local Route
Set (as described in Section 6.7.1), the following procedure applies.
If AdvRte is learned from an RREQ message, the link to the next hop
neighbor may not be confirmed as bidirectional (see Section 4.3).
The route will offer improvement to the Local Route Set if the
neighbor can be confirmed. If there is no existing matching route,
AdvRte allows a corresponding RREP to be sent. If a matching entry
already exists, AdvRte offers potential improvement.
The route update is applied as follows:
1. If no existing entry in the Local Route Set matches AdvRte's
address, prefix length and metric type, continue to Step 4 and
create a new entry in the Local Route Set.
2. If two matching LocalRoutes exist in the Local Route Set, one is
a valid route, and one is an Unconfirmed route. AdvRte may offer
further improvement to the Unconfirmed route, or may offer an
update to the valid route.
* If AdvRte.NextHop's Neighbor.State is Unknown, the advertised
route may offer improvement to the existing valid route, if
the link to the next hop can be confirmed as bidirectional.
Continue processing from Step 5 to update the existing
Unconfirmed LocalRoute.
* If AdvRte.NextHop's Neighbor.State is Confirmed, the
advertised route offers an update or improvement to the
existing valid route. Continue processing from Step 5 to
update the existing valid LocalRoute.
3. If only one matching LocalRoute exists in the Local Route Set:
* If AdvRte.NextHop's Neighbor.State is Confirmed, continue
processing from Step 5 to update the existing LocalRoute.
* If AdvRte.NextHop's Neighbor.State is Unknown, AdvRte may
offer improvement the existing LocalRoute, if the link to
AdvRte.NextHop can be confirmed as bidirectional.
* If LocalRoute.State is Unconfirmed, AdvRte is an improvement
to an existing Unconfirmed route. Continue processing from
Step 5 to update the existing LocalRoute.
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* If LocalRoute.State is Invalid, AdvRte can replace the
existing LocalRoute. Continue processing from Step 5 to
update the existing LocalRoute.
* If LocalRoute.State is Active or Idle, AdvRte SHOULD be stored
as an additional entry in the Local Route Set, with
LocalRoute.State set to Unconfirmed. Continue processing from
Step 4 to create a new LocalRoute.
4. Create an entry in the Local Route Set and initialize as follows:
* LocalRoute.Address := AdvRte.Address
* LocalRoute.PrefixLength := AdvRte.PrefixLength
* LocalRoute.MetricType := AdvRte.MetricType
5. Update the LocalRoute as follows:
* LocalRoute.SeqNum := AdvRte.SeqNum
* LocalRoute.NextHop := AdvRte.NextHop
* LocalRoute.NextHopInterface := interface on which RteMsg was
received
* LocalRoute.Metric := AdvRte.Cost
* LocalRoute.LastUsed := CurrentTime
* LocalRoute.LastSeqNumUpdate := CurrentTime
* LocalRoute.ExpirationTime := CurrentTime + AdvRte.ValidityTime
if a validity time exists, otherwise INFINITY_TIME
6. If a new LocalRoute was created, or if the existing
LocalRoute.State is Invalid or Unconfirmed, update LocalRoute as
follows:
* LocalRoute.State := Unconfirmed (if the next hop's
Neighbor.State is Unknown)
* LocalRoute.State := Idle (if the next hop's Neighbor.State is
Confirmed)
7. If an existing LocalRoute.State changed from Invalid or
Unconfirmed to become Idle, any matching Unconfirmed LocalRoute
with worse metric value SHOULD be expunged.
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8. If an existing LocalRoute was updated with a better metric value,
any matching Unconfirmed LocalRoute with worse metric value
SHOULD be expunged.
9. If this update results in LocalRoute.State of Active or Idle,
which matches a route request which is still in progress, the
associated route request retry timers can be cancelled.
If this update to the Local Route Set results in two LocalRoutes to
the same address, the best LocalRoute will be Unconfirmed. In order
to improve the route used for forwarding, the router SHOULD try to
determine if the link to the next hop of that LocalRoute is
bidirectional, by using that LocalRoute to forward future RREPs and
request acknowledgements (see Section 7.2.1).
6.8. Suppressing Redundant Messages Using the Multicast Route Message
Table
When route messages are flooded in a MANET, an AODVv2 router may
receive multiple similar messages. Regenerating every one of these
gives little additional benefit, and generates unnecessary signaling
traffic and might generate unnecessary interference.
Each AODVv2 router stores information about recently received route
messages in the AODVv2 Multicast Route Message Table (Section 4.6).
To create a Multicast Route Message Table Entry:
o RteMsg.MessageType := RREQ or RREP
o RteMsg.OrigAddr := OrigAddr from the message
o RteMsg.OrigPrefixLen := the prefix length associated with OrigAddr
o RteMsg.TargAddr := TargAddr from the message
o RteMsg.TargPrefixLen := the prefix length associated with TargAddr
o RteMsg.OrigSeqNum := the sequence number associated with OrigAddr,
if present in the message
o RteMsg.TargSeqNum := the sequence number associated with TargAddr,
if present in the message
o RteMsg.MetricType := the metric type of the route requested
o RteMsg.Metric := the metric value associated with OrigAddr in an
RREQ or TargAddr in an RREP
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o RteMsg.Timestamp := CurrentTime
o RteMsg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME
Entries in the Multicast Route Message Table SHOULD be maintained for
at least RteMsg_ENTRY_TIME after the last Timestamp update in order
to account for long-lived RREQs traversing the network. An entry
MUST be deleted when the sequence number is no longer valid, i.e.,
after MAX_SEQNUM_LIFETIME. Memory-constrained devices MAY remove the
entry before this time.
Received route messages are tested against previously received route
messages, and if determined to be redundant, regeneration or response
can be avoided.
To determine if a received message is redundant:
1. Search for an entry in the Multicast Route Message Table with the
same MessageType, OrigAddr, TargAddr, and MetricType
* If there is no entry, the message is not redundant.
* If there is an entry, continue to Step 2.
2. Compare sequence numbers using the technique described in
Section 4.4
* For RREQ messages, use OrigSeqNum of the entry for comparison.
For RREP messages, use TargSeqNum of the entry for comparison.
* If the entry has an older sequence number than the received
message, the message is not redundant.
* If the entry has a newer sequence number than the received
message, the message is redundant.
* If the entry has the same sequence number, continue to Step 3.
3. Compare the metric values
* If the entry has a Metric value that is worse than or equal to
the metric in the received message, the message is redundant.
* If the entry has a Metric value that is better than the metric
in the received message, the message is not redundant.
If the message is redundant, update the Timestamp and RemoveTime on
the entry, since matching route messages are still traversing the
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network and this entry should be maintained. This message MUST NOT
be regenerated or responded to.
If the message is not redundant, create an entry or update the
existing entry.
To update a Multicast Route Message Table entry, set:
o RteMsg.OrigSeqNum := the sequence number associated with OrigAddr,
if present in the received message
o RteMsg.TargSeqNum := the sequence number associated with TargAddr,
if present in the received message
o RteMsg.Metric := the metric value associated with OrigAddr in a
received RREQ or TargAddr in a received RREP
o RteMsg.Timestamp := CurrentTime
o RteMsg.RemoveTime := CurrentTime + MAX_SEQNUM_LIFETIME
Where the message is determined not redundant before Step 3, it MUST
be regenerated or responded to. Where the message is determined not
redundant in Step 3, it MAY be suppressed to avoid extra control
traffic. However, since the processing of the message will result in
an update to the Local Route Set, the message SHOULD be regenerated
or responded to, to ensure other routers have up-to-date information
and the best metrics. If not regenerated, the best route may not be
found. Where necessary, regeneration or response is performed using
the processes in Section 7.
6.9. Local Route Set Maintenance
Route maintenance involves monitoring LocalRoutes in the Local Route
Set, updating LocalRoute.State to handle route timeouts and reporting
routes that become Invalid.
6.9.1. LocalRoute State Changes
During normal operation, AODVv2 does not require any explicit
timeouts to manage the lifetime of a route. At any time, any
LocalRoute MAY be examined and updated according to the rules below.
If timers are not used to prompt updates of LocalRoute.State, the
LocalRoute.State MUST be checked before IP packet forwarding and
before any operation based on LocalRoute.State.
Route timeout behaviour is as follows:
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o An Unconfirmed route MUST be expunged at MAX_SEQNUM_LIFETIME after
LocalRoute.LastSeqNumUpdate.
o An Idle route MUST become Active when used to forward an IP
packet. If the route is not used to forward an IP packet within
MAX_IDLETIME, LocalRoute.State MUST become Invalid.
o An Active route which is a timed route (i.e., with
LocalRoute.ExpirationTime not equal to INFINITY_TIME) remains
Active until LocalRoute.ExpirationTime, after which it MUST become
Invalid. If it it not a timed route, it MUST become Idle if the
route is not used to forward an IP packet within ACTIVE_INTERVAL.
o An Invalid route SHOULD remain in the Local Route Set, since
LocalRoute.SeqNum is used to classify future information about
LocalRoute.Address as stale or fresh.
o In all cases, if the time since LocalRoute.LastSeqNumUpdate
exceeds MAX_SEQNUM_LIFETIME, LocalRoute.SeqNum must be set to
zero. This is required to ensure that any AODVv2 routers
following the initialization procedure can safely begin routing
functions using a new sequence number, and that their messages
will not be classified as stale and ignored. A LocalRoute with
LocalRoute.State set to Active or Idle can remain in the Local
Route Set after removing the sequence number, but if
LocalRoute.State is Invalid, or later becomes Invalid, the
LocalRoute MUST be expunged from the Local Route Set.
LocalRoutes can become Invalid before a timeout occurs:
o If a link breaks, all LocalRoutes using that link for
LocalRoute.NextHop MUST immediately have LocalRoute.State set to
Invalid.
o If a Route Error (RERR) message containing the route is received,
either from LocalRoute.NextHop, or with PktSource set to a Router
Client address, LocalRoute.State MUST immediately be set to
Invalid.
LocalRoutes are also updated when Neighbor.State is updated:
o While the value of Neighbor.State is set to Unknown, any routes in
the Local Route Set using that neighbor as a next hop MUST have
LocalRoute.State set to Unconfirmed.
o When the value of Neighbor.State is set to Confirmed, the
Unconfirmed routes in the Local Route Set using that neighbor as a
next hop MUST have LocalRoute.State set to Idle. Any other
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matching LocalRoutes with metric values worse than
LocalRoute.Metric MUST be expunged from the Local Route Set.
o When the value of Neighbor.State is set to Blacklisted, any valid
routes in the Local Route Set using that neighbor for their next
hop MUST have LocalRoute.State set to Invalid.
o When a Neighbor Table entry is removed, all routes in the Local
Route Set using that neighbor as next hop MUST have
LocalRoute.State set to Invalid.
In some cases, by setting LocalRoute.State to Confirmed when
Neighbor.State is set to Confirmed, an issue can occur if data
packets are forwarded to LocalRoute.Address before the links that
form the rest of the route are confirmed as bidirectional.
Intermediate routers will not have a valid route to forward these
data packets, and will generate a Route Error message. This in turn
results in routes to that destination being removed from other
routers. However, subsequent data packets will cause a new route
discovery attempt to be initiated by the router with the source
address of the data packet configured as a Router Client.
Memory constrained devices MAY choose to expunge routes from the
AODVv2 Local Route Set before LocalRoute.ExpirationTime, but MUST
adhere to the following rules:
o An Active route MUST NOT be expunged, as it is in use. If
deleted, IP traffic forwarded to this router will prompt
generation of a Route Error message, and it will be necessary for
a Route Request to be generated by the originator's router to re-
establish the route.
o An Idle route SHOULD NOT be expunged, as it is still valid for
forwarding IP traffic. If deleted, this could result in dropped
IP packets and a Route Request could be generated to re-establish
the route.
o Any Invalid route MAY be expunged. Least recently used Invalid
routes SHOULD be expunged first, since the sequence number
information is less likely to be useful.
o An Unconfirmed route MUST NOT be expunged if it was installed
within the last RREQ_WAIT_TIME, because it may correspond to a
route discovery in progress. A Route Reply message might be
received which needs to use the LocalRoute.NextHop information.
Otherwise, it MAY be expunged.
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6.9.2. Reporting Invalid Routes
When LocalRoute.State changes from Active to Invalid as a result of a
broken link or a received Route Error (RERR) message, other AODVv2
routers MUST be informed by sending an RERR message containing
details of the invalidated route.
An RERR message MUST also be sent when an AODVv2 router receives an
IP packet to forward on behalf of another router but does not have a
valid route in its Routing Information Base for the destination of
the packet.
An RERR message MUST also be sent when an AODVv2 router receives an
RREP message to regenerate, but the LocalRoute to the OrigAddr in the
RREP has been lost or is marked as Invalid.
The packet or message triggering the RERR MUST be discarded.
Generation of an RERR message is described in Section 7.4.1.
7. AODVv2 Protocol Messages
AODVv2 defines four message types: Route Request (RREQ), Route Reply
(RREP), Route Reply Acknowledgement (RREP_Ack), and Route Error
(RERR).
Each AODVv2 message is defined as a set of data. Rules for the
generation, reception and regeneration of each message type are
described in the following sections. Section 8 discusses how the
data is mapped to [RFC5444] Message TLVs, Address Blocks, and Address
TLVs.
7.1. Route Request (RREQ) Message
Route Request messages are used in route discovery operations to
request a route to a specified target address. RREQ messages have
the following contents:
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+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| OrigSeqNum, (optional) TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| OrigMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
Figure 1: RREQ message contents
AddressList
Contains OrigAddr and TargAddr, the source and destination
addresses of the IP packet for which a route is requested.
OrigAddr and TargAddr MUST be routable unicast addresses.
PrefixLengthList
Contains OrigPrefixLen, i.e., the length, in bits, of the prefix
associated with the Router Client entry which includes OrigAddr.
If omitted, the prefix length is equal to OrigAddr's address
length in bits.
OrigSeqNum
The sequence number associated with OrigAddr.
TargSeqNum
A sequence number associated with an existing Invalid route to
TargAddr. This MAY be included if available, and is useful for
the optional Intermediate RREP feature (see Section 10.3).
MetricType
The metric type associated with OrigMetric.
OrigMetric
The metric value associated with the LocalRoute to OrigAddr (and
to any other addresses included in the given prefix length), as
seen from the sender of the message.
ValidityTime
The length of time that the message sender is willing to offer a
route toward OrigAddr (and any other addresses included in the
given prefix length). Omitted if no time limit is imposed.
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7.1.1. RREQ Generation
An RREQ is generated when an IP packet needs to be forwarded for a
Router Client, and no valid route currently exists for the packet's
destination in the Routing Information Base.
Before creating an RREQ, the router SHOULD check if an RREQ has
recently been sent for the requested destination. If so, and the
wait time for a reply has not yet been reached, the router SHOULD
continue to await a response without generating a new RREQ. If the
timeout has been reached, a new RREQ MAY be generated. If buffering
is configured, incoming IP packets awaiting this route SHOULD be
buffered until the route discovery is completed.
If the limit for the rate of AODVv2 control message generation has
been reached, no message SHOULD be generated. If approaching the
limit, the message should be sent if the priorities in Section 6.5
allow it.
To generate the RREQ, the router (referred to as RREQ_Gen) follows
this procedure:
1. Set AddressList := {OrigAddr, TargAddr}
2. For the PrefixLengthList:
* If OrigAddr is part of an address range configured as a Router
Client, set PrefixLengthList := {RouterClient.PrefixLength,
null}. This allows receiving routers to learn a route to all
the addresses included by the prefix length, not only to
OrigAddr.
* Otherwise, omit PrefixLengthList.
3. For OrigSeqNum:
* Increment the router SeqNum as specified in Section 4.4.
* Set OrigSeqNum := SeqNum.
4. For TargSeqNum:
* If an Invalid route exists in the Local Route Set matching
TargAddr using longest prefix matching and has a valid
sequence number, set TargSeqNum := LocalRoute.SeqNum.
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* If no Invalid route exists in the Local Route Set matching
TargAddr, or the route doesn't have a sequence number, omit
TargSeqNum.
5. Include MetricType and set the type accordingly
6. Set OrigMetric := RouterClient.Cost for the Router Client entry
which includes OrigAddr
7. Include ValidityTime if advertising that the route to OrigAddr
(and any other addresses included in the given prefix length) via
this router is offered for a limited time, and set ValidityTime
accordingly
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is multicast, by default, to LL-MANET-
Routers on all interfaces configured for AODVv2 operation.
7.1.2. RREQ Reception
Upon receiving a Route Request, an AODVv2 router performs the
following steps:
1. Update the Neighbor Table according to Section 6.3
* If the sender has Neighbor.State set to Blacklisted after the
update, ignore this RREQ for further processing.
2. Verify that the message contains the required data: OrigAddr,
TargAddr, OrigSeqNum, and OrigMetric, and that OrigAddr and
TargAddr are valid addresses (routable and unicast)
* If not, ignore this RREQ for further processing.
3. Check that the MetricType is supported and configured for use
* If not, ignore this RREQ for further processing.
4. Verify that the cost of the advertised route will not exceed the
maximum allowed metric value for the metric type (Metric <=
MAX_METRIC[MetricType] - Cost(L))
* If it will, ignore this RREQ for further processing.
5. Process the route to OrigAddr (and any other addresses included
in the given prefix length) as specified in Section 6.7
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6. Check if the information in the message is redundant by comparing
to entries in the Multicast Route Message table, following the
procedure in Section 6.8
* If redundant, ignore this RREQ for further processing.
* If not redundant, continue processing.
7. Check if the TargAddr belongs to one of the Router Clients
* If so, generate an RREP as specified in Section 7.2.1.
* If not, continue to RREQ regeneration.
7.1.3. RREQ Regeneration
By regenerating an RREQ, a router advertises that it will forward IP
packets to the OrigAddr contained in the RREQ (and to other addresses
included in the given prefix length) according to the information
enclosed. The router MAY choose not to regenerate the RREQ, for
example if the router is heavily loaded or low on energy and
therefore unwilling to advertise routing capability for more traffic.
This could, however, decrease connectivity in the network or result
in non-optimal paths.
The RREQ SHOULD NOT be regenerated if the limit for the rate of
AODVv2 control message generation has been reached. If approaching
the limit, the message should be sent if the priorities in
Section 6.5 allow it.
The procedure for RREQ regeneration is as follows:
1. Set AddressList, PrefixLengthList, sequence numbers and
MetricType to the values in the received RREQ
2. Set OrigMetric := LocalRoute[OrigAddr].Metric
3. If the received RREQ contains a ValidityTime, or if the
regenerating router wishes to limit the time that it offers a
route to OrigAddr (and any other addresses included in the given
prefix length), the regenerated RREQ MUST include ValidityTime
* The ValidityTime is either the time limit the previous AODVv2
router specified, or the time limit this router wishes to
impose, whichever is lower.
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8) which is multicast, by default, to LL-MANET-
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Routers on all interfaces configured for AODVv2 operation. However,
the regenerated RREQ can be unicast to the next hop address of the
LocalRoute toward TargAddr, if known.
7.2. Route Reply (RREP) Message
When a Route Request message is received, requesting a route to a
target address (TargAddr) which is configured as part of a Router
Client entry, a Route Reply message is sent in response. The RREP
offers a route to TargAddr (and any other addresses included in the
prefix length).
RREP messages have the following contents:
+-----------------------------------------------------------------+
| AckReq (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| TargMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
Figure 2: RREP message contents
AckReq
The address of the intended next hop of the RREP. This is
included when the link to the next hop toward OrigAddr is not
known to be bidirectional. It indicates that an acknowledgement
of the RREP is requested by the sender from the intended next hop
(see Section 6.2).
AddressList
Contains OrigAddr and TargAddr, the source and destination
addresses of the IP packet for which a route is requested.
OrigAddr and TargAddr MUST be routable unicast addresses.
PrefixLengthList
Contains TargPrefixLen, i.e., the length, in bits, of the prefix
associated with the Router Client entry which includes TargAddr.
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If omitted, the prefix length is equal to TargAddr's address
length, in bits.
TargSeqNum
The sequence number associated with TargAddr.
MetricType
The metric type associated with TargMetric.
TargMetric
The metric value associated with the LocalRoute to TargAddr (and
any other addresses included in the given prefix length), as seen
from the sender of the message.
ValidityTime
The length of time that the message sender is willing to offer a
route toward TargAddr (and any other addresses included in the
given prefix length). Omitted if no time limit is imposed.
7.2.1. RREP Generation
A Route Reply message is generated when a Route Request arrives,
requesting a route to an address which is configured as a Router
Client of the AODVv2 router.
Before creating an RREP, the router SHOULD check if the corresponding
RREQ is redundant, i.e., a Route Reply has already been generated in
response to the RREQ, or if the limit for the rate of AODVv2 control
message generation has been reached. If so, the RREP SHOULD NOT be
created. If approaching the limit, the message should be sent if the
priorities in Section 6.5 allow it.
The RREP will follow the path of the route to OrigAddr. If the best
route to OrigAddr in the Local Route Set is Unconfirmed, the link to
the next hop neighbor is not yet confirmed as bidirectional (as
described in Section 6.2). In this case the RREP MUST include AckReq
set to the intended next hop address. The AckReq indicates that an
acknowledgement to the RREP is requested from the intended next hop
router in the form of a Route Reply Acknowledgement (RREP_Ack). If
the best route to OrigAddr in the Local Route Set is valid, the link
to the next hop neighbor is already confirmed as bidirectional, and
the AckReq can be omitted.
Implementations MAY allow a number of retries of the RREP if a
requested acknowledgement is not received within
RREP_Ack_SENT_TIMEOUT, doubling the timeout with each retry, up to a
maximum of RREP_RETRIES, using the same exponential backoff described
in Section 6.6 for RREQ retries. The acknowledgement MUST be
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considered to have failed after the wait time for an RREP_Ack
response to the final RREP.
To generate the RREP, the router (also referred to as RREP_Gen)
follows this procedure:
1. If the link to the next hop router toward OrigAddr is not known
to be bidirectional, include the AckReq with the address of the
intended next hop router
2. Set Address List := {OrigAddr, TargAddr}
3. For the PrefixLengthList:
* If TargAddr is part of an address range configured as a Router
Client, set PrefixLengthList := {null,
RouterClient.PrefixLength}. This allows receiving routers to
learn a route to all the addresses included by the prefix
length, not only to TargAddr.
* Otherwise, omit PrefixLengthList.
4. For the TargSeqNum:
* Increment the router SeqNum as specified in Section 4.4.
* Set TargSeqNum := SeqNum.
5. Include MetricType and set the type to match the MetricType in
the received RREQ message
6. Set TargMetric := RouterClient.Cost for the Router Client entry
which includes TargAddr
7. Include ValidityTime if advertising that the route to TargAddr
(and any other addresses included in the given prefix length) via
this router is offered for a limited time, and set ValidityTime
accordingly
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8). If the Neighbor Table contains an entry for
the neighbor stored as LocalRoute[OrigAddr].NextHop, with
Neighbor.State set to Confirmed, the RREP is sent by unicast to
LocalRoute[OrigAddr].NextHop. Otherwise, the RREP is sent multicast
to LL-MANET-Routers.
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7.2.2. RREP Reception
Upon receiving a Route Reply, an AODVv2 router performs the following
steps:
1. Verify that the message contains the required data: OrigAddr,
TargAddr, TargSeqNum, and TargMetric, and that OrigAddr and
TargAddr are valid addresses (routable and unicast)
* If not, ignore this RREP for further processing.
2. Check that the MetricType is supported and configured for use
* If not, ignore this RREP for further processing.
3. If this RREP does not correspond to a RREQ generated or
regenerated in the last RREQ_WAIT_TIME, ignore for further
processing.
4. Update the Neighbor Table according to Section 6.3
5. Verify that the cost of the advertised route does not exceed the
maximum allowed metric value for the metric type (Metric <=
MAX_METRIC[MetricType] - Cost(L))
* If it does, ignore this RREP for further processing.
6. If the AckReq is present, check the intended recipient of the
received RREP
* If the receiving router is the intended recipient, send an
acknowledgement as specified in Section 7.3 and continue
processing.
* If the receiving router is not the intended recipient, ignore
this RREP for further processing.
7. Process the route to TargAddr (and any other addresses included
in the given prefix length) as specified in Section 6.7
8. Check if the message is redundant by comparing to entries in the
Multicast Route Message table (Section 6.8)
* If redundant, ignore this RREP for further processing.
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* If not redundant, save the information in the Multicast Route
Message table to identify future redundant RREP messages and
continue processing.
9. Check if the OrigAddr belongs to one of the Router Clients
* If so, no further processing is necessary.
* If not, continue to Step 10.
10. Check if a valid (Active or Idle) or Unconfirmed LocalRoute
exists to OrigAddr
* If so, continue to RREP regeneration.
* If not, a Route Error message SHOULD be transmitted to
TargAddr according to Section 7.4.1 and the RREP SHOULD be
discarded and not regenerated.
7.2.3. RREP Regeneration
A received Route Reply message is regenerated toward OrigAddr.
Unless the router is prepared to advertise the route contained within
the received RREP, it halts processing. By regenerating a RREP, a
router advertises that it will forward IP packets to TargAddr (and
any other addresses included in the given prefix length) according to
the information enclosed. The router MAY choose not to regenerate
the RREP, in the same way it MAY choose not to regenerate an RREQ
(see Section 7.1.3), though this could decrease connectivity in the
network or result in non-optimal paths.
The RREP SHOULD NOT be regenerated if the limit for the rate of
AODVv2 control message generation has been reached. If approaching
the limit, the message should be sent if the priorities in
Section 6.5 allow it.
If the link to the next hop neighbor on the LocalRoute to OrigAddr is
not yet confirmed as bidirectional (as described in Section 6.2), the
RREP MUST include AckReq set to the intended next hop address, in
order to perform next hop monitoring. If bidirectionality is already
confirmed, the AckReq can be omitted. The AckReq indicates that an
acknowledgement to the RREP is requested in the form of a Route Reply
Acknowledgement (RREP_Ack) from the intended next hop router, within
RREP_Ack_SENT_TIMEOUT.
The procedure for RREP regeneration is as follows:
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1. If the link to the next hop router toward OrigAddr is not known
to be bidirectional, include the AckReq with the address of the
intended next hop router
2. Set AddressList, PrefixLengthList, TargSeqNum and MetricType to
the values in the received RREP
3. Set TargMetric := LocalRoute[TargAddr].Metric
4. If the received RREP contains a ValidityTime, or if the
regenerating router wishes to limit the time that it will offer a
route to TargAddr (and any other addresses included in the given
prefix length), the regenerated RREP MUST include ValidityTime
* The ValidityTime is either the time limit the previous AODVv2
router specified, or the time limit this router wishes to
impose, whichever is lower.
This AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8). If the Neighbor Table contains an entry for
the neighbor stored as LocalRoute[OrigAddr].NextHop, with
Neighbor.State set to Confirmed, the RREP is sent by unicast to
LocalRoute[OrigAddr].NextHop. Otherwise, the RREP is sent multicast
to LL-MANET-Routers.
7.3. Route Reply Acknowledgement (RREP_Ack) Message
The Route Reply Acknowledgement is a response to a Route Reply
message. When the RREP_Ack message is received by the sender of the
RREP, it confirms that the link between the two routers is
bidirectional (see Section 6.2). The RREP_Ack has no further data.
7.3.1. RREP_Ack Generation
An RREP_Ack MUST be generated if a received Route Reply includes an
AckReq with an address matching one of the receiving router's IP
addresses. The RREP_Ack SHOULD NOT be generated if the limit for the
rate of AODVv2 control message generation has been reached.
There is no further data in an RREP_Ack. The [RFC5444]
representation is discussed in Section 8. The RREP_Ack is unicast,
by default, to the source IP address of the RREP message that
requested it.
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7.3.2. RREP_Ack Reception
Upon receiving an RREP_Ack, an AODVv2 router performs the following
steps:
1. Check if the RREP_Ack was expected from the IP source address of
the RREP_Ack, in response to an RREP sent previously by this
router
* If it was expected, the router cancels any associated timeouts
and processing continues to Step 2.
* If it was not expected, no actions are required and processing
ends.
2. Update the Neighbor Table according to Section 6.3
7.4. Route Error (RERR) Message
A Route Error message is generated by an AODVv2 router to notify
other AODVv2 routers of routes that are no longer available. An RERR
message has the following contents:
+-----------------------------------------------------------------+
| PktSource (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| SeqNumList (optional) |
+-----------------------------------------------------------------+
| MetricTypeList |
+-----------------------------------------------------------------+
Figure 3: RERR message contents
PktSource
The source address of the IP packet triggering the RERR. If the
RERR is triggered by a broken link, PktSource is not required.
AddressList
The addresses of the routes not available through RERR_Gen.
PrefixLengthList
The prefix lengths, in bits, associated with the routes not
available through RERR_Gen. These values indicate whether routes
represent a single device or an address range.
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SeqNumList
The sequence numbers of the routes not available through RERR_Gen
(where known).
MetricTypeList
The metric types associated with the routes not available through
RERR_Gen.
7.4.1. RERR Generation
A Route Error message is generated when an AODVv2 router (also
referred to as RERR_Gen) needs to report that a destination is not
reachable. There are three events that cause this response:
o When an IP packet that has been forwarded from another router, but
cannot be forwarded further because there is no valid route in the
Routing Information Base for its destination, the source of the
packet needs to be informed that the route to the destination of
the packet does not exist. The RERR generated MUST include
PktSource set to the source address of the IP packet, and MUST
contain only one unreachable address in the AddressList, i.e., the
destination address of the IP packet. RERR_Gen MUST discard the
IP packet that triggered generation of the RERR. The prefix
length and sequence number MAY be included if known from an
Invalid LocalRoute entry to PktSource. The MetricTypeList MUST
also be included if a MetricType can be determined from the IP
packet or an existing Invalid LocalRoute to the unreachable
address.
o When an RREP message cannot be regenerated because the LocalRoute
to OrigAddr has been lost or is Invalid, RREP_Gen needs to be
informed that the route to OrigAddr does not exist. The RERR
generated MUST include PktSource set to the TargAddr of the RREP,
and MUST contain only one unreachable address in the AddressList,
the OrigAddr from the RREP. RERR_Gen MUST discard the RREP
message that triggered generation of the RERR. The prefix length,
sequence number and metric type SHOULD be included if known from
an Invalid LocalRoute to the unreachable address.
o When a link breaks, multiple LocalRoutes may become Invalid, and
the RERR generated MAY contain multiple unreachable addresses.
The RERR MUST include MetricTypeList. PktSource is omitted. All
previously Active LocalRoutes that used the broken link MUST be
reported. The AddressList, PrefixLengthList, SeqNumList, and
MetricTypeList will contain entries for each LocalRoute which has
become Invalid. An RERR message is only sent if an Active
LocalRoute becomes Invalid, though an AODVv2 router can also
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include Idle LocalRoutes that become Invalid if the configuration
parameter ENABLE_IDLE_IN_RERR is set (see Section 11.3).
In order to avoid flooding the network with RERR messages when a
stream of IP packets to an unreachable address arrives, an AODVv2
router SHOULD determine whether an RERR has recently been sent with
the same unreachable address and PktSource, and SHOULD avoid creating
duplicate RERR messages.
The RERR SHOULD NOT be generated if the limit for the rate of AODVv2
control message generation has been reached. If approaching the
limit, the message should be sent if the priorities in Section 6.5
allow it.
Incidentally, if an AODVv2 router receives an ICMP error packet to or
from the address of one of its Router Clients, it forwards the ICMP
packet in the same way as any other IP packet, and will not generate
any RERR message based on the contents of the ICMP packet.
To generate the RERR, the router follows this procedure:
1. If necessary, include PktSource and set the value as given above
2. For each LocalRoute that needs to be reported:
* Insert LocalRoute.Address into the AddressList.
* Insert LocalRoute.PrefixLength into PrefixLengthList, if known
and not equal to the address length.
* Insert LocalRoute.SeqNum into SeqNumList, if known.
* Insert LocalRoute.MetricType into MetricTypeList.
The AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8).
If the RERR is sent in response to an undeliverable IP packet or RREP
message, i.e., if PktSource is included, the RERR SHOULD be sent
unicast to the next hop on the route to PktSource, or alternatively,
if there is no route to PktSource, the RERR MUST be multicast to LL-
MANET-Routers. If the RERR is sent in response to a broken link,
i.e., PktSource is not included, the RERR is, by default, multicast
to LL-MANET-Routers.
Section 10.2 describes processing steps when the optional precursor
lists feature is enabled.
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7.4.2. RERR Reception
Upon receiving a Route Error, an AODVv2 router performs the following
steps:
1. Verify that the message contains the required data: at least one
unreachable address
* If not, ignore this RERR for further processing.
2. For each address in the AddressList, check that:
* The address is valid (routable and unicast)
* The MetricType is supported and configured for use
* There is a LocalRoute with the same MetricType matching the
address using longest prefix matching
* Either the LocalRoute's next hop is the sender of the RERR and
the next hop interface is the interface on which the RERR was
received, or PktSource is present in the RERR and is a Router
Client address
* The unreachable address' sequence number is either unknown, or
is greater than the LocalRoute's sequence number
If any of the above are false, a matching LocalRoute MUST NOT be
made Invalid and the unreachable address MUST NOT be advertised
in a regenerated RERR.
If all of the above are true, the LocalRoute is no longer valid.
If the LocalRoute was previously Active, it MUST be reported in a
regenerated RERR. If the LocalRoute was previously Idle, it MAY
be reported in a regenerated RERR, if ENABLE_IDLE_IN_RERR is
configured. The Local Route Set MUST be updated according to
these rules:
* If the LocalRoute's prefix length is the same as the
unreachable address' prefix length, set LocalRoute.State to
Invalid.
* If the LocalRoute's prefix length is longer than the
unreachable address' prefix length, the LocalRoute MUST be
expunged from the Local Route Set, since it is a sub-route of
the route which is reported to be Invalid.
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* If the prefix length is different, create a new LocalRoute
with the unreachable address, and its prefix length and
sequence number, and set LocalRoute.State to Invalid.
* Update the sequence number on the existing LocalRoute, if the
reported sequence number is determined to be newer using the
comparison technique described in Section 4.4.
3. Check if there are unreachable addresses which MUST be reported
in a regenerated RERR
* If so, regenerate the RERR as detailed in Section 7.4.3.
* If not, take no further action.
7.4.3. RERR Regeneration
The Route Error message SHOULD NOT be regenerated if the limit for
the rate of AODVv2 control message generation has been reached. If
approaching the limit, the message should be sent if the priorities
in Section 6.5 allow it.
The procedure for RERR regeneration is as follows:
1. If PktSource was included in the original RERR, and PktSource is
not a Router Client, copy it into the regenerated RERR
2. For each LocalRoute that needs to be reported:
* Insert LocalRoute.Address into the AddressList.
* Insert LocalRoute.PrefixLength into PrefixLengthList, if known
and not equal to the address length.
* Insert LocalRoute.SeqNum into SeqNumList, if known.
* Insert LocalRoute.MetricType into MetricTypeList.
The AODVv2 message is used to create a corresponding [RFC5444]
message (see Section 8). If the RERR contains PktSource, the
regenerated RERR SHOULD be sent unicast to the next hop on the
LocalRoute to PktSource, or alternatively if there is no route to
PktSource, or PktSource is a Router Client, it MUST be multicast to
LL-MANET-Routers. If the RERR is sent in response to a broken link,
the RERR is, by default, multicast to LL-MANET-Routers.
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8. RFC 5444 Representation
AODVv2 specifies that all control messages between routers MUST use
the Generalized Mobile Ad Hoc Network Packet/Message Format
[RFC5444], and therefore AODVv2's route messages comprise data which
is mapped to message elements in [RFC5444].
[RFC5444] provides a multiplexed transport for multiple protocols.
An [RFC5444] multiplexer MAY choose to optimize the content of
certain message elements to reduce control message overhead.
A brief summary of the [RFC5444] format:
1. A packet contains zero or more messages
2. A message contains a Message Header, one Message TLV Block, zero
or more Address Blocks, and one Address Block TLV Block per
Address Block
3. The Message TLV Block MAY contain zero or more Message TLVs
4. An Address Block TLV Block MAY include zero or more Address Block
TLVs
5. Each TLV value in an Address Block TLV Block can be associated
with all of the addresses, or with a contiguous set of addresses,
or with a single address in the Address Block
AODVv2 does not require access to the [RFC5444] packet header.
In the message header, AODVv2 uses <msg-type> and <msg-addr-length>.
The <msg-addr-length> field indicates the length of any addresses in
the message, using <msg-addr-length> := (address length in octets -
1), i.e. 3 for IPv4 and 15 for IPv6.
The addresses in an Address Block MAY appear in any order, and values
in a TLV in the Address Block TLV Block must be associated with the
correct address in the Address Block by the [RFC5444] implementation.
To indicate which value is associated with each address, the AODVv2
message representation uses lists where the order of the addresses in
the AODVv2 AddressList matches the order of values in other data
lists, e.g., the order of SeqNums in the SeqNumList in an RERR.
[RFC5444] maps this information to Address Block TLVs associated with
the relevant addresses in the Address Block.
Each address included in the Address Block is identified as OrigAddr,
TargAddr, PktSource, or Unreachable Address by including an
ADDRESS_TYPE TLV in the Address Block TLV Block.
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The following sections show how AODVv2 data is represented in
[RFC5444] messages. AODVv2 makes use of the VALIDITY_TIME Address
Block TLV from [RFC5497], and defines (in Section 12) a number of new
TLVs. To calculate the time-value for the VALIDITY_TIME Address
Block TLV, the value of C is defined in Section 11.2.
Where the extension type of a TLV is set to zero, this is the default
[RFC5444] value and the extension type will not be included in the
message.
8.1. Route Request Message Representation
8.1.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RREQ |
+-------+---------------+--------+
8.1.2. Message TLV Block
An RREQ contains no Message TLVs.
8.1.3. Address Block
An RREQ contains two addresses, OrigAddr and TargAddr, and each
address has an associated prefix length. If the prefix length has
not been included in the AODVv2 message, it is equal to the address
length in bits.
+-------------------------+------------------------------+
| Data | Address Block |
+-------------------------+------------------------------+
| OrigAddr/OrigPrefixLen | <address> + <prefix-length> |
| TargAddr/TargPrefixLen | <address> + <prefix-length> |
+-------------------------+------------------------------+
8.1.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each address.
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8.1.4.1. Address Block TLVs for OrigAddr
+--------------+---------------+------------+-----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+--------------+---------------+------------+-----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR |
| OrigSeqNum | SEQ_NUM | 0 | Sequence number of |
| | | | RREQ_Gen, the router |
| | | | which initiated route |
| | | | discovery. |
| OrigMetric | PATH_METRIC | MetricType | Metric value for the |
| /MetricType | | | route to OrigAddr, |
| | | | using MetricType. |
| ValidityTime | VALIDITY_TIME | 0 | ValidityTime for |
| | | | route to OrigAddr, |
| | | | represented as |
| | | | detailed in |
| | | | [RFC5497]. |
+--------------+---------------+------------+-----------------------+
8.1.4.2. Address Block TLVs for TargAddr
+------------+--------------+-------------+-------------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+------------+--------------+-------------+-------------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR |
| TargSeqNum | SEQ_NUM | 0 | The last known |
| | | | TargSeqNum for |
| | | | TargAddr. |
+------------+--------------+-------------+-------------------------+
8.2. Route Reply Message Representation
8.2.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RREP |
+-------+---------------+--------+
8.2.2. Message TLV Block
An RREP contains no Message TLVs.
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8.2.3. Address Block
An RREP contains a minimum of two addresses, OrigAddr and TargAddr,
and each address has an associated prefix length. If the prefix
length has not been included in the AODVv2 message, it is equal to
the address length in bits.
It MAY also contain the address of the intended next hop, in order to
request acknowledgement to confirm bidirectionality of the link, as
described in Section 6.2. The prefix length associated with this
address is equal to the address length in bits.
+-------------------------+------------------------------+
| Data | Address Block |
+-------------------------+------------------------------+
| OrigAddr/OrigPrefixLen | <address> + <prefix-length> |
| TargAddr/TargPrefixLen | <address> + <prefix-length> |
| AckReq | <address> + <prefix-length> |
+-------------------------+------------------------------+
8.2.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each address.
8.2.4.1. Address Block TLVs for OrigAddr
+-------+---------------+-----------------+--------------------+
| Data | TLV Type | Extension Type | Value |
+-------+---------------+-----------------+--------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_ORIGADDR |
+-------+---------------+-----------------+--------------------+
8.2.4.2. Address Block TLVs for TargAddr
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+--------------+---------------+------------+-----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+--------------+---------------+------------+-----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_TARGADDR |
| TargSeqNum | SEQ_NUM | 0 | Sequence number of |
| | | | RREP_Gen, the router |
| | | | which created the |
| | | | RREP. |
| TargMetric | PATH_METRIC | MetricType | Metric value for the |
| /MetricType | | | route to TargAddr, |
| | | | using MetricType. |
| ValidityTime | VALIDITY_TIME | 0 | ValidityTime for |
| | | | route to TargAddr, |
| | | | represented as |
| | | | detailed in |
| | | | [RFC5497]. |
+--------------+---------------+------------+-----------------------+
8.2.4.3. Address Block TLVs for AckReq Intended Recipient Address
+-------+---------------+-----------------+------------------+
| Data | TLV Type | Extension Type | Value |
+-------+---------------+-----------------+------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_INTEND |
+-------+---------------+-----------------+------------------+
8.3. Route Reply Acknowledgement Message Representation
8.3.1. Message Header
+-------+---------------+-----------+
| Data | Header Field | Value |
+-------+---------------+-----------+
| None | <msg-type> | RREP_Ack |
+-------+---------------+-----------+
8.3.2. Message TLV Block
An RREP_Ack contains no Message TLVs.
8.3.3. Address Block
An RREP_Ack contains no Address Block.
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8.3.4. Address Block TLV Block
An RREP_Ack contains no Address Block TLV Block.
8.4. Route Error Message Representation
Route Error Messages MAY be split into multiple [RFC5444] messages
when the desired contents would exceed the MTU. However, all of the
resulting messages MUST have the same message header as described
below. If PktSource is included in the AODVv2 message, it MUST be
included in all of the resulting [RFC5444] messages.
8.4.1. Message Header
+-------+---------------+--------+
| Data | Header Field | Value |
+-------+---------------+--------+
| None | <msg-type> | RERR |
+-------+---------------+--------+
8.4.2. Message TLV Block
An RERR contains no Message TLVs.
8.4.3. Address Block
The Address Block in an RERR MAY contain PktSource, the source
address of the IP packet triggering RERR generation, as detailed in
Section 7.4. The prefix length associated with PktSource is equal to
the address length in bits.
Address Block always contains one address per route that is no longer
valid, and each address has an associated prefix length. If a prefix
length has not been included for this address, it is equal to the
address length in bits.
+------------------------------+------------------------------------+
| Data | Address Block |
+------------------------------+------------------------------------+
| PktSource | <address> + <prefix-length> for |
| | PktSource |
| AddressList/PrefixLengthList | <address> + <prefix-length> for |
| | each unreachable address in |
| | AddressList |
+------------------------------+------------------------------------+
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8.4.4. Address Block TLV Block
Address Block TLVs are always associated with one or more addresses
in the Address Block. The following sections show the TLVs that
apply to each type of address in the RERR.
8.4.4.1. Address Block TLVs for PktSource
+------------+---------------+----------------+---------------------+
| Data | TLV Type | Extension Type | Value |
+------------+---------------+----------------+---------------------+
| PktSource | ADDRESS_TYPE | 0 | ADDRTYPE_PKTSOURCE |
+------------+---------------+----------------+---------------------+
8.4.4.2. Address Block TLVs for Unreachable Addresses
+----------------+--------------+------------+----------------------+
| Data | TLV Type | Extension | Value |
| | | Type | |
+----------------+--------------+------------+----------------------+
| None | ADDRESS_TYPE | 0 | ADDRTYPE_UNREACHABLE |
| SeqNumList | SEQ_NUM | 0 | Sequence number |
| | | | associated with |
| | | | invalid route to the |
| | | | unreachable address. |
| MetricTypeList | PATH_METRIC | MetricType | None. Extension Type |
| | | | set to MetricType of |
| | | | the route to the |
| | | | unreachable address. |
+----------------+--------------+------------+----------------------+
9. Simple External Network Attachment
Figure 4 shows a stub (i.e., non-transit) network of AODVv2 routers
which is attached to an external network via a single External
Network Access Router (ENAR). The interface to the external network
MUST NOT be configured in the AODVv2_INTERFACES list.
As in any externally-attached network, AODVv2 routers and Router
Clients that wish to be reachable from the external network MUST have
IP addresses within the ENAR's routable and topologically correct
prefix (i.e., 191.0.2.0/24 in Figure 4). This AODVv2 network and
networks attached to routers within it will be advertised to the
external network using procedures which are out of scope for this
specification.
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/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | ENAR | /191.0.2.0/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ External \
| | 191.0.2.0/24 | \ Network /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
Figure 4: Simple External Network Attachment Example
When an AODVv2 router within the AODVv2 MANET wants to discover a
route toward an address on the external network, it uses the normal
AODVv2 route discovery for that IP Destination Address. The ENAR
MUST respond to RREQ on behalf of all external network destinations,
i.e., destinations not on the configured 191.0.2.0/24 network. RREQs
for addresses inside the AODVv2 network, i.e. destinations on the
configured 191.0.2.0/24 network, are handled using the standard
processes described in Section 7.
When an IP packet from an address on the external network destined
for an address in the AODVv2 MANET reaches the ENAR, if the ENAR does
not have a route toward that exact destination in its Routing
Information Base, it will perform normal AODVv2 route discovery for
that destination.
Configuring the ENAR as a default router is outside the scope of this
specification.
10. Optional Features
A number of optional features for AODVv2, associated initially with
AODV, MAY be useful in networks with greater mobility or larger
populations, or networks requiring reduced latency for application
launches. These features are not required by minimal
implementations.
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10.1. Expanding Rings Multicast
For multicast RREQ, the [RFC5444] message may initially be limited to
a low number of hops to limit the RREQ propagation to a subset of the
local network and possibly reduce route discovery overhead. If the
route is not discovered, the number of hops allowed for distribution
of the RREQ is increased, in accordance with an expanding ring
search, as described in [RFC3561].
10.2. Precursor Lists
This section specifies an interoperable enhancement to AODVv2
enabling more economical Route Error notifications.
There can be several sources of traffic for a certain destination.
Each source of traffic and each upstream router between the
forwarding AODVv2 router and the traffic source is known as a
"precursor" for the destination. For each destination, an AODVv2
router MAY choose to keep track of precursors that have provided
traffic for that destination. Route Error messages about that
destination can be sent unicast to these precursors instead of
multicast to all AODVv2 routers.
Since an RERR will be regenerated if it comes from a next hop on a
valid LocalRoute, the RERR SHOULD ideally be sent backwards along the
route that the source of the traffic uses, to ensure it is
regenerated at each hop and reaches the traffic source. If the
reverse path is unknown, the RERR SHOULD be sent toward the source
along some other route. Therefore, the options for saving precursor
information are as follows:
o Save the next hop on an existing route to the IP packet's source
address as the precursor. In this case, it is not guaranteed that
an RERR that is sent will follow the reverse of the source's
route. In rare situations, this may prevent the route from being
invalidated at the source of the data traffic.
o Save the IP packet's source address as the precursor. In this
case, the RERR can be sent along any existing route to the source
of the data traffic, and SHOULD include PktSource to ensure that
the route will be invalidated at the source of the traffic, in
case the RERR does not follow the reverse of the source's route.
o By inspecting the MAC address of each forwarded IP packet,
determine which router forwarded the packet, and save the router
address as a precursor. This ensures that when an RERR is sent to
the precursor router, the route will be invalidated at that
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router, and the RERR will be regenerated toward the source of the
IP packet.
During normal operation, each AODVv2 router maintaining precursor
lists for a LocalRoute must update the precursor list whenever it
uses this route to forward traffic to the destination. Precursors
are classified as Active if traffic has recently been forwarded by
the precursor. The precursor is marked with a timestamp to indicate
the time it last forwarded traffic on this route.
When an AODVv2 router detects that one or more LocalRoutes are
broken, it MAY notify each Active precursor using a unicast Route
Error message instead of creating multicast traffic. Unicast is
applicable when there are few Active precursors compared to the
number of neighboring AODVv2 routers. However, the default multicast
behavior is still preferable when there are many precursors, since
fewer message transmissions are required.
When an AODVv2 router supporting precursor lists receives an RERR
message, it MAY identify the list of its own affected Active
precursors for the routes in the RERR, and choose to send a unicast
RERR to those, rather than send a multicast RERR.
When a LocalRoute is expunged, any precursor list associated with it
MUST also be expunged.
10.3. Intermediate RREP
Without iRREP, only the AODVv2 router responsible for the target
address can respond to an RREQ. Using iRREP, route discoveries can
be faster and create less control traffic. This specification has
been published as a separate Internet Draft [I-D.perkins-irrep].
10.4. Message Aggregation Delay
The aggregation of multiple messages into a packet is specified in
[RFC5444].
Implementations MAY choose to briefly delay transmission of messages
for the purpose of aggregation (into a single packet) or to improve
performance by using jitter [RFC5148].
11. Configuration
AODVv2 uses various parameters which can be grouped into the
following categories:
o Timers
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o Protocol constants
o Administrative parameters and controls
This section show the parameters along with their definitions and
default values (if any).
Note that several fields have limited size (bits or bytes). These
sizes and their encoding may place specific limitations on the values
that can be set.
11.1. Timers
AODVv2 requires certain timing information to be associated with
Local Route Set entries and message replies. The default values are
as follows:
+------------------------+----------------+
| Name | Default Value |
+------------------------+----------------+
| ACTIVE_INTERVAL | 5 second |
| MAX_IDLETIME | 200 seconds |
| MAX_BLACKLIST_TIME | 200 seconds |
| MAX_SEQNUM_LIFETIME | 300 seconds |
| RteMsg_ENTRY_TIME | 12 seconds |
| RREQ_WAIT_TIME | 2 seconds |
| RREP_Ack_SENT_TIMEOUT | 1 second |
| RREQ_HOLDDOWN_TIME | 10 seconds |
+------------------------+----------------+
Table 2: Timing Parameter Values
The above timing parameter values have worked well for small and
medium well-connected networks with moderate topology changes. The
timing parameters SHOULD be administratively configurable. Ideally,
for networks with frequent topology changes the AODVv2 parameters
SHOULD be adjusted using experimentally determined values or dynamic
adaptation. For example, in networks with infrequent topology
changes MAX_IDLETIME MAY be set to a much larger value.
If MAX_SEQNUM_LIFETIME was configured differently across the network,
and any of the routers lost their sequence number or rebooted, this
could result in their next route messages being classified as stale
at any AODVv2 router using a greater value for MAX_SEQNUM_LIFETIME.
This would delay route discovery from and to the re-initializing
router.
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11.2. Protocol Constants
AODVv2 protocol constants typically do not require changes. The
following table lists these constants, along with their values and a
reference to the section describing their use.
+------------------------+---------+--------------------------------+
| Name | Default | Description |
+------------------------+---------+--------------------------------+
| DISCOVERY_ATTEMPTS_MAX | 3 | Section 6.6 |
| RREP_RETRIES | 2 | Section 7.2.1 |
| MAX_METRIC[MetricType] | [TBD] | Section 5 |
| MAX_METRIC[HopCount] | 255 | Section 5 and Section 7 |
| INFINITY_TIME | [TBD] | Maximum expressible clock time |
| | | (Section 6.7.2) |
| C | 1/1024 | Constant used in validity time |
| | | calculation [RFC5497] |
+------------------------+---------+--------------------------------+
Table 3: AODVv2 Constants
MAX_METRIC[MetricType] MUST always be the maximum expressible metric
value of type MetricType. Field lengths associated with metric
values are found in Section 11.6.
These protocol constants MUST have the same values for all AODVv2
routers in the ad hoc network. If the values were configured
differently, the following consequences may be observed:
o DISCOVERY_ATTEMPTS_MAX: Routers with higher values are likely to
be more successful at finding routes, at the cost of additional
control traffic.
o RREP_RETRIES: Routers with lower values are more likely to
blacklist neighbors when there is a
o MAX_METRIC[MetricType]: No interoperability problems due to
variations on different routers, but routers with lower values may
exhibit overly restrictive behavior during route comparisons.
temporary fluctuation in link quality.
o INFINITY_TIME: No interoperability problems due to variations on
different routers, but if a lower value is used, route state
management may exhibit overly restrictive behavior.
o C: Routers with lower values will invalidate timed routes before
routers with higher values, which will cause Route Error messages
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to be generated and the route will effectively take on the shorter
validity time.
11.3. Local Settings
The following table lists AODVv2 parameters which SHOULD be
administratively configured for each router:
+------------------------+------------------------+--------------+
| Name | Default Value | Description |
+------------------------+------------------------+--------------+
| AODVv2_INTERFACES | | Section 3 |
| BUFFER_SIZE_PACKETS | 2 | Section 6.6 |
| BUFFER_SIZE_BYTES | MAX_PACKET_SIZE [TBD] | Section 6.6 |
| CONTROL_TRAFFIC_LIMIT | [TBD - 50 pkts/sec?] | Section 7 |
+------------------------+------------------------+--------------+
Table 4: Configuration for Local Settings
11.4. Network-Wide Settings
The following administrative controls MAY be used to change the
operation of the network. The same settings SHOULD be used across
the network. Inconsistent settings at different routers in the
network will not result in protocol errors, but poor performance may
result.
+----------------------+-----------+----------------+
| Name | Default | Description |
+----------------------+-----------+----------------+
| ENABLE_IDLE_IN_RERR | Disabled | Section 7.4.1 |
+----------------------+-----------+----------------+
Table 5: Configuration for Network-Wide Settings
11.5. Optional Feature Settings
These options are not required for correct routing behavior, although
they may reduce AODVv2 protocol overhead in certain situations. The
default behavior is to leave these options disabled.
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+---------------------------+----------+----------------------------+
| Name | Default | Description |
+---------------------------+----------+----------------------------+
| PRECURSOR_LISTS | Disabled | Local setting (Section |
| | | 10.2) |
| MSG_AGGREGATION | Disabled | Local setting (Section |
| | | 10.4) |
| ENABLE_IRREP | Disabled | Network-wide setting |
| | | (Section 10.3) |
| EXPANDING_RINGS_MULTICAST | Disabled | Network-wide setting |
| | | (Section 10.1) |
+---------------------------+----------+----------------------------+
Table 6: Configuration for Optional Features
11.6. MetricType Allocation
The metric types used by AODVv2 are identified according to the
assignments in [RFC6551]. All implementations MUST use these values.
+---------------------+----------+--------------------+
| Name of MetricType | Type | Metric Value Size |
+---------------------+----------+--------------------+
| Unassigned | 0 | Undefined |
| Hop Count | 3 [TBD] | 1 octet |
| Unallocated | 9 - 254 | TBD |
| Reserved | 255 | Undefined |
+---------------------+----------+--------------------+
Table 7: AODVv2 Metric Types
12. IANA Considerations
This section specifies several [RFC5444] message types and address
tlv-types required for AODVv2.
12.1. RFC 5444 Message Types
This specification defines four Message Types, to be allocated from
the 0-223 range of the "Message Types" namespace defined in
[RFC5444], as specified in Table 8.
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+-----------------------------------------+-----------+
| Name of Message | Type |
+-----------------------------------------+-----------+
| Route Request (RREQ) | 10 (TBD) |
| Route Reply (RREP) | 11 (TBD) |
| Route Error (RERR) | 12 (TBD) |
| Route Reply Acknowledgement (RREP_Ack) | 13 (TBD) |
+-----------------------------------------+-----------+
Table 8: AODVv2 Message Types
12.2. RFC 5444 Address Block TLV Types
This specification defines three Address Block TLV Types, to be
allocated from the "Address Block TLV Types" namespace defined in
[RFC5444], as specified in Table 9.
+------------------------+----------+---------------+---------------+
| Name of TLV | Type | Length | Reference |
| | | (octets) | |
+------------------------+----------+---------------+---------------+
| PATH_METRIC | 11 (TBD) | depends on | Section 7 |
| | | MetricType | |
| SEQ_NUM | 12 (TBD) | 2 | Section 7 |
| ADDRESS_TYPE | 13 (TBD) | 1 | Section 8 |
+------------------------+----------+---------------+---------------+
Table 9: AODVv2 Address Block TLV Types
12.3. ADDRESS_TYPE TLV Values
These values are used in the [RFC5444] Address Type TLV discussed in
Section 8. All implementations MUST use these values.
+---------------+--------+
| Address Type | Value |
+---------------+--------+
| ORIGADDR | 0 |
| TARGADDR | 1 |
| UNREACHABLE | 2 |
| PKTSOURCE | 3 |
| INTEND | 4 |
| UNSPECIFIED | 255 |
+---------------+--------+
Table 10: AODVv2 Address Types
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13. Security Considerations
This section describes various security considerations and potential
avenues to secure AODVv2 routing. The objective of the AODVv2
protocol is for each router to communicate reachability information
about addresses for which it is responsible, and for routes it has
learned from other AODVv2 routers. Positive routing information
(i.e. a route exists) is distributed via RREQ and RREP messages.
AODVv2 routers store the information contained in these messages in
order to properly forward IP packets, and they generally provide this
information to other AODVv2 routers. Negative routing information
(i.e. a route does not exist) is distributed via RERR messages.
AODVv2 routers process these messages and remove routes, and forward
this information to other AODVv2 routers.
Networks using AODVv2 to maintain connectivity and establish routes
on demand may be vulnerable to certain well-known types of threats.
Flooding attacks using RREQ amount to a denial of service for route
discovery. Valid route table entries can be replaced by maliciously
constructed RREQ and RREP messages. Links could be erroneously
treated as bidirectional if malicious unsolicited RREP or RREP_Ack
messages were to be accepted. Replay attacks using RERR messages
could, in some circumstances, be used to disrupt active routes.
Passive inspection of AODVv2 control messages could enable
unauthorized devices to gain information about the network topology,
since exchanging such information is the main purpose of AODVv2.
The on-demand nature of AODVv2 route discovery reduces the
vulnerability to route disruption. Since control traffic for
updating route tables is diminished, there is less opportunity for
failure. Processing requirements for AODVv2 are typically quite
small, and would typically be dominated by calculations to verify
integrity. This has the effect of reducing (but by no means
eliminating) AODVv2's vulnerability to denial of service attacks.
Encryption MAY be used for AODVv2 messages. If the routers share a
packet-level security association, the message data can be encrypted
prior to message transmission. The establishment of such security
associations is outside the scope of this specification. Encryption
will not only protect against unauthorized devices obtaining
information about network topology but will ensure that only trusted
routers participate in routing operations.
Message integrity checking is enabled by the Integrity Check Value
mechanisms defined in [RFC7182]. The data contained in AODVv2
routing protocol messages SHOULD be verified using ICV values, to
avoid the use of message data if the message has been tampered with
or replayed. Otherwise, it would be possible to disrupt
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communications by injecting nonexistent or malicious routes into the
route tables of routers within the ad hoc network. This can result
in loss of data or message processing by unauthorized devices.
The remainder of this section provides specific recommendations for
the use of the integrity checking and timestamp functions defined in
[RFC7182] to ensure the integrity of each AODVv2 message. The
calculation used for the Integrity Check Value will depend on the
message type. Sequence numbers can be used as timestamps to protect
against replay, since they are known to be strictly increasing.
RREQ messages advertise a route to OrigAddr, and impose very little
processing requirement for receivers. The main threat presented by
sending an RREQ message with false information is that traffic to
OrigAddr could be disrupted. Since RREQ is multicast and likely to
be received by all routers in the ad hoc network, this threat could
have serious impact on applications communicating by way of OrigAddr.
The actual threat to disrupt routes to OrigAddr is reduced by the
AODVv2 mechanism of marking RREQ-derived routes as "Unconfirmed"
until the link to the next hop is confirmed. If AODVv2 routers
always verify the integrity of the RREQ message data, then the threat
of disruption is minimized. The ICV mechanisms offered in [RFC7182]
are sufficient for this purpose. Since OrigAddr is included in the
RREQ, the ICV can be calculated and verified using message contents.
The ICV SHOULD be verified at every step along the dispersal path of
the RREQ to mitigate the threat. Since RREQ_Gen's sequence number is
incremented for each new RREQ, replay protection is already afforded
and no extra timestamp mechanism is required.
RREP messages advertise a route to TargAddr, and impose very little
processing requirement for receivers. The main threat presented by
sending an RREP message with false information is that traffic to
TargAddr could be disrupted. Since RREP is unicast, this threat is
restricted to receivers along the path from OrigAddr to TargAddr. If
AODVv2 routers always verify the integrity of the RREP message data,
then this threat is minimized. This facility is offered by the ICV
mechanisms in [RFC7182]. Since TargAddr is included as a Data
Element of the RREP, the ICV can be calculated and verified using
message contents. The ICV SHOULD be verified at every step along the
unicast path of the RREP. Since RREP_Gen's sequence number is
incremented for each new RREP, replay protection is afforded and no
extra timestamp mechanism is required.
RREP_Ack messages are intended to verify bidirectional neighbor
connectivity, and impose very little processing requirement for
receivers. The main threat presented by sending an RREP_Ack message
with false information is that the route advertised to a target
address in an RREP might be erroneously accepted even though the
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route would contain a unidirectional link and thus not be suitable
for most traffic. Since RREP_Ack is unicast, this threat is strictly
local to the RREP transmitter expecting the acknowledgement. A
malicious router could also attempt to send an unsolicited RREP_Ack
to convince another router that a bidirectional link exists and
subsequently use further messages to divert traffic along a route
which is not valid. If AODVv2 routers always verify the integrity of
the RREP_Ack message data, then this threat is minimized. This
facility is offered by the ICV mechanisms in [RFC7182]. The RREP_Gen
SHOULD use the source IP address of the RREP_Ack to identify the
sender, and so the ICV SHOULD be calculated using the message
contents and the IP source address. The message must also include
the Timestamp defined in [RFC7182] to protect against replay attacks,
using TargSeqNum from the RREP as the value in the TIMESTAMP TLV.
RERR messages remove routes, and impose very little processing
requirement for receivers. The main threat presented by sending an
RERR message with false information is that traffic to the advertised
destinations could be disrupted. Since RERR is multicast and can be
received by many routers in the ad hoc network, this threat could
have serious impact on applications communicating by way of the
sender of the RERR message. However, since the sender of the RERR
message with erroneous information MAY be presumed to be either
malicious or broken, it is better that such routes not be used
anyway. Another threat is that a malicious RERR message MAY be sent
with a PktSource included, to disrupt PktSource's ability to send to
the addresses contained in the RERR. If AODVv2 routers always verify
the integrity of the RERR message data, then this threat is reduced.
This facility is offered by the ICV mechanisms in [RFC7182]. The
receiver of the RERR SHOULD use the source IP address of the RERR to
identify the sender. The message must also include the Timestamp
defined in [RFC7182] to protect against replay attacks, using SeqNum
from RERR_Gen as the value in the TIMESTAMP TLV.
14. Acknowledgments
AODVv2 is a descendant of the design of previous MANET on-demand
protocols, especially AODV [RFC3561] and DSR [RFC4728]. Changes to
previous MANET on-demand protocols stem from research and
implementation experiences. Thanks to Elizabeth Belding and Ian
Chakeres for their long time authorship of AODV. Additional thanks
to Derek Atkins, Emmanuel Baccelli, Abdussalam Baryun, Ramon Caceres,
Thomas Clausen, Justin Dean, Christopher Dearlove, Fatemeh Ghassemi,
Ulrich Herberg, Henner Jakob, Ramtin Khosravi, Luke Klein-Berndt,
Lars Kristensen, Tronje Krop, Koojana Kuladinithi, Kedar Namjoshi,
Keyur Patel, Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro
Ruiz, Christoph Sommer, Romain Thouvenin, Richard Trefler, Jiazi Yi,
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Seung Yi, Behnaz Yousefi, and Cong Yuan, for their reviews of AODVv2
and DYMO, as well as numerous specification suggestions.
15. References
15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561, DOI
10.17487/RFC3561, July 2003,
<http://www.rfc-editor.org/info/rfc3561>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<http://www.rfc-editor.org/info/rfc5082>.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, DOI 10.17487/RFC5444, February 2009,
<http://www.rfc-editor.org/info/rfc5444>.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497, DOI
10.17487/RFC5497, March 2009,
<http://www.rfc-editor.org/info/rfc5497>.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
(MANET) Protocols", RFC 5498, DOI 10.17487/RFC5498, March
2009, <http://www.rfc-editor.org/info/rfc5498>.
[RFC6551] Vasseur, JP., Ed., Kim, M., Ed., Pister, K., Dejean, N.,
and D. Barthel, "Routing Metrics Used for Path Calculation
in Low-Power and Lossy Networks", RFC 6551, DOI 10.17487/
RFC6551, March 2012,
<http://www.rfc-editor.org/info/rfc6551>.
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[RFC7182] Herberg, U., Clausen, T., and C. Dearlove, "Integrity
Check Value and Timestamp TLV Definitions for Mobile Ad
Hoc Networks (MANETs)", RFC 7182, DOI 10.17487/RFC7182,
April 2014, <http://www.rfc-editor.org/info/rfc7182>.
15.2. Informative References
[I-D.perkins-irrep]
Perkins, C., "Intermediate RREP for dynamic MANET On-
demand (AODVv2) Routing", draft-perkins-irrep-03 (work in
progress), May 2015.
[Koodli01]
Koodli, R. and C. Perkins, "Fast handovers and context
transfers in mobile networks", Proceedings of the ACM
SIGCOMM Computer Communication Review 2001, Volume 31
Issue 5, 37-47, October 2001.
[Perkins94]
Perkins, C. and P. Bhagwat, "Highly Dynamic Destination-
Sequenced Distance-Vector Routing (DSDV) for Mobile
Computers", Proceedings of the ACM SIGCOMM '94 Conference
on Communications Architectures, Protocols and
Applications, London, UK, pp. 234-244, August 1994.
[Perkins99]
Perkins, C. and E. Royer, "Ad hoc On-Demand Distance
Vector (AODV) Routing", Proceedings of the 2nd IEEE
Workshop on Mobile Computing Systems and Applications, New
Orleans, LA, pp. 90-100, February 1999.
[RFC2501] Corson, S. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, DOI 10.17487/
RFC2501, January 1999,
<http://www.rfc-editor.org/info/rfc2501>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<http://www.rfc-editor.org/info/rfc4193>.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, DOI 10.17487/RFC4728, February 2007,
<http://www.rfc-editor.org/info/rfc4728>.
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[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)", RFC
5148, DOI 10.17487/RFC5148, February 2008,
<http://www.rfc-editor.org/info/rfc5148>.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, DOI 10.17487/RFC6130, April 2011,
<http://www.rfc-editor.org/info/rfc6130>.
[Sholander02]
Sholander, P., Coccoli, P., Oakes, T., and S. Swank, "A
Portable Software Implementation of a Hybrid MANET Routing
Protocol", 2002.
Appendix A. AODVv2 Draft Updates
This section lists the changes between AODVv2 revisions ...-13.txt
and ...-14.txt.
o Moved Address Type TLV Value definitions to IANA section.
o Removed use of MAX_HOPCOUNT and [RFC5444] msg-hop-limit, msg-hop-
count.
o Allow only one Unconfirmed route.
o Incorporate changes from Justin Dean's review.
Authors' Addresses
Charles E. Perkins
Futurewei Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Phone: +1-408-330-4586
Email: charliep@xxxxxxxxxxxx
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Stan Ratliff
Idirect
13861 Sunrise Valley Drive, Suite 300
Herndon, VA 20171
USA
Email: ratliffstan@xxxxxxxxx
John Dowdell
Airbus Defence and Space
Celtic Springs
Newport, Wales NP10 8FZ
United Kingdom
Email: john.dowdell@xxxxxxxxxx
Lotte Steenbrink
HAW Hamburg, Dept. Informatik
Berliner Tor 7
D-20099 Hamburg
Germany
Email: lotte.steenbrink@xxxxxxxxxxxxxx
Victoria Mercieca
Airbus Defence and Space
Celtic Springs
Newport, Wales NP10 8FZ
United Kingdom
Email: victoria.mercieca@xxxxxxxxxx
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<?rfc strict="yes" ?>
<!-- give errors regarding ID-nits and DTD validation -->
<rfc category="std" docName="draft-ietf-manet-aodvv2-14" ipr="trust200902"
obsoletes="" updates="" submissionType="IETF" xml:lang="en">
<front>
<title abbrev="AODVv2">Ad Hoc On-demand Distance Vector Version 2 (AODVv2)
Routing</title>
<author fullname="Charles E. Perkins" initials="C.E." surname="Perkins">
<organization abbrev="Futurewei">Futurewei Inc. </organization>
<address>
<postal>
<street>2330 Central Expressway</street>
<city>Santa Clara</city>
<code>95050</code>
<region>CA</region>
<country>USA</country>
</postal>
<phone>+1-408-330-4586</phone>
<email>charliep@xxxxxxxxxxxx</email>
</address>
</author>
<author fullname="Stan Ratliff" initials="S." surname="Ratliff">
<organization>Idirect</organization>
<address>
<postal>
<street>13861 Sunrise Valley Drive, Suite 300</street>
<city>Herndon</city>
<region>VA</region>
<code>20171</code>
<country>USA</country>
</postal>
<email>ratliffstan@xxxxxxxxx</email>
</address>
</author>
<author fullname="John Dowdell" initials="J." surname="Dowdell">
<organization>Airbus Defence and Space</organization>
<address>
<postal>
<street>Celtic Springs</street>
<city>Newport</city>
<region>Wales</region>
<code>NP10 8FZ</code>
<country>United Kingdom</country>
</postal>
<email>john.dowdell@xxxxxxxxxx</email>
</address>
</author>
<author fullname="Lotte Steenbrink" initials="L." surname="Steenbrink">
<organization>HAW Hamburg, Dept. Informatik</organization>
<address>
<postal>
<street>Berliner Tor 7</street>
<city>D-20099 Hamburg</city>
<!--<code>D-20099</code> -->
<country>Germany</country>
</postal>
<email>lotte.steenbrink@xxxxxxxxxxxxxx</email>
</address>
</author>
<author fullname="Victoria Mercieca" initials="V." surname="Mercieca">
<organization>Airbus Defence and Space</organization>
<address>
<postal>
<street>Celtic Springs</street>
<city>Newport</city>
<region>Wales</region>
<code>NP10 8FZ</code>
<country>United Kingdom</country>
</postal>
<email>victoria.mercieca@xxxxxxxxxx</email>
</address>
</author>
<date/>
<area>Routing</area>
<workgroup>Mobile Ad hoc Networks Working Group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>XML</keyword>
<keyword>reactive protocol</keyword>
<abstract><!--This document was prepared using Pandoc2rfc,
https://github.com/miekg/pandoc2rfc --><t>The Ad Hoc On-demand Distance Vector
Version 2 (AODVv2) routing protocol is intended for use by mobile routers in
wireless, multihop networks. AODVv2 determines unicast routes among AODVv2
routers within the network in an on-demand fashion. </t> </abstract>
</front>
<middle><!--This document was prepared using Pandoc2rfc,
https://github.com/miekg/pandoc2rfc --><section title="Overview"
anchor="overview" toc="default"><t>The Ad Hoc On-demand Distance Vector Version
2 (AODVv2) routing protocol (formerly named DYMO) enables on-demand, multihop
unicast routing among AODVv2 routers in mobile ad hoc networks (MANETs) <xref
target="RFC2501" pageno="false" format="default"/>. </t><t>Although AODVv2 is
closely related to AODV <xref target="RFC3561" pageno="false"
format="default"/>, and shares some features of DSR <xref target="RFC4728"
pageno="false" format="default"/>, AODVv2 is not interoperable with either of
those protocols. Compared to AODV, AODVv2 makes some features optional, notably
intermediate route replies, expanding ring search, and precursor lists. Hello
messages and local repair have been removed. AODVv2 provides a mechanism for
the use of multiple metric types. Message formats have been updated and made
compliant with <xref target="RFC5444" pageno="false" format="default"/>.
</t><t>AODVv2 control messages are defined as sets of data, which are mapped to
messages using the Generalized MANET Packet/Message Format defined in <xref
target="RFC5444" pageno="false" format="default"/> and sent using the
parameters in <xref target="RFC5498" pageno="false" format="default"/>.
</t><t>The basic operations of the AODVv2 protocol are route discovery and
route maintenance. </t><t>An AODVv2 router is configured to perform route
discovery on behalf of a configured set of IP addresses known as Router
Clients. Route discovery is performed when an AODVv2 router needs to forward an
IP packet from one of its Router Clients, but does not have a valid route to
the packet's destination. AODVv2 routers use Route Request (RREQ) and Route
Reply (RREP) messages to carry route information between the originator of the
route discovery and the router responsible for the target, establishing a route
to both endpoints on all intermediate routers. A metric value is included to
represent the cost of the route contained within the message. AODVv2 uses
sequence numbers to identify stale routing information, and compares route
metric values to determine if advertised routes could form loops. </t><t>Route
maintenance includes confirming bidirectionality of links to next hop AODVv2
routers before considering discovered routes to be valid, issuing Route Error
(RERR) messages if link failures invalidate routes, reacting to received Route
Error messages, and extending and enforcing route timeouts. </t><t>To enable
the on-demand nature of AODVv2, signals are required to be exchanged between
AODVv2 and the forwarding plane, to indicate when a packet is to be forwarded,
in order to initiate route discovery, when packet forwarding fails, in order to
initiate route error reporting, and when a packet is successfully forwarded,
for route maintenance. </t><t>Security for authentication of AODVv2 routers
and encryption of control messages is accomplished using the TIMESTAMP and ICV
TLVs defined in <xref target="RFC7182" pageno="false" format="default"/>.
</t></section><section title="Terminology" anchor="terminology"
toc="default"><t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in <xref
target="RFC2119" pageno="false" format="default"/>. In addition, this document
uses terminology from <xref target="RFC5444" pageno="false" format="default"/>,
and defines the following terms: </t><t><list style="hanging"><t
hangText="AddressList"><vspace blankLines="0"/>A list of IP addresses as used
in AODVv2 messages. </t><t hangText="AckReq"><vspace blankLines="0"/>Used in a
Route Reply message to indicate the IP address of the router from which a Route
Reply Acknowledgement is expected. </t><t hangText="AdvRte"><vspace
blankLines="0"/>A route advertised in an incoming route message. </t><t
hangText="AODVv2 Router"><vspace blankLines="0"/>An IP addressable device in
the ad hoc network that performs the AODVv2 protocol operations specified in
this document. </t><t hangText="CurrentTime"><vspace blankLines="0"/>The
current time as maintained by the AODVv2 router. </t></list></t><t><list
style="hanging"><t hangText="ENAR (External Network Access Router)"><vspace
blankLines="0"/>An AODVv2 router with an interface to an external, non-AODVv2
network. </t><t hangText="Invalid route"><vspace blankLines="0"/>A route that
cannot be used for forwarding but still contains useful sequence number
information. </t><t hangText="LocalRoute"><vspace blankLines="0"/>An entry in
the Local Route Set. </t><t hangText="MANET"><vspace blankLines="0"/>A Mobile
Ad Hoc Network as defined in <xref target="RFC2501" pageno="false"
format="default"/>. </t><t hangText="MetricType"><vspace blankLines="0"/>The
metric type for a metric value included in a message. </t><t
hangText="MetricTypeList"><vspace blankLines="0"/>A list of metric types
associated with the addresses in the AddressList of a Route Error message.
</t><t hangText="Neighbor"><vspace blankLines="0"/>An AODVv2 router from which
an RREQ or RREP message has been received. Neighbors exchange routing
information and verify bidirectionality of the link to a neighbor before
installing a route via that neighbor into the Local Route Set. </t><t
hangText="OrigAddr"><vspace blankLines="0"/>The source IP address of the IP
packet triggering route discovery. </t><t hangText="OrigMetric"><vspace
blankLines="0"/>The metric value associated with the route to OrigAddr (and any
other addresses included in the given prefix length). </t><t
hangText="OrigPrefixLen"><vspace blankLines="0"/>The prefix length, in bits,
configured in the Router Client entry which includes OrigAddr. </t><t
hangText="OrigSeqNum"><vspace blankLines="0"/>The sequence number of the AODVv2
router which originated the Route Request on behalf of OrigAddr. </t><t
hangText="PktSource"><vspace blankLines="0"/>The source address of the IP
packet which triggered a Route Error message. </t><t
hangText="PrefixLengthList"><vspace blankLines="0"/>A list of routing prefix
lengths associated with the addresses in the AddressList of a message. </t><t
hangText="Reactive"><vspace blankLines="0"/>Performed only in reaction to
specific events. In AODVv2, routes are requested only when data packets need to
be forwarded. In this document, "reactive" is synonymous with "on-demand".
</t><t hangText="RERR (Route Error)"><vspace blankLines="0"/>The AODVv2 message
type used to indicate that an AODVv2 router does not have a valid LocalRoute
toward one or more particular destinations. </t><t hangText="RERR_Gen (RERR
Generating Router)"><vspace blankLines="0"/>The AODVv2 router generating a
Route Error message. </t><t hangText="Routable Unicast IP Address"><vspace
blankLines="0"/>A routable unicast IP address is a unicast IP address that is
scoped sufficiently to be forwarded by a router. Globally-scoped unicast IP
addresses and Unique Local Addresses (ULAs) <xref target="RFC4193"
pageno="false" format="default"/> are examples of routable unicast IP
addresses. </t><t hangText="Router Client"><vspace blankLines="0"/>An address
or address range configured on an AODVv2 router, on behalf of which that router
will initiate and respond to route discoveries, so that devices configured to
use these addresses can send and receive IP traffic to and from remote
destinations. These addresses may be used by the AODVv2 router itself or by
non-routing devices that are reachable without traversing another AODVv2
router. </t><t hangText="RREP (Route Reply)"><vspace blankLines="0"/>The
AODVv2 message type used to reply to a Route Request message. </t><t
hangText="RREP_Gen (RREP Generating Router)"><vspace blankLines="0"/>The AODVv2
router that generates the Route Reply message, i.e., the router configured with
TargAddr as a Router Client. </t><t hangText="RREQ (Route Request)"><vspace
blankLines="0"/>The AODVv2 message type used to discover a route to TargAddr
and distribute information about a route to OrigAddr. </t><t
hangText="RREQ_Gen (RREQ Generating Router)"><vspace blankLines="0"/>The AODVv2
router that generates the Route Request message, i.e., the router configured
with OrigAddr as a Router Client. </t><t hangText="RteMsg (Route
Message)"><vspace blankLines="0"/>A Route Request (RREQ) or Route Reply (RREP)
message. </t><t hangText="SeqNum"><vspace blankLines="0"/>The sequence number
maintained by an AODVv2 router to indicate freshness of route information.
</t><t hangText="SeqNumList"><vspace blankLines="0"/>A list of sequence numbers
associated with the addresses in the AddressList of a message. </t><t
hangText="TargAddr"><vspace blankLines="0"/>The target address of a route
request, i.e., the destination address of the IP packet triggering route
discovery. </t><t hangText="TargMetric"><vspace blankLines="0"/>The metric
value associated with the route to TargAddr (and any other addresses included
in the given prefix length). </t><t hangText="TargPrefixLen"><vspace
blankLines="0"/>The prefix length, in bits, configured in the Router Client
entry which includes TargAddr. </t><t hangText="TargSeqNum"><vspace
blankLines="0"/>The sequence number of the AODVv2 router which originated the
Route Reply on behalf of TargAddr. </t><t hangText="Valid route"><vspace
blankLines="0"/>A route that can be used for forwarding, which has been
confirmed as having a bidirectional link to the next hop, and has not timed out
or been made invalid by a route error. </t><t hangText="Unreachable
Address"><vspace blankLines="0"/>An address reported in a Route Error message,
either the address on a LocalRoute which became Invalid, or the destination
address of an IP packet that could not be forwarded because a valid LocalRoute
to the destination is not known, and will not be requested. </t><t
hangText="Upstream"><vspace blankLines="0"/>In the direction from destination
to source (from TargAddr to OrigAddr). </t><t hangText="ValidityTime"><vspace
blankLines="0"/>The length of time the route described by the message is
offered. </t></list></t><t>This document uses the notational conventions in
<xref target="conventions" pageno="false" format="default"/> to simplify the
text. </t><texttable anchor="conventions" align="center" title="Notational
Conventions" suppress-title="false" style="full"><ttcol align="left">Notation
</ttcol><ttcol align="left">Meaning </ttcol><c>Route[Address] </c><c>A route
toward Address </c><c>Route[Address].Field </c><c>A field in a route toward
Address </c><c>RteMsg.Field </c><c>A field in either RREQ or RREP
</c></texttable><t></t></section><section title="Applicability Statement"
anchor="apply" toc="default"><t></t><t>The AODVv2 routing protocol is a
reactive routing protocol. While proactive routing protocols send frequent
messages and determine routes in advance of them being used, a reactive
protocol only sends messages to discover a route when there is data to send on
that route. Therefore, a reactive routing protocol requires certain
interactions with the forwarding plane, for example, to indicate when a packet
is to be forwarded, in order to initiate route discovery, route error
reporting, or route maintenance. The set of signals exchanged between AODVv2
and the forwarding plane are discussed in <xref target="fwdplane"
pageno="false" format="default"/>. </t><t>AODVv2 is designed for stub or
disconnected mobile ad hoc networks, i.e., non-transit networks or those not
connected to the internet. AODVv2 can, however, be configured to perform
gateway functions when attached to external networks, as discussed in <xref
target="gateway" pageno="false" format="default"/>. </t><t>AODVv2 handles a
wide variety of mobility and traffic patterns by determining routes on-demand.
In networks with a large number of routers, AODVv2 is best suited for
relatively sparse traffic scenarios where each router forwards IP packets to a
small percentage of other AODVv2 routers in the network. In this case fewer
routes are needed, and therefore less control traffic is produced.
</t><t>Providing security for a reactive routing protocol can be difficult.
AODVv2 provides for message integrity and security against replay attacks by
using integrity check values, timestamps and sequence numbers, as described in
<xref target="Security" pageno="false" format="default"/>. If security
associations can be established, encryption can be used for AODVv2 messages to
ensure that only trusted routers participate in routing operations.
</t><t>Since the route discovery process aims for a route to be established in
both directions along the same path, uni-directional links are not suitable.
AODVv2 will detect and exclude those links from route discovery. The route
discovered is optimised for the requesting router, and the return path may not
be the optimal route. </t><t>AODVv2 is applicable to memory constrained
devices, since only a little routing state is maintained in each AODVv2 router.
In contrast to proactive routing protocols, which maintain routing information
for all destinations within the MANET, AODVv2 routes that are not needed for
forwarding data do not need to be maintained. On routers unable to store
persistent AODVv2 state, recovery can impose a performance penalty (e.g., in
case of AODVv2 router reboot), since if a router loses its sequence number,
there is a delay before the router can resume full operations. This is
described in <xref target="boot" pageno="false" format="default"/>.
</t><t>AODVv2 supports routers with multiple interfaces and multiple IP
addresses per interface. A router may also use the same IP address on multiple
interfaces. AODVv2 requires only that each interface configured for AODVv2 has
at least one unicast IP address. Address assignment procedures are out of scope
for AODVv2. </t><t>AODVv2 supports Router Clients with multiple interfaces, as
long as each interface is configured with its own unicast IP address.
Multi-homing of a Router Client IP address is not supported by AODVv2, and
therefore an IP address SHOULD NOT be configured as a Router Client on more
than one AODVv2 router at any one time. </t><t>The routing algorithm in AODVv2
MAY be operated at layers other than the network layer, using layer-appropriate
addresses. </t></section><section title="Data Structures"
anchor="data-structures" toc="default"><section title="Interface List"
anchor="interfaceslist" toc="default"><t>If multiple interfaces of the AODVv2
router are configured for use by AODVv2, a list of the interfaces MUST be
configured in the AODVv2_INTERFACES list. </t></section><section title="Router
Client Table" anchor="clients" toc="default"><t>An AODVv2 router provides route
discovery services for its own local applications and for other non-routing
devices that are reachable without traversing another AODVv2 router. The
addresses used by these devices, and the AODVv2 router itself, are configured
in the Router Client Table. An AODVv2 router will only originate Route Request
and Route Reply messages on behalf of configured Router Client addresses.
</t><t>Router Client Table entries MUST contain: </t><t><list
style="hanging"><t hangText="RouterClient.IPAddress"><vspace blankLines="0"/>An
IP address or the start of an address range that requires route discovery
services from the AODVv2 router. </t></list></t><t><list style="hanging"><t
hangText="RouterClient.PrefixLength"><vspace blankLines="0"/>The length, in
bits, of the routing prefix associated with the RouterClient.IPAddress. If a
prefix length is included, the AODVv2 router MUST provide connectivity for all
addresses within that prefix. </t><t hangText="RouterClient.Cost"><vspace
blankLines="0"/>The cost associated with reaching this address or address
range. </t></list></t><t>The Router Client Table for an AODVv2 router is never
empty, since an AODVv2 router's interface addresses are always configured in
Router Client entries. <vspace blankLines="0"/> </t><t>In the initial state,
an AODVv2 router is not required to have information about the Router Clients
of any other AODVv2 router. </t><t>A Router Client address MUST NOT be served
by more than one AODVv2 router at any one time. To shift responsibility for a
Router Client to a different AODVv2 router, correct AODVv2 routing behavior
MUST be observed. The AODVv2 router adding the Router Client MUST wait for any
existing routing information about this Router Client to be purged from the
network, i.e., at least MAX_SEQNUM_LIFETIME since the last SeqNum update on the
router which is removing this Router Client. </t></section><section
title="Neighbor Table" anchor="nbrlist" toc="default"><t>A Neighbor Table MUST
be maintained with information about neighboring AODVv2 routers. Neighbor Table
entries are stored when AODVv2 messages are received. If the Neighbor is chosen
as a next hop on an installed route, the link to the Neighbor MUST be tested
for bidirectionality and the result stored in this table. A route will only be
considered valid when the link is confirmed to be bidirectional.
</t><t>Neighbor Table entries MUST contain: </t><t><list style="hanging"><t
hangText="Neighbor.IPAddress"><vspace blankLines="0"/>An IP address of the
neighboring router, learned from the source IP address of a received route
message. </t><t hangText="Neighbor.State"><vspace blankLines="0"/>Indicates
whether the link to the neighbor is bidirectional. There are three possible
states: Confirmed, Unknown, and Blacklisted. Unknown is the initial state.
Confirmed indicates that the link to the neighbor has been confirmed as
bidirectional. Blacklisted indicates that the link to the neighbor is
uni-directional. <xref target="nexthopmonitoring" pageno="false"
format="default"/> discusses how to monitor link bidirectionality. </t><t
hangText="Neighbor.ResetTime"><vspace blankLines="0"/>When the value of
Neighbor.State is Blacklisted, this indicates the time at which the value of
Neighbor.State will revert to Unknown. By default this value is calculated at
the time the router is blacklisted and is equal to CurrentTime +
MAX_BLACKLIST_TIME. When the value of Neighbor.State is not Blacklisted, this
time is set to INFINITY_TIME. </t></list></t></section><section
title="Sequence Numbers" anchor="seqnum" toc="default"><t>Sequence numbers
enable AODVv2 routers to determine the temporal order of route discovery
messages, identifying stale routing information so that it can be discarded.
The sequence number fulfills the same roles as the "Destination Sequence
Number" of DSDV <xref target="Perkins94" pageno="false" format="default"/>, and
the AODV Sequence Number in <xref target="RFC3561" pageno="false"
format="default"/>. </t><t>Each AODVv2 router in the network MUST maintain its
own sequence number. All RREQ and RREP messages created by an AODVv2 router
include the router's sequence number, reported as a 16-bit unsigned integer.
Each AODVv2 router MUST ensure that its sequence number is strictly increasing,
and that it is incremented by one (1) whenever an RREQ or RREP is created,
except when the sequence number is 65,535 (the maximum value of a 16-bit
unsigned integer), in which case it MUST be reset to one (1). The value zero
(0) is reserved to indicate that the sequence number is unknown. </t><t>An
AODVv2 router MUST only attach its own sequence number to information about a
route to one of its configured Router Clients. All route messages regenerated
by other routers retain the originator's sequence number. Therefore, when two
pieces of information about a route are received, they both contain a sequence
number from the originating router. Comparing the sequence number will identify
which information is stale. The previously stored sequence number is subtracted
from the incoming sequence number. The result of the subtraction is to be
interpreted as a signed 16-bit integer, and if less than zero, the information
in the new AODVv2 message is stale and MUST be discarded. </t><t>This, along
with the processes in <xref target="test" pageno="false" format="default"/>,
ensures loop freedom. </t><t>An AODVv2 router SHOULD maintain its sequence
number in persistent storage. If the sequence number is lost, the router MUST
follow the procedure in <xref target="boot" pageno="false" format="default"/>
to safely resume routing operations with a new sequence number.
</t></section><section title="Local Route Set" anchor="rte"
toc="default"><t>All AODVv2 routers MUST maintain a Local Route Set, containing
information about routes learned from AODVv2 route messages. The Local Route
Set is stored separately from the Routing Information Base, and the Routing
Information Base is updated using information from the Local Route Set.
Alternatively, implementations MAY choose to modify the Routing Information
Base directly. </t><t>Routes learned from AODVv2 route messages are referred
to in this document as LocalRoutes, and MUST contain the following information:
</t><t><list style="hanging"><t hangText="LocalRoute.Address"><vspace
blankLines="0"/>An address, which, when combined with LocalRoute.PrefixLength,
describes the set of destination addresses this route includes. </t><t
hangText="LocalRoute.PrefixLength"><vspace blankLines="0"/>The prefix length,
in bits, associated with LocalRoute.Address. </t><t
hangText="LocalRoute.SeqNum"><vspace blankLines="0"/>The sequence number
associated with LocalRoute.Address, obtained from the last route message that
successfully updated this entry. </t><t hangText="LocalRoute.NextHop"><vspace
blankLines="0"/>The source IP address of the IP packet containing the AODVv2
message advertising the route to LocalRoute.Address, i.e. an IP address of the
AODVv2 router used for the next hop on the path toward LocalRoute.Address.
</t><t hangText="LocalRoute.NextHopInterface"><vspace blankLines="0"/>The
interface used to send IP packets toward LocalRoute.Address. </t><t
hangText="LocalRoute.LastUsed"><vspace blankLines="0"/>If this route is
installed in the Routing Information Base, the time it was last used to forward
an IP packet. </t><t hangText="LocalRoute.LastSeqNumUpdate"><vspace
blankLines="0"/>The time LocalRoute.SeqNum was last updated. </t><t
hangText="LocalRoute.ExpirationTime"><vspace blankLines="0"/>The time at which
this LocalRoute MUST be marked as Invalid. An AODVv2 router MAY be offered a
route for a limited time. In this case, the route is referred to as a timed
route. If a route is not timed, LocalRoute.ExpirationTime is INFINITY_TIME.
</t><t hangText="LocalRoute.MetricType"><vspace blankLines="0"/>The type of
metric associated with this route. </t><t hangText="LocalRoute.Metric"><vspace
blankLines="0"/>The cost of the route toward LocalRoute.Address expressed in
units consistent with LocalRoute.MetricType. </t><t
hangText="LocalRoute.State"><vspace blankLines="0"/>The last known state
(Unconfirmed, Idle, Active, or Invalid) of the route. </t><t
hangText="LocalRoute.Precursors (optional feature)"><vspace blankLines="0"/>A
list of upstream neighbors using the route (see <xref target="precursor"
pageno="false" format="default"/>). </t></list></t><t>There are four possible
states for a LocalRoute: </t><t><list style="hanging"><t
hangText="Unconfirmed"><vspace blankLines="0"/>A route learned from a Route
Request message, which has not yet been confirmed as bidirectional. It MUST NOT
be used for forwarding IP packets, and therefore it is not referred to as a
valid route. </t><t hangText="Idle"><vspace blankLines="0"/>A route which has
been learned from a route message, and has also been confirmed, but has not
been used in the last ACTIVE_INTERVAL. It is able to be used for forwarding IP
packets, and therefore it is referred to as a valid route. </t><t
hangText="Active"><vspace blankLines="0"/>A route which has been learned from a
route message, and has also been confirmed, and has been used in the last
ACTIVE_INTERVAL. It is able to be used for forwarding IP packets, and therefore
it is referred to as a valid route. </t><t hangText="Invalid"><vspace
blankLines="0"/>A route which has expired or been lost. It MUST NOT be used for
forwarding IP packets, and therefore it is not referred to as a valid route.
Invalid routes contain sequence number information which allows incoming
information to be assessed for freshness. </t></list></t><t>When the Local
Route Set is stored separately from the Routing Information Base, routes are
added to the Routing Information Base when LocalRoute.State is valid (set to
Active or Idle), and removed from the Routing Information Base LocalRoute.State
becomes Invalid. </t><t>Changes to LocalRoute state are detailed in <xref
target="routestatechanges" pageno="false" format="default"/>. </t><t>Note that
multiple entries for the same address, prefix length and metric type may exist
in the Local Route Set, but only one will be a valid entry. Any others will be
Unconfirmed, but may offer improvement to the existing valid route, if they can
be confirmed as valid routes (see <xref target="nexthopmonitoring"
pageno="false" format="default"/>). </t><t>Multiple valid routes for the same
address and prefix length but for different metric types may exist in the Local
Route Set, but the decision of which of these routes to install in the Routing
Information Base to use for forwarding is outside the scope of AODVv2.
</t></section><section title="Multicast Route Message Table"
anchor="rtemsgtable" toc="default"><t>A route message (RteMsg) is either a
Route Request or Route Reply message. RREQ messages are multicast by default
and regenerated multiple times, and RREP messages may be multicast when the
link to the next router is not known to be bidirectional. Multiple similar
route messages might be received by any one router during one route discovery
attempt. The AODVv2 router does not need to regenerate or respond to every one
of these messages. </t><t>The Multicast Route Message Table is a conceptual
table which contains information about previously received multicast route
messages, so that incoming route messages can be compared with previously
received messages to determine if the incoming information is redundant, and
the router can avoid sending redundant control traffic. </t><t>Multicast Route
Message Table entries MUST contain the following information: </t><t><list
style="hanging"><t hangText="RteMsg.MessageType"><vspace blankLines="0"/>Either
RREQ or RREP. </t><t hangText="RteMsg.OrigAddr"><vspace blankLines="0"/>The
source address of the IP packet triggering the route request. </t><t
hangText="RteMsg.OrigPrefixLen"><vspace blankLines="0"/>The prefix length
associated with RteMsg.OrigAddr, originally from the Router Client entry on
RREQ_Gen which includes RteMsg.OrigAddr. </t><t
hangText="RteMsg.TargAddr"><vspace blankLines="0"/>The destination address of
the IP packet triggering the route request. </t><t
hangText="RteMsg.TargPrefixLen"><vspace blankLines="0"/>The prefix length
associated with RteMsg.TargAddr, originally from the Router Client entry on
RREP_Gen which includes RteMsg.TargAddr. </t><t
hangText="RteMsg.OrigSeqNum"><vspace blankLines="0"/>The sequence number
associated with the route to OrigAddr, if RteMsg is an RREQ. </t><t
hangText="RteMsg.TargSeqNum"><vspace blankLines="0"/>The sequence number
associated with the route to TargAddr, if present in the RteMsg. </t><t
hangText="RteMsg.MetricType"><vspace blankLines="0"/>The metric type of the
route requested. </t><t hangText="RteMsg.Metric"><vspace blankLines="0"/>The
metric value received in the RteMsg. </t><t
hangText="RteMsg.Timestamp"><vspace blankLines="0"/>The last time this
Multicast Route Message Table entry was updated. </t><t
hangText="RteMsg.RemoveTime"><vspace blankLines="0"/>The time at which this
entry MUST be removed from the Multicast Route Message Table. This is set to
CurrentTime + MAX_SEQNUM_LIFETIME, whenever the sequence number of this entry
(RteMsg.OrigSeqNum for an RREQ, or RteMsg.TargSeqNum for an RREP) is updated.
</t></list></t><t>The Multicast Route Message Table is maintained so that no
two entries have the same MessageType, OrigAddr, TargAddr, and MetricType. See
<xref target="suppress" pageno="false" format="default"/> for details about
updating this table. </t></section></section><section title="Metrics"
anchor="metrics" toc="default"><t>Metrics measure a cost or quality associated
with a route or a link, e.g., latency, delay, financial cost, energy, etc.
Metric values are reported in Route Request and Route Reply messages.
</t><t>In Route Request messages, the metric describes the cost of the route
from OrigAddr (and any other addresses included in the prefix length of
RREQ_Gen's Router Client entry for OrigAddr) to the router sending the Route
Request. For RREQ_Gen, this is the cost associated with the Router Client entry
which includes OrigAddr. For routers which regenerate the RREQ, this is the
cost from OrigAddr to the regenerating router, combining the metric value from
the received RREQ message with knowledge of the link cost from the sender to
the receiver, i.e., the incoming link cost. This updated route cost is included
when regenerating the Route Request message, and used to install a route back
toward OrigAddr. </t><t>Similarly, in Route Reply messages, the metric
reflects the cost of the route from TargAddr (and any other addresses included
in the prefix length of RREP_Gen's Router Client entry for TargAddr) to the
router sending the Route Reply. For RREP_Gen, this is the cost associated with
the Router Client entry which includes TargAddr. For routers which regenerate
the RREP, this is the cost from TargAddr to the regenerating router, combining
the metric value from the received RREP message with knowledge of the link cost
from the sender to the receiver, i.e., the incoming link cost. This updated
route cost is included when regenerating the Route Reply message, and used to
install a route back toward TargAddr. </t><t>Assuming link metrics are
symmetric, the cost of the routes installed in the Local Route Set at each
router will be correct. The route discovered is optimised for the requesting
router, and the return path may not be the optimal route. </t><t>AODVv2
enables the use of multiple metric types. Each route discovery attempt
indicates the metric type which is requested for the route. Only one metric
type MUST be used in each route discovery attempt. However, routes to a single
destination might be requested and created in the Local Route Set for multiple
metric types. The decision of which of these routes to install in the Routing
Information Base to use for forwarding is outside the scope of AODVv2.
</t><t>For each MetricType, AODVv2 requires: </t><t><list style="symbols"><t>A
MetricType number, to indicate the metric type of a route. MetricType numbers
allocated are detailed in <xref target="metric-type" pageno="false"
format="default"/>. </t><t>A maximum value, denoted MAX_METRIC[MetricType].
This MUST always be the maximum expressible metric value of type MetricType.
Field lengths associated with metric values are found in <xref
target="metric-type" pageno="false" format="default"/>. If the cost of a route
exceeds MAX_METRIC[MetricType], the route is ignored. </t><t>A function for
incoming link cost, denoted Cost(L). Using incoming link costs means that the
route learned has a path optimized for the direction from OrigAddr to TargAddr.
</t><t>A function for route cost, denoted Cost(R). </t><t>A function to
analyze routes for potential loops based on metric information, denoted
LoopFree(R1, R2). LoopFree verifies that a route R2 is not a sub-section of
another route R1. An AODVv2 router invokes LoopFree() as part of the process in
<xref target="test" pageno="false" format="default"/>, when an advertised route
(R1) and an existing LocalRoute (R2) have the same destination address, metric
type, and sequence number. LoopFree returns FALSE to indicate that an
advertised route is not to be used to update a stored LocalRoute, as it may
cause a routing loop. In the case where the existing LocalRoute is Invalid, it
is possible that the advertised route includes the existing LocalRoute and came
from a router which did not yet receive notification of the route becoming
Invalid, so the advertised route should not be used to update the Local Route
Set, in case it forms a loop to a broken route. </t></list></t><t>AODVv2
currently supports cost metrics where Cost(R) is strictly increasing, by
defining: </t><t><list style="symbols"><t>Cost(R) := Sum of Cost(L) of each
link in the route </t><t>LoopFree(R1, R2) := ( Cost(R1) <= Cost(R2) )
</t></list></t><t>Implementers MAY consider other metric types, but the
definitions of Cost and LoopFree functions for such types are undefined, and
interoperability issues need to be considered. </t></section><section
title="AODVv2 Protocol Operations" anchor="aodv_ops" toc="default"><t>The
AODVv2 protocol's operations include managing sequence numbers, monitoring next
hop AODVv2 routers on discovered routes and updating the Neighbor Table,
performing route discovery and dealing with requests from other routers,
processing incoming route information and updating the Local Route Set,
updating the Multicast Route Message Table and suppressing redundant messages,
and reporting broken routes. These processes are discussed in detail in the
following sections. </t><section title="Initialization" anchor="boot"
toc="default"><t>During initialization where an AODVv2 router does not have
information about its previous sequence number, or if its sequence number is
lost at any point, the router resets its sequence number to one (1). However,
other AODVv2 routers may still hold sequence number information that this
router previously issued. Since sequence number information is removed if there
has been no update to the sequence number in MAX_SEQNUM_LIFETIME, the
initializing router MUST wait for MAX_SEQNUM_LIFETIME before it creates any
messages containing its new sequence number. It can then be sure that the
information it sends will not be considered stale. </t><t>Until
MAX_SEQNUM_LIFETIME after its sequence number is reset, the router SHOULD NOT
create RREQ or RREP messages. </t><t>During this wait period, the router is
permitted to do the following: </t><t><list style="symbols"><t>Process
information in a received RREQ or RREP message to learn a route to the
originator or target of that route discovery </t><t>Regenerate a received RREQ
or RREP </t><t>Send an RREP_Ack </t><t>Maintain valid routes in the Local Route
Set </t><t>Create, process and regenerate RERR messages
</t></list></t></section><section title="Next Hop Monitoring"
anchor="nexthopmonitoring" toc="default"><t>AODVv2 routers MUST NOT establish
routes over uni-directional links. Consider the following. An RREQ is forwarded
toward TargAddr, and intermediate routers create a LocalRoute corresponding to
OrigAddr. An RREP arrives to be forwarded toward OrigAddr, but the link to the
next hop toward OrigAddr is uni-directional. The RREP sent toward OrigAddr
using this link would not reach the next hop, and would therefore never reach
RREQ_Gen. End-to-end route establishment will fail. If the route discovery is
retried by RREQ_Gen, the same will happen. Further, if an intermediate router
used the route toward OrigAddr to forward data traffic, the data packets would
be lost. </t><t>AODVv2 provides a mechanism for testing bidirectional
connectivity during route discovery, and blacklisting routers where
bidirectional connectivity is not available. If a route discovery is retried by
RREQ_Gen, the blacklisted routers can be excluded from the process, and a
different route can be discovered. Further, a route is not to be used for
forwarding until the bidirectionality of the link to the next hop is confirmed.
AODVv2 routers do not need to monitor bidirectionality for links to neighboring
routers which are not used as next hops on routes in the Local Route Set.
</t><t><list style="symbols"><t>For the next hop router on the route toward
OrigAddr, the approach for testing bidirectional connectivity is to request
acknowledgement of Route Reply messages. Receipt of an acknowledgement proves
that bidirectional connectivity exists. All AODVv2 routers MUST support this
process, which is explained in <xref target="RREP_msgs" pageno="false"
format="default"/> and <xref target="rrep_ack_msgs" pageno="false"
format="default"/>. A link to a neighbor is determined to be unidirectional if
a requested acknowledgement is not received within RREP_Ack_SENT_TIMEOUT, or
bidirectional if the acknowledgement is received within the timeout.
</t><t>For the next hop router on the route toward TargAddr, receipt of the
Route Reply message containing the route to TargAddr is confirmation of
bidirectionality, since a Route Reply message is a reply to a Route Request
message which previously crossed the link in the opposite direction.
</t></list></t><t>To assist with next hop monitoring, a Neighbor Table (<xref
target="nbrlist" pageno="false" format="default"/>) is maintained. When an RREQ
or RREP is received from an IP address which does not already have an entry in
the Neighbor Table, a new entry is created as described in <xref
target="nbrupdate" pageno="false" format="default"/>. While the value of
Neighbor.State is Unknown, acknowledgement of RREP messages sent to that
neighbor MUST be requested. If an acknowledgement is not received within the
timeout period, the neighbor MUST have Neighbor.State set to Blacklisted. If an
acknowledgement is received within the timeout period, Neighbor.State is set to
Confirmed. While the value of Neighbor.State is Confirmed, the request for an
acknowledgement of any other RREP message is unnecessary. </t><t>When routers
perform other operations such as those from the list below, these MAY be used
as additional indications of connectivity: </t><t><list style="symbols"><t>NHDP
HELLO Messages <xref target="RFC6130" pageno="false" format="default"/>
</t><t>Route timeout </t><t>Lower layer triggers, e.g. message reception or
link status notifications </t><t>TCP timeouts </t><t>Promiscuous listening
</t><t>Other monitoring mechanisms or heuristics </t></list></t><t>If such an
external process signals that the link to a neighbor is bidirectional, the
AODVv2 router MAY update the matching Neighbor Table entry by changing the
value of Neighbor.State to Confirmed. If an external process signals that a
link is not bidirectional, the value of Neighbor.State MAY be changed to
Blacklisted. If an external process signals that the link might not be
bidirectional, and the value of Neighbor.State is currently Confirmed, it MAY
be set to Unknown. </t><t>For example, receipt of a Neighborhood Discovery
Protocol HELLO message with the receiving router listed as a neighbor is a
signal of bidirectional connectivity. The AODVv2 router MAY update the matching
Neighbor Table entry by changing the value of Neighbor.State to Confirmed.
</t><t>Similarly, if AODVv2 receives notification of a timeout, for example,
from TCP or some other protocol, this may be due to a disconnection. The AODVv2
router MAY update the matching Neighbor Table entry by setting the value of
Neighbor.State to Unknown. </t></section><section title="Neighbor Table
Update" anchor="nbrupdate" toc="default"><t>On receipt of an RREQ or RREP
message, the Neighbor Table MUST be checked for an entry with
Neighbor.IPAddress which matches the source IP address of the message. If no
matching entry is found, a new entry is created. </t><t>A new Neighbor Table
entry is created as follows: </t><t><list style="symbols"><t>Neighbor.IPAddress
:= Source IP address of the received route message </t><t>Neighbor.State :=
Unknown </t><t>Neighbor.ResetTime := INFINITY_TIME </t></list></t><t>If the
message is an RREP which answers a recently sent RREQ, or an RREP_Ack which
answers a recently sent RREP, the link to the neighbor is bidirectional and the
Neighbor Table entry is updated as follows: </t><t><list
style="symbols"><t>Neighbor.State := Confirmed </t><t>Neighbor.ResetTime :=
INFINITY_TIME </t></list></t><t>If an RREP_Ack is not received within the
expected time, the link is considered to be uni-directional and the Neighbor
Table entry is updated as follows: </t><t><list
style="symbols"><t>Neighbor.State := Blacklisted </t><t>Neighbor.ResetTime :=
CurrentTime + MAX_BLACKLIST_TIME </t></list></t><t>When the Neighbor.ResetTime
is reached, the Neighbor Table entry is updated as follows: </t><t><list
style="symbols"><t>Neighbor.State := Unknown </t></list></t><t>When a link to a
neighbor is determined to be broken, the Neighbor Table entry SHOULD be
removed. </t><t>Route requests from neighbors with Neighbor.State set to
Blacklisted are ignored to avoid persistent IP packet loss or protocol
failures. However, Neighbor.ResetTime allows the neighbor to again be allowed
to participate in route discoveries after MAX_BLACKLIST_TIME, in case the link
between the routers has become bidirectional. </t></section><section
title="Interaction with the Forwarding Plane" anchor="fwdplane"
toc="default"><t>A reactive routing protocol only reacts when a route is
needed, i.e., when an application tries to send a packet and the forwarding
plane has no route to the destination of the packet. </t><t>AODVv2 requires
signals from the forwarding plane: </t><t><list style="symbols"><t>A packet
cannot be forwarded because a route is unavailable: AODVv2 needs to know the
source and destination IP addresses of the packet, to determine if the source
of the packet is configured as a Router Client, in which case the router should
initiate route discovery. If it is not a Router Client, the router should
create a Route Error message. </t><t>A packet is to be forwarded: AODVv2 needs
to check the state of the route to deal with timeouts to ensure the route is
still valid. </t><t>Packet forwarding succeeds: AODVv2 needs to update the
record of when a route was last used to forward a packet. </t><t>Packet
forwarding failure occurs: AODVv2 needs to create a Route Error message.
</t></list></t><t>AODVv2 needs to send signals to the forwarding plane:
</t><t><list style="symbols"><t>A route discovery is in progress: buffering
might be configured for packets requiring a route, while route discovery is
attempted. </t><t>A route discovery failed: any buffered packets requiring
that route should be discarded, and the source of the packet should be notified
that the destination is unreachable (using an ICMP Destination Unreachable
message). Route discovery fails if an RREQ cannot be generated because the
control message generation limit has been reached, or if an RREP is not
received within the expected time. </t><t>A route discovery is not permitted:
any buffered packets requiring that route should be discarded. A route
discovery will not be attempted if the source address of the packet needing a
route is not configured as a Router Client. </t><t>A route discovery
succeeded: install a corresponding route into the Routing Information Base and
begin transmitting any buffered packets. </t><t>A route has been made invalid:
remove the corresponding route from the Routing Information Base. </t><t>A
route has been updated: update the corresponding route in the Routing
Information Base. </t></list></t><t>These are conceptual signals, and can be
implemented in various ways. Conformant implementations of AODVv2 are not
mandated to implement the forwarding plane separately from the control plane or
data plane; these signals and interactions are identified simply as assistance
for implementers who may find them useful. </t></section><section
title="Message Transmission" anchor="MsgXmit" toc="default"><t>AODVv2 sends
<xref target="RFC5444" pageno="false" format="default"/> formatted messages
using the parameters for port number and IP protocol specified in <xref
target="RFC5498" pageno="false" format="default"/>. Mapping of AODVv2 data to
<xref target="RFC5444" pageno="false" format="default"/> messages is detailed
in <xref target="represent" pageno="false" format="default"/>. AODVv2 multicast
messages are sent to the link-local multicast address LL-MANET-Routers <xref
target="RFC5498" pageno="false" format="default"/>. All AODVv2 routers MUST
subscribe to LL-MANET-Routers on all AODVv2 interfaces <xref target="RFC5498"
pageno="false" format="default"/> to receive AODVv2 messages. Note that
multicast messages MAY be sent via unicast. For example, this may occur for
certain link-types (non-broadcast media), for manually configured router
adjacencies, or in order to improve robustness. </t><t>When multiple
interfaces are available, an AODVv2 router transmitting a multicast message to
LL-MANET-Routers MUST send the message on all interfaces that have been
configured for AODVv2 operation, as given in the AODVv2_INTERFACES list (<xref
target="interfaceslist" pageno="false" format="default"/>). </t><t>To avoid
congestion, each AODVv2 router's rate of message generation SHOULD be limited
(CONTROL_TRAFFIC_LIMIT) and administratively configurable. To prioritize
transmission of AODVv2 control messages in order to respect the
CONTROL_TRAFFIC_LIMIT: </t><t><list style="symbols"><t>Highest priority SHOULD
be given to RREP_Ack messages. This allows links between routers to be
confirmed as bidirectional and avoids undesirable blacklisting of next hop
routers. </t><t>Second priority SHOULD be given to RERR messages for
undeliverable IP packets, so that broken routes that are still in use by other
AODVv2 routers can be reported to those routers, to avoid IP data packets being
repeatedly forwarded to AODVv2 routers which cannot forward them to their
destination. </t><t>Third priority SHOULD be given to RREP messages in order
that RREQs do not time out. </t><t>RREQ messages SHOULD be given priority over
RERR messages for newly invalidated routes, since the invalidated routes may
not still be in use, and if there is an attempt to use the route, a new RERR
message will be generated. </t><t>Lowest priority SHOULD be given to RERR
messages generated in response to RREP messages which cannot be regenerated. In
this case the route request will be retried at a later point.
</t></list></t></section><section title="Route Discovery, Retries and
Buffering" anchor="route_discovery" toc="default"><t>AODVv2's RREQ and RREP
messages are used for route discovery. RREQ messages are multicast to solicit
an RREP, whereas RREP is unicast where possible. The constants used in this
section are defined in <xref target="param" pageno="false" format="default"/>.
</t><t>When an AODVv2 router needs to forward an IP packet (with source address
OrigAddr and destination address TargAddr) from one of its Router Clients, it
needs a route to TargAddr in its Routing Information Base. If no route exists,
the AODVv2 router generates and multicasts a Route Request message (RREQ)
containing OrigAddr and TargAddr. The procedure for this is described in <xref
target="RREQ_gen" pageno="false" format="default"/>. Each generated RREQ
results in an increment to the router's sequence number. The AODVv2 router
generating an RREQ is referred to as RREQ_Gen. </t><t>Buffering might be
configured for IP packets awaiting a route for forwarding by RREQ_Gen, if
sufficient memory is available. Buffering of IP packets might have both
positive and negative effects. Real-time traffic, voice, and scheduled delivery
may suffer if packets are buffered and subjected to delays, but TCP connection
establishment will benefit if packets are queued while route discovery is
performed <xref target="Koodli01" pageno="false" format="default"/>. If packets
are not queued, no notification should be sent to the source. Determining which
packets to discard first when the buffer is full is a matter of policy at each
AODVv2 router. </t><t>RREQ_Gen awaits reception of a Route Reply message
(RREP) containing a route toward TargAddr. If a valid route to TargAddr is not
learned within RREQ_WAIT_TIME, RREQ_Gen will retry the route discovery. To
reduce congestion in a network, repeated attempts at route discovery for a
particular target address utilize a binary exponential backoff: for each
additional attempt, the time to wait for receipt of the RREP is multiplied by
2. If the requested route is not learned within the wait period, another RREQ
is sent, up to a total of DISCOVERY_ATTEMPTS_MAX. This is the same technique
used in AODV <xref target="RFC3561" pageno="false" format="default"/>.
</t><t>The RREQ is received by neighboring AODVv2 routers, and processed and
regenerated as described in <xref target="RREQ_msgs" pageno="false"
format="default"/>. Routers learn a potential route to OrigAddr (and other
addresses as indicated by OrigPrefixLen) from the RREQ and store it in the
Local Route Set. The router responsible for TargAddr responds by generating a
Route Reply message (RREP) and sends it back toward RREQ_Gen via the next hop
on the potential route to OrigAddr. Each intermediate router learns the route
to TargAddr (and other addresses as indicated by TargPrefixLen), regenerates
the RREP and sends toward OrigAddr. </t><t>Links which are not bidirectional
cause problems. If a link is unavailable in the direction toward OrigAddr, an
RREP is not received at the next hop, so cannot be regenerated, and it will
never reach RREQ_Gen. However, since routers monitor bidirectionality to next
hops (<xref target="nexthopmonitoring" pageno="false" format="default"/>), the
loss of the RREP will cause the last router which regenerated the RREP to
blacklist the router which did not receive it. Later, a timeout occurs at
RREQ_Gen, and a new RREQ is generated. If the new RREQ arrives via the
blacklisted router, it will be ignored, enabling the RREQ, if also received
from a different neighbor, to discover a different path toward TargAddr.
</t><t>Route discovery is considered to have failed after
DISCOVERY_ATTEMPTS_MAX and the corresponding wait time for an RREP response to
the final RREQ. After the attempted route discovery has failed, RREQ_Gen waits
at least RREQ_HOLDDOWN_TIME before attempting another route discovery to the
same destination, in order to avoid repeatedly generating control traffic that
is unlikely to discover a route. Any IP packets buffered for TargAddr are also
dropped and a Destination Unreachable ICMP message (Type 3) with a code of 1
(Host Unreachable Error) is delivered to the source of the packet, so that the
application knows about the failure. The source might be an application on
RREQ_Gen itself, or on a difference device. </t><t>If RREQ_Gen does receive a
route message containing a route to TargAddr within the timeout, it processes
the message according to <xref target="aodv_msgs" pageno="false"
format="default"/>. When a valid LocalRoute entry is created in the Local Route
Set, the route is also installed in the Routing Information Base, and the
router will begin sending the buffered IP packets. Any retry timers for the
corresponding RREQ are then cancelled. </t><t>During route discovery, all
routers on the path learn a route to both OrigAddr and TargAddr, so that routes
are constructed in both directions. The route is optimized for the forward
route. </t></section><section title="Processing Received Route Information"
anchor="processingrte" toc="default"><t>All AODVv2 route messages contain a
route. A Route Request (RREQ) contains a route toward OrigAddr (and other
addresses as indicated by OrigPrefixLen), and a Route Reply (RREP) contains a
route toward TargAddr (and other addresses as indicated by TargPrefixLen). All
AODVv2 routers that receive a route message are able to store the route
contained within it in their Local Route Set. Incoming information is first
checked to verify that it is both safe to use and offers an improvement to
existing information, as explained in <xref target="test" pageno="false"
format="default"/>. The Local Route Set MAY then be updated according to <xref
target="update_rte" pageno="false" format="default"/>. </t><t>In the processes
below, RteMsg is used to denote the route message, AdvRte is used to denote the
route contained within it, and LocalRoute denotes an existing entry in the
Local Route Set which matches AdvRte on address, prefix length, and metric
type. </t><t>AdvRte has the following properties: </t><t><list
style="symbols"><t>AdvRte.Address := network address given by combining
RteMsg.OrigAddr and RteMsg.OrigPrefixLen (in RREQ) or RteMsg.TargAddr and
RteMsg.TargPrefixLen (in RREP) </t><t>AdvRte.PrefixLength :=
RteMsg.OrigPrefixLen (in RREQ) or RteMsg.TargPrefixLen (in RREP). If no prefix
length was included in RteMsg, prefix length is the address length, in bits, of
RteMsg.OrigAddr (in RREQ) or RteMsg.TargAddr (in RREP) </t><t>AdvRte.SeqNum :=
RteMsg.OrigSeqNum (in RREQ) or RteMsg.TargSeqNum (in RREP)
</t><t>AdvRte.NextHop := RteMsg.IPSourceAddress (an address of the router from
which the RteMsg was received) </t><t>AdvRte.MetricType := RteMsg.MetricType
</t><t>AdvRte.Metric := RteMsg.Metric </t><t>AdvRte.Cost := Cost(R) using the
cost function associated with the route's metric type, i.e. Cost(R) =
AdvRte.Metric + Cost(L), as described in <xref target="metrics" pageno="false"
format="default"/>, where L is the link from the advertising router
</t><t>AdvRte.ValidityTime := RteMsg.ValidityTime, if included
</t></list></t><section title="Evaluating Route Information" anchor="test"
toc="default"><t>An incoming advertised route (AdvRte) is compared to existing
LocalRoutes to determine whether the advertised route is to be used to update
the AODVv2 Local Route Set. The incoming route information MUST be processed as
follows: </t><t><list style="numbers"><t>Search for LocalRoutes in the Local
Route Set matching AdvRte's address, prefix length and metric type <list
style="symbols"><t>If no matching LocalRoute exists, AdvRte MUST be used to
update the Local Route Set. </t><t>If matching LocalRoutes are found, continue
to Step 2. </t></list> </t><t>Compare sequence numbers using the technique
described in <xref target="seqnum" pageno="false" format="default"/> <list
style="symbols"><t>If AdvRte is more recent than all matching LocalRoutes,
AdvRte MUST be used to update the Local Route Set. </t><t>If AdvRte is stale,
AdvRte MUST NOT be used to update the Local Route Set. </t><t>If the sequence
numbers are equal, continue to Step 3. </t></list> </t><t>Check that AdvRte is
safe against routing loops compared to all matching LocalRoutes (see <xref
target="metrics" pageno="false" format="default"/>) <list style="symbols"><t>If
LoopFree(AdvRte, LocalRoute) returns FALSE, AdvRte MUST NOT be used to update
the Local Route Set because using the incoming information might cause a
routing loop. </t><t>If LoopFree(AdvRte, LocalRoute) returns TRUE, continue to
Step 4. </t></list> </t><t>Compare route costs <list style="symbols"><t>If
AdvRte is better than all matching LocalRoutes, it SHOULD be used to update the
Local Route Set because it offers improvement. If it is not used to update the
Local Route Set, the existing non-optimal LocalRoute will continue to be used,
causing data traffic to use a non-optimal route. </t><t>If AdvRte is equal in
cost and LocalRoute is valid, AdvRte SHOULD NOT be used to update the Local
Route Set because it will offer no improvement. </t><t>If AdvRte is worse and
LocalRoute is valid, AdvRte MUST NOT be used to update the Local Route Set
because it does not offer any improvement. </t><t>If AdvRte is not better
(i.e., it is worse or equal) but LocalRoute is Invalid, AdvRte SHOULD be used
to update the Local Route Set because it can safely repair the existing Invalid
LocalRoute. </t></list> </t></list></t><t>If the advertised route is to be
used to update the Local Route Set, the procedure in <xref target="update_rte"
pageno="false" format="default"/> MUST be followed. If not, non-optimal routes
will remain in the Local Route Set. </t></section><section title="Applying
Route Updates" anchor="update_rte" toc="default"><t>After determining that
AdvRte is to be used to update the Local Route Set (as described in <xref
target="test" pageno="false" format="default"/>), the following procedure
applies. </t><t>If AdvRte is learned from an RREQ message, the link to the
next hop neighbor may not be confirmed as bidirectional (see <xref
target="nbrlist" pageno="false" format="default"/>). The route will offer
improvement to the Local Route Set if the neighbor can be confirmed. If there
is no existing matching route, AdvRte allows a corresponding RREP to be sent.
If a matching entry already exists, AdvRte offers potential improvement.
</t><t>The route update is applied as follows: </t><t><list
style="numbers"><t>If no existing entry in the Local Route Set matches AdvRte's
address, prefix length and metric type, continue to Step 4 and create a new
entry in the Local Route Set. </t><t>If two matching LocalRoutes exist in the
Local Route Set, one is a valid route, and one is an Unconfirmed route. AdvRte
may offer further improvement to the Unconfirmed route, or may offer an update
to the valid route. <list style="symbols"><t>If AdvRte.NextHop's
Neighbor.State is Unknown, the advertised route may offer improvement to the
existing valid route, if the link to the next hop can be confirmed as
bidirectional. Continue processing from Step 5 to update the existing
Unconfirmed LocalRoute. </t><t>If AdvRte.NextHop's Neighbor.State is
Confirmed, the advertised route offers an update or improvement to the existing
valid route. Continue processing from Step 5 to update the existing valid
LocalRoute. </t></list> </t><t>If only one matching LocalRoute exists in the
Local Route Set: <list style="symbols"><t>If AdvRte.NextHop's Neighbor.State is
Confirmed, continue processing from Step 5 to update the existing LocalRoute.
</t><t>If AdvRte.NextHop's Neighbor.State is Unknown, AdvRte may offer
improvement the existing LocalRoute, if the link to AdvRte.NextHop can be
confirmed as bidirectional. </t><t>If LocalRoute.State is Unconfirmed, AdvRte
is an improvement to an existing Unconfirmed route. Continue processing from
Step 5 to update the existing LocalRoute. </t><t>If LocalRoute.State is
Invalid, AdvRte can replace the existing LocalRoute. Continue processing from
Step 5 to update the existing LocalRoute. </t><t>If LocalRoute.State is Active
or Idle, AdvRte SHOULD be stored as an additional entry in the Local Route Set,
with LocalRoute.State set to Unconfirmed. Continue processing from Step 4 to
create a new LocalRoute. </t></list> </t><t>Create an entry in the Local Route
Set and initialize as follows: <list style="symbols"><t>LocalRoute.Address :=
AdvRte.Address </t><t>LocalRoute.PrefixLength := AdvRte.PrefixLength
</t><t>LocalRoute.MetricType := AdvRte.MetricType </t></list> </t><t>Update the
LocalRoute as follows: <list style="symbols"><t>LocalRoute.SeqNum :=
AdvRte.SeqNum </t><t>LocalRoute.NextHop := AdvRte.NextHop
</t><t>LocalRoute.NextHopInterface := interface on which RteMsg was received
</t><t>LocalRoute.Metric := AdvRte.Cost </t><t>LocalRoute.LastUsed :=
CurrentTime </t><t>LocalRoute.LastSeqNumUpdate := CurrentTime
</t><t>LocalRoute.ExpirationTime := CurrentTime + AdvRte.ValidityTime if a
validity time exists, otherwise INFINITY_TIME </t></list> </t><t>If a new
LocalRoute was created, or if the existing LocalRoute.State is Invalid or
Unconfirmed, update LocalRoute as follows: <list
style="symbols"><t>LocalRoute.State := Unconfirmed (if the next hop's
Neighbor.State is Unknown) </t><t>LocalRoute.State := Idle (if the next hop's
Neighbor.State is Confirmed) </t></list> </t><t>If an existing LocalRoute.State
changed from Invalid or Unconfirmed to become Idle, any matching Unconfirmed
LocalRoute with worse metric value SHOULD be expunged. </t><t>If an existing
LocalRoute was updated with a better metric value, any matching Unconfirmed
LocalRoute with worse metric value SHOULD be expunged. </t><t>If this update
results in LocalRoute.State of Active or Idle, which matches a route request
which is still in progress, the associated route request retry timers can be
cancelled. </t></list></t><t>If this update to the Local Route Set results in
two LocalRoutes to the same address, the best LocalRoute will be Unconfirmed.
In order to improve the route used for forwarding, the router SHOULD try to
determine if the link to the next hop of that LocalRoute is bidirectional, by
using that LocalRoute to forward future RREPs and request acknowledgements (see
<xref target="RREP_gen" pageno="false" format="default"/>).
</t></section></section><section title="Suppressing Redundant Messages Using
the Multicast Route Message Table" anchor="suppress" toc="default"><t>When
route messages are flooded in a MANET, an AODVv2 router may receive multiple
similar messages. Regenerating every one of these gives little additional
benefit, and generates unnecessary signaling traffic and might generate
unnecessary interference. </t><t>Each AODVv2 router stores information about
recently received route messages in the AODVv2 Multicast Route Message Table
(<xref target="rtemsgtable" pageno="false" format="default"/>). </t><t>To
create a Multicast Route Message Table Entry: </t><t><list
style="symbols"><t>RteMsg.MessageType := RREQ or RREP </t><t>RteMsg.OrigAddr :=
OrigAddr from the message </t><t>RteMsg.OrigPrefixLen := the prefix length
associated with OrigAddr </t><t>RteMsg.TargAddr := TargAddr from the message
</t><t>RteMsg.TargPrefixLen := the prefix length associated with TargAddr
</t><t>RteMsg.OrigSeqNum := the sequence number associated with OrigAddr, if
present in the message </t><t>RteMsg.TargSeqNum := the sequence number
associated with TargAddr, if present in the message </t><t>RteMsg.MetricType :=
the metric type of the route requested </t><t>RteMsg.Metric := the metric value
associated with OrigAddr in an RREQ or TargAddr in an RREP
</t><t>RteMsg.Timestamp := CurrentTime </t><t>RteMsg.RemoveTime := CurrentTime
+ MAX_SEQNUM_LIFETIME </t></list></t><t>Entries in the Multicast Route Message
Table SHOULD be maintained for at least RteMsg_ENTRY_TIME after the last
Timestamp update in order to account for long-lived RREQs traversing the
network. An entry MUST be deleted when the sequence number is no longer valid,
i.e., after MAX_SEQNUM_LIFETIME. Memory-constrained devices MAY remove the
entry before this time. </t><t>Received route messages are tested against
previously received route messages, and if determined to be redundant,
regeneration or response can be avoided. </t><t>To determine if a received
message is redundant: </t><t><list style="numbers"><t>Search for an entry in
the Multicast Route Message Table with the same MessageType, OrigAddr,
TargAddr, and MetricType <list style="symbols"><t>If there is no entry, the
message is not redundant. </t><t>If there is an entry, continue to Step 2.
</t></list> </t><t>Compare sequence numbers using the technique described in
<xref target="seqnum" pageno="false" format="default"/> <list
style="symbols"><t>For RREQ messages, use OrigSeqNum of the entry for
comparison. For RREP messages, use TargSeqNum of the entry for comparison.
</t><t>If the entry has an older sequence number than the received message, the
message is not redundant. </t><t>If the entry has a newer sequence number than
the received message, the message is redundant. </t><t>If the entry has the
same sequence number, continue to Step 3. </t></list> </t><t>Compare the
metric values <list style="symbols"><t>If the entry has a Metric value that is
worse than or equal to the metric in the received message, the message is
redundant. </t><t>If the entry has a Metric value that is better than the
metric in the received message, the message is not redundant. </t></list>
</t></list></t><t>If the message is redundant, update the Timestamp and
RemoveTime on the entry, since matching route messages are still traversing the
network and this entry should be maintained. This message MUST NOT be
regenerated or responded to. </t><t>If the message is not redundant, create an
entry or update the existing entry. </t><t>To update a Multicast Route Message
Table entry, set: </t><t><list style="symbols"><t>RteMsg.OrigSeqNum := the
sequence number associated with OrigAddr, if present in the received message
</t><t>RteMsg.TargSeqNum := the sequence number associated with TargAddr, if
present in the received message </t><t>RteMsg.Metric := the metric value
associated with OrigAddr in a received RREQ or TargAddr in a received RREP
</t><t>RteMsg.Timestamp := CurrentTime </t><t>RteMsg.RemoveTime := CurrentTime
+ MAX_SEQNUM_LIFETIME </t></list></t><t>Where the message is determined not
redundant before Step 3, it MUST be regenerated or responded to. Where the
message is determined not redundant in Step 3, it MAY be suppressed to avoid
extra control traffic. However, since the processing of the message will result
in an update to the Local Route Set, the message SHOULD be regenerated or
responded to, to ensure other routers have up-to-date information and the best
metrics. If not regenerated, the best route may not be found. Where necessary,
regeneration or response is performed using the processes in <xref
target="aodv_msgs" pageno="false" format="default"/>. </t></section><section
title="Local Route Set Maintenance" anchor="route_maint" toc="default"><t>Route
maintenance involves monitoring LocalRoutes in the Local Route Set, updating
LocalRoute.State to handle route timeouts and reporting routes that become
Invalid. </t><section title="LocalRoute State Changes"
anchor="routestatechanges" toc="default"><t>During normal operation, AODVv2
does not require any explicit timeouts to manage the lifetime of a route. At
any time, any LocalRoute MAY be examined and updated according to the rules
below. If timers are not used to prompt updates of LocalRoute.State, the
LocalRoute.State MUST be checked before IP packet forwarding and before any
operation based on LocalRoute.State. </t><t>Route timeout behaviour is as
follows: </t><t><list style="symbols"><t>An Unconfirmed route MUST be expunged
at MAX_SEQNUM_LIFETIME after LocalRoute.LastSeqNumUpdate. </t><t>An Idle route
MUST become Active when used to forward an IP packet. If the route is not used
to forward an IP packet within MAX_IDLETIME, LocalRoute.State MUST become
Invalid. </t><t>An Active route which is a timed route (i.e., with
LocalRoute.ExpirationTime not equal to INFINITY_TIME) remains Active until
LocalRoute.ExpirationTime, after which it MUST become Invalid. If it it not a
timed route, it MUST become Idle if the route is not used to forward an IP
packet within ACTIVE_INTERVAL. </t><t>An Invalid route SHOULD remain in the
Local Route Set, since LocalRoute.SeqNum is used to classify future information
about LocalRoute.Address as stale or fresh. </t><t>In all cases, if the time
since LocalRoute.LastSeqNumUpdate exceeds MAX_SEQNUM_LIFETIME,
LocalRoute.SeqNum must be set to zero. This is required to ensure that any
AODVv2 routers following the initialization procedure can safely begin routing
functions using a new sequence number, and that their messages will not be
classified as stale and ignored. A LocalRoute with LocalRoute.State set to
Active or Idle can remain in the Local Route Set after removing the sequence
number, but if LocalRoute.State is Invalid, or later becomes Invalid, the
LocalRoute MUST be expunged from the Local Route Set.
</t></list></t><t>LocalRoutes can become Invalid before a timeout occurs:
</t><t><list style="symbols"><t>If a link breaks, all LocalRoutes using that
link for LocalRoute.NextHop MUST immediately have LocalRoute.State set to
Invalid. </t><t>If a Route Error (RERR) message containing the route is
received, either from LocalRoute.NextHop, or with PktSource set to a Router
Client address, LocalRoute.State MUST immediately be set to Invalid.
</t></list></t><t>LocalRoutes are also updated when Neighbor.State is updated:
</t><t><list style="symbols"><t>While the value of Neighbor.State is set to
Unknown, any routes in the Local Route Set using that neighbor as a next hop
MUST have LocalRoute.State set to Unconfirmed. </t><t>When the value of
Neighbor.State is set to Confirmed, the Unconfirmed routes in the Local Route
Set using that neighbor as a next hop MUST have LocalRoute.State set to Idle.
Any other matching LocalRoutes with metric values worse than LocalRoute.Metric
MUST be expunged from the Local Route Set. </t><t>When the value of
Neighbor.State is set to Blacklisted, any valid routes in the Local Route Set
using that neighbor for their next hop MUST have LocalRoute.State set to
Invalid. </t><t>When a Neighbor Table entry is removed, all routes in the
Local Route Set using that neighbor as next hop MUST have LocalRoute.State set
to Invalid. </t></list></t><t>In some cases, by setting LocalRoute.State to
Confirmed when Neighbor.State is set to Confirmed, an issue can occur if data
packets are forwarded to LocalRoute.Address before the links that form the rest
of the route are confirmed as bidirectional. Intermediate routers will not
have a valid route to forward these data packets, and will generate a Route
Error message. This in turn results in routes to that destination being
removed from other routers. However, subsequent data packets will cause a new
route discovery attempt to be initiated by the router with the source address
of the data packet configured as a Router Client. </t><t>Memory constrained
devices MAY choose to expunge routes from the AODVv2 Local Route Set before
LocalRoute.ExpirationTime, but MUST adhere to the following rules: </t><t><list
style="symbols"><t>An Active route MUST NOT be expunged, as it is in use. If
deleted, IP traffic forwarded to this router will prompt generation of a Route
Error message, and it will be necessary for a Route Request to be generated by
the originator's router to re-establish the route. </t><t>An Idle route SHOULD
NOT be expunged, as it is still valid for forwarding IP traffic. If deleted,
this could result in dropped IP packets and a Route Request could be generated
to re-establish the route. </t><t>Any Invalid route MAY be expunged. Least
recently used Invalid routes SHOULD be expunged first, since the sequence
number information is less likely to be useful. </t><t>An Unconfirmed route
MUST NOT be expunged if it was installed within the last RREQ_WAIT_TIME,
because it may correspond to a route discovery in progress. A Route Reply
message might be received which needs to use the LocalRoute.NextHop
information. Otherwise, it MAY be expunged. </t></list></t></section><section
title="Reporting Invalid Routes" anchor="brokenrerr" toc="default"><t>When
LocalRoute.State changes from Active to Invalid as a result of a broken link or
a received Route Error (RERR) message, other AODVv2 routers MUST be informed by
sending an RERR message containing details of the invalidated route. </t><t>An
RERR message MUST also be sent when an AODVv2 router receives an IP packet to
forward on behalf of another router but does not have a valid route in its
Routing Information Base for the destination of the packet. </t><t>An RERR
message MUST also be sent when an AODVv2 router receives an RREP message to
regenerate, but the LocalRoute to the OrigAddr in the RREP has been lost or is
marked as Invalid. </t><t>The packet or message triggering the RERR MUST be
discarded. </t><t>Generation of an RERR message is described in <xref
target="RERR_gen" pageno="false" format="default"/>.
</t></section></section></section><section title="AODVv2 Protocol Messages"
anchor="aodv_msgs" toc="default"><t>AODVv2 defines four message types: Route
Request (RREQ), Route Reply (RREP), Route Reply Acknowledgement (RREP_Ack), and
Route Error (RERR). </t><t>Each AODVv2 message is defined as a set of data.
Rules for the generation, reception and regeneration of each message type are
described in the following sections. <xref target="represent" pageno="false"
format="default"/> discusses how the data is mapped to <xref target="RFC5444"
pageno="false" format="default"/> Message TLVs, Address Blocks, and Address
TLVs. </t><section title="Route Request (RREQ) Message" anchor="RREQ_msgs"
toc="default"><t>Route Request messages are used in route discovery operations
to request a route to a specified target address. RREQ messages have the
following contents: </t><figure anchor="RREQ_elem" align="center" title="RREQ
message contents" suppress-title="false" alt="" width="" height=""><artwork
align="center" xml:space="preserve" name="" type="" alt="" width="" height="">
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| OrigSeqNum, (optional) TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| OrigMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
</artwork></figure><t></t><t><list style="hanging"><t
hangText="AddressList"><vspace blankLines="0"/>Contains OrigAddr and TargAddr,
the source and destination addresses of the IP packet for which a route is
requested. OrigAddr and TargAddr MUST be routable unicast addresses. </t><t
hangText="PrefixLengthList"><vspace blankLines="0"/>Contains OrigPrefixLen,
i.e., the length, in bits, of the prefix associated with the Router Client
entry which includes OrigAddr. If omitted, the prefix length is equal to
OrigAddr's address length in bits. </t><t hangText="OrigSeqNum"><vspace
blankLines="0"/>The sequence number associated with OrigAddr. </t><t
hangText="TargSeqNum"><vspace blankLines="0"/>A sequence number associated with
an existing Invalid route to TargAddr. This MAY be included if available, and
is useful for the optional Intermediate RREP feature (see <xref target="iRREP"
pageno="false" format="default"/>). </t><t hangText="MetricType"><vspace
blankLines="0"/>The metric type associated with OrigMetric. </t><t
hangText="OrigMetric"><vspace blankLines="0"/>The metric value associated with
the LocalRoute to OrigAddr (and to any other addresses included in the given
prefix length), as seen from the sender of the message. </t><t
hangText="ValidityTime"><vspace blankLines="0"/>The length of time that the
message sender is willing to offer a route toward OrigAddr (and any other
addresses included in the given prefix length). Omitted if no time limit is
imposed. </t></list></t><section title="RREQ Generation" anchor="RREQ_gen"
toc="default"><t>An RREQ is generated when an IP packet needs to be forwarded
for a Router Client, and no valid route currently exists for the packet's
destination in the Routing Information Base. </t><t>Before creating an RREQ,
the router SHOULD check if an RREQ has recently been sent for the requested
destination. If so, and the wait time for a reply has not yet been reached, the
router SHOULD continue to await a response without generating a new RREQ. If
the timeout has been reached, a new RREQ MAY be generated. If buffering is
configured, incoming IP packets awaiting this route SHOULD be buffered until
the route discovery is completed. </t><t>If the limit for the rate of AODVv2
control message generation has been reached, no message SHOULD be generated. If
approaching the limit, the message should be sent if the priorities in <xref
target="MsgXmit" pageno="false" format="default"/> allow it. </t><t>To
generate the RREQ, the router (referred to as RREQ_Gen) follows this procedure:
</t><t><list style="numbers"><t>Set AddressList := {OrigAddr, TargAddr}
</t><t>For the PrefixLengthList: <list style="symbols"><t>If OrigAddr is part
of an address range configured as a Router Client, set PrefixLengthList :=
{RouterClient.PrefixLength, null}. This allows receiving routers to learn a
route to all the addresses included by the prefix length, not only to OrigAddr.
</t><t>Otherwise, omit PrefixLengthList. </t></list> </t><t>For OrigSeqNum:
<list style="symbols"><t>Increment the router SeqNum as specified in <xref
target="seqnum" pageno="false" format="default"/>. </t><t>Set OrigSeqNum :=
SeqNum. </t></list> </t><t>For TargSeqNum: <list style="symbols"><t>If an
Invalid route exists in the Local Route Set matching TargAddr using longest
prefix matching and has a valid sequence number, set TargSeqNum :=
LocalRoute.SeqNum. </t><t>If no Invalid route exists in the Local Route Set
matching TargAddr, or the route doesn't have a sequence number, omit
TargSeqNum. </t></list> </t><t>Include MetricType and set the type accordingly
</t><t>Set OrigMetric := RouterClient.Cost for the Router Client entry which
includes OrigAddr </t><t>Include ValidityTime if advertising that the route to
OrigAddr (and any other addresses included in the given prefix length) via this
router is offered for a limited time, and set ValidityTime accordingly
</t></list></t><t>This AODVv2 message is used to create a corresponding <xref
target="RFC5444" pageno="false" format="default"/> message (see <xref
target="represent" pageno="false" format="default"/>) which is multicast, by
default, to LL-MANET-Routers on all interfaces configured for AODVv2 operation.
</t></section><section title="RREQ Reception" anchor="RREQ_rcv"
toc="default"><t>Upon receiving a Route Request, an AODVv2 router performs the
following steps: </t><t><list style="numbers"><t>Update the Neighbor Table
according to <xref target="nbrupdate" pageno="false" format="default"/> <list
style="symbols"><t>If the sender has Neighbor.State set to Blacklisted after
the update, ignore this RREQ for further processing. </t></list> </t><t>Verify
that the message contains the required data: OrigAddr, TargAddr, OrigSeqNum,
and OrigMetric, and that OrigAddr and TargAddr are valid addresses (routable
and unicast) <list style="symbols"><t>If not, ignore this RREQ for further
processing. </t></list> </t><t>Check that the MetricType is supported and
configured for use <list style="symbols"><t>If not, ignore this RREQ for
further processing. </t></list> </t><t>Verify that the cost of the advertised
route will not exceed the maximum allowed metric value for the metric type
(Metric <= MAX_METRIC[MetricType] - Cost(L)) <list style="symbols"><t>If it
will, ignore this RREQ for further processing. </t></list> </t><t>Process the
route to OrigAddr (and any other addresses included in the given prefix length)
as specified in <xref target="processingrte" pageno="false" format="default"/>
</t><t>Check if the information in the message is redundant by comparing to
entries in the Multicast Route Message table, following the procedure in <xref
target="suppress" pageno="false" format="default"/> <list style="symbols"><t>If
redundant, ignore this RREQ for further processing. </t><t>If not redundant,
continue processing. </t></list> </t><t>Check if the TargAddr belongs to one
of the Router Clients <list style="symbols"><t>If so, generate an RREP as
specified in <xref target="RREP_gen" pageno="false" format="default"/>.
</t><t>If not, continue to RREQ regeneration. </t></list>
</t></list></t></section><section title="RREQ Regeneration" anchor="RREQ_regen"
toc="default"><t>By regenerating an RREQ, a router advertises that it will
forward IP packets to the OrigAddr contained in the RREQ (and to other
addresses included in the given prefix length) according to the information
enclosed. The router MAY choose not to regenerate the RREQ, for example if the
router is heavily loaded or low on energy and therefore unwilling to advertise
routing capability for more traffic. This could, however, decrease connectivity
in the network or result in non-optimal paths. </t><t>The RREQ SHOULD NOT be
regenerated if the limit for the rate of AODVv2 control message generation has
been reached. If approaching the limit, the message should be sent if the
priorities in <xref target="MsgXmit" pageno="false" format="default"/> allow
it. </t><t>The procedure for RREQ regeneration is as follows: </t><t><list
style="numbers"><t>Set AddressList, PrefixLengthList, sequence numbers and
MetricType to the values in the received RREQ </t><t>Set OrigMetric :=
LocalRoute[OrigAddr].Metric </t><t>If the received RREQ contains a
ValidityTime, or if the regenerating router wishes to limit the time that it
offers a route to OrigAddr (and any other addresses included in the given
prefix length), the regenerated RREQ MUST include ValidityTime <list
style="symbols"><t>The ValidityTime is either the time limit the previous
AODVv2 router specified, or the time limit this router wishes to impose,
whichever is lower. </t></list> </t></list></t><t>This AODVv2 message is used
to create a corresponding <xref target="RFC5444" pageno="false"
format="default"/> message (see <xref target="represent" pageno="false"
format="default"/>) which is multicast, by default, to LL-MANET-Routers on all
interfaces configured for AODVv2 operation. However, the regenerated RREQ can
be unicast to the next hop address of the LocalRoute toward TargAddr, if known.
</t></section></section><section title="Route Reply (RREP) Message"
anchor="RREP_msgs" toc="default"><t>When a Route Request message is received,
requesting a route to a target address (TargAddr) which is configured as part
of a Router Client entry, a Route Reply message is sent in response. The RREP
offers a route to TargAddr (and any other addresses included in the prefix
length). </t><t>RREP messages have the following contents: </t><figure
anchor="figRREP" align="center" title="RREP message contents"
suppress-title="false" alt="" width="" height=""><artwork align="center"
xml:space="preserve" name="" type="" alt="" width="" height="">
+-----------------------------------------------------------------+
| AckReq (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| TargSeqNum |
+-----------------------------------------------------------------+
| MetricType |
+-----------------------------------------------------------------+
| TargMetric |
+-----------------------------------------------------------------+
| ValidityTime (optional) |
+-----------------------------------------------------------------+
</artwork></figure><t></t><t><list style="hanging"><t hangText="AckReq"><vspace
blankLines="0"/>The address of the intended next hop of the RREP. This is
included when the link to the next hop toward OrigAddr is not known to be
bidirectional. It indicates that an acknowledgement of the RREP is requested by
the sender from the intended next hop (see <xref target="nexthopmonitoring"
pageno="false" format="default"/>). </t><t hangText="AddressList"><vspace
blankLines="0"/>Contains OrigAddr and TargAddr, the source and destination
addresses of the IP packet for which a route is requested. OrigAddr and
TargAddr MUST be routable unicast addresses. </t><t
hangText="PrefixLengthList"><vspace blankLines="0"/>Contains TargPrefixLen,
i.e., the length, in bits, of the prefix associated with the Router Client
entry which includes TargAddr. If omitted, the prefix length is equal to
TargAddr's address length, in bits. </t><t hangText="TargSeqNum"><vspace
blankLines="0"/>The sequence number associated with TargAddr. </t><t
hangText="MetricType"><vspace blankLines="0"/>The metric type associated with
TargMetric. </t><t hangText="TargMetric"><vspace blankLines="0"/>The metric
value associated with the LocalRoute to TargAddr (and any other addresses
included in the given prefix length), as seen from the sender of the message.
</t><t hangText="ValidityTime"><vspace blankLines="0"/>The length of time that
the message sender is willing to offer a route toward TargAddr (and any other
addresses included in the given prefix length). Omitted if no time limit is
imposed. </t></list></t><section title="RREP Generation" anchor="RREP_gen"
toc="default"><t>A Route Reply message is generated when a Route Request
arrives, requesting a route to an address which is configured as a Router
Client of the AODVv2 router. </t><t>Before creating an RREP, the router SHOULD
check if the corresponding RREQ is redundant, i.e., a Route Reply has already
been generated in response to the RREQ, or if the limit for the rate of AODVv2
control message generation has been reached. If so, the RREP SHOULD NOT be
created. If approaching the limit, the message should be sent if the priorities
in <xref target="MsgXmit" pageno="false" format="default"/> allow it.
</t><t>The RREP will follow the path of the route to OrigAddr. If the best
route to OrigAddr in the Local Route Set is Unconfirmed, the link to the next
hop neighbor is not yet confirmed as bidirectional (as described in <xref
target="nexthopmonitoring" pageno="false" format="default"/>). In this case the
RREP MUST include AckReq set to the intended next hop address. The AckReq
indicates that an acknowledgement to the RREP is requested from the intended
next hop router in the form of a Route Reply Acknowledgement (RREP_Ack). If the
best route to OrigAddr in the Local Route Set is valid, the link to the next
hop neighbor is already confirmed as bidirectional, and the AckReq can be
omitted. </t><t>Implementations MAY allow a number of retries of the RREP if a
requested acknowledgement is not received within RREP_Ack_SENT_TIMEOUT,
doubling the timeout with each retry, up to a maximum of RREP_RETRIES, using
the same exponential backoff described in <xref target="route_discovery"
pageno="false" format="default"/> for RREQ retries. The acknowledgement MUST be
considered to have failed after the wait time for an RREP_Ack response to the
final RREP. </t><t>To generate the RREP, the router (also referred to as
RREP_Gen) follows this procedure: </t><t><list style="numbers"><t>If the link
to the next hop router toward OrigAddr is not known to be bidirectional,
include the AckReq with the address of the intended next hop router </t><t>Set
Address List := {OrigAddr, TargAddr} </t><t>For the PrefixLengthList: <list
style="symbols"><t>If TargAddr is part of an address range configured as a
Router Client, set PrefixLengthList := {null, RouterClient.PrefixLength}. This
allows receiving routers to learn a route to all the addresses included by the
prefix length, not only to TargAddr. </t><t>Otherwise, omit PrefixLengthList.
</t></list> </t><t>For the TargSeqNum: <list style="symbols"><t>Increment the
router SeqNum as specified in <xref target="seqnum" pageno="false"
format="default"/>. </t><t>Set TargSeqNum := SeqNum. </t></list>
</t><t>Include MetricType and set the type to match the MetricType in the
received RREQ message </t><t>Set TargMetric := RouterClient.Cost for the Router
Client entry which includes TargAddr </t><t>Include ValidityTime if advertising
that the route to TargAddr (and any other addresses included in the given
prefix length) via this router is offered for a limited time, and set
ValidityTime accordingly </t></list></t><t>This AODVv2 message is used to
create a corresponding <xref target="RFC5444" pageno="false" format="default"/>
message (see <xref target="represent" pageno="false" format="default"/>). If
the Neighbor Table contains an entry for the neighbor stored as
LocalRoute[OrigAddr].NextHop, with Neighbor.State set to Confirmed, the RREP is
sent by unicast to LocalRoute[OrigAddr].NextHop. Otherwise, the RREP is sent
multicast to LL-MANET-Routers. </t></section><section title="RREP Reception"
anchor="RREP_rcv" toc="default"><t>Upon receiving a Route Reply, an AODVv2
router performs the following steps: </t><t><list style="numbers"><t>Verify
that the message contains the required data: OrigAddr, TargAddr, TargSeqNum,
and TargMetric, and that OrigAddr and TargAddr are valid addresses (routable
and unicast) <list style="symbols"><t>If not, ignore this RREP for further
processing. </t></list> </t><t>Check that the MetricType is supported and
configured for use <list style="symbols"><t>If not, ignore this RREP for
further processing. </t></list> </t><t>If this RREP does not correspond to a
RREQ generated or regenerated in the last RREQ_WAIT_TIME, ignore for further
processing. <vspace blankLines="0"/> </t><t>Update the Neighbor Table
according to <xref target="nbrupdate" pageno="false" format="default"/>
</t><t>Verify that the cost of the advertised route does not exceed the maximum
allowed metric value for the metric type (Metric <= MAX_METRIC[MetricType] -
Cost(L)) <list style="symbols"><t>If it does, ignore this RREP for further
processing. </t></list> </t><t>If the AckReq is present, check the intended
recipient of the received RREP <list style="symbols"><t>If the receiving router
is the intended recipient, send an acknowledgement as specified in <xref
target="rrep_ack_msgs" pageno="false" format="default"/> and continue
processing. </t><t>If the receiving router is not the intended recipient,
ignore this RREP for further processing. </t></list> </t><t>Process the route
to TargAddr (and any other addresses included in the given prefix length) as
specified in <xref target="processingrte" pageno="false" format="default"/>
</t><t>Check if the message is redundant by comparing to entries in the
Multicast Route Message table (<xref target="suppress" pageno="false"
format="default"/>) <list style="symbols"><t>If redundant, ignore this RREP for
further processing. </t><t>If not redundant, save the information in the
Multicast Route Message table to identify future redundant RREP messages and
continue processing. </t></list> </t><t>Check if the OrigAddr belongs to one
of the Router Clients <list style="symbols"><t>If so, no further processing is
necessary. </t><t>If not, continue to Step 10. </t></list> </t><t>Check if a
valid (Active or Idle) or Unconfirmed LocalRoute exists to OrigAddr <list
style="symbols"><t>If so, continue to RREP regeneration. </t><t>If not, a
Route Error message SHOULD be transmitted to TargAddr according to <xref
target="RERR_gen" pageno="false" format="default"/> and the RREP SHOULD be
discarded and not regenerated. </t></list> </t></list></t></section><section
title="RREP Regeneration" anchor="RREP_regen" toc="default"><t>A received Route
Reply message is regenerated toward OrigAddr. Unless the router is prepared to
advertise the route contained within the received RREP, it halts processing. By
regenerating a RREP, a router advertises that it will forward IP packets to
TargAddr (and any other addresses included in the given prefix length)
according to the information enclosed. The router MAY choose not to regenerate
the RREP, in the same way it MAY choose not to regenerate an RREQ (see <xref
target="RREQ_regen" pageno="false" format="default"/>), though this could
decrease connectivity in the network or result in non-optimal paths.
</t><t>The RREP SHOULD NOT be regenerated if the limit for the rate of AODVv2
control message generation has been reached. If approaching the limit, the
message should be sent if the priorities in <xref target="MsgXmit"
pageno="false" format="default"/> allow it. </t><t>If the link to the next hop
neighbor on the LocalRoute to OrigAddr is not yet confirmed as bidirectional
(as described in <xref target="nexthopmonitoring" pageno="false"
format="default"/>), the RREP MUST include AckReq set to the intended next hop
address, in order to perform next hop monitoring. If bidirectionality is
already confirmed, the AckReq can be omitted. The AckReq indicates that an
acknowledgement to the RREP is requested in the form of a Route Reply
Acknowledgement (RREP_Ack) from the intended next hop router, within
RREP_Ack_SENT_TIMEOUT. </t><t>The procedure for RREP regeneration is as
follows: </t><t><list style="numbers"><t>If the link to the next hop router
toward OrigAddr is not known to be bidirectional, include the AckReq with the
address of the intended next hop router </t><t>Set AddressList,
PrefixLengthList, TargSeqNum and MetricType to the values in the received RREP
</t><t>Set TargMetric := LocalRoute[TargAddr].Metric </t><t>If the received
RREP contains a ValidityTime, or if the regenerating router wishes to limit the
time that it will offer a route to TargAddr (and any other addresses included
in the given prefix length), the regenerated RREP MUST include ValidityTime
<list style="symbols"><t>The ValidityTime is either the time limit the previous
AODVv2 router specified, or the time limit this router wishes to impose,
whichever is lower. </t></list> </t></list></t><t>This AODVv2 message is used
to create a corresponding <xref target="RFC5444" pageno="false"
format="default"/> message (see <xref target="represent" pageno="false"
format="default"/>). If the Neighbor Table contains an entry for the neighbor
stored as LocalRoute[OrigAddr].NextHop, with Neighbor.State set to Confirmed,
the RREP is sent by unicast to LocalRoute[OrigAddr].NextHop. Otherwise, the
RREP is sent multicast to LL-MANET-Routers. </t></section></section><section
title="Route Reply Acknowledgement (RREP_Ack) Message" anchor="rrep_ack_msgs"
toc="default"><t>The Route Reply Acknowledgement is a response to a Route Reply
message. When the RREP_Ack message is received by the sender of the RREP, it
confirms that the link between the two routers is bidirectional (see <xref
target="nexthopmonitoring" pageno="false" format="default"/>). The RREP_Ack has
no further data. </t><section title="RREP_Ack Generation"
anchor="RREP_Ack_gen" toc="default"><t>An RREP_Ack MUST be generated if a
received Route Reply includes an AckReq with an address matching one of the
receiving router's IP addresses. The RREP_Ack SHOULD NOT be generated if the
limit for the rate of AODVv2 control message generation has been reached.
</t><t>There is no further data in an RREP_Ack. The <xref target="RFC5444"
pageno="false" format="default"/> representation is discussed in <xref
target="represent" pageno="false" format="default"/>. The RREP_Ack is unicast,
by default, to the source IP address of the RREP message that requested it.
</t></section><section title="RREP_Ack Reception" anchor="RREP_Ack_rcv"
toc="default"><t>Upon receiving an RREP_Ack, an AODVv2 router performs the
following steps: </t><t><list style="numbers"><t>Check if the RREP_Ack was
expected from the IP source address of the RREP_Ack, in response to an RREP
sent previously by this router <list style="symbols"><t>If it was expected, the
router cancels any associated timeouts and processing continues to Step 2.
</t><t>If it was not expected, no actions are required and processing ends.
</t></list> </t><t>Update the Neighbor Table according to <xref
target="nbrupdate" pageno="false" format="default"/>
</t></list></t></section></section><section title="Route Error (RERR) Message"
anchor="RERR_msgs" toc="default"><t>A Route Error message is generated by an
AODVv2 router to notify other AODVv2 routers of routes that are no longer
available. An RERR message has the following contents: </t><figure
anchor="figRERRstruct" align="center" title="RERR message contents"
suppress-title="false" alt="" width="" height=""><artwork align="center"
xml:space="preserve" name="" type="" alt="" width="" height="">
+-----------------------------------------------------------------+
| PktSource (optional) |
+-----------------------------------------------------------------+
| AddressList |
+-----------------------------------------------------------------+
| PrefixLengthList (optional) |
+-----------------------------------------------------------------+
| SeqNumList (optional) |
+-----------------------------------------------------------------+
| MetricTypeList |
+-----------------------------------------------------------------+
</artwork></figure><t></t><t><list style="hanging"><t
hangText="PktSource"><vspace blankLines="0"/>The source address of the IP
packet triggering the RERR. If the RERR is triggered by a broken link,
PktSource is not required. </t><t hangText="AddressList"><vspace
blankLines="0"/>The addresses of the routes not available through RERR_Gen.
</t><t hangText="PrefixLengthList"><vspace blankLines="0"/>The prefix lengths,
in bits, associated with the routes not available through RERR_Gen. These
values indicate whether routes represent a single device or an address range.
</t><t hangText="SeqNumList"><vspace blankLines="0"/>The sequence numbers of
the routes not available through RERR_Gen (where known). </t><t
hangText="MetricTypeList"><vspace blankLines="0"/>The metric types associated
with the routes not available through RERR_Gen. </t></list></t><section
title="RERR Generation" anchor="RERR_gen" toc="default"><t>A Route Error
message is generated when an AODVv2 router (also referred to as RERR_Gen) needs
to report that a destination is not reachable. There are three events that
cause this response: </t><t><list style="symbols"><t>When an IP packet that has
been forwarded from another router, but cannot be forwarded further because
there is no valid route in the Routing Information Base for its destination,
the source of the packet needs to be informed that the route to the destination
of the packet does not exist. The RERR generated MUST include PktSource set to
the source address of the IP packet, and MUST contain only one unreachable
address in the AddressList, i.e., the destination address of the IP packet.
RERR_Gen MUST discard the IP packet that triggered generation of the RERR. The
prefix length and sequence number MAY be included if known from an Invalid
LocalRoute entry to PktSource. The MetricTypeList MUST also be included if a
MetricType can be determined from the IP packet or an existing Invalid
LocalRoute to the unreachable address. </t><t>When an RREP message cannot be
regenerated because the LocalRoute to OrigAddr has been lost or is Invalid,
RREP_Gen needs to be informed that the route to OrigAddr does not exist. The
RERR generated MUST include PktSource set to the TargAddr of the RREP, and MUST
contain only one unreachable address in the AddressList, the OrigAddr from the
RREP. RERR_Gen MUST discard the RREP message that triggered generation of the
RERR. The prefix length, sequence number and metric type SHOULD be included if
known from an Invalid LocalRoute to the unreachable address. </t><t>When a
link breaks, multiple LocalRoutes may become Invalid, and the RERR generated
MAY contain multiple unreachable addresses. The RERR MUST include
MetricTypeList. PktSource is omitted. All previously Active LocalRoutes that
used the broken link MUST be reported. The AddressList, PrefixLengthList,
SeqNumList, and MetricTypeList will contain entries for each LocalRoute which
has become Invalid. An RERR message is only sent if an Active LocalRoute
becomes Invalid, though an AODVv2 router can also include Idle LocalRoutes that
become Invalid if the configuration parameter ENABLE_IDLE_IN_RERR is set (see
<xref target="other" pageno="false" format="default"/>). </t></list></t><t>In
order to avoid flooding the network with RERR messages when a stream of IP
packets to an unreachable address arrives, an AODVv2 router SHOULD determine
whether an RERR has recently been sent with the same unreachable address and
PktSource, and SHOULD avoid creating duplicate RERR messages. </t><t>The RERR
SHOULD NOT be generated if the limit for the rate of AODVv2 control message
generation has been reached. If approaching the limit, the message should be
sent if the priorities in <xref target="MsgXmit" pageno="false"
format="default"/> allow it. </t><t>Incidentally, if an AODVv2 router receives
an ICMP error packet to or from the address of one of its Router Clients, it
forwards the ICMP packet in the same way as any other IP packet, and will not
generate any RERR message based on the contents of the ICMP packet. </t><t>To
generate the RERR, the router follows this procedure: </t><t><list
style="numbers"><t>If necessary, include PktSource and set the value as given
above </t><t>For each LocalRoute that needs to be reported: <list
style="symbols"><t>Insert LocalRoute.Address into the AddressList.
</t><t>Insert LocalRoute.PrefixLength into PrefixLengthList, if known and not
equal to the address length. </t><t>Insert LocalRoute.SeqNum into SeqNumList,
if known. </t><t>Insert LocalRoute.MetricType into MetricTypeList.
</t></list> </t></list></t><t>The AODVv2 message is used to create a
corresponding <xref target="RFC5444" pageno="false" format="default"/> message
(see <xref target="represent" pageno="false" format="default"/>). </t><t>If
the RERR is sent in response to an undeliverable IP packet or RREP message,
i.e., if PktSource is included, the RERR SHOULD be sent unicast to the next hop
on the route to PktSource, or alternatively, if there is no route to PktSource,
the RERR MUST be multicast to LL-MANET-Routers. If the RERR is sent in response
to a broken link, i.e., PktSource is not included, the RERR is, by default,
multicast to LL-MANET-Routers. </t><t><xref target="precursor" pageno="false"
format="default"/> describes processing steps when the optional precursor lists
feature is enabled. </t></section><section title="RERR Reception"
anchor="RERR_rcv" toc="default"><t>Upon receiving a Route Error, an AODVv2
router performs the following steps: </t><t><list style="numbers"><t>Verify
that the message contains the required data: at least one unreachable address
<list style="symbols"><t>If not, ignore this RERR for further processing.
</t></list> </t><t>For each address in the AddressList, check that: <list
style="symbols"><t>The address is valid (routable and unicast) </t><t>The
MetricType is supported and configured for use </t><t>There is a LocalRoute
with the same MetricType matching the address using longest prefix matching
</t><t>Either the LocalRoute's next hop is the sender of the RERR and the next
hop interface is the interface on which the RERR was received, or PktSource is
present in the RERR and is a Router Client address </t><t>The unreachable
address' sequence number is either unknown, or is greater than the LocalRoute's
sequence number </t></list> <vspace blankLines="1"/> If any of the above are
false, a matching LocalRoute MUST NOT be made Invalid and the unreachable
address MUST NOT be advertised in a regenerated RERR. <vspace blankLines="1"/>
If all of the above are true, the LocalRoute is no longer valid. If the
LocalRoute was previously Active, it MUST be reported in a regenerated RERR. If
the LocalRoute was previously Idle, it MAY be reported in a regenerated RERR,
if ENABLE_IDLE_IN_RERR is configured. The Local Route Set MUST be updated
according to these rules: <list style="symbols"><t>If the LocalRoute's prefix
length is the same as the unreachable address' prefix length, set
LocalRoute.State to Invalid. </t><t>If the LocalRoute's prefix length is
longer than the unreachable address' prefix length, the LocalRoute MUST be
expunged from the Local Route Set, since it is a sub-route of the route which
is reported to be Invalid. </t><t>If the prefix length is different, create a
new LocalRoute with the unreachable address, and its prefix length and sequence
number, and set LocalRoute.State to Invalid. </t><t>Update the sequence number
on the existing LocalRoute, if the reported sequence number is determined to be
newer using the comparison technique described in <xref target="seqnum"
pageno="false" format="default"/>. </t></list> </t><t>Check if there are
unreachable addresses which MUST be reported in a regenerated RERR <list
style="symbols"><t>If so, regenerate the RERR as detailed in <xref
target="RERR_regen" pageno="false" format="default"/>. </t><t>If not, take no
further action. </t></list> </t></list></t></section><section title="RERR
Regeneration" anchor="RERR_regen" toc="default"><t>The Route Error message
SHOULD NOT be regenerated if the limit for the rate of AODVv2 control message
generation has been reached. If approaching the limit, the message should be
sent if the priorities in <xref target="MsgXmit" pageno="false"
format="default"/> allow it. </t><t>The procedure for RERR regeneration is as
follows: </t><t><list style="numbers"><t>If PktSource was included in the
original RERR, and PktSource is not a Router Client, copy it into the
regenerated RERR </t><t>For each LocalRoute that needs to be reported: <list
style="symbols"><t>Insert LocalRoute.Address into the AddressList.
</t><t>Insert LocalRoute.PrefixLength into PrefixLengthList, if known and not
equal to the address length. </t><t>Insert LocalRoute.SeqNum into SeqNumList,
if known. </t><t>Insert LocalRoute.MetricType into MetricTypeList.
</t></list> </t></list></t><t>The AODVv2 message is used to create a
corresponding <xref target="RFC5444" pageno="false" format="default"/> message
(see <xref target="represent" pageno="false" format="default"/>). If the RERR
contains PktSource, the regenerated RERR SHOULD be sent unicast to the next hop
on the LocalRoute to PktSource, or alternatively if there is no route to
PktSource, or PktSource is a Router Client, it MUST be multicast to
LL-MANET-Routers. If the RERR is sent in response to a broken link, the RERR
is, by default, multicast to LL-MANET-Routers.
</t></section></section></section><section title="RFC 5444 Representation"
anchor="represent" toc="default"><t>AODVv2 specifies that all control messages
between routers MUST use the Generalized Mobile Ad Hoc Network Packet/Message
Format <xref target="RFC5444" pageno="false" format="default"/>, and therefore
AODVv2's route messages comprise data which is mapped to message elements in
<xref target="RFC5444" pageno="false" format="default"/>. </t><t><xref
target="RFC5444" pageno="false" format="default"/> provides a multiplexed
transport for multiple protocols. An <xref target="RFC5444" pageno="false"
format="default"/> multiplexer MAY choose to optimize the content of certain
message elements to reduce control message overhead. </t><t>A brief summary of
the <xref target="RFC5444" pageno="false" format="default"/> format:
</t><t><list style="numbers"><t>A packet contains zero or more messages
</t><t>A message contains a Message Header, one Message TLV Block, zero or more
Address Blocks, and one Address Block TLV Block per Address Block </t><t>The
Message TLV Block MAY contain zero or more Message TLVs </t><t>An Address Block
TLV Block MAY include zero or more Address Block TLVs </t><t>Each TLV value in
an Address Block TLV Block can be associated with all of the addresses, or with
a contiguous set of addresses, or with a single address in the Address Block
</t></list></t><t>AODVv2 does not require access to the <xref target="RFC5444"
pageno="false" format="default"/> packet header. </t><t>In the message header,
AODVv2 uses <msg-type> and <msg-addr-length>. The
<msg-addr-length> field indicates the length of any addresses in the
message, using <msg-addr-length> := (address length in octets - 1), i.e.
3 for IPv4 and 15 for IPv6. </t><t>The addresses in an Address Block MAY
appear in any order, and values in a TLV in the Address Block TLV Block must be
associated with the correct address in the Address Block by the <xref
target="RFC5444" pageno="false" format="default"/> implementation. To indicate
which value is associated with each address, the AODVv2 message representation
uses lists where the order of the addresses in the AODVv2 AddressList matches
the order of values in other data lists, e.g., the order of SeqNums in the
SeqNumList in an RERR. <xref target="RFC5444" pageno="false"
format="default"/> maps this information to Address Block TLVs associated with
the relevant addresses in the Address Block. </t><t>Each address included in
the Address Block is identified as OrigAddr, TargAddr, PktSource, or
Unreachable Address by including an ADDRESS_TYPE TLV in the Address Block TLV
Block. </t><t>The following sections show how AODVv2 data is represented in
<xref target="RFC5444" pageno="false" format="default"/> messages. AODVv2 makes
use of the VALIDITY_TIME Address Block TLV from <xref target="RFC5497"
pageno="false" format="default"/>, and defines (in <xref target="IANA"
pageno="false" format="default"/>) a number of new TLVs. To calculate the
time-value for the VALIDITY_TIME Address Block TLV, the value of C is defined
in <xref target="constants" pageno="false" format="default"/>. </t><t>Where
the extension type of a TLV is set to zero, this is the default <xref
target="RFC5444" pageno="false" format="default"/> value and the extension type
will not be included in the message. </t><section title="Route Request Message
Representation" anchor="route-request-message-representation"
toc="default"><section title="Message Header" anchor="message-header"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">Header Field
</ttcol><ttcol align="left">Value </ttcol><c>None </c><c><msg-type>
</c><c>RREQ </c></texttable></section><section title="Message TLV Block"
anchor="message-tlv-block" toc="default"><t>An RREQ contains no Message TLVs.
</t></section><section title="Address Block" anchor="address-block"
toc="default"><t>An RREQ contains two addresses, OrigAddr and TargAddr, and
each address has an associated prefix length. If the prefix length has not been
included in the AODVv2 message, it is equal to the address length in bits.
</t><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">Address Block
</ttcol><c>OrigAddr/OrigPrefixLen </c><c><address> +
<prefix-length> </c><c>TargAddr/TargPrefixLen </c><c><address> +
<prefix-length> </c></texttable></section><section title="Address Block
TLV Block" anchor="address-block-tlv-block" toc="default"><t>Address Block TLVs
are always associated with one or more addresses in the Address Block. The
following sections show the TLVs that apply to each address. </t><section
title="Address Block TLVs for OrigAddr"
anchor="address-block-tlvs-for-origaddr" toc="default"><texttable title=""
suppress-title="false" align="center" style="full"><ttcol align="left">Data
</ttcol><ttcol align="left">TLV Type </ttcol><ttcol align="left">Extension Type
</ttcol><ttcol align="left">Value </ttcol><c>None </c><c>ADDRESS_TYPE </c><c>0
</c><c>ADDRTYPE_ORIGADDR </c><c>OrigSeqNum </c><c>SEQ_NUM </c><c>0
</c><c>Sequence number of RREQ_Gen, the router which initiated route discovery.
</c><c>OrigMetric /MetricType </c><c>PATH_METRIC </c><c>MetricType
</c><c>Metric value for the route to OrigAddr, using MetricType.
</c><c>ValidityTime </c><c>VALIDITY_TIME </c><c>0 </c><c>ValidityTime for route
to OrigAddr, represented as detailed in <xref target="RFC5497" pageno="false"
format="default"/>. </c></texttable></section><section title="Address Block
TLVs for TargAddr" anchor="address-block-tlvs-for-targaddr"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">TLV Type
</ttcol><ttcol align="left">Extension Type </ttcol><ttcol align="left">Value
</ttcol><c>None </c><c>ADDRESS_TYPE </c><c>0 </c><c>ADDRTYPE_TARGADDR
</c><c>TargSeqNum </c><c>SEQ_NUM </c><c>0 </c><c>The last known TargSeqNum for
TargAddr. </c></texttable></section></section></section><section title="Route
Reply Message Representation" anchor="route-reply-message-representation"
toc="default"><section title="Message Header" anchor="message-header-1"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">Header Field
</ttcol><ttcol align="left">Value </ttcol><c>None </c><c><msg-type>
</c><c>RREP </c></texttable></section><section title="Message TLV Block"
anchor="message-tlv-block-1" toc="default"><t>An RREP contains no Message TLVs.
</t></section><section title="Address Block" anchor="address-block-1"
toc="default"><t>An RREP contains a minimum of two addresses, OrigAddr and
TargAddr, and each address has an associated prefix length. If the prefix
length has not been included in the AODVv2 message, it is equal to the address
length in bits. </t><t>It MAY also contain the address of the intended next
hop, in order to request acknowledgement to confirm bidirectionality of the
link, as described in <xref target="nexthopmonitoring" pageno="false"
format="default"/>. The prefix length associated with this address is equal to
the address length in bits. </t><texttable title="" suppress-title="false"
align="center" style="full"><ttcol align="left">Data </ttcol><ttcol
align="left">Address Block </ttcol><c>OrigAddr/OrigPrefixLen
</c><c><address> + <prefix-length> </c><c>TargAddr/TargPrefixLen
</c><c><address> + <prefix-length> </c><c>AckReq
</c><c><address> + <prefix-length>
</c></texttable></section><section title="Address Block TLV Block"
anchor="address-block-tlv-block-1" toc="default"><t>Address Block TLVs are
always associated with one or more addresses in the Address Block. The
following sections show the TLVs that apply to each address. </t><section
title="Address Block TLVs for OrigAddr"
anchor="address-block-tlvs-for-origaddr-1" toc="default"><texttable title=""
suppress-title="false" align="center" style="full"><ttcol align="left">Data
</ttcol><ttcol align="left">TLV Type </ttcol><ttcol align="left">Extension Type
</ttcol><ttcol align="left">Value </ttcol><c>None </c><c>ADDRESS_TYPE </c><c>0
</c><c>ADDRTYPE_ORIGADDR </c></texttable></section><section title="Address
Block TLVs for TargAddr" anchor="address-block-tlvs-for-targaddr-1"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">TLV Type
</ttcol><ttcol align="left">Extension Type </ttcol><ttcol align="left">Value
</ttcol><c>None </c><c>ADDRESS_TYPE </c><c>0 </c><c>ADDRTYPE_TARGADDR
</c><c>TargSeqNum </c><c>SEQ_NUM </c><c>0 </c><c>Sequence number of RREP_Gen,
the router which created the RREP. </c><c>TargMetric /MetricType
</c><c>PATH_METRIC </c><c>MetricType </c><c>Metric value for the route to
TargAddr, using MetricType. </c><c>ValidityTime </c><c>VALIDITY_TIME </c><c>0
</c><c>ValidityTime for route to TargAddr, represented as detailed in <xref
target="RFC5497" pageno="false" format="default"/>.
</c></texttable></section><section title="Address Block TLVs for AckReq
Intended Recipient Address"
anchor="address-block-tlvs-for-ackreq-intended-recipient-address"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">TLV Type
</ttcol><ttcol align="left">Extension Type </ttcol><ttcol align="left">Value
</ttcol><c>None </c><c>ADDRESS_TYPE </c><c>0 </c><c>ADDRTYPE_INTEND
</c></texttable></section></section></section><section title="Route Reply
Acknowledgement Message Representation"
anchor="route-reply-acknowledgement-message-representation"
toc="default"><section title="Message Header" anchor="message-header-2"
toc="default"><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">Header Field
</ttcol><ttcol align="left">Value </ttcol><c>None </c><c><msg-type>
</c><c>RREP_Ack </c></texttable></section><section title="Message TLV Block"
anchor="message-tlv-block-2" toc="default"><t>An RREP_Ack contains no Message
TLVs. </t></section><section title="Address Block" anchor="address-block-2"
toc="default"><t>An RREP_Ack contains no Address Block. </t></section><section
title="Address Block TLV Block" anchor="address-block-tlv-block-2"
toc="default"><t>An RREP_Ack contains no Address Block TLV Block.
</t></section></section><section title="Route Error Message Representation"
anchor="route-error-message-representation" toc="default"><t>Route Error
Messages MAY be split into multiple <xref target="RFC5444" pageno="false"
format="default"/> messages when the desired contents would exceed the MTU.
However, all of the resulting messages MUST have the same message header as
described below. If PktSource is included in the AODVv2 message, it MUST be
included in all of the resulting <xref target="RFC5444" pageno="false"
format="default"/> messages. </t><section title="Message Header"
anchor="message-header-3" toc="default"><texttable title=""
suppress-title="false" align="center" style="full"><ttcol align="left">Data
</ttcol><ttcol align="left">Header Field </ttcol><ttcol align="left">Value
</ttcol><c>None </c><c><msg-type> </c><c>RERR
</c></texttable></section><section title="Message TLV Block"
anchor="message-tlv-block-3" toc="default"><t>An RERR contains no Message TLVs.
</t></section><section title="Address Block" anchor="address-block-3"
toc="default"><t>The Address Block in an RERR MAY contain PktSource, the source
address of the IP packet triggering RERR generation, as detailed in <xref
target="RERR_msgs" pageno="false" format="default"/>. The prefix length
associated with PktSource is equal to the address length in bits.
</t><t>Address Block always contains one address per route that is no longer
valid, and each address has an associated prefix length. If a prefix length
has not been included for this address, it is equal to the address length in
bits. </t><texttable title="" suppress-title="false" align="center"
style="full"><ttcol align="left">Data </ttcol><ttcol align="left">Address Block
</ttcol><c>PktSource </c><c><address> + <prefix-length> for
PktSource </c><c>AddressList/PrefixLengthList </c><c><address> +
<prefix-length> for each unreachable address in AddressList
</c></texttable></section><section title="Address Block TLV Block"
anchor="address-block-tlv-block-3" toc="default"><t>Address Block TLVs are
always associated with one or more addresses in the Address Block. The
following sections show the TLVs that apply to each type of address in the
RERR. </t><section title="Address Block TLVs for PktSource"
anchor="address-block-tlvs-for-pktsource" toc="default"><texttable title=""
suppress-title="false" align="center" style="full"><ttcol align="left">Data
</ttcol><ttcol align="left">TLV Type </ttcol><ttcol align="left">Extension Type
</ttcol><ttcol align="left">Value </ttcol><c>PktSource </c><c>ADDRESS_TYPE
</c><c>0 </c><c>ADDRTYPE_PKTSOURCE </c></texttable></section><section
title="Address Block TLVs for Unreachable Addresses"
anchor="address-block-tlvs-for-unreachable-addresses" toc="default"><texttable
title="" suppress-title="false" align="center" style="full"><ttcol
align="left">Data </ttcol><ttcol align="left">TLV Type </ttcol><ttcol
align="left">Extension Type </ttcol><ttcol align="left">Value </ttcol><c>None
</c><c>ADDRESS_TYPE </c><c>0 </c><c>ADDRTYPE_UNREACHABLE </c><c>SeqNumList
</c><c>SEQ_NUM </c><c>0 </c><c>Sequence number associated with invalid route to
the unreachable address. </c><c>MetricTypeList </c><c>PATH_METRIC
</c><c>MetricType </c><c>None. Extension Type set to MetricType of the route to
the unreachable address.
</c></texttable></section></section></section></section><section title="Simple
External Network Attachment" anchor="gateway" toc="default"><t><xref
target="net_top" pageno="false" format="default"/> shows a stub (i.e.,
non-transit) network of AODVv2 routers which is attached to an external network
via a single External Network Access Router (ENAR). The interface to the
external network MUST NOT be configured in the AODVv2_INTERFACES list.
</t><t>As in any externally-attached network, AODVv2 routers and Router Clients
that wish to be reachable from the external network MUST have IP addresses
within the ENAR's routable and topologically correct prefix (i.e., 191.0.2.0/24
in <xref target="net_top" pageno="false" format="default"/>). This AODVv2
network and networks attached to routers within it will be advertised to the
external network using procedures which are out of scope for this
specification. </t><figure anchor="net_top" align="center" title="Simple
External Network Attachment Example" suppress-title="false" alt="" width=""
height=""><artwork align="center" xml:space="preserve" name="" type="" alt=""
width="" height="">
/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | ENAR | /191.0.2.0/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ External \
| | 191.0.2.0/24 | \ Network /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
</artwork></figure><t></t><t>When an AODVv2 router within the AODVv2 MANET
wants to discover a route toward an address on the external network, it uses
the normal AODVv2 route discovery for that IP Destination Address. The ENAR
MUST respond to RREQ on behalf of all external network destinations, i.e.,
destinations not on the configured 191.0.2.0/24 network. RREQs for addresses
inside the AODVv2 network, i.e. destinations on the configured 191.0.2.0/24
network, are handled using the standard processes described in <xref
target="aodv_msgs" pageno="false" format="default"/>. </t><t>When an IP packet
from an address on the external network destined for an address in the AODVv2
MANET reaches the ENAR, if the ENAR does not have a route toward that exact
destination in its Routing Information Base, it will perform normal AODVv2
route discovery for that destination. </t><t>Configuring the ENAR as a default
router is outside the scope of this specification. </t></section><section
title="Optional Features" anchor="optional" toc="default"><t>A number of
optional features for AODVv2, associated initially with AODV, MAY be useful in
networks with greater mobility or larger populations, or networks requiring
reduced latency for application launches. These features are not required by
minimal implementations. </t><section title="Expanding Rings Multicast"
anchor="rings" toc="default"><t>For multicast RREQ, the <xref target="RFC5444"
pageno="false" format="default"/> message may initially be limited to a low
number of hops to limit the RREQ propagation to a subset of the local network
and possibly reduce route discovery overhead. If the route is not discovered,
the number of hops allowed for distribution of the RREQ is increased, in
accordance with an expanding ring search, as described in <xref
target="RFC3561" pageno="false" format="default"/>. </t></section><section
title="Precursor Lists" anchor="precursor" toc="default"><t>This section
specifies an interoperable enhancement to AODVv2 enabling more economical Route
Error notifications. </t><t>There can be several sources of traffic for a
certain destination. Each source of traffic and each upstream router between
the forwarding AODVv2 router and the traffic source is known as a "precursor"
for the destination. For each destination, an AODVv2 router MAY choose to keep
track of precursors that have provided traffic for that destination. Route
Error messages about that destination can be sent unicast to these precursors
instead of multicast to all AODVv2 routers. </t><t>Since an RERR will be
regenerated if it comes from a next hop on a valid LocalRoute, the RERR SHOULD
ideally be sent backwards along the route that the source of the traffic uses,
to ensure it is regenerated at each hop and reaches the traffic source. If the
reverse path is unknown, the RERR SHOULD be sent toward the source along some
other route. Therefore, the options for saving precursor information are as
follows: </t><t><list style="symbols"><t>Save the next hop on an existing route
to the IP packet's source address as the precursor. In this case, it is not
guaranteed that an RERR that is sent will follow the reverse of the source's
route. In rare situations, this may prevent the route from being invalidated at
the source of the data traffic. </t><t>Save the IP packet's source address as
the precursor. In this case, the RERR can be sent along any existing route to
the source of the data traffic, and SHOULD include PktSource to ensure that the
route will be invalidated at the source of the traffic, in case the RERR does
not follow the reverse of the source's route. </t><t>By inspecting the MAC
address of each forwarded IP packet, determine which router forwarded the
packet, and save the router address as a precursor. This ensures that when an
RERR is sent to the precursor router, the route will be invalidated at that
router, and the RERR will be regenerated toward the source of the IP packet.
</t></list></t><t>During normal operation, each AODVv2 router maintaining
precursor lists for a LocalRoute must update the precursor list whenever it
uses this route to forward traffic to the destination. Precursors are
classified as Active if traffic has recently been forwarded by the precursor.
The precursor is marked with a timestamp to indicate the time it last forwarded
traffic on this route. </t><t>When an AODVv2 router detects that one or more
LocalRoutes are broken, it MAY notify each Active precursor using a unicast
Route Error message instead of creating multicast traffic. Unicast is
applicable when there are few Active precursors compared to the number of
neighboring AODVv2 routers. However, the default multicast behavior is still
preferable when there are many precursors, since fewer message transmissions
are required. </t><t>When an AODVv2 router supporting precursor lists receives
an RERR message, it MAY identify the list of its own affected Active precursors
for the routes in the RERR, and choose to send a unicast RERR to those, rather
than send a multicast RERR. </t><t>When a LocalRoute is expunged, any
precursor list associated with it MUST also be expunged.
</t></section><section title="Intermediate RREP" anchor="iRREP"
toc="default"><t>Without iRREP, only the AODVv2 router responsible for the
target address can respond to an RREQ. Using iRREP, route discoveries can be
faster and create less control traffic. This specification has been published
as a separate Internet Draft <xref target="I-D.perkins-irrep" pageno="false"
format="default"/>. </t><t></t></section><section title="Message Aggregation
Delay" anchor="aggreg" toc="default"><t>The aggregation of multiple messages
into a packet is specified in <xref target="RFC5444" pageno="false"
format="default"/>. </t><t>Implementations MAY choose to briefly delay
transmission of messages for the purpose of aggregation (into a single packet)
or to improve performance by using jitter <xref target="RFC5148" pageno="false"
format="default"/>. </t></section></section><section title="Configuration"
anchor="param" toc="default"><t>AODVv2 uses various parameters which can be
grouped into the following categories: </t><t><list style="symbols"><t>Timers
</t><t>Protocol constants </t><t>Administrative parameters and controls
</t></list></t><t>This section show the parameters along with their definitions
and default values (if any). </t><t>Note that several fields have limited size
(bits or bytes). These sizes and their encoding may place specific limitations
on the values that can be set. </t><section title="Timers" anchor="timers"
toc="default"><t>AODVv2 requires certain timing information to be associated
with Local Route Set entries and message replies. The default values are as
follows: </t><texttable anchor="timer-tbl" align="center" title="Timing
Parameter Values" suppress-title="false" style="full"><ttcol align="left">Name
</ttcol><ttcol align="left">Default Value </ttcol><c>ACTIVE_INTERVAL </c><c>5
second </c><c>MAX_IDLETIME </c><c>200 seconds </c><c>MAX_BLACKLIST_TIME
</c><c>200 seconds </c><c>MAX_SEQNUM_LIFETIME </c><c>300 seconds
</c><c>RteMsg_ENTRY_TIME </c><c>12 seconds </c><c>RREQ_WAIT_TIME </c><c>2
seconds </c><c>RREP_Ack_SENT_TIMEOUT </c><c>1 second </c><c>RREQ_HOLDDOWN_TIME
</c><c>10 seconds </c></texttable><t></t><t>The above timing parameter values
have worked well for small and medium well-connected networks with moderate
topology changes. The timing parameters SHOULD be administratively
configurable. Ideally, for networks with frequent topology changes the AODVv2
parameters SHOULD be adjusted using experimentally determined values or dynamic
adaptation. For example, in networks with infrequent topology changes
MAX_IDLETIME MAY be set to a much larger value. </t><t>If MAX_SEQNUM_LIFETIME
was configured differently across the network, and any of the routers lost
their sequence number or rebooted, this could result in their next route
messages being classified as stale at any AODVv2 router using a greater value
for MAX_SEQNUM_LIFETIME. This would delay route discovery from and to the
re-initializing router. </t></section><section title="Protocol Constants"
anchor="constants" toc="default"><t>AODVv2 protocol constants typically do not
require changes. The following table lists these constants, along with their
values and a reference to the section describing their use. </t><texttable
anchor="const-tbl" align="center" title="AODVv2 Constants"
suppress-title="false" style="full"><ttcol align="left">Name </ttcol><ttcol
align="left">Default </ttcol><ttcol align="left">Description
</ttcol><c>DISCOVERY_ATTEMPTS_MAX </c><c>3 </c><c><xref
target="route_discovery" pageno="false" format="default"/> </c><c>RREP_RETRIES
</c><c>2 </c><c><xref target="RREP_gen" pageno="false" format="default"/>
</c><c>MAX_METRIC[MetricType] </c><c>[TBD] </c><c><xref target="metrics"
pageno="false" format="default"/> </c><c>MAX_METRIC[HopCount] </c><c>255
</c><c><xref target="metrics" pageno="false" format="default"/> and <xref
target="aodv_msgs" pageno="false" format="default"/> </c><c>INFINITY_TIME
</c><c>[TBD] </c><c>Maximum expressible clock time (<xref target="update_rte"
pageno="false" format="default"/>) </c><c>C </c><c>1/1024 </c><c>Constant used
in validity time calculation <xref target="RFC5497" pageno="false"
format="default"/> </c></texttable><t></t><t>MAX_METRIC[MetricType] MUST always
be the maximum expressible metric value of type MetricType. Field lengths
associated with metric values are found in <xref target="metric-type"
pageno="false" format="default"/>. </t><t>These protocol constants MUST have
the same values for all AODVv2 routers in the ad hoc network. If the values
were configured differently, the following consequences may be observed:
</t><t><list style="symbols"><t>DISCOVERY_ATTEMPTS_MAX: Routers with higher
values are likely to be more successful at finding routes, at the cost of
additional control traffic. </t><t>RREP_RETRIES: Routers with lower values are
more likely to blacklist neighbors when there is a
</t><t>MAX_METRIC[MetricType]: No interoperability problems due to variations
on different routers, but routers with lower values may exhibit overly
restrictive behavior during route comparisons. temporary fluctuation in link
quality. </t><t>INFINITY_TIME: No interoperability problems due to variations
on different routers, but if a lower value is used, route state management may
exhibit overly restrictive behavior. </t><t>C: Routers with lower values will
invalidate timed routes before routers with higher values, which will cause
Route Error messages to be generated and the route will effectively take on the
shorter validity time. </t></list></t></section><section title="Local
Settings" anchor="other" toc="default"><t>The following table lists AODVv2
parameters which SHOULD be administratively configured for each router:
</t><texttable anchor="admincontrol" align="center" title="Configuration for
Local Settings" suppress-title="false" style="full"><ttcol align="left">Name
</ttcol><ttcol align="left">Default Value </ttcol><ttcol
align="left">Description </ttcol><c>AODVv2_INTERFACES </c><c></c><c><xref
target="apply" pageno="false" format="default"/> </c><c>BUFFER_SIZE_PACKETS
</c><c>2 </c><c><xref target="route_discovery" pageno="false"
format="default"/> </c><c>BUFFER_SIZE_BYTES </c><c>MAX_PACKET_SIZE [TBD]
</c><c><xref target="route_discovery" pageno="false" format="default"/>
</c><c>CONTROL_TRAFFIC_LIMIT </c><c>[TBD - 50 pkts/sec?] </c><c><xref
target="aodv_msgs" pageno="false" format="default"/>
</c></texttable><t></t></section><section title="Network-Wide Settings"
anchor="network-wide-settings" toc="default"><t>The following administrative
controls MAY be used to change the operation of the network. The same settings
SHOULD be used across the network. Inconsistent settings at different routers
in the network will not result in protocol errors, but poor performance may
result. </t><texttable anchor="suggestedoptions" align="center"
title="Configuration for Network-Wide Settings" suppress-title="false"
style="full"><ttcol align="left">Name </ttcol><ttcol align="left">Default
</ttcol><ttcol align="left">Description </ttcol><c>ENABLE_IDLE_IN_RERR
</c><c>Disabled </c><c><xref target="RERR_gen" pageno="false"
format="default"/> </c></texttable><t></t></section><section title="Optional
Feature Settings" anchor="optional-feature-settings" toc="default"><t>These
options are not required for correct routing behavior, although they may reduce
AODVv2 protocol overhead in certain situations. The default behavior is to
leave these options disabled. </t><texttable anchor="optionsettings"
align="center" title="Configuration for Optional Features"
suppress-title="false" style="full"><ttcol align="left">Name </ttcol><ttcol
align="left">Default </ttcol><ttcol align="left">Description
</ttcol><c>PRECURSOR_LISTS </c><c>Disabled </c><c>Local setting (<xref
target="precursor" pageno="false" format="default"/>) </c><c>MSG_AGGREGATION
</c><c>Disabled </c><c>Local setting (<xref target="aggreg" pageno="false"
format="default"/>) </c><c>ENABLE_IRREP </c><c>Disabled </c><c>Network-wide
setting (<xref target="iRREP" pageno="false" format="default"/>)
</c><c>EXPANDING_RINGS_MULTICAST </c><c>Disabled </c><c>Network-wide setting
(<xref target="rings" pageno="false" format="default"/>)
</c></texttable><t></t></section><section title="MetricType Allocation"
anchor="metric-type" toc="default"><t>The metric types used by AODVv2 are
identified according to the assignments in <xref target="RFC6551"
pageno="false" format="default"/>. All implementations MUST use these values.
</t><texttable anchor="metric-tbl" align="center" title="AODVv2 Metric Types"
suppress-title="false" style="full"><ttcol align="left">Name of MetricType
</ttcol><ttcol align="left">Type </ttcol><ttcol align="left">Metric Value Size
</ttcol><c>Unassigned </c><c>0 </c><c>Undefined </c><c>Hop Count </c><c>3 [TBD]
</c><c>1 octet </c><c>Unallocated </c><c>9 - 254 </c><c>TBD </c><c>Reserved
</c><c>255 </c><c>Undefined </c></texttable><t></t></section></section><section
title="IANA Considerations" anchor="IANA" toc="default"><t>This section
specifies several <xref target="RFC5444" pageno="false" format="default"/>
message types and address tlv-types required for AODVv2. </t><section
title="RFC 5444 Message Types" anchor="msgtype" toc="default"><t>This
specification defines four Message Types, to be allocated from the 0-223 range
of the "Message Types" namespace defined in <xref target="RFC5444"
pageno="false" format="default"/>, as specified in <xref target="msgtypes"
pageno="false" format="default"/>. </t><texttable anchor="msgtypes"
align="center" title="AODVv2 Message Types" suppress-title="false"
style="full"><ttcol align="left">Name of Message </ttcol><ttcol
align="left">Type </ttcol><c>Route Request (RREQ) </c><c>10 (TBD) </c><c>Route
Reply (RREP) </c><c>11 (TBD) </c><c>Route Error (RERR) </c><c>12 (TBD)
</c><c>Route Reply Acknowledgement (RREP_Ack) </c><c>13 (TBD)
</c></texttable><t></t></section><section title="RFC 5444 Address Block TLV
Types" anchor="addrtlvspec" toc="default"><t>This specification defines three
Address Block TLV Types, to be allocated from the "Address Block TLV Types"
namespace defined in <xref target="RFC5444" pageno="false" format="default"/>,
as specified in <xref target="addrtlvtypes" pageno="false" format="default"/>.
</t><texttable anchor="addrtlvtypes" align="center" title="AODVv2 Address Block
TLV Types" suppress-title="false" style="full"><ttcol align="left"
width="41%">Name of TLV </ttcol><ttcol align="left" width="13%">Type
</ttcol><ttcol align="left" width="22%">Length (octets) </ttcol><ttcol
align="left" width="22%">Reference </ttcol><c>PATH_METRIC </c><c>11 (TBD)
</c><c>depends on MetricType </c><c><xref target="aodv_msgs" pageno="false"
format="default"/> </c><c>SEQ_NUM </c><c>12 (TBD) </c><c>2 </c><c><xref
target="aodv_msgs" pageno="false" format="default"/> </c><c>ADDRESS_TYPE
</c><c>13 (TBD) </c><c>1 </c><c><xref target="represent" pageno="false"
format="default"/> </c></texttable><t></t></section><section
title="ADDRESS_TYPE TLV Values" anchor="address-type" toc="default"><t>These
values are used in the <xref target="RFC5444" pageno="false" format="default"/>
Address Type TLV discussed in <xref target="represent" pageno="false"
format="default"/>. All implementations MUST use these values. </t><texttable
anchor="addrtype-tbl" align="center" title="AODVv2 Address Types"
suppress-title="false" style="full"><ttcol align="left">Address Type
</ttcol><ttcol align="left">Value </ttcol><c>ORIGADDR </c><c>0 </c><c>TARGADDR
</c><c>1 </c><c>UNREACHABLE </c><c>2 </c><c>PKTSOURCE </c><c>3 </c><c>INTEND
</c><c>4 </c><c>UNSPECIFIED </c><c>255
</c></texttable><t></t></section></section><section title="Security
Considerations" anchor="Security" toc="default"><t>This section describes
various security considerations and potential avenues to secure AODVv2 routing.
The objective of the AODVv2 protocol is for each router to communicate
reachability information about addresses for which it is responsible, and for
routes it has learned from other AODVv2 routers. Positive routing information
(i.e. a route exists) is distributed via RREQ and RREP messages. AODVv2
routers store the information contained in these messages in order to properly
forward IP packets, and they generally provide this information to other AODVv2
routers. Negative routing information (i.e. a route does not exist) is
distributed via RERR messages. AODVv2 routers process these messages and remove
routes, and forward this information to other AODVv2 routers. </t><t>Networks
using AODVv2 to maintain connectivity and establish routes on demand may be
vulnerable to certain well-known types of threats. Flooding attacks using RREQ
amount to a denial of service for route discovery. Valid route table entries
can be replaced by maliciously constructed RREQ and RREP messages. Links could
be erroneously treated as bidirectional if malicious unsolicited RREP or
RREP_Ack messages were to be accepted. Replay attacks using RERR messages
could, in some circumstances, be used to disrupt active routes. Passive
inspection of AODVv2 control messages could enable unauthorized devices to gain
information about the network topology, since exchanging such information is
the main purpose of AODVv2. </t><t>The on-demand nature of AODVv2 route
discovery reduces the vulnerability to route disruption. Since control traffic
for updating route tables is diminished, there is less opportunity for failure.
Processing requirements for AODVv2 are typically quite small, and would
typically be dominated by calculations to verify integrity. This has the effect
of reducing (but by no means eliminating) AODVv2's vulnerability to denial of
service attacks. </t><t>Encryption MAY be used for AODVv2 messages. If the
routers share a packet-level security association, the message data can be
encrypted prior to message transmission. The establishment of such security
associations is outside the scope of this specification. Encryption will not
only protect against unauthorized devices obtaining information about network
topology but will ensure that only trusted routers participate in routing
operations. </t><t>Message integrity checking is enabled by the Integrity
Check Value mechanisms defined in <xref target="RFC7182" pageno="false"
format="default"/>. The data contained in AODVv2 routing protocol messages
SHOULD be verified using ICV values, to avoid the use of message data if the
message has been tampered with or replayed. Otherwise, it would be possible to
disrupt communications by injecting nonexistent or malicious routes into the
route tables of routers within the ad hoc network. This can result in loss of
data or message processing by unauthorized devices. </t><t>The remainder of
this section provides specific recommendations for the use of the integrity
checking and timestamp functions defined in <xref target="RFC7182"
pageno="false" format="default"/> to ensure the integrity of each AODVv2
message. The calculation used for the Integrity Check Value will depend on the
message type. Sequence numbers can be used as timestamps to protect against
replay, since they are known to be strictly increasing. </t><t>RREQ messages
advertise a route to OrigAddr, and impose very little processing requirement
for receivers. The main threat presented by sending an RREQ message with false
information is that traffic to OrigAddr could be disrupted. Since RREQ is
multicast and likely to be received by all routers in the ad hoc network, this
threat could have serious impact on applications communicating by way of
OrigAddr. The actual threat to disrupt routes to OrigAddr is reduced by the
AODVv2 mechanism of marking RREQ-derived routes as "Unconfirmed" until the link
to the next hop is confirmed. If AODVv2 routers always verify the integrity of
the RREQ message data, then the threat of disruption is minimized. The ICV
mechanisms offered in <xref target="RFC7182" pageno="false" format="default"/>
are sufficient for this purpose. Since OrigAddr is included in the RREQ, the
ICV can be calculated and verified using message contents. The ICV SHOULD be
verified at every step along the dispersal path of the RREQ to mitigate the
threat. Since RREQ_Gen's sequence number is incremented for each new RREQ,
replay protection is already afforded and no extra timestamp mechanism is
required. </t><t>RREP messages advertise a route to TargAddr, and impose very
little processing requirement for receivers. The main threat presented by
sending an RREP message with false information is that traffic to TargAddr
could be disrupted. Since RREP is unicast, this threat is restricted to
receivers along the path from OrigAddr to TargAddr. If AODVv2 routers always
verify the integrity of the RREP message data, then this threat is minimized.
This facility is offered by the ICV mechanisms in <xref target="RFC7182"
pageno="false" format="default"/>. Since TargAddr is included as a Data Element
of the RREP, the ICV can be calculated and verified using message contents. The
ICV SHOULD be verified at every step along the unicast path of the RREP. Since
RREP_Gen's sequence number is incremented for each new RREP, replay protection
is afforded and no extra timestamp mechanism is required. </t><t>RREP_Ack
messages are intended to verify bidirectional neighbor connectivity, and impose
very little processing requirement for receivers. The main threat presented by
sending an RREP_Ack message with false information is that the route advertised
to a target address in an RREP might be erroneously accepted even though the
route would contain a unidirectional link and thus not be suitable for most
traffic. Since RREP_Ack is unicast, this threat is strictly local to the RREP
transmitter expecting the acknowledgement. A malicious router could also
attempt to send an unsolicited RREP_Ack to convince another router that a
bidirectional link exists and subsequently use further messages to divert
traffic along a route which is not valid. If AODVv2 routers always verify the
integrity of the RREP_Ack message data, then this threat is minimized. This
facility is offered by the ICV mechanisms in <xref target="RFC7182"
pageno="false" format="default"/>. The RREP_Gen SHOULD use the source IP
address of the RREP_Ack to identify the sender, and so the ICV SHOULD be
calculated using the message contents and the IP source address. The message
must also include the Timestamp defined in <xref target="RFC7182"
pageno="false" format="default"/> to protect against replay attacks, using
TargSeqNum from the RREP as the value in the TIMESTAMP TLV. </t><t>RERR
messages remove routes, and impose very little processing requirement for
receivers. The main threat presented by sending an RERR message with false
information is that traffic to the advertised destinations could be disrupted.
Since RERR is multicast and can be received by many routers in the ad hoc
network, this threat could have serious impact on applications communicating by
way of the sender of the RERR message. However, since the sender of the RERR
message with erroneous information MAY be presumed to be either malicious or
broken, it is better that such routes not be used anyway. Another threat is
that a malicious RERR message MAY be sent with a PktSource included, to disrupt
PktSource's ability to send to the addresses contained in the RERR. If AODVv2
routers always verify the integrity of the RERR message data, then this threat
is reduced. This facility is offered by the ICV mechanisms in <xref
target="RFC7182" pageno="false" format="default"/>. The receiver of the RERR
SHOULD use the source IP address of the RERR to identify the sender. The
message must also include the Timestamp defined in <xref target="RFC7182"
pageno="false" format="default"/> to protect against replay attacks, using
SeqNum from RERR_Gen as the value in the TIMESTAMP TLV. </t></section><section
title="Acknowledgments" anchor="acknowledgments" toc="default"><t>AODVv2 is a
descendant of the design of previous MANET on-demand protocols, especially AODV
<xref target="RFC3561" pageno="false" format="default"/> and DSR <xref
target="RFC4728" pageno="false" format="default"/>. Changes to previous MANET
on-demand protocols stem from research and implementation experiences. Thanks
to Elizabeth Belding and Ian Chakeres for their long time authorship of AODV.
Additional thanks to Derek Atkins, Emmanuel Baccelli, Abdussalam Baryun, Ramon
Caceres, Thomas Clausen, Justin Dean, Christopher Dearlove, Fatemeh Ghassemi,
Ulrich Herberg, Henner Jakob, Ramtin Khosravi, Luke Klein-Berndt, Lars
Kristensen, Tronje Krop, Koojana Kuladinithi, Kedar Namjoshi, Keyur Patel,
Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro Ruiz, Christoph Sommer,
Romain Thouvenin, Richard Trefler, Jiazi Yi, Seung Yi, Behnaz Yousefi, and Cong
Yuan, for their reviews of AODVv2 and DYMO, as well as numerous specification
suggestions. </t></section> </middle>
<back><references title="Normative References"><reference anchor="RFC2119"
target="http://www.rfc-editor.org/info/rfc2119";><front><title>Key words for use
in RFCs to Indicate Requirement Levels</title><author initials="S."
surname="Bradner" fullname="S. Bradner"><organization/></author><date
year="1997" month="March"/><abstract><t>In many standards track documents
several words are used to signify the requirements in the specification. These
words are often capitalized. This document defines these words as they should
be interpreted in IETF documents. This document specifies an Internet Best
Current Practices for the Internet Community, and requests discussion and
suggestions for improvements.</t></abstract></front><seriesInfo name="BCP"
value="14"/><seriesInfo name="RFC" value="2119"/><seriesInfo name="DOI"
value="10.17487/RFC2119"/></reference><reference anchor="RFC3561"
target="http://www.rfc-editor.org/info/rfc3561";><front><title>Ad hoc On-Demand
Distance Vector (AODV) Routing</title><author initials="C." surname="Perkins"
fullname="C. Perkins"><organization/></author><author initials="E."
surname="Belding-Royer" fullname="E.
Belding-Royer"><organization/></author><author initials="S." surname="Das"
fullname="S. Das"><organization/></author><date year="2003"
month="July"/><abstract><t>The Ad hoc On-Demand Distance Vector (AODV) routing
protocol is intended for use by mobile nodes in an ad hoc network. It offers
quick adaptation to dynamic link conditions, low processing and memory
overhead, low network utilization, and determines unicast routes to
destinations within the ad hoc network. It uses destination sequence numbers
to ensure loop freedom at all times (even in the face of anomalous delivery of
routing control messages), avoiding problems (such as "counting to infinity")
associated with classical distance vector protocols. This memo defines an
Experimental Protocol for the Internet
community.</t></abstract></front><seriesInfo name="RFC"
value="3561"/><seriesInfo name="DOI"
value="10.17487/RFC3561"/></reference><reference anchor="RFC4291"
target="http://www.rfc-editor.org/info/rfc4291";><front><title>IP Version 6
Addressing Architecture</title><author initials="R." surname="Hinden"
fullname="R. Hinden"><organization/></author><author initials="S."
surname="Deering" fullname="S. Deering"><organization/></author><date
year="2006" month="February"/><abstract><t>This specification defines the
addressing architecture of the IP Version 6 (IPv6) protocol. The document
includes the IPv6 addressing model, text representations of IPv6 addresses,
definition of IPv6 unicast addresses, anycast addresses, and multicast
addresses, and an IPv6 node's required addresses.</t><t>This document obsoletes
RFC 3513, "IP Version 6 Addressing Architecture".
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="4291"/><seriesInfo name="DOI"
value="10.17487/RFC4291"/></reference><reference anchor="RFC5082"
target="http://www.rfc-editor.org/info/rfc5082";><front><title>The Generalized
TTL Security Mechanism (GTSM)</title><author initials="V." surname="Gill"
fullname="V. Gill"><organization/></author><author initials="J."
surname="Heasley" fullname="J. Heasley"><organization/></author><author
initials="D." surname="Meyer" fullname="D.
Meyer"><organization/></author><author initials="P." surname="Savola"
fullname="P. Savola" role="editor"><organization/></author><author
initials="C." surname="Pignataro" fullname="C.
Pignataro"><organization/></author><date year="2007"
month="October"/><abstract><t>The use of a packet's Time to Live (TTL) (IPv4)
or Hop Limit (IPv6) to verify whether the packet was originated by an adjacent
node on a connected link has been used in many recent protocols. This document
generalizes this technique. This document obsoletes Experimental RFC 3682.
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="5082"/><seriesInfo name="DOI"
value="10.17487/RFC5082"/></reference><reference anchor="RFC5444"
target="http://www.rfc-editor.org/info/rfc5444";><front><title>Generalized
Mobile Ad Hoc Network (MANET) Packet/Message Format</title><author
initials="T." surname="Clausen" fullname="T.
Clausen"><organization/></author><author initials="C." surname="Dearlove"
fullname="C. Dearlove"><organization/></author><author initials="J."
surname="Dean" fullname="J. Dean"><organization/></author><author initials="C."
surname="Adjih" fullname="C. Adjih"><organization/></author><date year="2009"
month="February"/><abstract><t>This document specifies a packet format capable
of carrying multiple messages that may be used by mobile ad hoc network routing
protocols. [STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="5444"/><seriesInfo name="DOI"
value="10.17487/RFC5444"/></reference><reference anchor="RFC5497"
target="http://www.rfc-editor.org/info/rfc5497";><front><title>Representing
Multi-Value Time in Mobile Ad Hoc Networks (MANETs)</title><author
initials="T." surname="Clausen" fullname="T.
Clausen"><organization/></author><author initials="C." surname="Dearlove"
fullname="C. Dearlove"><organization/></author><date year="2009"
month="March"/><abstract><t>This document describes a general and flexible TLV
(type-length-value structure) for representing time-values, such as an interval
or a duration, using the generalized Mobile Ad hoc NETwork (MANET) packet/
message format. It defines two Message TLVs and two Address Block TLVs for
representing validity and interval times for MANET routing protocols.
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="5497"/><seriesInfo name="DOI"
value="10.17487/RFC5497"/></reference><reference anchor="RFC5498"
target="http://www.rfc-editor.org/info/rfc5498";><front><title>IANA Allocations
for Mobile Ad Hoc Network (MANET) Protocols</title><author initials="I."
surname="Chakeres" fullname="I. Chakeres"><organization/></author><date
year="2009" month="March"/><abstract><t>This document enumerates several common
IANA allocations for use by Mobile Ad hoc NETwork (MANET) protocols. The
following well-known numbers are required: a UDP port number, an IP protocol
number, and a link-local multicast group address.
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="5498"/><seriesInfo name="DOI"
value="10.17487/RFC5498"/></reference><reference anchor="RFC6551"
target="http://www.rfc-editor.org/info/rfc6551";><front><title>Routing Metrics
Used for Path Calculation in Low-Power and Lossy Networks</title><author
initials="JP." surname="Vasseur" fullname="JP. Vasseur"
role="editor"><organization/></author><author initials="M." surname="Kim"
fullname="M. Kim" role="editor"><organization/></author><author initials="K."
surname="Pister" fullname="K. Pister"><organization/></author><author
initials="N." surname="Dejean" fullname="N.
Dejean"><organization/></author><author initials="D." surname="Barthel"
fullname="D. Barthel"><organization/></author><date year="2012"
month="March"/><abstract><t>Low-Power and Lossy Networks (LLNs) have unique
characteristics compared with traditional wired and ad hoc networks that
require the specification of new routing metrics and constraints. By contrast,
with typical Interior Gateway Protocol (IGP) routing metrics using hop counts
or link metrics, this document specifies a set of link and node routing metrics
and constraints suitable to LLNs to be used by the Routing Protocol for
Low-Power and Lossy Networks (RPL).
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="6551"/><seriesInfo name="DOI"
value="10.17487/RFC6551"/></reference><reference anchor="RFC7182"
target="http://www.rfc-editor.org/info/rfc7182";><front><title>Integrity Check
Value and Timestamp TLV Definitions for Mobile Ad Hoc Networks
(MANETs)</title><author initials="U." surname="Herberg" fullname="U.
Herberg"><organization/></author><author initials="T." surname="Clausen"
fullname="T. Clausen"><organization/></author><author initials="C."
surname="Dearlove" fullname="C. Dearlove"><organization/></author><date
year="2014" month="April"/><abstract><t>This document revises, extends, and
replaces RFC 6622. It describes general and flexible TLVs for representing
cryptographic Integrity Check Values (ICVs) and timestamps, using the
generalized Mobile Ad Hoc Network (MANET) packet/message format defined in RFC
5444. It defines two Packet TLVs, two Message TLVs, and two Address Block TLVs
for affixing ICVs and timestamps to a packet, a message, and one or more
addresses, respectively.</t></abstract></front><seriesInfo name="RFC"
value="7182"/><seriesInfo name="DOI"
value="10.17487/RFC7182"/></reference></references><references
title="Informative References"><reference anchor="RFC2501"
target="http://www.rfc-editor.org/info/rfc2501";><front><title>Mobile Ad hoc
Networking (MANET): Routing Protocol Performance Issues and Evaluation
Considerations</title><author initials="S." surname="Corson" fullname="S.
Corson"><organization/></author><author initials="J." surname="Macker"
fullname="J. Macker"><organization/></author><date year="1999"
month="January"/><abstract><t>This memo first describes the characteristics of
Mobile Ad hoc Networks (MANETs), and their idiosyncrasies with respect to
traditional, hardwired packet networks. It then discusses the effect these
differences have on the design and evaluation of network control protocols with
an emphasis on routing performance evaluation considerations. This memo
provides information for the Internet
community.</t></abstract></front><seriesInfo name="RFC"
value="2501"/><seriesInfo name="DOI"
value="10.17487/RFC2501"/></reference><reference anchor="RFC4193"
target="http://www.rfc-editor.org/info/rfc4193";><front><title>Unique Local IPv6
Unicast Addresses</title><author initials="R." surname="Hinden" fullname="R.
Hinden"><organization/></author><author initials="B." surname="Haberman"
fullname="B. Haberman"><organization/></author><date year="2005"
month="October"/><abstract><t>This document defines an IPv6 unicast address
format that is globally unique and is intended for local communications,
usually inside of a site. These addresses are not expected to be routable on
the global Internet. [STANDARDS-TRACK]</t></abstract></front><seriesInfo
name="RFC" value="4193"/><seriesInfo name="DOI"
value="10.17487/RFC4193"/></reference><reference anchor="RFC4728"
target="http://www.rfc-editor.org/info/rfc4728";><front><title>The Dynamic
Source Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4</title><author initials="D." surname="Johnson" fullname="D.
Johnson"><organization/></author><author initials="Y." surname="Hu"
fullname="Y. Hu"><organization/></author><author initials="D." surname="Maltz"
fullname="D. Maltz"><organization/></author><date year="2007"
month="February"/><abstract><t>The Dynamic Source Routing protocol (DSR) is a
simple and efficient routing protocol designed specifically for use in
multi-hop wireless ad hoc networks of mobile nodes. DSR allows the network to
be completely self-organizing and self-configuring, without the need for any
existing network infrastructure or administration. The protocol is composed of
the two main mechanisms of "Route Discovery" and "Route Maintenance", which
work together to allow nodes to discover and maintain routes to arbitrary
destinations in the ad hoc network. All aspects of the protocol operate
entirely on demand, allowing the routing packet overhead of DSR to scale
automatically to only what is needed to react to changes in the routes
currently in use. The protocol allows multiple routes to any destination and
allows each sender to select and control the routes used in routing its
packets, for example, for use in load balancing or for increased robustness.
Other advantages of the DSR protocol include easily guaranteed loop-free
routing, operation in networks containing unidirectional links, use of only
"soft state" in routing, and very rapid recovery when routes in the network
change. The DSR protocol is designed mainly for mobile ad hoc networks of up
to about two hundred nodes and is designed to work well even with very high
rates of mobility. This document specifies the operation of the DSR protocol
for routing unicast IPv4 packets. This memo defines an Experimental Protocol
for the Internet community.</t></abstract></front><seriesInfo name="RFC"
value="4728"/><seriesInfo name="DOI"
value="10.17487/RFC4728"/></reference><reference anchor="RFC4861"
target="http://www.rfc-editor.org/info/rfc4861";><front><title>Neighbor
Discovery for IP version 6 (IPv6)</title><author initials="T." surname="Narten"
fullname="T. Narten"><organization/></author><author initials="E."
surname="Nordmark" fullname="E. Nordmark"><organization/></author><author
initials="W." surname="Simpson" fullname="W.
Simpson"><organization/></author><author initials="H." surname="Soliman"
fullname="H. Soliman"><organization/></author><date year="2007"
month="September"/><abstract><t>This document specifies the Neighbor Discovery
protocol for IP Version 6. IPv6 nodes on the same link use Neighbor Discovery
to discover each other's presence, to determine each other's link-layer
addresses, to find routers, and to maintain reachability information about the
paths to active neighbors. [STANDARDS-TRACK]</t></abstract></front><seriesInfo
name="RFC" value="4861"/><seriesInfo name="DOI"
value="10.17487/RFC4861"/></reference><reference anchor="RFC5148"
target="http://www.rfc-editor.org/info/rfc5148";><front><title>Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)</title><author initials="T."
surname="Clausen" fullname="T. Clausen"><organization/></author><author
initials="C." surname="Dearlove" fullname="C.
Dearlove"><organization/></author><author initials="B." surname="Adamson"
fullname="B. Adamson"><organization/></author><date year="2008"
month="February"/><abstract><t>This document provides recommendations for
jittering (randomly modifying timing) of control traffic transmissions in
Mobile Ad hoc NETwork (MANET) routing protocols to reduce the probability of
transmission collisions. This memo provides information for the Internet
community.</t></abstract></front><seriesInfo name="RFC"
value="5148"/><seriesInfo name="DOI"
value="10.17487/RFC5148"/></reference><reference anchor="RFC6130"
target="http://www.rfc-editor.org/info/rfc6130";><front><title>Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)</title><author
initials="T." surname="Clausen" fullname="T.
Clausen"><organization/></author><author initials="C." surname="Dearlove"
fullname="C. Dearlove"><organization/></author><author initials="J."
surname="Dean" fullname="J. Dean"><organization/></author><date year="2011"
month="April"/><abstract><t>This document describes a 1-hop and symmetric 2-hop
neighborhood discovery protocol (NHDP) for mobile ad hoc networks (MANETs).
[STANDARDS-TRACK]</t></abstract></front><seriesInfo name="RFC"
value="6130"/><seriesInfo name="DOI"
value="10.17487/RFC6130"/></reference><!--<?rfc include="reference.RFC.6621" ?>
--><reference anchor="I-D.perkins-irrep"><front><title>Intermediate RREP for
dynamic MANET On-demand (AODVv2) Routing</title><author initials="C"
surname="Perkins" fullname="Charles Perkins"><organization/></author><date
month="May" day="30" year="2015"/><abstract><t>The Ad Hoc On-demand Distance
Vector (AODVv2) routing protocol is intended for use by mobile routers in
wireless, multihop networks. AODVv2 determines unicast routes among AODVv2
routers within the network in an on-demand fashion, offering on-demand
convergence in dynamic topologies. This document specifies an extension to
AODVv2 (possibly useful with other reactive routing protocols) enabling
intermediate nodes to shorten route discovery
times.</t></abstract></front><seriesInfo name="Internet-Draft"
value="draft-perkins-irrep-03"/><format type="TXT"
target="http://www.ietf.org/internet-drafts/draft-perkins-irrep-03.txt"/></reference><reference
anchor="Perkins94" quote-title="true"><front><title>Highly Dynamic
Destination-Sequenced Distance-Vector Routing (DSDV) for Mobile
Computers</title><author fullname="Charles E. Perkins" initials="C."
surname="Perkins"><organization>IBM, TJ Watson Research Center
</organization></author><author fullname="Pravin Bhagwat" initials="P."
surname="Bhagwat"><organization>Computer Science Department, University of
Maryland </organization></author><date month="August"
year="1994"/></front><seriesInfo name="Proceedings" value="of the ACM SIGCOMM
'94 Conference on Communications Architectures, Protocols and Applications,
London, UK, pp. 234-244"/></reference><reference anchor="Perkins99"
quote-title="true"><front><title>Ad hoc On-Demand Distance Vector (AODV)
Routing</title><author fullname="Charles E. Perkins" initials="C."
surname="Perkins"><organization/></author><author fullname="Elizabeth M. Royer"
initials="E." surname="Royer"><organization>University of
California</organization></author><date month="February"
year="1999"/></front><seriesInfo name="Proceedings" value="of the 2nd IEEE
Workshop on Mobile Computing Systems and Applications, New Orleans, LA, pp.
90-100"/></reference><reference anchor="Sholander02"
quote-title="true"><front><title>A Portable Software Implementation of a Hybrid
MANET Routing Protocol</title><author fullname="P. Sholander" initials="P."
surname="Sholander"/><author fullname="P. Coccoli" initials="P."
surname="Coccoli"/><author fullname="T. Oakes" initials="T."
surname="Oakes"/><author fullname="S. Swank" initials="S."
surname="Swank"/><date year="2002"/></front></reference><reference
anchor="Koodli01" quote-title="true"><front><title>Fast handovers and context
transfers in mobile networks</title><author fullname="Rajeev Koodli"
initials="R." surname="Koodli"/><author fullname="Charles E. Perkins"
initials="C." surname="Perkins"/><date month="October"
year="2001"/></front><seriesInfo name="Proceedings" value="of the ACM SIGCOMM
Computer Communication Review 2001, Volume 31 Issue 5,
37-47"/></reference><!--<?rfc include="reference.I-D.chakeres-manet-manetid" ?>
<?rfc include="reference.I-D.clausen-lln-loadng" ?> --></references><!--This
document was prepared using Pandoc2rfc, https://github.com/miekg/pandoc2rfc ;
--><section title="AODVv2 Draft Updates" anchor="aodvv2-draft-updates"
toc="default"><t>This section lists the changes between AODVv2 revisions
...-13.txt and ...-14.txt. </t><t><list style="symbols"><t>Moved Address Type
TLV Value definitions to IANA section. </t><t>Removed use of MAX_HOPCOUNT and
<xref target="RFC5444" pageno="false" format="default"/> msg-hop-limit,
msg-hop-count. </t><t>Allow only one Unconfirmed route. </t><t>Incorporate
changes from Justin Dean's review. </t></list></t></section> </back>
</rfc>
