[aodvv2-discuss] New draft revision
- From: Charlie Perkins <charles.perkins@xxxxxxxxxxxxx>
- To: aodvv2-discuss@xxxxxxxxxxxxx
- Date: Mon, 29 Dec 2014 15:00:39 -0800
Hello folks,
I have managed to get my local mirror of GitHub into a state that I
do not understand. So, here are some files for the revision that I could
submit to the IETF.
Lotte, you may want to have a better address -- if so, please let me
know and I'll make the correction.
Similarly for any other comments you may notice. Please also review
the new appendix about "Changes since ...-05.txt".
Hope your holidays are merry and bright!
Regards,
Charlie P.
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(using these PIs as follows is recommended by the RFC Editor) -->
<?rfc comments="yes"?>
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<!--
==================================== 80 ========================================
==================================== 72 ================================
-->
<!--
Check for lines containing the string "CEP".
Also for lines containing the string "JPD" (John Dowdell 20140827)
-->
<rfc category="std" docName="draft-ietf-manet-aodvv2-06" ipr="trust200902">
<front>
<title abbrev="AODVv2">Dynamic MANET On-demand (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.dowdell486@xxxxxxxxx</email>
</address>
</author>
<author fullname="Lotte Steenbrink" initials="L." surname="Steenbrink">
<organization>Hamburg University of Applied Sciences</organization>
<address>
<postal>
<street>Berliner Tor 5</street>
<city>Hamburg</city>
<code>20099</code>
<country>Germany</country>
</postal>
<email>lotte.steenbrink@xxxxxxxxxxxxxx</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>
<t>The revised 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 rapid
convergence in dynamic topologies.</t>
</abstract>
</front>
<middle>
<section title="Overview">
<t>The revised Ad Hoc On-demand Distance Vector (AODVv2) routing protocol
[formerly named DYMO] enables
on-demand, multihop unicast routing among AODVv2
routers in mobile ad hod networks [MANETs]<xref target="RFC2501"/>.
The basic operations of the AODVv2 protocol are route
discovery and route maintenance. Route discovery is performed when
an AODVv2 router must transmit a packet
towards a destination for which it does not have a route.
Route maintenance is performed to avoid prematurely expunging routes
from the route table, and to avoid dropping packets when a
route breaks.</t>
<t>During route discovery, the originating AODVv2 router (RREQ_Gen)
multicasts a Route Request message (RREQ) to find a route toward some
target
destination. Using a hop-by-hop regeneration algorithm, each AODVv2
router receiving the RREQ message records a route toward the originator.
When the target's AODVv2 router (RREP_Gen) receives the RREQ, it records a
route toward RREQ_Gen and generates a Route Reply (RREP) unicast
toward RREQ_Gen. Each AODVv2 router that receives the RREP stores a
route toward the target, and again unicasts the RREP toward the
originator. When RREQ_Gen receives the RREP, routes have then been
established between RREQ_Gen (the originating AODVv2 router) and
RREP_Gen (the target's AODVv2 router) in both directions.</t>
<t>Route maintenance consists of two operations. In order to
maintain routes, AODVv2 routers extend route lifetimes upon
successfully forwarding a packet. When a data packet is received to
be forwarded but there is no valid route for the destination,
then the AODVv2 router of the source of the packet is notified via
a Route Error (RERR) message. Each upstream router that receives
the RERR marks the route as broken. Before such an upstream AODVv2
router could forward a packet to the same destination, it would have
to perform route discovery again for that destination. RERR messages
are also used to notify upstream routers when routes break (say,
due to loss of a link to a neighbor).</t>
<t>AODVv2 uses sequence numbers to assure loop freedom
<xref target="Perkins99"/>, similarly to AODV. Sequence numbers
enable AODVv2 routers to determine the temporal order of AODVv2 route
discovery messages, thereby avoiding use of stale routing information.
See <xref target="represent"/> for the mapping of AODVv2 data elements
to RFC 5444 Address Block, Address TLV, and Message TLV formats.
</t>
</section>
<section title="Terminology">
<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"/>.</t>
<t>This document uses terminology from <xref target="RFC5444"/>.</t>
<!-- JPD Need to check the terminology from RFC5444 is used consistently
-->
<t>This document defines the following terms:</t>
<t><list style="hanging">
<t hangText="Adjacency"><vspace/> A bi-directional relationship
between neighboring AODVv2 routers for the purpose of
exchanging routing information. Not every pair of neighboring
routers will necessarily form an adjacency.
Monitoring of
adjacencies where packets are being forwarded is required (see
<xref target="link_breaks"/>).</t>
<t hangText="AODVv2 Router"><vspace/>An IP addressable device in the
ad-hoc network that performs the AODVv2 protocol operations
specified in this document.</t>
<t hangText="AODVv2 Sequence Number (SeqNum)"><vspace/>
Same as Sequence Number. </t>
<t hangText="Client Interface"><vspace/>An interface that directly connects
Router Clients to the Router.</t>
<t hangText="Current_Time"><vspace/>The current time as maintained by
the AODVv2 router. <!-- from which RFC?? CEP -->
<!-- [JPD] Need to have a discussion of time somewhere in the text.
If no security, only need locally scoped time. Add security, and you
need globally scoped time to support SSL etc -->
<!-- CEP: It would be wrong to require NTP for ad hoc networks -->
<!-- JPD: Completely agree, but to maintain security should we say that
some method of acquiring time either locally (eg from GPS) or
remotely (eg NTP or tlsdate) is necessary? I think it would be wrong to
mandate a particular method but I believe we need to say something -->
</t>
<t hangText="Data Element"><vspace/>A named object used within AODVv2
protocol messages</t>
<t hangText="Disregard"><vspace/>Ignore for further processing
(see <xref target="MsgXmit"/>).
<!-- CEP: Issue number goes here
, and discard unless it is
required to keep the message in the packet for purposes
of authentication. -->
<!-- CEP: Look for the string "CEP" and insert Issue #s as needed... -->
</t>
<!-- downstream never appears in the text, and there was a complaint about it.
<t hangText="downstream"><vspace /> In the direction from OrigAddr to
TargAddr.</t>
-->
<t hangText="Handling Router (HandlingRtr)"><vspace/> HandlingRtr denotes
the AODVv2 router receiving and handling an AODVv2 message.</t>
<t hangText="Incoming Link"><vspace/>A link over which an AODVv2 Router
has received a message from an adjacent router.</t>
<t hangText="MANET"><vspace/> A Mobile Ad Hoc Network as defined in
<xref target="RFC2501"/>.</t>
<t hangText="MetricList"><vspace/>
A MetricList is a list of Metrics associated with the addresses
in an AddressList.</t>
<t hangText="Node"><vspace/>An IP addressable device in the ad-hoc network.
A node may be an AODVv2 router, or it may be a device in the
network that does not perform any AODVv2 protocol operations.
All nodes in this document are either AODVv2 Routers or
else Router Clients.</t>
<t hangText="OrigAddr"><vspace/> The IP address of the Originating Node
used as a data element within AODVv2 messages.</t>
<t hangText="Originating Node (OrigNode)"><vspace/>
The Originating Node is the node that launched the application
requiring communication with the Target Address. If OrigNode is a
Router Client, its AODVv2 router (RREQ_Gen) has the
responsibility to generate a AODVv2 RREQ message on behalf of
OrigNode as necessary to discover a route.</t>
<!-- [JPD] "its AODV Router" implies only one router per
set of router clients -->
<!-- [CEP] Yes, that is correct; no multihoming yet -->
<t hangText="PrefixLengthList"><vspace/>
A PrefixLengthList is the list of prefix lengths associated with the
addresses in an AddressList.
</t>
<t hangText="Reactive"><vspace/> A protocol operation is called "reactive"
if it is performed only in reaction to specific events. As used in
this document, "reactive" is synonymous with "on-demand". </t>
<!-- word "essentially" deleted, either synonymous or not -->
<!-- [CEP] Well, O.K., but no two words are absolutely synonymous. -->
<t hangText="Routable Unicast IP Address"><vspace/>
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"/>
<!-- [JPD] ULAs are NOT globally routable -->
<!-- [CEP] That is true, but they *are* routable unicast addresses -->
are examples of routable unicast IP addresses.</t>
<!-- Can a node determine whether an address is multihop-capable? [CEP] -->
<t hangText="Route Error (RERR)"><vspace/>
A RERR message is used to indicate that an AODVv2 router does not
have a route toward one or more particular destinations.
</t>
<t hangText="Route Reply (RREP)"><vspace/>
A RREP message is used to establish a route between <!-- RREQ -->
the Target Address and the Originating Address, at all the AODVv2
routers between them.</t>
<t hangText="Route Request (RREQ)"><vspace/>
An AODVv2 router uses a RREQ message to discover a valid route
to a particular destination address, called the Target Address.
An AODVv2 router processing a RREQ receives routing information
for the Originating Address.</t>
<t hangText="Router Client"><vspace/>A node that requires
the services of an AODVv2 router for route discovery and
maintenance. An AODVv2 router is always its own client,
so that its list of client IP addresses is never empty.</t>
<t hangText="Router Interface"><vspace/>An interface supporting the
transmission or reception of Router Messages.</t>
<t hangText="RREP Generating Router (RREP_Gen)"><vspace/>
The RREP Generating Router is the AODVv2 router that serves TargNode.
RREP_Gen generates the RREP message to advertise a route towards
TargAddr from OrigAddr.
</t>
<t hangText="RREQ Generating Router (RREQ_Gen)"><vspace/>
The RREQ Generating Router is the AODVv2 router that serves OrigNode.
RREQ_Gen generates the RREQ message to discover a route for TargAddr.
</t>
<t hangText="Sequence Number (SeqNum)"><vspace/>
A Sequence Number is an unsigned integer maintained by an AODVv2
router to avoid re-use of stale messages. The router associates
SeqNum with the IP address of its network interface. If the router
has multiple network interfaces, it can use the same SeqNum for the
IP addresses of all of them, or it can assign different SeqNums for
use with different IP addresses. However, the router MUST NOT
use multiple SeqNums for any particular IP address.
A Router Client has the same SeqNum as the
IP address of the network interface that the AODVv2 router uses
to forward packets to that Router Client. Similarly, a route to
a subnet has the same SeqNum as the IP address of the network
interface that the AODVv2 router uses to forward packets to that
subnet. The Sequence Number guarantees the temporal
order of routing information to maintain loop-free routes,
and fulfills the same role as the "Destination Sequence Number" of
DSDV <xref target="Perkins94"/>, and as the AODV Sequence Number in
RFC 3561<xref target="RFC3561"/>.
The value zero (0) is reserved to indicate that the Sequence Number
for an address is unknown.</t>
<t hangText="SeqNumList"><vspace/>
A SeqNumList is the list of Sequence Numbers associated with the addresses
in an AddressList.
</t>
<t hangText="TargAddr"><vspace/> The IP address of the Target Node
used as a data element within AODVv2 messages.</t>
<t hangText="Target Node (TargNode)"><vspace/>
The Target Node denotes the node hosting the IP address towards
which a route is needed.</t>
<t hangText="Unreachable Addr (UnreachableAddr)"><vspace/> An UnreachableAddr
is an address for which a valid route is not known.</t>
<t hangText="upstream"><vspace/> In the direction from TargAddr to OrigAddr.
<!-- For any routing path, source of traffic
using the routing path, and router on that routing path, the other
routers between the source and that router, are called upstream
routers. -->
<!-- O.K. if the WG likes it, but it does not describe all cases of RERR -->
</t>
<t hangText="Valid route"><vspace/> A route that can be used for
forwarding; in other words a route that is not Broken or Expired.</t>
</list></t>
<t><vspace blankLines="19"/></t>
</section>
<section anchor="notation"
title="Data Elements and Notational Conventions">
<t>This document uses the Data Elements and conventions found in
<xref target="data-elements"/> and
<xref target="notational-conventions"/>.</t>
<texttable anchor="data-elements">
<ttcol align="left" width="20%">Data Elements</ttcol>
<ttcol align="left">Meaning</ttcol>
<c>msg_hop_limit</c>
<c>Number of hops allowable for the message.</c>
<c>msg_hop_count</c>
<c>Number of hops traversed so far by the message.</c>
<c>AckReq</c> <c>Acknowledgement Requested for RREP</c>
<c>MetricType</c> <c>Metric Type for Metric data element</c>
<c>PktSource</c> <c>The IP address which is unreachable.</c>
<c>AddressList</c> <c>A list of IP addresses</c>
<c>SeqNum</c> <c>Sequence Number</c>
<c>SeqNumList</c> <c>Sequence Number List</c>
<c>Metric</c> <c>Metric value for route to associated IP address</c>
<c>OrigSeqNum</c> <c>Originating Node Sequence Number</c>
<c>TargSeqNum</c> <c>Target Node Sequence Number</c>
</texttable>
<texttable anchor="notational-conventions">
<ttcol align="left" width="25%">Notation</ttcol>
<ttcol align="left">Meaning</ttcol>
<c>Route[Address]</c> <c>A route table entry towards Address</c>
<c>Route[Address].{field}</c> <c>A field in a route table entry</c>
<c> -- </c> <!-- Types of Nodes --> <c> -- </c>
<c>RREQ_Gen</c> <c>AODVv2 router originating an RREQ</c>
<c>RREP_Gen</c> <c>AODVv2 router responding to an RREQ</c>
<c>RteMsg</c> <c>Either RREQ or RREP</c>
<c>RteMsg.{field}</c> <c>Field in RREQ or RREP</c>
<c>AdvRte</c> <c>a route advertised in an incoming RteMsg</c>
<c>HandlingRtr</c> <c>Handling Router</c>
<c>UnreachableAddr</c> <c>Unreachable Addr</c>
</texttable>
</section>
<section anchor="apply" title="Applicability Statement">
<t>The AODVv2 routing protocol is a reactive routing protocol
designed for stub (i.e., non-transit) or
disconnected (i.e., from the Internet) mobile ad hoc networks (MANETs).
AODVv2 handles a wide variety of mobility patterns by determining
routes on-demand. AODVv2 also handles a wide variety of traffic
patterns. In networks with a large number of routers, AODVv2 is
best suited for relatively sparse traffic scenarios where any
particular router forwards packets to only a small percentage of
the AODVv2 routers in the network, due
to the on-demand nature of route discovery and route maintenance.
AODVv2 supports routers with multiple interfaces, as long
as each interface has its own (unicast routeable) IP address; the set
of all network interfaces supporting AODVv2 is administratively
configured in a list (namely, AODVv2_INTERFACES).
<!--
The nets do not have to be mobile, and AODVv2 may be applicable
in low power lossy sensor networks.
-->
</t>
<t>Although AODVv2 is closely related to AODV
<xref target="RFC3561"/>, and shares some features of DSR
<xref target="RFC4728"/>, AODVv2 is not interoperable with
either of those other two protocols.</t>
<!-- Issue #22 -->
<t>AODVv2 is applicable to memory constrained devices, since
only a little routing state is maintained in each AODVv2 router.
Routes that are not needed for forwarding data do
not have to be maintained,
in contrast to proactive routing protocols
that require routing information to all routers within the
MANET be maintained.</t>
<t>
In addition to routing for its own local applications, each AODVv2 router
can also route on behalf of other non-routing nodes (in this document,
"Router Clients"), reachable via Client Interfaces. Each AODVv2 router,
if serving router clients other than itself, SHOULD be configured with
information about the IP addresses of its clients,
using any suitable method.
In the initial state, no AODVv2 router is required to have information
about the relationship between any other AODVv2 router and its
Router Clients (see <xref target="clients"/>).
</t>
<t> The coordination among multiple AODVv2 routers to distribute
routing information correctly for a shared address (i.e. an address
that is advertised and can be reached via multiple AODVv2 routers) is
not described in this document. The AODVv2 router operation of shifting
responsibility for a routing client from one AODVv2 router to
another is described in <xref target="change_address_location"/>.
Address assignment procedures are entirely out of scope for AODVv2.
A Router Client SHOULD NOT
be served by more than one AODVv2 router at any one time.</t>
<t>AODVv2 routers perform route discovery to find a route toward a
particular destination. AODVv2 routers MUST must be
configured to respond to RREQs for themselves and their clients.
<!-- [JPD] "certain set of addresses? Which ones, described where? -->
<!-- [CEP]: themselves and their clients... -->
When AODVv2 is the only protocol interacting with the forwarding
table, AODVv2 MAY be configured to perform route discovery for
all unknown unicast destinations.</t>
<t>AODVv2 only supports bidirectional links. In the case of possible
unidirectional links, blacklists (see <xref target="blacklists"/>)
SHOULD be used,
<!-- [JPD] delete following text: -->
<!-- [CEP] see below ... -->
or other means (e.g. adjacency establishment
with only neighboring routers that have bidirectional
communication as indicated by NHDP <xref target="RFC6130"/>) of
assuring and monitoring bi-directionality are recommended.
<!-- If the text is deleted, the specification is suddenly wrong,
because implementations that use other methods do not need to
keep blacklists -->
Otherwise, persistent packet loss or persistent protocol
failures could occur. The cost of bidirectional link L (denoted Cost(L))
may depend upon the direction across the link for which the cost is
measured. If received over a link that is unidirectional, metric
information from incoming AODVv2 messages MUST NOT
be used for route table updates.
</t>
<!-- CEP : this can be deleted -->
<t>The routing algorithm in AODVv2 may be operated at layers other
than the network layer, using layer-appropriate addresses.
The routing algorithm makes use of some persistent state; if there
is no persistent storage available for this state, recovery can
impose a performance penalty (e.g., in case of AODVv2 router reboots).</t>
</section>
<!-- ============================================================= -->
<section anchor="MsgXmit" title="AODVv2 Message Transmission">
<t> In its default mode of operation, AODVv2 sends messages
using the parameters for port number and IP protocol specified in
<xref target="RFC5498"/>.
<!-- In addition, IP Protocol Number 138
has been reserved for MANET protocols <xref target="RFC5498" />. -->
By default, AODVv2 messages are sent with the IP destination address
set to the link-local multicast address LL-MANET-Routers
<xref target="RFC5498"/> unless otherwise specified. Therefore,
all AODVv2 routers
MUST <!-- MUST [CEP] -->
subscribe to LL-MANET-Routers <xref target="RFC5498"/> to
receive AODVv2 messages.
In order to reduce multicast overhead, regenerated multicast
packets in MANETs SHOULD be done according to
methods specified in <xref target="RFC6621"/>. AODVv2 does
not specify which method should be used to restrict the
set of AODVv2 routers that have the responsibility to
regenerate multicast packets. Note that multicast packets 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>The IPv4 TTL (IPv6 Hop Limit) field for all packets
containing AODVv2 messages is set to 255. If a packet is
received with a value other than 255, any AODVv2 message
contained in the packet MUST be disregarded by AODVv2.
This mechanism, known as "The Generalized TTL Security Mechanism"
(GTSM) <xref target="RFC5082"/> helps to assure that packets
have not traversed any intermediate routers.</t>
<t>IP packets containing AODVv2 protocol messages SHOULD be
given priority queuing and channel access.</t>
</section>
<!-- ============================================================= -->
<section title="Data Structures">
<section anchor="rte" title="Route Table Entry">
<t>The route table entry is a conceptual data structure.
Implementations MAY use any internal representation so long as
it provides access to the information specified below.</t>
<t>A route table entry has the following fields:
<list style="hanging">
<t hangText="Route.Address"><vspace/>An address or address prefix
of a node</t>
<t hangText="Route.PrefixLength"><vspace/>
The length of the address or prefix. If the value of
Route.PrefixLength is less than the length of addresses
in the address family used by the AODVv2 routers,
the associated address is a routing prefix, rather than an
address. A PrefixLength is stored for every
route in the route table.</t>
<t hangText="Route.SeqNum"><vspace/>
The Sequence Number associated with Route.Address,
as obtained from the last packet that successfully updated this
route table entry.</t>
<!-- CEP: The neighbor might have more than one IP address -->
<t hangText="Route.NextHopAddress"><vspace/>The IP
address of the adjacent AODVv2 router used for the path toward the
Route.Address</t>
<t hangText="Route.NextHopInterface"><vspace/>The
interface used to send packets toward
Route.Address</t>
<t hangText="Route.LastUsed"><vspace/>The time that this
route was last used</t>
<t hangText="Route.ExpirationTime"><vspace/>The time
at which this route must expire</t>
<t hangText="Route.MetricType"><vspace/>The type of the metric
for the route towards Route.Address</t>
<t hangText="Route.Metric"><vspace/>The cost of the route
towards Route.Address expressed in units consistent with
Route.MetricType</t>
<t hangText="Route.State"><vspace/>The last *known* state of the route.
Route.State is one of the following:
Active, Idle, Expired, or Broken.</t>
<t hangText="Route.Timed"><vspace/>
The Route.Timed flag is true if the route was specified to
have a specific lifetime for use.
</t>
<!-- [JPD] why are route precursors optional? -->
<!-- [CEP] They should be "SHOULD" but don't affect interoperability -->
<t hangText="Route.Precursors (optional)"><vspace/>
A list of upstream nodes using the route.
</t>
</list></t>
<!-- [CEP]: If these are definitional, then the operational details
should be located elsewhere, I think. They were just below. -->
<!-- The route's state determines the
operations that can be performed
on the route table entry. -->
<t>A route table entry (i.e., a route) is in one of the
following states:
<list style="hanging">
<t hangText="Active"><vspace/> An Active route is in current
use for forwarding packets. An Active route is
maintained continuously by AODVv2 and is considered to remain
active as long as it is used at least once during every
ACTIVE_INTERVAL, or if the Route.Timed flag is true. When
a route that is not a timed route is no longer active
the route becomes an Idle route.
</t>
<t hangText="Idle"><vspace/> An Idle route can be used for
forwarding packets, even though it is not in current use.
If an Idle route is used to forward a packet, it becomes
an Active route once again.
<!-- "update_rte" -->
After an Idle route remains idle for
MAX_IDLETIME, it becomes an Expired route.
</t>
<t hangText="Expired"><vspace/> After a route has been idle for
too long, it expires, and may no longer be used for
forwarding packets. An Expired
route is not used for forwarding, but the sequence
number information can be maintained until the destination
sequence number has had no updates for MAX_SEQNUM_LIFETIME;
after that time, old sequence number information is considered
no longer valuable and the Expired route MUST BE expunged.
</t>
<t hangText="Broken"><vspace/> A route marked as Broken cannot be
used for forwarding packets but still has valid destination
sequence number information. When the link to a route's next hop
is broken, the route is marked
as being Broken, and afterwards the route MAY NOT be used.
</t>
<t hangText="Timed"><vspace/> The expiration of a Timed route
is controlled by the Route.ExpirationTime time of the
route table entry (instead of MAX_IDLETIME). Until that time,
a Timed route can be used for forwarding packets. A route
is indicated to be a Timed route by the setting of the
Route.Timed flag in the route table entry.
Afterwards, the route MAY be expunged; otherwise the
route must be must be marked as Expired.
</t>
</list> </t>
<t>MAX_SEQNUM_LIFETIME is the time after a reboot during which an
AODVv2 router MUST NOT transmit any routing messages. Thus,
if all other AODVv2 routers expunge routes to the rebooted
router after that time interval, the rebooted AODVv2 router's
sequence number will not be considered stale by any other
AODVv2 router in the MANET.
</t>
</section>
<section anchor="blacklists"
title="Bidirectional Connectivity and Blacklists">
<!-- [JPD] I believe that the following section should be mandatory and
therefore the SHOULDs and MAYs should become MUST and WILL. Personally I
feel that the 'any unicast packet' method should be changed for an
explicit
AODVv2 method such as RREP AckReply, to give interoperability between
different implementations. Also, given that AODVv2 does not support
unidirectional links, the SHOULD NOT regarding regeneration of messages
received over known unidirectional links must be changed to a MUST NOT.
However, I am a RFC newbie, and reading RFC2119 am aware that a method
expressed as SHOULD must appear in an implementation unless there is a
really good reason not to put it in..... thus my proposed text is
as below and I am happy to be taken down if I am getting this wrong! -->
<t>To avoid repeated failure of Route Discovery, an AODVv2 router
<!-- [CEP]: to discuss MUST versus MAY here... -->
(HandlingRtr) handling a RREP message MUST attempt to verify
connectivity towards RREQ_Gen. This MAY be done by
including the Acknowledgement Request (AckReq) data element
in the RREP. In reply to an AckReq, an RREP_ACK message
message MUST be sent.
If the verification
is not received within UNICAST_MESSAGE_SENT_TIMEOUT,
HandlingRtr MUST put the upstream neighbor in the
blacklist. RREQs received from a blacklisted router, or any
router over a link that is known to be incoming-only, MUST NOT
be regenerated by HandlingRtr.
However, the upstream neighbor SHOULD NOT be permanently
blacklisted; after a certain time (MAX_BLACKLIST_TIME),
it SHOULD once again be considered as a viable upstream
neighbor for route discovery operations.
</t>
<t>For this purpose, a list of blacklisted routers along with
their time of removal SHOULD be maintained:
<list style="hanging">
<t hangText="Blacklist.Router"><vspace/>The IP address of the
router that did not verify bidirectional connectivity. </t>
<t hangText="Blacklist.RemoveTime"><vspace/>The time at which
Blacklist.Router MAY be removed from the blacklist. </t>
</list>
</t>
</section>
<section anchor="clients" title="Router Clients and Client Networks">
<t>An AODVv2 router may offer routing services to other nodes that
are not AODVv2 routers; such nodes are defined as Router Clients
in this document.
<!-- [JPD] not sure what the following text is doing here, perhaps
should be relocated to section on Sequence Numbers. .... "AODVv2
defines the Sequence Number to be the same for the AODVv2 router
and each of its clients." -->
<!-- [CEP]: it was here because it's about clients...? But if
we don't need it at all, it's O.K. with me to delete -->
</t>
<t>For this purpose, CLIENT_ADDRESSES must be configured on each
AODVv2 router with the following information:
<list style="hanging">
<t hangText="Client IP address"><vspace/>The IP address of the
node that requires routing service from the AODVv2
router.</t>
<t hangText="Client Prefix Length"><vspace/>The length of the
routing prefix associated with the client IP address.
</t>
</list>
</t>
<t>If the Client Prefix Length is not the full length of the
Client IP address, then the prefix defines a Client
Network. If an AODVv2 router is configured to serve
a Client Network, then the AODVv2 router MUST serve
every node that has an address within the range defined
by the routing prefix of the Client Network. The list
of Routing Clients for an AODVv2 router is never empty,
since an AODVv2 router is always its own client as well.
</t>
<!-- [JPD] Question: does the built-in Route Client always have to
have a different IP address to the Router itself? -->
<!-- [CEP]: No, in fact I never imagined that the IP addresses
would be different -->
</section>
<!-- ============================================================= -->
<section anchor="seqnum" title="Sequence Numbers">
<t>
Sequence Numbers allow AODVv2 routers to evaluate the freshness of
routing information. Each AODVv2 router in the network MUST maintain its
own sequence number. Each RREQ and RREP generated by an AODVv2
router includes that sequence number.
Each AODVv2 router MUST make sure that its sequence number is
unique and monotonically increasing. This can be achieved by incrementing
it with every RREQ or RREP it generates.
</t>
<t>
Every router receiving a RREQ or RREP can thus use the Sequence Number
of a RREQ or RREP as information concerning the freshness of the packet's
route update: if the new packet's Sequence Number is lower than the one
already stored in the route table, its information is considered stale.
</t>
<t>
As a consequence, loop freedom is assured.
</t>
<!-- TODO: enable Seq# == 0 -->
<t>
An AODVv2 router increments its SeqNum as follows. Most of the time,
SeqNum is incremented by simply adding one (1). But when the
SeqNum has the value of the largest possible number representable as a
16-bit unsigned integer (i.e., 65,535), it MUST be incremented by setting
to one (1). In other words, the sequence number after 65,535 is 1.
</t>
<t>
An AODVv2 router SHOULD maintain its SeqNum in persistent storage.
If an AODVv2 router's SeqNum is lost, it MUST take the following
actions to avoid the danger of routing loops. First, the AODVv2
router MUST set Route.State =
Broken for each entry. Furthermore the AODVv2 router MUST wait
for at least MAX_SEQNUM_LIFETIME before transmitting or
regenerating any AODVv2 RREQ or RREP messages.
<!-- TODO: CEP: What about relaying RREQ? -->
If an AODVv2
protocol message is received during this waiting period, the AODVv2
router SHOULD perform normal route table entry updates, but not
forward the message to other nodes. If a data packet is received for
forwarding to another destination during this waiting period, the
AODVv2 router MUST transmit a RERR message indicating that no route
is available. At the end of the waiting period the AODVv2 router
sets its SeqNum to one (1) and begins performing AODVv2 protocol
operations again.
<!-- TODO: CEP: Actually, could forward...? -->
<!-- TODO: CEP: Actually, usual RERR rules? -->
</t>
</section>
<section anchor="metrics" title="Metrics">
<t>
Metrics describe the quality of a route or a link. They can
take various aspects into account, such as latency, delay,
financial, energy, etc. Whenever an AODV router receives metric
information in an incoming message, the value of the metric is
as measured by the transmitting router, and does not reflect
the cost of traversing the incoming link.
</t>
<t>
Each routing table entry is associated with metric information.
When presented with information which may update a route, deciding
whether to use the information involves evaluating the metric.
For some metrics, a maximum value is defined, namely MAX_METRIC[i]
where 'i' is the Metric Type. AODVv2 does not store routes in its
route table that cost more than MAX_METRIC[i].
</t>
<t>
Each metric has to have a Metric Type, and the Metric Type is
allocated by IANA as specified in <xref target="RFC6551"/>.
Apart from its default metric type, which is detailed in
<xref target="default_metric"/>, AODVv2 enables the use of
generic metrics, whose data type depends on the metric used.
The Metric Type is specified by the MetricType TLV of each RteMsg.
As a natural result of the way routes are looked up according to
conformant metric type, all intermediate routers handling a
RteMsg will assign the same metric type to all metric information
in the RteMsg.
</t>
<section anchor="cost_function" title="The Cost() function">
<t>
In order to simplify the description of storing accumulated
route costs in the route table, a Cost() function is defined.
This function returns the Cost of traversing a Route ('Cost(R)')
or a Link ('Cost(L)'). The specification of Cost(L) for metric
types other than DEFAULT_METRIC_TYPE is beyond the scope of
this document.
<!--
<t>
Let "Cost(R)", where 'R' is the route for which
the Cost is to be evaluated; the route table entry for R
includes the information about the metric type for R.
</t>
-->
</t>
</section>
<section anchor="loopfree" title="The LoopFree() function">
<t>
Since determining loop freedom is known to depend
on comparing the Cost(R) of route update information to the
Cost(R) of an existing stored route using the same metric,
AODVv2 must also be able to invoke an abstract
routine which in this document is called "LoopFree(R1, R2)".
LoopFree(R1, R2) returns TRUE when, (under the assumption of
nondecreasing SeqNum during Route Discovery) given that R2 is
loop-free and Cost(R2) is the cost of route R2, Cost(R1) is
known to guarantee loop freedom of the route R1.
In this document, an AODVv2 router will only invoke
LoopFree (AdvRte, Route), for routes AdvRte and Route
which use the same metric to the same destination.
AdvRte is the route advertised in an incoming RREQ
or RREP, and is used as parameter R1 for LoopFree.
Route is a route already existing in the AODVv2 router's
route table, and is used as parameter R2 for LoopFree.
</t>
</section>
<section anchor="default_metric" title="Default Metric type">
<t>
HopCount is still the default metric for use in MANETs,
notwithstanding the above objections.
Therefore, the default Metric Type DEFAULT_METRIC_TYPE is
Hop Count. It is also the only metric described in detail
by this protocol. With this metric, Cost(L) is always 1,
and Cost(R) is simply the hop count between the router
and the destination.
</t>
<t>
MAX_METRIC[DEFAULT_METRIC_TYPE] is defined to be MAX_HOPCOUNT.
MAX_HOPCOUNT MUST be larger than the AODVv2 network diameter.
Otherwise, AODVv2 protocol messages may not reach their
intended destinations.
</t>
<t>
Using Metric Type DEFAULT_METRIC_TYPE, LoopFree (AdvRte, Route)
is TRUE when Cost(AdvRte) ≤ Cost(Route). The specification of
Cost(R) and LoopFree(AdvRte, Route) for metric types other than
DEFAULT_METRIC_TYPE is beyond the scope of this document.
</t>
</section>
<section anchor="alternate_metrics" title="Alternate Metrics">
<t>
Some applications may require metric
information other than Hop Count, which has traditionally been
the default metric associated with routes in MANET.
It is well known that reliance on Hop Count can cause selection
of the worst possible route in many situations. For this reason,
it is important to enable route selection based on metric
information other than Hop Count -- in other words, based on
"alternate metrics".
</t>
<t>
The range and data type of each such alternate metric may be
different. For instance, the data type might be integers, or
floating point numbers, or restricted subsets thereof.
It is out of the scope of this document to specify for alternate
metrics the Cost(L) and Cost(R) functions, or their return type.
</t>
</section>
</section>
<section anchor="supp-tbl" title="RREQ Table: Received RREQ Messages">
<t>
Two incoming RREQ messages are considered to be "comparable" if
they were generated by the same AODVv2 router in order to
discover a route for the same destination with the same metric
type. According to that notion
of comparability, when RREQ messages are flooded in a MANET,
an AODVv2 router may well receive comparable RREQ messages
from more than one of its neighbors. A router, after receiving
an RREQ message, MUST check against previous RREQs to assure
that its response message would contain information that
is not redundant (see <xref target="suppress"/> regarding
suppression of redundant RREQ messages).
Otherwise, multicast RREQs are likely to be regenerated
again and again with almost no additional benefit,
but generating a great deal of unnecessary signaling traffic
and interference.
</t>
<t>
To avoid transmission of redundant RREQ messages,
while still enabling the proper handling of earlier RREQ
messages that may have somehow been delayed in the network,
it is needed for each AODVv2 router to keep a list of the
certain information about RREQ messages which it
has recently received.
</t>
<t>
This list is called the AODVv2
Received RREQ Table -- or, more briefly, the RREQ Table.
Two AODVv2 RREQ messages are comparable if:
<list style="symbols">
<t>they have the same metric type</t>
<t>they have the same OrigAddr and TargAddr</t>
</list>
</t>
<t>
Each entry in the RREQ Table has the following fields:
<list style="symbols">
<t>OrigAddr</t>
<t>TargAddr</t>
<t>OrigNode Sequence Number</t>
<t>TargNode Sequence Number (if present in RREQ)</t>
<t>Metric Type</t>
<t>Metric</t>
<t>Timestamp</t>
</list>
The RREQ Table is maintained so that no two entries in the
RREQ Table are comparable -- that is, all RREQs represented
in the RREQ Table either have a different OrigAddr,
different TargAddr, or different metric types.
If two RREQs have the same metric type, OrigAddr, and
TargAddr, the information from
the one with the older Sequence Number is not needed in the
table; in case
they have the same Sequence Number, the one with the greater
Metric value is not needed; in case they have the same Metric
as well, it does not matter which table entry is maintained.
Whenever a RREQ Table entry is updated, its Timestamp field
should also be updated to reflect the Current_Time.
</t>
<t>
When optional multicast RREP (see <xref target="mcast-to-RREQ"/>) is
used to enable selection from among multiple possible return routes,
an AODVv2 router can eliminate redundant RREP messages using the
analogous mechanism along with a RREP Table.
The description in this section only refers to RREQ multicast messages.
</t>
<t>
Protocol handling of RERR messages eliminates the need for
tracking RERR messages, since the rules for RERR regeneration
prevent the phenomenon of redundant retansmission
that affects RREQ and RREP multicast.
</t>
</section>
</section>
<section anchor="route-ops" title="AODVv2 Operations on Route Table Entries">
<t> In this section, operations are specified for updating the route
table due to timeouts and route updates within AODVv2 messages.
Route update information in AODVv2 messages includes IP addresses, along
with the SeqNum and prefix length associated with each IP address,
and including the Metric measured from the node transmitting the AODVv2
message to the IP address in the route update.
A RREQ message advertises a route to OrigAddr, and
a RREP message analogously advertises a route to TargAddr.
In this section, RteMsg is either RREQ or RREP, and AdvRte is the route
advertised by the RteMsg.
All SeqNum comparisons use signed 16-bit arithmetic. </t>
<section anchor="test" title="Evaluating Incoming Routing Information">
<t> If the incoming RteMsg does not have a Metric Type data element,
then the metric information contained by AdvRte is considered
to be of type DEFAULT_METRIC_TYPE -- in other words, 3
(for HopCount) unless changed by administrative action.
The AODVv2 router (HandlingRtr) checks the advertised
route (AdvRte) to see whether the AdvRte should be used to
update an existing route table entry.
HandlingRtr searches its route table to see if
there is a route table entry with the same Metric Type as the
AdvRte, matching AdvRte.Address.
If not, HandlingRtr creates
a route table entry for AdvRte.Address as described
in <xref target="update_rte"/>.
Otherwise, HandlingRtr compares
the incoming routing information for AdvRte against the
already stored routing information in the route table
entry (Route) for AdvRte.Address, as described next.
</t>
<t>Route[AdvRte.Address] uses the same metric
type as the incoming routing information, and the route
entry contains Route.SeqNum, Route.Metric, and Route.State.
Define AdvRte.SeqNum and AdvRte.Metric to be the corresponding
routing information for Route.Address in the incoming
RteMsg. Define AdvRte.Cost to be (AdvRte.Metric + Cost(L)),
where L is the link from which the incoming message was
received. The incoming routing information is classified
as follows:
<list style="hanging">
<t hangText="1. Stale::">
<![CDATA[ AdvRte.SeqNum < Route.SeqNum : ]]><vspace/>
If AdvRte.SeqNum < Route.SeqNum
the incoming information is stale. Using stale
routing information is not allowed, since that might
result in routing loops. In this case, HandlingRtr
MUST NOT update the route table entry using the
routing information for AdvRte.Address.
</t>
<t hangText="2. Unsafe against loops::">
<![CDATA[ (TRUE != LoopFree (AdvRte, Route)) :]]><vspace/>
If AdvRte is not Stale (as in (1) above), AdvRte.Cost is
next considered to insure loop freedom.
If (TRUE != LoopFree (AdvRte, Route))
(see <xref target="metrics"/>), then the
incoming AdvRte information is not guaranteed to prevent routing
loops, and it MUST NOT be used to update any route table entry.
</t>
<t hangText="3. More costly::"><vspace/><![CDATA[
(AdvRte.Cost >= Route.Metric) && (Route.State != Broken)]]>
<vspace/>
When AdvRte.SeqNum is the same as in a valid route table
entry, and LoopFree (AdvRte, Route) assures loop freedom,
incoming information still does not offer any improvement over
the existing route table information if
AdvRte.Cost ≥ Route.Metric.
Using such incoming routing information to update a route
table entry is not recommended.</t>
<t hangText="4. Offers improvement::"><vspace/> Advertised
routing information that does not match any of the above
criteria is better than existing route table information and
SHOULD be used to improve the route table.
The following pseudo-code illustrates whether advertised
routing information should be used to update an existing
route table entry as described in <xref target="update_rte"/>.
<figure>
<artwork><![CDATA[
(AdvRte.SeqNum > Route.SeqNum) OR
((AdvRte.SeqNum == Route.SeqNum) AND
[(AdvRte.Cost < Route.Metric) OR
((Route.State == Broken) && LoopFree (AdvRte, Route))])
]]></artwork>
</figure>
The above logic corresponds to placing the following conditions
(compared to the existing route table entry) on the advertised
route update before it can be used:
<list style="symbols"><t>it is more recent, or</t>
<t>it is not stale and is less costly, or</t>
<t>it can safely repair a broken route.</t>
</list></t>
</list></t>
</section>
<section anchor="update_rte"
title="Applying Route Updates To Route Table Entries">
<t>To apply the route update, a route table entry for
AdvRte.Address is either found to already exist in the
route table, or else a new route table entry for
AdvRte.Address is created and inserted into the route
table. If the route table entry already exists, and the
state is Expired or Broken,
then the state is reset to be Idle. If the route table
entry had to be created, the state is set to be Active.
<!-- Issue #39 -->
The route table entry is populated
with the following information:
<list style="symbols">
<t>If AdvRte.PrefixLength exists, then Route.PrefixLength :=
AdvRte.PrefixLength. Otherwise, Route.PrefixLength :=
maximum length for address family (either 32 or 128).</t>
<t>Route.SeqNum := AdvRte.SeqNum</t>
<t>Route.NextHopAddress := IP.SourceAddress (i.e., an
address of the node from which the RteMsg was received)</t>
<t>Route.NextHopInterface is set to the interface on which
RteMsg was received</t>
<t>Route.MetricType := AdvRte.MetricType</t>
<t>Route.Metric := AdvRte.Cost</t>
<t>Route.LastUsed := Current_Time</t>
<t>If RteMsg.VALIDITY_TIME is included, then <vspace/>
Route.Timed := TRUE and
Route.ExpirationTime := Current_Time + RteMsg.VALIDITY_TIME.
Otherwise, Route.ExpirationTime :=
Current_Time + (ACTIVE_INTERVAL + MAX_IDLETIME).
</t>
</list>
</t>
<t>With these assignments to the route table entry, a route has been
made available, and the route can be used to send any buffered data
packets and subsequently to forward any incoming data packets for
Route.Address. An updated route entry also fulfills any outstanding route
discovery (RREQ) attempts for Route.Address.</t>
</section>
<section anchor="timeout" title="Route Table Entry Timeouts">
<t>During normal operation, AODVv2 does not require any
explicit timeouts to manage the lifetime of a route.
However, the route table entry MUST be examined
before using it to forward a packet,
as discussed in <xref target="e2edata"/>.
Any required expiry or deletion can occur at
that time. Alternatively, timers and timeouts MAY
be implemented to achieve the same effect. </t>
<t>At any time, the route table can be examined and route
table entries can be expunged according to their
current state at the time of examination, as follows.
<list style="symbols">
<t>An Active route MUST NOT be expunged.</t>
<t>An Idle route SHOULD NOT be expunged.</t>
<t>An Expired route MAY be expunged
(least recently used first).</t>
<t>A route MUST be expunged if
(Current_Time - Route.LastUsed) >= MAX_SEQNUM_LIFETIME.
</t>
<t>A route MUST be expunged if
Current_Time >= Route.ExpirationTime </t>
<!-- JPD: Is this a security vulnerability if a faulty
or malicious router sets a short validity time?
CEP: I don't think it affects authenticity, but
it could be a form of denial of service.
In that case, it's no worse than if the malicious
router simply refuses to route the packets it has
agreed to route. -->
</list>
If precursor lists are maintained for the route
(as described in <xref target="precursor"/>)
then the precursor lists must also be expunged at the
same time that the route itself is expunged.
</t>
</section>
</section>
<section anchor="RteMsg" title="Routing Messages RREQ and RREP (RteMsgs)">
<t>AODVv2 message types RREQ and RREP are together known as Routing
Messages (RteMsgs) and are used to discover a route between
an Originating and Target Addr, denoted by OrigAddr and
TargAddr. The constructed route is bidirectional, enabling
packets to flow between OrigAddr and TargAddr. RREQ and RREP
have similar information and function, but have some
differences in their rules for handling. When a node receives
a RREQ or a RREP, the node then creates or updates a route to
the OrigAddr or the TargAddr respectively. The main difference
between the two messages is that RREQ messages are typically
multicast to solicit a RREP, whereas RREP is typically
unicast as a response to RREQ.</t>
<!--
RteMsg generation and
handling are described in <xref target="RteMsg"/>.
-->
<t>When an AODVv2 router needs to forward a data packet from a node
(with IP address OrigAddr) in its set of router clients, and it
does not have a forwarding route toward the packet's IP
destination address (TargAddr), the AODVv2 router
(RREQ_Gen) generates a
RREQ (as described in <xref target="RREQ_gen"/>) to
discover a route toward TargAddr. Subsequently RREQ_Gen awaits
reception of an RREP message (see <xref target="RREP_gen"/>)
or other route table update (see <xref target="update_rte"/>)
to establish a route toward TargAddr.
<!-- CEP: Issue # to be generated for moving DestOnly to the irrep draft...
Optionally, RREQ_Gen MAY specify that only the router serving
TargAddr is allowed to generate an RREP message, by including
the DestOnly data element (see <xref target="RREQ_gen" />).
-->
The RREQ message contains routing information to enable
RREQ recipients to route packets back to OrigAddr, and the
RREP message contains routing information enabling RREP
recipients to route packets to TargAddr.</t>
<section anchor="route_discovery"
title="Route Discovery Retries and Buffering">
<t>After issuing a RREQ, as described above RREQ_Gen awaits a
RREP providing a bidirectional route toward the Target Address.
If the RREP is not received within RREQ_WAIT_TIME, RREQ_Gen MAY retry
the Route Discovery by generating another RREQ. Route
Discovery SHOULD be considered to have failed after
DISCOVERY_ATTEMPTS_MAX and the corresponding
wait time for a RREP response to the final RREQ.
After the attempted Route Discovery has failed, RREQ_Gen
MUST wait at least RREQ_HOLDDOWN_TIME before attempting
another Route Discovery to the same destination.
</t>
<t>To reduce congestion in a network, repeated attempts at
route discovery for a particular Target Address SHOULD utilize a
binary exponential backoff.</t>
<t>Data packets awaiting a route SHOULD be buffered by RREQ_Gen.
This buffer SHOULD have a fixed limited
size (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES). Determining
which packets to discard first is a matter of policy at each
AODVv2 router; in the absence of policy constraints, by
default older data packets SHOULD be discarded first.
Buffering of data packets can have both positive and
negative effects (albeit usually positive). Nodes without sufficient
memory available for buffering SHOULD be configured to disable buffering
by configuring BUFFER_SIZE_PACKETS == 0 and BUFFER_SIZE_BYTES == 0.
Doing so will affect the latency
required for launching TCP applications to new destinations.</t>
<t>If a route discovery attempt has failed (i.e.,
DISCOVERY_ATTEMPTS_MAX attempts have been made without
receiving a RREP) to
find a route toward the Target Address, any data packets buffered for
the corresponding Target Address MUST BE dropped and a Destination
Unreachable ICMP message (Type 3) SHOULD be delivered to the
source of the data packet. The code for the ICMP message is 1
(Host unreachable error). If RREQ_Gen is not the source
(OrigNode), then the ICMP is sent to OrigAddr.</t>
</section>
<section anchor="RteMsgStruct" title="RteMsg Structure">
<t>RteMsgs have the following general format:</t>
<t><figure anchor="figRteMsg"
title="RREQ and RREP (RteMsg) message structure">
<artwork><![CDATA[
+---------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+---------------------------------------------------------------+
| AckReq, MetricType |
+---------------------------------------------------------------+
| AddressList := {OrigAddr,TargAddr} |
+---------------------------------------------------------------+
| Address Prefix Length for OrigAddr OR TargAddr |
+---------------------------------------------------------------+
| SeqNumList (OrigSeqNum AND/OR TargSeqNum) |
+---------------------------------------------------------------+
| MetricList (Metric for OrigAddr OR TargAddr) |
+---------------------------------------------------------------+
]]></artwork>
</figure></t>
<t> <list style="hanging">
<t hangText="RteMsg Data Elements">
<list style="hanging">
<t hangText="msg_hop_limit"><vspace/>
The remaining number of hops allowed for dissemination of
the RteMsg message. </t>
<t hangText="msg_hop_count"><vspace/>
The number of hops already traversed during dissemination of
the RteMsg message. </t>
<t hangText="AckReq"><vspace/>
(RREP Only) Acknowledgement Requested by sender (optional). </t>
<t hangText="MetricType"><vspace/>
If MetricType != DEFAULT_METRIC_TYPE, the MetricType
associated with route to OrigAddr or TargAddr. </t>
<t hangText="AddressList"><vspace/>
AddressList contains OrigAddr and TargAddr. </t>
<t hangText="OrigSeqNum AND/OR TargSeqNum"><vspace/>
At least one of OrigSeqNum or TargSeqNum is REQUIRED and
carries the destination sequence number(s) associated with
OrigNode or TargNode respectively. </t>
<t hangText="MetricList"><vspace/>
The MetricList data element is REQUIRED, and carries the
route metric information associated with either
OrigAddr or TargAddr (but not both). </t>
</list> </t>
</list>
RteMsgs carry information about OrigAddr and TargAddr, as identified
in the context of the RREQ_Gen. Either the OrigSeqNum or TargSeqNum
MUST appear. Both MAY appear in the same RteMsg when SeqNum
is available for both OrigAddr and TargAddr.
<!-- The TLV flag thassingleindex MUST be set for these TLVs. -->
</t>
<t> If the OrigSeqNum data element appears, then it MUST apply only to
OrigAddr. The other address in the Address List is TargAddr. </t>
<t> If the TargSeqNum data element appears, then it MUST apply only to
TargAddr. The other address in the AddressList is OrigAddr. </t>
</section>
<section anchor="RREQ_gen" title="RREQ Generation">
<t> RREQ_Gen (the AODVv2 router generating the RREQ and associated data
elements on behalf of its client
OrigNode) follows the steps in this section. OrigAddr MUST be a unicast
address. The order of data elements is illustrated schematically in
<xref target="figRteMsg"/>. RREQ_Gen SHOULD include TargSeqNum,
if a previous value of the TargNode's SeqNum is known (e.g.,
from an invalid route table entry using longest-prefix matching).
If TargSeqNum is not included, AODVv2 routers handling the
RREQ assume that RREQ_Gen does not have that information.
<list style="numbers">
<t>RREQ_Gen MUST increment the SeqNum for OrigAddr by one (1)
according to the rules specified in <xref target="seqnum"/>.
This assures that each node receiving the RREQ will update
its route table using the information in the RREQ. </t>
<!-- CEP: Issue # to be generated for moving DestOnly to the irrep draft...
<t>If RREQ_Gen requires that only the router providing connectivity
to TargAddr is allowed to generate a RREP, then RREQ_Gen includes
the "Destination RREP Only" (DestOnly) TLV as part of the RFC 5444
message header. This also assures that RREP_Gen increments its
sequence number. Otherwise, (if the optional behavior is enabled)
other AODVv2 routers MAY respond to the RREQ if they have a
valid route to TargAddr (see <xref target="iRREP" />). </t>
-->
<t> msg_hop_limit SHOULD be set to MAX_HOPCOUNT. </t>
<t> msg_hop_count, if included, MUST be set to 0.
<list style="symbols"> <t> This RFC 5444 constraint causes certain
RREQ payloads to incur additional enlargement (otherwise,
msg_hop_count could often be used as the metric). </t>
</list> </t>
<t> AddressList := {OrigAddr, TargAddr} </t>
<!-- CEP: Why count bytes instead of bits?? -->
<!-- CEP: Note that Prefix Length is part of the AddressList, not a TLV -->
<t> If Route[OrigAddr].PrefixLength is equal to the number of bits
in the addresses of the RREQ (32 for IPv4, 128 for IPv6),
then no PrefixLengthList is included. Otherwise,
PrefixLengthList := {Route[OrigAddr].PrefixLength, null}. </t>
<t> OrigSeqNum := OrigAddr's SeqNum number </t>
<t> If known, TargSeqNum := Route[TargAddr].SeqNum </t>
<!-- CEP: Issue # to be generated for moving DestOnly to the irrep draft...
If ENABLE_IRREP is enabled, then any route to TargAddr
will satisfy the RREQ <xref target="I-D.perkins-irrep"/>. </t>
-->
<t> RREQ.MetricList := {Route[OrigAddr].Metric, null} </t>
</list> </t>
<t> By default, the RREQ message is multicast to LL-MANET-Routers. An example
RREQ message format is illustrated in <xref target="RREQ-format"/>. </t>
</section>
<section anchor="RREP_gen" title="RREP Generation">
<!-- CEP: prefix is associated with the OrigAddr or TargAddr, not the router -->
<t>This section specifies the generation of an RREP by an AODVv2
router (RREP_Gen) that provides connectivity for TargAddr, thus
enabling the establishment of a route between OrigAddr and TargAddr.
If TargAddr is not a unicast IP address, the RREP MUST NOT
be generated, and processing for the RREQ is complete.
Before transmitting a RREP, the routing information of the RREQ
is processed as specified in <xref target="update_rte"/>; after
such processing, RREP_Gen has an updated route to OrigAddr as well
as TargAddr. The basic format of an RREP conforms to the structure
for RteMsgs as shown in <xref target="figRteMsg"/>. </t>
<t>RREP_Gen creates data elements and generates the RREP as follows:
<list style="numbers">
<t>RREP_Gen checks the RREQ against recently received RREQ messages
as specified in <xref target="suppress"/>.
If a previously received RREQ has made the information in
the incoming RREQ to be redundant, no RREP is generated and
processing is complete. </t>
<t>RREP_Gen MUST increment TargAddr's SeqNum by one (1) according to
the rules specified in <xref target="seqnum"/>. </t>
<t>msg_hop_count, if included, MUST be set to 0. </t>
<t>msg_hop_limit SHOULD be set to RREQ.msg_hop_count. </t>
<t>If (DEFAULT_METRIC_TYPE != Route[TargAddr].MetricType) then include
the MetricType data element and set
MetricType := Route[TargAddr].MetricType </t>
<t>AddressList := {OrigAddr, TargAddr} </t>
<t>TargSeqNum := Route[TargAddr].SeqNum </t>
<t>If Route[TargAddr].PrefixLength is equal to the number of bits
in the addresses of the RREQ (32 for IPv4, 128 for IPv6),
then no PrefixLengthList is included in the RREP. Otherwise,
PrefixLengthList := {null, Route[TargAddr].PrefixLength} </t>
<t>MetricList := {null, Route[TargAddr].Metric}} </t>
</list> </t>
<t> By default, the RREP message is unicast to OrigAddr. An example message
format for RREP is illustrated in <xref target="RREP-format"/>. </t>
</section>
<section anchor="RM_hand" title="Handling a Received RteMsg">
<t> Before an AODVv2 router can make use of a received RteMsg (i.e.,
RREQ or RREP), the router must verify that the RteMsg is valid
according to the following steps. First the router extracts the
data elements from the message (see <xref target="represent"/>).
RteMsg_Metric is the single Metric. In this section (unless
qualified by additional description) all occurrences of the term
"router" refer to the AODVv2 router handling the received RteMsg.
<list style="numbers">
<t> A router MUST handle RteMsgs only from neighbors as specified in
<xref target="MsgXmit"/>. RteMsgs from other sources MUST be
disregarded. </t>
<t> The router verifies that the RteMsg contains the required data
elements: msg_hop_limit, OrigAddr, TargAddr, RteMsg_Metric, and
either OrigSeqNum or TargSeqNum. If the required
data elements are absent, the message is disregarded. </t>
<t> The router checks that OrigAddr and TargAddr are routable
unicast addresses. If not, the message is disregarded. </t>
<t> If the MetricType is absent, the router uses DEFAULT_METRIC_TYPE
for the metric type. Otherwise the router verifies that the
MetricType is known; if not, the message is disregarded.
<list style="symbols">
<t>DISCUSSION: or, can change Metric data element to use
HopCount, e.g., measured from msg_hop_count. </t>
</list></t>
<t> If (MAX_METRIC[MetricType] - Cost(L)) ≤ RteMsg_Metric,
where L denotes the incoming link, the RteMsg is disregarded. </t>
</list>
An AODVv2 router handles a valid RteMsg as follows:
<list style="numbers">
<t> The router MUST process the advertised route for OrigAddr
or TargAddr contained in the RteMsg as specified in
<xref target="test"/>. </t>
<t> If msg_hop_limit is zero (0), no further action is taken, and
the RteMsg is not regenerated. Otherwise, the router MUST
decrement msg_hop_limit. </t>
<t> If the RteMsg.msg_hop_count is present, and
MAX_HOPCOUNT <= msg_hop_count, then no further action is
taken. Otherwise, the router MUST increment msg_hop_count. </t>
</list>
Further actions to regenerate an updated RteMsg depend upon whether
the incoming RteMsg is an RREP or an RREQ. </t>
<section anchor="RREQ_handle" title="Additional Handling for Incoming RREQ">
<t><list style="symbols">
<t> By sending a RREQ, a router advertises that it will forward
packets to the OrigAddr contained in the RteMsg according
to the information enclosed. The router MAY choose not to
regenerate the RREQ, though not regenerating the RREQ could
decrease connectivity in the network or result in nonoptimal
paths. The circumstances under which a router might choose
not to re-transmit a RREQ are not specified in this document.
Some examples might include the following:
<list style="symbols">
<t>The router is already heavily loaded and does not want
to advertise routing for more traffic </t>
<t>The router recently transmitted the same routing
information (e.g. in a RREQ advertising the same
metric) <xref target="suppress"/> </t>
<t>The router is low on energy and has to reduce energy
expended for sending protocol messages or
packet forwarding </t>
</list>
Unless the router is prepared to advertise the new route, it halts
processing. </t>
<t>If the upstream router sending a RREQ is in the Blacklist, and
Current_Time < Blacklist.RemoveTime, then the router receiving
that RREQ MUST NOT transmit any outgoing RteMsg, and processing
is complete. </t>
<t> Otherwise, if the upstream router is in the Blacklist, and
Current_Time ≥ Blacklist.RemoveTime, then the upstream router
SHOULD be removed from the Blacklist, and message processing
continued. </t>
<t> The incoming RREQ MUST be checked against previously received
information from the RREQ Table (<xref target="suppress"/>).
If the information in the incoming RteMsg is redundant, then
then no further action is taken. </t>
<t> If TargNode is a client of the router receiving the RREQ, then the
router generates a RREP message as specified in
<xref target="RREP_gen"/>, and subsequently processing for the
RREQ is complete. Otherwise, processing continues as follows. </t>
<t> If (DEFAULT_METRIC_TYPE != Route[OrigAddr].MetricType) then include the
MetricType data element and assign
MetricType := Route[OrigAddr].MetricType </t>
<t> Metric := Route[OrigAddr].Metric </t>
<t> The RREQ (with updated fields as specified above>) SHOULD be multicast
the IP address LL-MANET-Routers <xref target="RFC5498"/>.
If the RREQ is unicast, the IP.DestinationAddress is set to
Route[RREQ.TargAddr].NextHopAddress. </t>
</list></t>
</section>
<section anchor="RREP_handle" title="Additional Handling for Incoming RREP">
<t>
The OrigAddr and TargAddr data elements are extracted from
the AddressList of the incoming RREP, for instance according
to the format of
message elements as shown in <xref target="represent"/>.
<list style="symbols">
<t> If no forwarding route exists to OrigAddr, then a RERR SHOULD be
transmitted to TargAddr. Otherwise, if
HandlingRtr is not RREQ_Gen then the outgoing RREP is sent to
the Route.NextHopAddress for OrigAddr.
</t>
<t>If HandlingRtr is RREQ_Gen then the RREP satisfies
RREQ_Gen's earlier RREQ, and RREP processing is completed.
Any packets buffered for OrigAddr should be transmitted.
</t>
</list></t>
</section>
<!-- CEP: TODO: Should specify that repeated RREQs deserve more attention -->
</section>
<section anchor="suppress" title="Suppressing Redundant RREQ messages">
<t> Since RREQ messages are multicast, there are common circumstances
under which an AODVv2 router might transmit a redundant response
(RREQ or RREP), duplicating the information transmitted in response
to some other recent RREQ (see <xref target="supp-tbl"/>). Before
responding, an AODVv2 router MUST suppress such RREQ messages.
This is done by checking the list of recently received RREQs to
determine whether the incoming RREQ is redundant, as follows:
<list style="symbols">
<t> The AODVv2 router searches the RREQ Table for recent entries
with the same OrigAddr, TargAddr, and MetricType. If not, the
incoming RREQ message is not suppressed, and a new entry
for the incoming RREQ is created in the RREQ Table. </t>
<t> If there is such an entry, and the incoming RREQ has a newer
sequence number, the incoming RREQ is not suppressed, and the
existing table entry MUST be updated to reflect the
new Sequence Number and Metric. </t>
<t> Similarly, if the Sequence Numbers are the same, and the
incoming RREQ offers a better Metric, the incoming
RREQ is not suppressed, and the RREQ Table entry MUST
be updated to reflect the new Metric. </t>
<t> Otherwise, the incoming RREQ is suppressed. </t>
</list>
</t>
</section>
</section>
<section anchor="route_maint" title="Route Maintenance and RERR Messages">
<t> AODVv2 routers attempt to maintain active routes. When a routing
problem is encountered, an AODVv2 router (denoted RERR_Gen)
sends the RERR to quickly notify upstream routers. Two kinds
of routing problems can trigger generation of a RERR message.
The first case happens when the router receives a packet
but does not have a route for the destination of the packet.
The second case happens immediately upon detection of a broken
link (see <xref target="link_breaks"/>) for an Active route.
</t>
<section anchor="e2edata"
title="Maintaining Route Lifetimes During Packet Forwarding">
<t> Before using a route to forward a packet, an AODVv2 router MUST
check the status of the route as follows.
<list style="symbols">
<t> If the route is marked has been
marked as Broken, it cannot be used for forwarding.</t>
<t> If Current_Time > Route.ExpirationTime, the route table
entry has expired, and cannot be used for forwarding.</t>
<t> Similarly, if (Route.ExpirationTime == MAXTIME), and if
(Current_Time - Route.LastUsed) >
(ACTIVE_INTERVAL + MAX_IDLETIME), the
route has expired, and cannot be used for forwarding. </t>
<t> Furthermore, if Current_Time - Route.LastUsed >
MAX_SEQNUM_LIFETIME, the
route table entry MUST be expunged. </t>
</list></t>
<t> If any of the above route error conditions hold true, the route
cannot be used to forward the packet, and an RERR message
MUST be generated (see <xref target="RERR_gen"/>). </t>
<t> Otherwise, Route.LastUsed := Current_Time, and
the packet is forwarded to the route's next hop. </t>
<t> Optionally, if a precursor list is maintained for the route, see
<xref target="precursor"/> for precursor lifetime operations. </t>
</section>
<section anchor="link_breaks"
title="Next-hop Router Adjacency Monitoring">
<t> Neighboring routers MAY form an adjacency based on AODVv2 messages,
other protocols (e.g. NDP <xref target="RFC4861"/>
or NHDP <xref target="RFC6130"/>), or manual configuration.
Loss of a routing adjacency may also be indicated by similar
information. AODVv2 routers SHOULD monitor connectivity to
adjacent routers along active routes. This monitoring can be
accomplished by one or several mechanisms, including:
<list style="symbols">
<t> Neighborhood discovery <xref target="RFC6130"/> </t>
<t> Route timeout </t>
<t> Lower layer trigger that a link is broken </t>
<t> TCP timeouts </t>
<t> Promiscuous listening </t>
<t> Other monitoring mechanisms or heuristics </t>
</list>
</t>
<t> If a next-hop AODVv2 router has become unreachable, RERR_Gen
follows the procedures in <xref target="RERR_gen_2"/>. </t>
</section>
<section anchor="RERR_gen" title="RERR Generation">
<t> An RERR message is generated by a AODVv2 router (i.e., RERR_Gen)
in order to notify upstream routers that
packets cannot be delivered to one or more destinations.
An RERR message has the following general structure:
<figure anchor="figRERRstruct" title="RERR message structure">
<artwork><![CDATA[
+---------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+---------------------------------------------------------------+
| PktSource, MetricType |
+---------------------------------------------------------------+
| Unreachable Address List |
+---------------------------------------------------------------+
| Unreachable Address PrefixLength List |
+---------------------------------------------------------------+
| Unreachable Address Sequence Number List |
+---------------------------------------------------------------+
]]></artwork>
</figure>
<list style="hanging">
<t hangText="RERR Data Elements">
<list style="hanging">
<t hangText="msg_hop_limit"><vspace/>
The remaining number of hops allowed for dissemination of
the RERR message. </t>
<t hangText="msg_hop_count"><vspace/>
The number of hops already traversed during dissemination of
the RERR message. </t>
<t hangText="PktSource"><vspace/>
The IP address of the unreachable destination triggering
RERR generation. </t>
<t hangText="MetricType"><vspace/>
If MetricType != DEFAULT_METRIC_TYPE, the MetricType
associated with routes affected by a broken link. </t>
<t hangText="AddressList"><vspace/>
A list of IP addresses not reachable by the AODVv2 router
transmitting the RERR. </t>
<t hangText="PrefixLengthList"><vspace/>
The list of prefix lengths associated with the addresses
in the Unreachable Address List. </t>
<t hangText="SeqNumList"><vspace/>
The list of destination sequence numbers associated with
the Unreachable Address List. </t>
</list> </t>
</list>
There are two kinds of events indicating that packets cannot
be delivered to certain destinations.
The two cases differ in the way that the neighboring
IP destination address for the RERR is chosen,
and in the way that the set of UnreachableAddrs is identified. </t>
<t> In both cases, the msg_hop_limit MUST be included and SHOULD
be set to MAX_HOPCOUNT. msg_hop_count SHOULD be included
and set to 0, to facilitate use of various route repair strategies
including expanding rings multicast and Intermediate RREP
<xref target="I-D.perkins-irrep"/>. </t>
<section anchor="RERR_gen_1" title="Case 1: Undeliverable Packet">
<t> The first case happens when the router receives a packet
from another AODVv2 router but does not have a valid route
for the destination of the packet. In this case, there is
exactly one UnreachableAddr to be included in the RERR's
AddressList (either the Destination Address of the IP header
from a data packet, or the OrigAddr found in the
AddressList of an RREP message).
The RERR SHOULD be sent to the multicast address LL-MANET-Routers,
but RERR_Gen MAY instead send the RERR to the next hop towards the
source IP address of the packet which was undeliverable. For
unicast RERR, the PktSource data element MUST be included,
containing the the source IP address of the undeliverable packet,
or TargAddr in case the undeliverable packet was an RREP message
for a route to TargAddr. If a Sequence Number for UnreachableAddr
is known, that Sequence Number SHOULD be included in a Seqnum
data element the RERR. Otherwise all nodes handling the RERR
will assume their route through RERR_Gen towards the
UnreachableAddr is no longer valid and mark those routes as broken,
regardless of the Sequence Number
information for those routes. RERR_Gen MUST discard the
packet or message that triggered generation of the RERR.
<!-- CEP: This should be reconsidered if we re-specify local repair.. -->
</t>
<t> If an AODVv2 router receives an ICMP packet from
the address of one of its client nodes, it simply relays
the packet to the ICMP packet's destination address,
and does not generate any RERR message. </t>
<!-- NOTE: CEP: Verify unicast delivery of IP multicast packets ... -->
<!--
If the neighbor's IP address is
unavailable, RERR_Gen MAY attempt layer-2 unicast delivery
to the multicast address LL-MANET-Routers.
-->
</section>
<section anchor="RERR_gen_2" title="Case 2: Broken Link">
<t> The second case happens when the link breaks to an active
adjacent AODVv2 router (i.e., the next hop of an active route).
In this case, the RERR MUST be sent to the multicast address
LL-MANET-Routers, except when the optional
feature of maintaining precursor lists is used as specified
in <xref target="precursor"/>.
All routes (Active, Idle and Expired) that use the broken
link MUST be marked as Broken.
The AddressList (which will contain the Unreachable Addresses)
is initialized by first identifying those Active routes which use
the broken link. For each such Active Route, Route.Dest is added
to the AddressList.
After the Active Routes using the broken link have all been
indicated in the AddressList, Idle routes MAY also be included,
if allowed by the setting of ENABLE_IDLE_IN_RERR, as long as
the packet size of the RERR does not exceed the MTU
(interface "Maximum Transfer Unit") of the physical medium. </t>
<t> If there are no Unreachable Addresses in the AddressList, no RERR
is generated. Otherwise, RERR_Gen generates a new RERR using the
AddressList. If any Unreachable Address is associated with a
routing prefix (i.e., a prefix length shorter than the maximum
length for the address family), then the AddressList MUST be
accompanied by a PrefixLengthList; otherwise, if no such entry,
the PrefixLengthList SHOULD NOT be included. The value (from the
route table) for each Unreachable Address's SeqNum
MUST be placed in the SeqNum data element. </t>
<t> Every broken route reported in the RERR MUST have the
same MetricType. If the MetricType is not DEFAULT_METRIC_TYPE, then
the RERR message MUST contain a MetricType data element
indicating the MetricType of the broken route(s). </t>
</section>
</section>
<section anchor="RERR_hand" title="Receiving and Handling RERR Messages">
<t> When an AODVv2 router (HandlingRtr) receives a RERR message, it
uses the information provided to mark affected routes as broken.
If HandlingRtr has neighbors that are using the affected routes,
then HandlingRtr subsequently sends an RERR message to those
neighbors. This regeneration of the RERR message
is counted as another "hop" for purposes of properly modifying
msg_hop_limit and msg_hop_count in the RERR message header. </t>
<t> HandlingRtr examines the incoming RERR to assure that it contains
msg_hop_limit and at least one Unreachable Address; otherwise,
the incoming RERR message is disregarded and further processing
stopped. For each UnreachableAddr, HandlingRtr
searches its route table for a route using longest prefix matching.
If no such Route is found, processing is complete for that
UnreachableAddr. Otherwise, HandlingRtr verifies the
following:
<list style="numbers">
<t> The UnreachableAddr is a routable unicast address. </t>
<t> Route.NextHopAddress is the same as the SourceAddress in
the IP header of the RERR packet. </t>
<t> Route.NextHopInterface is the same as the interface on
which the RERR was received. </t>
<!-- TODO?: CEP: the route should be invalidated regardless of SeqNum -->
<t> The UnreachableAddr.SeqNum is unknown, OR
Route.SeqNum <= UnreachableAddr.SeqNum (using
signed 16-bit arithmetic). </t>
</list>
</t>
<t> If the Route satisfies all of the above conditions, HandlingRtr
checks whether Route.PrefixLength is the same as the prefix
length for UnreachableAddr. If so, HandlingRtr simply
sets the state for that Route to be Broken. Otherwise,
HandlingRtr creates a new route (call it BrokenRoute) with
the same PrefixLength as the prefix length for
UnreachableAddr, and sets Route.State == Broken
for BrokenRoute. If the prefix length for the new route
is shorter than Route.PrefixLength, then Route MUST be
expunged from the route table (since it is a subroute
of the larger route which is reported to be broken).
If msg_hop_limit is 0, then HandlingRtr takes no further
action on the RERR message. </t>
<t> If there are no UnreachableAddrs to be transmitted in an RERR to
upstream routers, HandlingRtr takes no further action on the
RERR message. </t>
<t> Otherwise, msg_hop_limit is decremented by one (1) and
processing continues as follows:
<list style="symbols">
<t> The UnreachableAddrs data element is included in the RERR. </t>
<t> msg_hop_limit is decremented by one (1). </t>
<t> (Optional) If precursor lists are maintained, the outgoing RERR
SHOULD be sent to the active precursors of the broken route as
specified in <xref target="precursor"/>. </t>
<t> Otherwise, if the incoming RERR message was received at the
LL-MANET-Routers <xref target="RFC5498"/> multicast address,
the outgoing RERR SHOULD be sent to LL-MANET-Routers. </t>
<t> Otherwise, if the PktSource data element is present, and HandlingRtr
has a Route to PktSource.Addr, then HandlingRtr MUST send the
outgoing RERR to Route[PktSource.Addr].NextHop. </t>
<t> Otherwise, the outgoing RERR MUST be sent to LL-MANET-Routers. </t>
</list>
</t>
</section>
</section>
<section anchor="represent"
title="Representing AODVv2 data elements using RFC 5444">
<t>AODVv2 specifies that all control plane messages between
Routers SHOULD use the Generalised Mobile Ad-hoc Network Packet
and Message Format <xref target="RFC5444"/>, which provides a
multiplexed transport for multiple protocols.
AODVv2 therefore specifies Route Messages comprising data elements
that map to message elements in RFC5444 but, in line with the
concept of use, does not specify which order the messages
should be arranged in an RFC5444 packet. An implementation of
an RFC5444 parser may choose to optimise the content of certain
message elements to reduce control plane overhead.
</t>
<t>
Here is a brief summary of the RFC 5444 format.
<list style="hanging">
<t> A packet formatted according to RFC 5444
contains zero or more messages. </t>
<t> A message contains a message header,
message TLV block, and zero or more address blocks.</t>
<t> Each address block MAY also have an associated TLV
block; this TLV block MAY encode multiple TLVs.
Each such TLV may include an array of values.
The list of TLV values may be associated with
various subsets of the addresses in the address block.
</t>
</list>
If a packet contains only a single AODVv2 message and no packet TLVs,
it need only include a minimal Packet-Header <xref target="RFC5444"/>.
The length of an address (32 bits for IPv4 and 128 bits
for IPv6) inside an AODVv2 message is indicated by the
msg-addr-length (MAL) in the msg-header, as specified in
<xref target="RFC5444"/>.</t>
<!-- Deleted / Issue #28 - - >
<t> When multiple messages are aggregated
into a single packet according to RFC 5444 formatting, and the
aggregation of messages is also authenticated (e.g., with IPsec),
and the IP destination is multiple hops away,
it becomes infeasible to delete individual messages. In such
cases, instead of deleting individual messages, they are maintained
in the aggregation of messages, but simply ignored for further
processing. In such cases where individual messages cannot be
deleted, in this document "disregarded" means "ignored". Otherwise,
any such "disregarded" AODVv2 messages SHOULD be deleted from
the aggregated messages in the RFC 5444 packet.
</t>
< ! - - Deleted / Issue #28 -->
<t>This section specifies a way to represent the data elements
specified by AODVv2 within RFC 5444 message format.
</t>
<t><list style="hanging">
<t hangText="Type-Length-Value structure (TLV)"><vspace/>
A generic way to represent information, conformant to use
in <xref target="RFC5444"/>.</t>
</list>
</t>
<t>
<list style="hanging">
<t hangText="AODVv2 uses the following RFC5444 message elements:">
<vspace/>
</t>
</list>
<list style="symbols">
<!--
<t>Address of the originating node, OrigAddr, which should
be mapped to the <msg-orig-addr> element in
<msg-header>.
</t>
-->
<t>Message Hop Count, <msg-hop-count>, which should be
mapped to the <msg-hop-count> element in
<msg-header>.
</t>
<t>Message Hop Limit, <msg-hop-limit>, which should be
mapped to the <msg-hop-limit> element in
<msg-header>.
</t>
</list>
</t>
<texttable anchor="DE_to_5444">
<ttcol align="left" width="30%">Data Element</ttcol>
<ttcol align="left">RFC 5444 Message Representation</ttcol>
<c>msg_hop_limit</c>
<c>RFC 5444 Message Header <msg-hop-count></c>
<c>msg_hop_count</c>
<c>RFC 5444 Message Header <msg-hop-limit></c>
<c>AckReq</c> <c>Acknowledgement Requested Message TLV</c>
<c>MetricType</c> <c>Metric Type Message TLV</c>
<c>AddressList</c> <c>RFC 5444 Address TLV Block</c>
<c>PrefixLengthsList</c> <c>Included in RFC 5444 Address TLV Block</c>
<c>MetricList</c> <c>Metric Address Block TLV</c>
<c>SeqNumList</c> <c>Sequence Number Address Block TLV</c>
<c>OrigSeqNum</c>
<c>Originating Node Sequence Number Address Block TLV</c>
<c>TargSeqNum</c>
<c>Target Node Sequence Number Address Block TLV</c>
<!--
<c>OrigNdx</c> <c>The index of OrigAddr within the AddrBlk</c>
<c>TargNdx</c> <c>The index of TargAddr within the AddrBlk</c>
-->
<c>OrigAddr</c> <c>Included in AddressList</c>
<c>TargAddr</c> <c>Included in AddressList</c>
<c>UnreachableAddr</c> <c>Included in AddressList</c>
<c>SeqNum</c> <c>Included in SeqNumList</c>
<c>Metric</c> <c>Included in MetricList</c>
</texttable>
<t>For handling of messages that contain unknown TLV types,
ignore the information for processing, but preserve it
unmodified for forwarding.</t>
</section>
<section anchor="gateway" title="Simple Internet Attachment">
<t>Simple Internet attachment means attachment of a stub
(i.e., non-transit) network of AODVv2 routers to the
Internet via a single Internet AODVv2 router (called IAR).</t>
<t>As in any Internet-attached network,
AODVv2 routers, and their clients, wishing to be
reachable from hosts on the Internet MUST have IP addresses
within the IAR's routable and topologically correct prefix
(e.g. 191.0.2.0/24).</t>
<figure anchor="net_top" title="Simple Internet Attachment Example">
<artwork><![CDATA[
/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | Internet | /191.0.2/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ Internet \
| | 191.0.2/24 | \ /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
]]></artwork>
</figure>
<t>When an AODVv2 router within the AODVv2 MANET wants to discover
a route toward a node on the Internet, it uses the normal AODVv2
route discovery for that IP Destination Address. The IAR MUST
respond to RREQ on behalf of all Internet destinations.</t>
<t>When a packet from a node on the Internet destined for a
node in the AODVv2 MANET reaches the IAR, if the IAR does not
have a route toward that destination it will perform normal AODVv2
route discovery for that destination.</t>
</section>
<section title="Multiple Interfaces">
<t>AODVv2 MAY be used with multiple interfaces; therefore, the
particular interface over which packets arrive MUST be known
whenever a packet is received. Whenever a new route is
created, the interface through which the route's destination can be
reached is also recorded in the route table entry.</t>
<t>When multiple interfaces are available, a node transmitting
a multicast packet to
LL-MANET-Routers MUST send the packet on all interfaces that
have been configured for AODVv2 operation.</t>
<!-- CEP: TODO: SHOULD ==> MUST?? -->
<t>Similarly, AODVv2 routers MUST subscribe to
LL-MANET-Routers on all their AODVv2 interfaces.</t>
<!-- CEP: TODO: SHOULD ==> MUST?? -->
</section>
<section anchor="limit" title="AODVv2 Control Message Generation Limits">
<t>To avoid congestion, each AODVv2 router's rate
of packet/message generation SHOULD be limited. The rate and
algorithm for limiting messages (CONTROL_TRAFFIC_LIMITS) is
left to the implementor and should be administratively
configurable. AODVv2
messages SHOULD be discarded in the following order of
preference: RREQ, RREP, and finally RERR.</t>
</section>
<!-- ======================== Optional Features ======================== -->
<section anchor="optional" title="Optional Features">
<t> Some optional features of AODVv2, associated with AODV,
are not required by minimal implementations. These features are
expected to apply in networks with greater mobility, or
larger node populations, or requiring reduced latency for
application launches. The optional features are as follows:</t>
<t><list style="symbols">
<t>Expanding Rings Multicast</t>
<t>Intermediate RREPs (iRREPs): Without iRREP, only the
destination can respond to a RREQ. </t>
<t>Precursor lists.</t>
<t>Reporting Multiple Unreachable Addresses: a RERR message can carry
more than one Unreachable Destination Address for cases when
a single link breakage causes multiple destinations to become
unreachable from an intermediate router.</t>
<!-- CEP: issue #40 should be revisited!! -->
<!-- Removed: issue #40 -->
<t>RREP_ACK.</t>
<!-- Removed: issue #40 -->
<t>Message Aggregation.</t>
</list>
</t>
<section anchor="rings" title="Expanding Rings Multicast">
<t>For multicast RREQ, msg_hop_limit MAY be set in
accordance with an expanding ring search as described in
<xref target="RFC3561"/> to limit the RREQ propagation to a
subset of the local network and possibly reduce route
discovery overhead.</t>
</section>
<section anchor="iRREP" title="Intermediate RREP">
<t>This specification has been published as a separate
Internet Draft <xref target="I-D.perkins-irrep"/>.
</t>
</section>
<section anchor="precursor" title="Precursor Lists and Notifications">
<t>This section specifies an interoperable enhancement to AODVv2
(and possibly other reactive routing protocols) enabling
<!-- Issue #22 -->
more economical notifications to traffic sources
upon determination that a route needed to forward such traffic to
its destination has become Broken.</t>
<!-- NOTE! CEP: TODO: Precursors should NOT be notified if
Precursor.LastUsed < (MAX_IDLETIME + ACTIVE_INTERVAL) -->
<!--
, then for
the IP.SourceAddress of the packet, Precursor[LastHop].LastUsed :=
Current_time.
the packet is forwarded to the route's next hop.
-->
<section title="Overview">
<t>In many circumstances, there can be several sources of traffic
for a certain destination. Each such source of traffic
is known as a "precursor" for the destination, as well as all
upstream routers between the forwarding AODVv2 router and the
traffic source. For each destination, an AODVv2 router
MAY choose to keep track of the upstream neighbors that have
provided traffic for that destination; there is no need to
keep track of upstream routers any farther away than the next hop.
</t>
<t>Moreover, any particular link to an adjacent AODVv2 router may be
a path component of multiple routes towards various destinations.
The precursors for all destinations using the next hop across any
link are collectively known as the precursors for that next hop.
</t>
<t>When an AODVv2 router determines that an link to one of its
neighbors has broken,
the AODVv2 router detecting the broken link must mark multiple
routes as Broken, for each of the newly unreachable destinations,
as described in <xref target="RERR_gen"/>.
Each route that relies on the newly broken link is no longer valid.
Furthermore, the precursors of the broken link should be notified
(using RERR) about the change in status of their route
to a destination relying upon the broken next hop.
</t>
</section>
<section anchor="Precursor-Notify" title="Precursor Notification Details">
<t>During normal operation, each AODVv2 router wishing to maintain
precursor lists as described above,
maintains a precursor table and updates
the table whenever the node forwards traffic to one of
the destinations in its route table. For each precursor
in the precursor list, a record must be maintained to indicate
whether the precursor has been used for recent traffic (in other
words, whether the precursor is an Active precursor).
So, when traffic arrives from a precursor, the Current_Time is
used to mark the time of last use for the precursor list element
associated with that precursor.
</t>
<t>When an AODVv2 router detects that a link is broken, then for
each precursor using that next hop, the node MAY notify the
precursor using either unicast or multicast RERR:
<list style="hanging">
<t hangText="unicast RERR to each Active precursor"><vspace/>
This option is applicable when there are few Active precursors
compared to the number of neighboring AODVv2 routers.</t>
<t hangText="multicast RERR to RERR_PRECURSORS"><vspace/>
RERR_PRECURSORS is, by default, LL-MANET-Routers
<xref target="RFC5498"/>. This option is typically
preferable when there are many precursors,
since fewer packet transmissions are required.</t>
</list>
Each upstream neighbor (i.e., precursor) MAY then execute
the same procedure until all upstream routers have
received the RERR notification.</t>
</section>
</section>
<section anchor="mcast-to-RREQ" title="Multicast RREP Response to RREQ">
<t>The RREQ Target Router (RREP_Gen) MAY, as an alternative to
unicasting a RREP, be configured
to distribute routing information about the route toward
TargAddr. That is, RREP_Gen
MAY be configured respond to a route discovery by generating a RREP,
using the procedure in <xref target="RREP_gen"/>, but
multicasting the RREP to LL-MANET-Routers <xref target="RFC5498"/>
(subject to similar suppression algorithm for redundant RREP
multicasts as described in
<xref target="suppress"/>). The redundant message suppression must
occur at every router handling the multicast RREP.
Afterwards, RREP_Gen processing for the incoming RREQ is complete.</t>
<t>Broadcast RREP response to incoming RREQ was originally specified
to handle unidirectional links, but it is expensive.
Due to the significant overhead, AODVv2 routers MUST NOT
use multicast RREP unless configured to do so by
setting the administrative parameter USE_MULTICAST_RREP.</t>
</section>
<!-- Removed: issue #40 -->
<section anchor="rrep_ack" title="RREP_ACK">
<t>Instead of relying on existing mechanisms for requesting
verification of link bidirectionality during Route
Discovery, RREP_Ack is provided as an optional feature
and modeled on the RREP_Ack message type from
AODV <xref target="RFC3561"/>.</t>
<t>Since the RREP_ACK is simply echoed back to the node from
which the RREP was received, there is no need for other
data elements.
Considerations of packet TTL are as specified
in <xref target="MsgXmit"/>. An example message format
is illustrated in section <xref target="RREP_ACK-format"/>.</t>
</section>
<!-- End removed section: issue #40 -->
<section anchor="aggreg" title="Message Aggregation">
<t>The aggregation of multiple messages into a packet is
specified in RFC 5444 <xref target="RFC5444"/>.</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"/>.</t>
</section>
</section>
<!-- =================== Administrative Parameters ===================== -->
<section anchor="param"
title="Administratively Configurable Parameters and Timer Values">
<t>AODVv2 uses various configurable parameters of various types:
<list style="symbols">
<t>Timers</t>
<t>Protocol constants</t>
<t>Administrative (functional) controls</t>
<t>Other administrative parameters and lists</t>
</list>
The tables in the following sections show the parameters along
their definitions and default values (if any).</t>
<t>Note: several fields have limited size (bits or bytes). These
sizes and their encoding may place specific limitations on the values
that can be set. For example, <msg-hop-count> is a 8-bit
field and therefore MAX_HOPCOUNT cannot be larger than 255.</t>
<section anchor="timers" title="Timers">
<t>AODVv2 requires certain timing information to be associated
with route table entries. The default values
are as follows, subject to future experience:</t>
<texttable anchor="timer-tbl" title="Timing Parameter Values">
<ttcol align="center" width="35%">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>RREQ_WAIT_TIME</c>
<c>2 seconds</c>
<c>UNICAST_MESSAGE_SENT_TIMEOUT</c>
<c>1 second</c>
<c>RREQ_HOLDDOWN_TIME</c>
<c>10 seconds</c>
</texttable>
<t>The above timing parameter values have worked well for small and
medium well-connected networks with moderate topology changes.</t>
<t>The timing parameters SHOULD be administratively configurable
for the network where AODVv2 is used. Ideally, for networks with
frequent topology changes the AODVv2 parameters should be adjusted
using either 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>
</section>
<section anchor="constants" title="Protocol constants">
<t>AODVv2 protocol constants typically do not require changes.
The following table lists these constants, along with their values
and a reference to the specification describing their use.</t>
<texttable anchor="const-tbl" title="Parameter Values">
<ttcol align="left" width="35%">Name</ttcol>
<ttcol align="left">Default Value</ttcol>
<ttcol align="left">Description</ttcol>
<c>DISCOVERY_ATTEMPTS_MAX</c>
<c>3</c>
<c><xref target="route_discovery"/></c>
<c>MAX_HOPCOUNT</c>
<c>20 hops</c>
<c><xref target="metrics"/></c>
<c>MAX_METRIC[i]</c>
<c>Specified only for HopCount</c>
<c><xref target="metrics"/></c>
<c>MAXTIME</c>
<c>[TBD]</c>
<c>Maximum expressible clock time</c>
<!-- Need to figure out what the time format. -->
</texttable>
</section>
<section anchor="controls" title="Administrative (functional) controls">
<t>The following administrative controls may be used to change the
operation of the network, by enabling optional behaviors.
These options are not required for
correct routing behavior, although they may
potentially reduce AODVv2 protocol messaging in certain
situations. The default behavior is to NOT enable most such options,
options. Packet buffering is enabled by default.</t>
<texttable anchor="suggestedoptions"
title="Administratively Configured Controls">
<ttcol align="center" width="35%">Name</ttcol>
<ttcol align="left">Description</ttcol>
<c>DEFAULT_METRIC_TYPE</c>
<c>3 (i.e, Hop Count (see <xref target="RFC6551"/>))</c>
<c>ENABLE_IDLE_IN_RERR</c>
<c><xref target="RERR_gen_2"/></c>
<c>ENABLE_IRREP</c>
<c><xref target="RREQ_gen"/></c>
<c>USE_MULTICAST_RREP</c>
<c><xref target="mcast-to-RREQ"/></c>
</texttable>
</section>
<section anchor="other" title="Other administrative parameters and lists">
<t>The following table lists contains AODVv2 parameters which should
be administratively configured for each specific network.</t>
<texttable anchor="admincontrol" title="Other Administrative Parameters">
<ttcol align="left" width="35%">Name</ttcol>
<ttcol align="left">Default Value</ttcol>
<ttcol align="left">Cross Reference</ttcol>
<c>AODVv2_INTERFACES</c>
<c/>
<c><xref target="apply"/></c>
<c>BUFFER_SIZE_PACKETS</c>
<c>2</c>
<c><xref target="route_discovery"/></c>
<c>BUFFER_SIZE_BYTES</c>
<c>MAX_PACKET_SIZE [TBD]</c>
<c><xref target="route_discovery"/></c>
<c>CLIENT_ADDRESSES</c>
<c>AODVv2_INTERFACES</c>
<c><xref target="clients"/></c>
<c>CONTROL_TRAFFIC_LIMIT</c>
<c>TBD [50 packets/sec?]</c>
<c><xref target="limit"/></c>
</texttable>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This section specifies several RFC 5444 message types, message
tlv-types, and address tlv-types. Also, a new registry of
16-bit alternate metric types is specified.</t>
<section anchor="msgtype" title="AODVv2 Message Types Specification">
<texttable anchor="msgtypes" title="AODVv2 Message Types">
<ttcol align="center" width="45%">Name</ttcol>
<ttcol align="center">Type (TBD)</ttcol>
<c>Route Request (RREQ)</c> <c>10</c>
<c>Route Reply (RREP)</c> <c>11</c>
<c>Route Error (RERR)</c> <c>12</c>
<!-- Removed: issue #40 -->
<c>Route Reply Acknowledgement (RREP_ACK)</c> <c>13</c>
<!-- Removed: issue #40 -->
</texttable>
</section>
<section anchor="msgtlvtypes" title="Message TLV Type Specification">
<texttable anchor="msgtlvtbl" title="Message TLV Types">
<ttcol align="left" width="58%">Name</ttcol>
<ttcol align="center">Type (TBD)</ttcol>
<ttcol align="center">Length in octets</ttcol>
<ttcol align="left">Cross Reference</ttcol>
<c>AckReq (Acknowledgment Request)</c>
<c>10</c>
<c>0</c>
<c><xref target="blacklists"/></c>
<!-- CEP: Issue # to be generated for moving DestOnly to the irrep draft...
<c>Destination RREP Only (DestOnly)</c>
<c>11</c> ##!!## Note renumbering below...
<c>0</c>
<c><xref target="RREQ_gen"/></c>
-->
<c>PktSource (Packet Source)</c>
<c>11</c>
<c>4 or 16</c>
<c><xref target="RERR_gen"/></c>
<c>MetricType</c>
<c>12</c>
<c>1</c>
<c><xref target="RteMsgStruct"/></c>
</texttable>
</section>
<section anchor="addrtlvspec" title="Address Block TLV Specification">
<texttable anchor="addrtlvtypes"
title="Address Block TLV (AddrTLV) Types">
<ttcol align="left" width="45%">Name</ttcol>
<ttcol align="center">Type (TBD)</ttcol>
<ttcol align="left">Length</ttcol>
<ttcol align="left">Value</ttcol>
<c>Metric</c>
<c>10</c>
<c>depends on Metric Type</c>
<c><xref target="RteMsgStruct"/></c>
<c>Sequence Number (SeqNum)</c>
<c>11</c>
<c>2 octets</c>
<c><xref target="RteMsgStruct"/></c>
<c>Originating Node Sequence Number (OrigSeqNum)</c>
<c>12</c>
<c>2 octets</c>
<c><xref target="RteMsgStruct"/></c>
<c>Target Node Sequence Number (TargSeqNum)</c>
<c>13</c>
<c>2 octets</c>
<c><xref target="RteMsgStruct"/></c>
<c>VALIDITY_TIME</c>
<c>1</c>
<c>1 octet</c>
<c><xref target="RFC5497"/></c>
</texttable>
</section>
<section anchor="metric-type" title="Metric Type Number Allocation">
<t>Metric types are identified according to the assignments as specified
in <xref target="RFC6551"/>.
The metric type of the Hop Count metric is assigned to
be 3, in order to maintain compatibility with that existing
table of values from RFC 6551.
Non-addititve metrics are not supported in this draft.</t>
<texttable anchor="metric-tbl" title="Metric Types">
<ttcol align="center" width="35%">Name</ttcol>
<ttcol align="center">Type</ttcol>
<ttcol align="center">Metric Size</ttcol>
<!--
<c>Reserved</c>
<c>0</c>
<c>Undefined</c>
-->
<c>Unallocated</c>
<c>0 -- 2</c>
<c>TBD</c>
<c>Hop Count</c>
<c>3 - TBD</c>
<c>1 octet</c>
<c>Unallocated</c>
<c>4 -- 254</c>
<c>TBD</c>
<c>Reserved</c>
<c>255</c>
<c>Undefined</c>
</texttable>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>The objective of the AODVv2 protocol is for each router to
communicate reachability information about addresses for which it
is responsible. Positive routing information (i.e. a route
exists) is distributed via RREQ and RREP messages. Negative routing
information (i.e. a route does not exist) is distributed via RERRs.
AODVv2 routers store the information contained in these messages in
order to properly forward data packets, and they generally provide
this information to other AODVv2 routers.</t>
<!--t>If a router transmits incorrect or false routing information,
it will likely be stored and propagated.</t-->
<!--IDC should we remove all mutable fields-->
<!--IDC Notify Reflection Attack-->
<t>This section does not mandate any specific security
measures. Instead, this section describes various security
considerations and potential avenues to secure AODVv2 routing.</t>
<t>The most important security mechanisms for AODVv2
routing are integrity/authentication and confidentiality. </t>
<t>In situations where routing information or router identity
are suspect, integrity and authentication techniques SHOULD be
applied to AODVv2 messages. In these situations, routing
information that is distributed over multiple hops SHOULD also
verify the integrity and identity of information based on
originator of the routing information. </t>
<t>A digital signature could be used to identify the source of
AODVv2 messages and information, along with its authenticity. A
nonce or timestamp SHOULD also be used to protect against replay
attacks. S/MIME and OpenPGP are two authentication/integrity
protocols that could be adapted for this purpose.</t>
<t>In situations where confidentiality of AODVv2 messages is
important, cryptographic techniques can be applied.</t>
<t>In certain situations, for example sending a RREP or RERR, an AODVv2
router could include proof that it has previously received valid
routing information to reach the destination, at one point of
time in the past. In situations where routers are suspected of
transmitting maliciously erroneous information, the original
routing information along with its security credentials SHOULD
be included.</t>
<t>Note that if multicast is used, any confidentiality and
integrity algorithms used MUST permit multiple receivers to
handle the message.</t>
<t>Routing protocols, however, are prime targets for
impersonation attacks. In networks where the node membership is
not known, it is difficult to determine the occurrence of
impersonation attacks, and security prevention techniques are
difficult at best. However, when the network membership is known
and there is a danger of such attacks, AODVv2 messages must be
protected by the use of authentication techniques, such as those
involving generation of unforgeable and cryptographically strong
message digests or digital signatures. While AODVv2 does not place
restrictions on the authentication mechanism used for this
purpose, IPsec Authentication Message (AH) is an appropriate
choice for cases where the nodes share an appropriate security
association that enables the use of AH.</t>
<t>In particular, routing messages SHOULD be authenticated to avoid
creation of spurious routes to a destination. Otherwise, an
attacker could masquerade as that destination and maliciously
deny service to the destination and/or maliciously inspect and
consume traffic intended for delivery to the destination. RERR
messages SHOULD be authenticated in order to prevent malicious
nodes from disrupting routes between communicating
nodes.</t>
<t>If the mobile nodes in the ad hoc network have pre-established
security associations, the purposes for which the security associations
are created should include that of authorizing the processing of AODVv2
control packets. Given this understanding, the mobile nodes should be
able to use the same authentication mechanisms based on their IP
addresses as they would have used otherwise.</t>
<!--DEREK comments
Some threats to the system could include an injection of RERR message
either by an outside attacker, a rogue router, or a compromised
router. The TTL check protects against some injection techniques
unless it's injected by an actual rogue or compromised router.
In terms of source identification of a RREQ or RREP you might want to
add a digital signature field (which also requires some nonce or
timestamp to protect against replay attacks). There's also a question
of how you authorize a router to supply an RREP. For example a rogue
or compromised router could decide to "advertize" a route by
responding with an RREP even though it's not necessarily the "best"
route or it might not even have a route toward the destination.
When an intermediate router generates an RREP it needs to authenticate
that it has the original route. Perhaps what needs to happen is that
it includes the original RREP signed by the TargNode in order to
prove
that it HAD (at one point in the past) a valid route toward the
TargAddr.
This is particularly an issue in generating the RREP on the fly to the
TargAddr from the OrigAddr because there IS no RREP. In this case
it might want to include the original RREQ from the OrigAddr as the
authentication token.
-->
<t>If the mobile nodes in the ad hoc network have pre-established
security associations, the purposes for which the security associations
Most AODVv2 messages are transmitted to the multicast address
LL-MANET-Routers <xref target="RFC5498"/>. It is therefore
required for security that AODVv2 neighbors exchange security
information that can be used to insert an ICV <xref target="RFC6621"/>
into the AODVv2 message block <xref target="RFC5444"/>.
This enables hop-by-hop security. <!-- Issue #Q which is proper for these
message types that may have mutable fields.--> For destination-only
RREP discovery procedures, AODVv2 routers that share a security
association SHOULD use the appropriate mechanisms as specified
in RFC 6621.
The establishment of these security associations is out of scope
for this document.</t>
</section>
<section title="Acknowledgments">
<t>AODVv2 is a descendant of the design of previous MANET on-demand
protocols, especially AODV <xref target="RFC3561"/> and
DSR <xref target="RFC4728"/>. Changes to previous MANET
on-demand protocols stem from research and implementation
experiences. Thanks to Elizabeth Belding-Royer for her long time
authorship of AODV. Additional thanks to
Derek Atkins,
Emmanuel Baccelli,
Abdussalam Baryun,
Ramon Caceres,
Thomas Clausen,
Christopher Dearlove,
Ulrich Herberg,
Henner Jakob,
Luke Klein-Berndt,
Lars Kristensen,
Tronje Krop,
Koojana Kuladinithi,
Kedar Namjoshi,
Alexandru Petrescu,
Henning Rogge,
Fransisco Ros,
Pedro Ruiz,
Christoph Sommer,
Lotte Steenbrink,
Romain Thouvenin,
Richard Trefler,
Jiazi Yi,
Seung Yi,
and
Cong Yuan,
for their reviews AODVv2 and DYMO, as well as numerous specification
suggestions.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119" ?>
<?rfc include="reference.RFC.5082" ?>
<?rfc include="reference.RFC.5444" ?>
<?rfc include="reference.RFC.5497" ?>
<?rfc include="reference.RFC.5498" ?>
<?rfc include="reference.RFC.6551" ?>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.2501" ?>
<?rfc include="reference.RFC.3561" ?>
<?rfc include="reference.RFC.4193" ?>
<?rfc include="reference.RFC.4728" ?>
<?rfc include="reference.RFC.4861" ?>
<?rfc include="reference.RFC.5148" ?>
<?rfc include="reference.RFC.6130" ?>
<?rfc include="reference.RFC.6621" ?>
<?rfc include="reference.I-D.perkins-irrep" ?>
<reference anchor="Perkins94">
<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">
<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>
<!--
<?rfc include="reference.I-D.chakeres-manet-manetid" ?>
<?rfc include="reference.I-D.clausen-lln-loadng" ?>
-->
</references>
<section anchor="algorithms"
title="Example Algorithms for AODVv2 Protocol Operations">
<t>The following subsections show example algorithms for protocol
operations required by AODVv2, including RREQ, RREP, RERR, and
RREP-ACK.
</t>
<t>
Processing for RREQ, RREP, and RERR messages follows
the following general outline:
<list style="numbers">
<t>Receive incoming message.</t>
<t>Update route table as appropriate.</t>
<t>Respond as needed, often regenerating the incoming message with
updated information.</t>
</list>
Once the route table has been updated, the information contained
there is known to be the most recent available information
for any fields in the outgoing message. For this reason, the
algorithms are written as if outgoing message field values are
assigned from the route table information, even though it is often
equally appropriate to use fields from the incoming message.
</t>
<t>AODVv2_algorithms:
<list style="symbols">
<t> Process_Routing_Info </t>
<t> Generate_RREQ </t>
<t> Receive_RREQ </t>
<t> Regenerate_RREQ </t>
<t> Generate_RREP </t>
<t> Receive_RREP </t>
<t> Regenerate_RREP </t>
<t> Generate_RERR </t>
<t> Receive_RERR </t>
<t> Regenerate_RERR </t>
<t> Generate_RREP_Ack </t>
<t> Consume_RREP_Ack() </t>
<t> Timeout RREP_Ack() </t>
</list>
</t>
<t>
The following lists indicate the meaning of the field
names used in subsequent sections to describe message
processing for the above algorithms.
</t>
<t>Incoming RREQ message parameters:
<list style="empty">
<t> inRREQ.origIP := originator IP address </t>
<t> inRREQ.origSeq := originator IP sequence # </t>
<t> inRREQ.metType := metric type </t>
<t> inRREQ.origMet := metric to originator </t>
<t> inRREQ.targIP := target IP address </t>
<t> inRREQ.targSeq := target sequence # (if known) </t>
<t> inRREQ.hopLim := msg-hop-limit /* from RFC 5444 header */ </t>
<t> inRREQ.nbrIP := IP address of the neighbor that sent the RREQ </t>
</list>
</t>
<t>Outgoing RREQ message parameters:
<list style="empty">
<t> outRREQ.origIP := originator IP address </t>
<t> outRREQ.origSeq := originator IP sequence # </t>
<t> outRREQ.metType := metric type </t>
<t> outRREQ.origMet := metric to origNode
{initially MIN_METRIC[MetType]} </t>
<t> outRREQ.targIP := target IP address </t>
<t> outRREQ.targSeq := target sequence # (if known) </t>
<t> outRREQ.hopLim /* initially MAX_HOPCOUNT at originator */ </t>
</list>
</t>
<t>Incoming RREP message parameters:
<list style="empty">
<t> inRREP.hoplim /* msg-hop-limit from RFC 5444 header */ </t>
<t> inRREP.origIP := originator's IP address </t>
<t> inRREP.metType := metric type </t>
<t> inRREP.targIP := target IP address </t>
<t> inRREP.targSeq := target sequence # </t>
<t> inRREP.targMet := target's metric
{initially MIN_METRIC[MetType]} </t>
<t> inRREP.PfxLen </t>
</list>
</t>
<t>Outgoing RREP message parameters:
<list style="empty">
<t> outRREP.origIP := originator's IP address </t>
<t> outRREP.metType := metric type </t>
<t> outRREP.targIP := target IP address </t>
<t> outRREP.targSeq := target sequence # </t>
<t> outRREP.targMet := target's metric {starting with zero} </t>
<t> outRREP.PfxLen </t>
<t> outRREP.hopLim /* initially MAX_HOPCOUNT at originator */ </t>
</list>
</t>
<t>Incoming RERR message parameters:
<list style="empty">
<t> inRERR.PktSrc := source IP of unforwardable packet (if present) </t>
<t> inRERR.metType := metric type for routes to unreachable destinations </t>
<t> inRERR.PfxLen[] := prefix lengths for unreachable destinations </t>
<t> inRERR.LostDest[] := unreachable destinations </t>
<t> inRERR.LostSeq[] := sequence #s for unreachable destinations </t>
</list>
</t>
<t>Outgoing RERR message parameters:
<list style="empty">
<t> outRERR.PktSrc := source IP of unforwardable packet (if present) </t>
<t> outRERR.metType := metric type for routes to unreachable destinations </t>
<t> outRERR.PfxLen[] := prefix lengths for unreachable destinations </t>
<t> outRERR.LostDest[] := unreachable destinations </t>
<t> outRERR.LostSeq[] := sequence #s for unreachable destinations </t>
</list>
</t>
<!-- for cutting and pasting...
<t>
<figure>
<artwork>
</artwork>
</figure>
</t>
for cutting and pasting... -->
<section anchor="sub-algorithms"
title="Subroutines for AODVv2 Protocol Operations">
<t>
<figure>
<artwork>
/* Compare incoming route information to current route, maybe use */
Process_Routing_Info (dest, seq#, metric_type, metric,
last_hop_metric)
/* last_hop_metric: either Cost(inRREQ.netif) or (inRREP.netif) */
{
new_metric := metric + last_hop_metric;
rte := Fetch_Route_Table_Entry (dest, seq#, metric_type);
if (NULL == rte) {
rte := Create_Route_Table_Entry
(dest, seq#, metric_type, new_metric);
} else if (seq# > rte.seq#) { /* stale rte route entry */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else if (seq# < rte.seq#) { /* stale incoming route infor */
return(NULL);
} else if (rte.state == broken) { /* when (seq# == rte.seq#) */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else if (rte.metric > (new_metric) { /* and (seq# == rte.seq#) */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else { /* incoming route information is not useful */
return(NULL);
}
return (rte);
}
</artwork>
</figure>
</t>
</section> <!-- end of "Subroutines" subsection -->
<section anchor="rreq-algorithms"
title="Example Algorithms for AODVv2 RREQ Operations">
<section anchor="Generate_RREQ" title="Generate_RREQ">
<t>
<figure>
<artwork>
Generate_RREQ {
/* Marshall parameters */
outRREQ.origIP := IP address used by application
outRREQ.origSeq := originating router's sequence #
outRREQ.metType := (if included) metric type needed by application
outRREQ.origMet := 0 (default) or MIN_METRIC(Metric_type)
outRREQ.targIP := target IP address
outRREQ.targSeq := target sequence # /* if known from route table */
outRREQ.hopLim := msg-hop-limit /* RFC 5444 */
/* build RFC 5444 message header fields */
{
msg-type=RREQ (message is of type RREQ)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_HOPCOUNT
if (Metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* Include each available Sequence Number in appropriate AddrTLV */
/* put outRREQ.origSeq in OrigSeqNum AddrTLV */
if (NULL != targSeq) {
/* put outRREQ.targSeq in TargSeqNum AddrTLV */
}
/* Build Metric AddrTLV containing OrigAddr metric */
/* use MIN_METRIC(metric type) [==0 for default metric type */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Generate_RREQ" subsection -->
<section anchor="Receive_RREQ " title="Receive_RREQ ">
<t>
<figure>
<artwork>
Receive_RREQ (inRREQ) {
/* Extract inRREQ values */
origRTE = Process_Routing_Info (inRREQ.origIP, inRREQ.origSeq, ...)
if (inRREQ.targIP belongs to me or my client subnet) {
Generate_RREP()
} else if (inRREQ present in RREQ_table) {
return; /* don't regenerate RREQ... */
} else if (inRREQ.nbrIP not present in blacklist) {
Regenerate_RREQ(origRTE, inRREQ)
} else if (blacklist_expiration_time > current_time) {
return; /* don't regenerate RREQ... */
} else {
Remove nbrIP from blacklist;
Regenerate_RREQ(origRTE, inRREQ)
}
}
</artwork>
</figure>
</t>
</section> <!-- end of "Receive_RREQ " subsection -->
<section anchor="Regenerate_RREQ " title="Regenerate_RREQ ">
<t>
<figure>
<artwork>
Regenerate_RREQ (origRTE, inRREQ) { /* called from receive_RREQ() */
outRREQ.hopLim := inRREQ.hopLim - 1
if (outRREQ.hopLim == 0) { /* don't regenerate */
return()
}
/* Marshall parameters */
outRREQ.origIP := origRTE.origIP
outRREQ.origSeq := origRTE.origSeq
outRREQ.origMet := origRTE.origMet
outRREQ.metType := origRTE.metType
outRREQ.targIP := inRREQ.targIP
outRREQ.targSeq := inRREQ.targSeq /* if present */
/* build RFC 5444 message header fields */
{
msg-type=RREQ (message is of type RREQ)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_METRIC(Metric Type) (default, MAX_HOPCOUNT)
if (Metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* Include each available Sequence Number in its proper AddrTLV */
/* put outRREQ.origSeq in OrigSeqNum AddrTLV */
if (NULL != targSeq) {
/* put outRREQ.targSeq in TargSeqNum AddrTLV */
}
/* Build Metric AddrTLV to contain outRREQ.origMet */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Regenerate_RREQ " subsection -->
</section> <!-- end of "RREQ Algorithms" subsection -->
<section anchor="rrep-algorithms"
title="Example Algorithms for AODVv2 RREP Operations">
<section anchor="Generate_RREP " title="Generate_RREP ">
<t>
<figure>
<artwork>
Generate_RREP {
/* Marshall parameters */
outRREP.origIP := origRTE.origIP
metric_type := origRTE.metType /* if not default */
if (DEFAULT != metric_type)
outRREP.metType := metric_type
outRREP.targIP := inRREQ.targIP
outRREP.targMet := MIN_METRIC(outRREP.metType) (0 by default)
my_sequence_# := (1 + my_sequence_#) /* from nonvolatile storage */
outRREP.targSeq := my_sequence_#
/* build RFC 5444 message header fields */
{
msg-type=RREP
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_HOPCOUNT
/* Include the AckReq TLV when:
- previous RREP does not seem to enable any data flow, OR
- when RREQ is received from same OrigAddr after RREP was
unicast to targRTE.nextHop
*/
if (DEFAULT != metric_type) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* put outRREP.TargSeq in TargSeqNum AddrTLV */
/* Build Metric AddrTLV containing TargAddr metric */
/* use MIN_METRIC(origRTE.metType) */
}
</artwork>
</figure>
<vspace blankLines="17"/>
</t>
</section> <!-- end of "Generate_RREP " subsection -->
<section anchor="Receive_RREP" title="Receive_RREP">
<t>
<figure>
<artwork>
Receive_RREP (inRREP)
{
If (RREP includes AckReq data element) {
Generate_RREP_Ack()
}
/* Extract inRREP values */
targRTE := Process_Routing_Info (inRREP.targIP, inRREP.targSeq, ...)
if (inRREP.targIP belongs to me, a client, or a client subnet) {
Consume_RREP(inRREP)
} else {
Regenerate_RREP(targRTE, inRREP)
}
}
</artwork>
</figure>
<vspace blankLines="27"/>
</t>
</section> <!-- end of "Receive_RREP" subsection -->
<section anchor="Regenerate_RREP" title="Regenerate_RREP">
<t>
<figure>
<artwork>
Regenerate_RREP(targRTE, inRREP) {
outRREP.hopLim := inRREP.hopLim - 1
if (outRREP.hopLim == 0) { /* don't regenerate */
return()
}
/* Marshall parameters */
outRREP.targIP := targRTE.targIP
outRREP.targSeq := targRTE.targSeq
outRREP.targMet := targRTE.targMet
metric_type := origRTE.metType /* if not default */
if (DEFAULT != metric_type)
outRREP.metType := metric_type
outRREP.origIP := inRREP.origIP
outRREP.nextHop := targRTE.nextHop
/* build RFC 5444 message header fields */
{
msg-type=RREP (message is of type RREP)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
/* Include the AckReq data element when:
- previous RREP does not seem to enable any data flow, OR
- when RREQ is received from same OrigAddr after RREP was
unicast to targRTE.nextHop
*/
msg-hop-limit := outRREP.hopLim;
if (metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* put outRREP.targSeq in TargSeqNum AddrTLV */
/* Build Metric AddrTLV containing TargAddr metric */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Regenerate_RREP" subsection -->
<section anchor="Consume_RREP" title="Consume_RREP">
<t>
<figure>
<artwork>
/* executed by RREQ_Gen */
/* TargAddr route table entry was updated by Receive_RREP() */
Consume_RREP() {
/* Transmit buffered packet(s) (if any) to TargAddr */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Consume_RREP" subsection -->
</section> <!-- end of "RREP Algorithms" subsection -->
<section anchor="rerr-algorithms"
title="Example Algorithms for AODVv2 RERR Operations">
<section anchor="Generate_RERR" title="Generate_RERR">
<t>
<figure>
<artwork>
Generate_RERR()
{
metric_type := DEFAULT;
switch (error_type) in {
case (broken_link):
num-broken-addr=0
/* find unreachable destinations, seqNums, prefixes */
for (every rte (route table entry) in route table) {
if (broken_link == rte.next_hop) {
rte.state := broken;
outRERR.LostDest[num-broken-addr] := rte.dest
outRERR.LostSeq[num-broken-addr] := rte.seq#
outRERR.PfxLen[num-broken-addr] := rte.pfx
metric_type := rte.metType
num-broken-addr := (num-broken-addr+1)
}
}
/* No offending-src for this case */
case (undeliverable packet):
offending-src := undeliverable_packet.srcIP
outRERR.LostDest[] := undeliverable_packet.destIP
outRERR.LostPfxSiz[] := MAX_PFX_SIZE /* 31 or 127 */
num-broken-addr=1
}
/* build RFC 5444 message header fields */
{
msg-type=RERR (message is of type RERR)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := outRERR.hopLim;
if (NULL != offending-src) {
/* Build PktSource Message TLV */
}
if (metric_type != DEFAULT) { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := num-broken-addr;
AddrBlk := outRERR.LostDest[];
/* Add AddrBlk Seq# TLV */
Seq#TLV := outRERR.LostSeq[]
/* only add AddrBlk PfxSiz TLV if prefixes are nondefault */
for (pfx in outRERR.LostPfx[]) {
if (pfx != Max_Prefix_Size) { /* 31 for IPv4, 127 for IPv6 */
PfxSizTLV := outRERR.LostPfx[]
return;
}
}
}
</artwork>
</figure>
</t>
</section> <!-- end of "Generate_RERR" subsection -->
<section anchor="Receive_RERR" title="Receive_RERR">
<t>
<figure>
<artwork>
Receive_RERR (inERR)
{
/* Extract inERR values */
next_hop := inRERR.nbrIP
offending-src := inRERR.offending-src; /* NULL if not present */
precursors[] := NULL;
num-broken-addr := 0;
in-broken-addr := 0;
for (IPaddr := inRERR.LostDest[in-broken-addr]) {
rte := Fetch_Route_Table_Entry (dest, metric_type);
if (NULL == rte) {
continue;
} else if (rte.nextHop != inRERR.fromIP) {
continue;
} else if (NULL != rte.precursors) {
/* add rte.precursors to precursors */
} else if (rte.PfxSiz < inRERR.PfxSiz) {
/***********************************************************
If the reported prefix from the incoming RERR is *longer*
than the prefix from Route Table, then create a new route
with the longer prefix.
The newly created route will be marked as broken, and used
to regenerate RERR, NOT using shorter the routing prefix.
This avoids unnecessarily invalidating the larger subnet.
**********************************************************/
rte := Create_Route_Table_Entry (IPaddr, seq#,
metric_type, new_metric, inRERR.PfxSiz);
}
LostDest[num-broken-addr] := rte.Dest;
Seq#[num-broken-addr] := rte.Seq#;
PfxSiz[num-broken-addr] := rte.PfxSiz;
rte.state = broken;
num-broken-addr := (num-broken-addr + 1);
in-broken-addr := (in-broken-addr + 1);
}
if (num-broken-addr > 0) {
Regenerate_RERR (offending-src, precursors,
LostDest[], Seq#[], PfxSiz[])
}
}
</artwork>
</figure>
</t>
</section> <!-- end of "Receive_RERR" subsection -->
<section anchor="Regenerate_RERR" title="Regenerate_RERR">
<t>
<figure>
<artwork>
Regenerate_RERR (offending-src, precursors,
LostDest[], LostSeq#[], PfxSiz[])
{
/* build RFC 5444 message header fields */
{
msg-type=RERR (message is of type RERR)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
outRERR.hopLim := inRERR.hopLim - 1
msg-hop-limit := outRERR.hopLim;
if (NULL != offending-src) {
/* Build PktSource Message TLV */
}
if (metric_type != DEFAULT) { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := num-broken-addr;
AddrBlk := LostDest[];
/* Add AddrBlk Seq# TLV */
Seq#TLV := LostSeq[]
/* only add AddrBlk PfxSiz TLV if prefixes are nondefault */
for (pfx in PfxSiz[]) {
if (pfx != Max_Prefix_Size) { /* 31 for IPv4, 127 for IPv6 */
PfxSizTLV := PfxSiz[]
}
} /* If all are default, don't include PfxSize AddrTLV */
if (#precursors == 1) {
unicast RERR to precursor[0];
} else if (#precursors > 1) {
multicast RERR to RERR_PRECURSORS;
} else if (offending-src != NULL) {
unicast RERR to offending-src;
} else {
multicast RERR to RERR_PRECURSORS;
}
}
</artwork>
</figure>
</t>
</section> <!-- end of "Regenerate_RERR" subsection -->
</section> <!-- end of "RERR Algorithms" subsection -->
<section anchor="rrep_ack-algorithms"
title="Example Algorithms for AODVv2 RREP-Ack Operations">
<section anchor="Generate_RREP_Ack" title="Generate_RREP_Ack">
<t>
<figure>
<artwork>
/* To be sent when RREP includes the AckReq TLV */
Generate_RREP_Ack()
{
/* assign RFC 5444 fields */
msgtype := RREPAck
MF := 0
MAL := 3
msg-size := 4
}
</artwork>
</figure>
</t>
</section> <!-- end of "Generate_RREP_Ack" subsection -->
<section anchor="Consume_RREP_Ack" title="Consume_RREP_Ack">
<t>
<figure>
<artwork>
Consume_RREP_Ack()
{
/* turn off timeout event for the node sending RREP_Ack */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Consume_RREP_Ack" subsection -->
<section anchor="Timeout_RREP_Ack" title="Timeout_RREP_Ack">
<t>
<figure>
<artwork>
Timeout_RREP_Ack()
{
/* insert unresponsive node into blacklist */
}
</artwork>
</figure>
</t>
</section> <!-- end of "Timeout_RREP_Ack" subsection -->
</section> <!-- end of "RREP-Ack Algorithms" subsection -->
</section> <!-- end of "Example Algorithms" major section -->
<section anchor="rfc5444-formats"
title="Example RFC 5444-compliant packet formats">
<t>The following subsections show example RFC 5444-compliant
packets for AODVv2 message types RREQ, RREP, RERR, and RREP-Ack.
These
proposed message formats are designed based on expected savings
from IPv6 addressable MANET nodes, and a layout for the Address TLVs
that may be viewed as natural, even if perhaps not the absolute
most compact possible encoding.</t>
<t>For RteMsgs, the msg-hdr fields are followed by
at least one and optionally two Address Blocks. The first AddrBlk
contains OrigAddr and TargAddr. For each AddrBlk,
there must be AddrTLVs of type Metric and one of the SeqNum types
(i.e, OrigSeqNum, TargSeqNum, or Seqnum).
</t>
<t>
There is no Metric Type Message TLV present, so the Metric
AddrTLV measures HopCount.
<!-- CEP: This does not belong here... -->
The Metric AddrTLV also provides a way for the AODV router generating
the RREQ or RREP to supply an initial nonzero cost for the route
to its client node (OrigAddr or TargAddr,
for RREQ or RREP respectively).</t>
<t>In all cases, the length of an address (32 bits for IPv4 and
128 bits for IPv6) inside an AODVv2 message is indicated
by the msg-addr-length (MAL) in the msg-header, as specified
in <xref target="RFC5444"/>.</t>
<t>The RFC 5444 header preceding AODVv2 messages in this document
has the format illustrated in <xref target="fig5444_header"/>.
<figure anchor="fig5444_header" title="RFC 5444 Packet Header">
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| PV=0 | PF=0 |
+-+-+-+-+-+-+-+-+
]]></artwork>
<!-- <postamble></postamble> -->
</figure>
<vspace blankLines="1"/>
The fields in <xref target="fig5444_header"/> are to be interpreted
as follows:
<?rfc compact="yes" ?> <!-- conserve vertical whitespace -->
<?rfc subcompact="yes" ?> <!-- don't keep a blank line between list items -->
<list style="symbols">
<t>PV=0 (Packet Header Version = 0)</t>
<t>PF=0 (Packet Flags = 0)</t>
</list>
</t>
<section anchor="RREQ-format" title="RREQ Message Format">
<t><xref target="figRREQ"/> illustrates an example RREQ message format.
<figure anchor="figRREQ"
title="Example IPv4 RREQ, with OrigSeqNum and Metric AddrTLVs">
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RREQ | MF=4 | MAL=3 | msg-size=28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (bytes for Orig & Target):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head(Orig&Targ)| Orig.Mid | Target.Mid |addr.TLV.len=11:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=11|type=OrigSeqNum|0|1|0|1|0|0|Rsv| Index-start=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| tlv-length=2 | Orig.Node Sequence # | type=Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|0|1|0|0|Rsv| Index-start=0 | tlv-length=1 | OrigAddrHopCt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<!-- <postamble></postamble> -->
</figure>
<!-- <vspace blankLines="2" /> -->
The fields in <xref target="figRREQ"/> are to be interpreted as follows:
<?rfc compact="yes" ?> <!-- conserve vertical whitespace -->
<?rfc subcompact="yes" ?> <!-- don't keep a blank line between list items -->
<list style="symbols">
<t>msg-type=RREQ (first [and only] message is of type RREQ)</t>
<t>MF=4 (Message Flags = 4 [only msg-hop-limit field is present])</t>
<t>MAL=3
(Message Address Length indicator [3 for IPv4, 15 for IPv6])</t>
<t>msg-size=28 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)</t>
<t>msg-hop-limit (initially MAX_HOPCOUNT by default)</t>
<t>msg.tlvs-length=0 (no Message TLVs)</t>
<t>num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)</t>
<t>AddrBlk flags:
<list style="symbols">
<t>bit 0 (ahashead): 1</t>
<t>bit 1 (ahasfulltail): 0</t>
<t>bit 2 (ahaszerotail): 0</t>
<t>bit 3 (ahassingleprelen): 0</t>
<t>bit 4 (ahasmultiprelen): 0</t>
<t>bits 5-7: RESERVED</t>
</list></t>
<t>head-length=3 (length of head part of each address is 3 octets)</t>
<t>Head
(3 initial bytes for both Originating & Target addresses)</t>
<t>Orig.Mid (4th byte of Originating Address)</t>
<t>Target.Mid (4th byte of Target Address)</t>
<t>addr.TLV.len = 11 (length in bytes for OrigSeqNum and Metric TLVs</t>
<t>type=OrigSeqNum (type of first AddrBlk TLV, value 2 octets)</t>
<t>AddrTLV flags for the OrigSeqNum TLV:
<list style="symbols">
<t>bit 0 (thastypeext): 0</t>
<t>bit 1 (thassingleindex): 1</t>
<t>bit 2 (thasmultiindex): 0</t>
<t>bit 3 (thasvalue): 1</t>
<t>bit 4 (thasextlen): 0</t>
<t>bit 5 (tismultivalue): 0</t>
<t>bits 6-7: RESERVED</t>
</list></t>
<t>Index-start=0 (OrigSeqNum TLV value applies at index 0)</t>
<t>tlv-length=2 (so there is only one TLV value, [1 = 2/2])</t>
<t>Orig.Node Sequence # (TLV value for the OrigSeqNum TLV</t>
<t>type=Metric (AddrTLV type of second AddrBlk TLV, values 1 octet)</t>
<t>AddrTLV flags for Metric_TLV:
<list style="symbols">
<t>bit 0 (thastypeext): 0</t>
<t>bit 1 (thassingleindex): 1</t>
<t>bit 2 (thasmultiindex): 0</t>
<t>bit 3 (thasvalue): 1</t>
<t>bit 4 (thasextlen): 0</t>
<t>bit 5 (tismultivalue): 0</t>
<t>bits 6-7: RESERVED</t>
</list></t>
<t>Index-start=0 (Metric TLV values start at index 0)</t>
<t>tlv-length=1 (so there is only one TLV value, [1 = 1/1])</t>
<t>OrigAddrHopCt (first [and only] TLV value for the Metric TLV)</t>
</list>
</t>
</section>
<section anchor="RREP-format" title="RREP Message Format">
<t><xref target="figRREP"/> illustrates a packet format for
an example RREP message.
<figure anchor="figRREP"
title="Example IPv4 RREP, with TargSeqNum TLV and 1 Metric">
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RREP | MF=4 | MAL=3 | msg-size=28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (bytes for Orig & Target):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head(Orig&Targ)| Orig.Mid | Target.Mid |addr.TLV.len=11:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=11|type=TargSeqNum|0|1|0|1|0|0|Rsv| Index-start=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| tlv-length=2 | Targ.Node Sequence # | type=Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|0|1|0|0|Rsv| Index-start=1 | tlv-length=1 | TargAddrHopCt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<!-- <postamble></postamble> -->
</figure>
<vspace blankLines="4"/>
The fields in <xref target="figRREP"/> are to be interpreted as follows:
<list style="symbols">
<t>msg-type=RREP (first [and only] message is of type RREP)</t>
<t>MF=4 (Message Flags = 4 [only msg-hop-limit field is present])</t>
<t>MAL=3
(Message Address Length indicator [3 for IPv4, 15 for IPv6])</t>
<t>msg-size=28 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)</t>
<t>msg-hop-limit (initially MAX_HOPCOUNT by default)</t>
<t>msg.tlvs-length=0 (no Message TLVs)</t>
<t>num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)</t>
<t>AddrBlk flags:
<list style="symbols">
<t>bit 0 (ahashead): 1</t>
<t>bit 1 (ahasfulltail): 0</t>
<t>bit 2 (ahaszerotail): 0</t>
<t>bit 3 (ahassingleprelen): 0</t>
<t>bit 4 (ahasmultiprelen): 0</t>
<t>bits 5-7: RESERVED</t>
</list></t>
<t>head-length=3 (length of head part of each address is 3 octets)</t>
<t>Head
(3 initial bytes for both Originating & Target addresses)</t>
<t>Orig.Mid (4th byte of Originating Address)</t>
<t>Target.Mid (4th byte of Target Address)</t>
<t>addr.TLV.len = 11
(length in bytes for TargSeqNum TLV and Metric TLV</t>
<t>type=TargSeqNum (type of first AddrBlk TLV, value 2 octets)</t>
<t>AddrTLV flags for the TargSeqNum TLV:
<list style="symbols">
<t>bit 0 (thastypeext): 0</t>
<t>bit 1 (thassingleindex): 1</t>
<t>bit 2 (thasmultiindex): 0</t>
<t>bit 3 (thasvalue): 1</t>
<t>bit 4 (thasextlen): 0</t>
<t>bit 5 (tismultivalue): 0</t>
<t>bits 6-7: RESERVED</t>
</list></t>
<t>Index-start=1
(TargSeqNum TLV value applies to address at index 1)</t>
<t>tlv-length=2 (there is one TLV value, 2 bytes in length)</t>
<t>Targ.Node Sequence # (value for the TargSeqNum TLV)</t>
<t>type=Metric (AddrTLV type of second AddrBlk TLV, value 1 octet)</t>
<t>AddrTLV flags for the Metric TLV
[01010000, same as for TargSeqNum TLV]</t>
<t>Index-start=1 (Metric TLV values start at index 1)</t>
<t>tlv-length=1 (there is one TLV value, 1 byte in length)</t>
<t>TargAddrHopCt (first [and only] TLV value for Metric TLV)</t>
</list>
<vspace blankLines="23"/>
</t>
</section>
<section anchor="RERR-format" title="RERR Message Format">
<t><xref target="figRERR"/> illustrates an example RERR
message format.
<figure anchor="figRERR"
title="Example IPv4 RERR with Two Unreachable Addresses">
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RERR | MF=4 | MAL=3 | msg-size=24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (for both destinations) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head (3rd byte)| Mid (Dest_1) | Mid (Dest_2) | addr.TLV.len=7:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=7 | type=SeqNum |0|0|1|1|0|1|Rsv| tlv-length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dest_1 Sequence # | Dest_2 Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<!-- <postamble>RERR </postamble> -->
</figure>
The fields in <xref target="figRERR"/> are to be interpreted as follows:
<list style="symbols">
<t>msg-type=RERR (first [and only] message is of type RERR)</t>
<t>MF=4 (Message Flags = 4 [only msg-hop-limit field is present])</t>
<t>MAL=3
(Message Address Length indicator [3 for IPv4, 15 for IPv6])</t>
<t>msg-size=24 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)</t>
<t>msg-hop-limit (initially MAX_HOPCOUNT by default)</t>
<t>msg.tlvs-length=0 (no Message TLVs)</t>
<t>num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)</t>
<t>AddrBlk flags == 10000000
[same as RREQ and RREP AddrBlk examples]</t>
<t>head-length=3 (length of head part of each address is 3 octets)</t>
<t>Head
(3 initial bytes for both Unreachable Addresses, Dest_1 and Dest_2)</t>
<t>Dest_1.Mid (4th byte of Dest_1 IP address)</t>
<t>Dest_2.Mid (4th byte of Dest_2 IP address)</t>
<t>addr.TLV.len = 7 (length in bytes for SeqNum TLV</t>
<t>type=SeqNum (AddrTLV type of AddrBlk TLV, values 2 octets each)</t>
<t>AddrTLV flags for SeqNum TLV:
<list style="symbols">
<t>bit 0 (thastypeext): 0</t>
<t>bit 1 (thassingleindex): 0</t>
<t>bit 2 (thasmultiindex): 1</t>
<t>bit 3 (thasvalue): 1</t>
<t>bit 4 (thasextlen): 0</t>
<t>bit 5 (tismultivalue): 1</t>
<t>bits 6-7: RESERVED</t>
</list></t>
<t>tlv-length=4 (so there are two TLV values, [2 = 4/2])</t>
<t>Dest_1 Sequence # (first of two TLV values for the SeqNum TLV)</t>
<t>Dest_2 Sequence # (second of two TLV values for the SeqNum TLV)</t>
</list>
</t>
</section>
<!-- Removed: issue #40 -->
<section anchor="RREP_ACK-format" title="RREP_ACK Message Format">
<t>The figure below illustrates a packet format for an example
RREP_ACK message. </t>
<t><figure anchor="figRREPAk" title="Example IPv4 RREP_ACK">
<artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|msgtype=RREPAck| MF=0 | MAL=3 | msg-size=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<vspace blankLines="7"/>
</t>
</section>
<!-- End removed section: issue #40 -->
</section>
<section anchor="changes-05" title="Changes since revision ...-05.txt">
<!-- CEP: section obviously needs work :-) -->
<t> This section lists the changes since AODVv2 revision ...-05.txt
</t>
<t><list style="symbols">
<t>
Added Lotte Steenbrink as co-author.
</t>
<t>
Reorganized section on Metrics to improve readability by putting
specific topics into subsections.
</t>
<t>
Introduced concept of data element, which is used to clarify the method
of enabling RFC 5444 representation for AODVv2 data elements. A list of
Data Elements was introduced in section 3, which provides a better
understanding of their role than was previously supplied by the
table of notational devices.
</t>
<t>
Replaced instances of OrigNode by OrigAddr whenever the more
specific meaning is appropriate. Similarly for instances of other
node versus address terminology.
</t>
<t>
Introduced concepts of PrefixLengthList and MetricList in order to
avoid use of index-based terminology such as OrigNdx and TargNdx.
</t>
<t>
Added section 5, "AODVv2 Message Transmission", describing the
intended interface to RFC 5444.
</t>
<t>
Included within the main body of the specification the
mandatory setting of the TLV flag thassingleindex
for TLVs OrigSeqNum and TargSeqNum.
</t>
<t>
Removed the Route.Timed state. Created a new flag for route table
entries known as Route.Timed. This flag can be set when the route
is in the active state. Previous description would require that the
route table entry be in two states at the same time, which seems
to be misleading. The new flag is used to clarify other specification
details for Timed routes.
</t>
<t>
Created table 3 to show the correspondence between AODVv2 data elements
and RFC 5444 message components.
</t>
<t>
Replaced "invalid" terminology by the more specific terms
"broken" or "expired" where appropriate.
</t>
<t>
Eliminated the instance of duplicate specification for inclusion of
OrigNode (now, OrigAddr) in the message.
</t>
<t>
Corrected the terminology to be Mid instead of Tail for the trailing
address bits of OrigAddr and TargAddr for the example message formats in
the appendices.
</t>
<!--
<t>
xxxxx
</t>
<t>
xxxxx
</t>
<t>
xxxxx
xxxxx
</t>
-->
</list>
</t>
</section>
<section anchor="changes-04" title="Changes since revision ...-04.txt">
<t> This section lists the changes since AODVv2 revision ...-04.txt
</t>
<t><list style="symbols">
<t>
Normative text moved out of definitions into the
relevant section of the body of the specification.
</t>
<t>
Editorial improvements and improvements to
consistent terminology were made. Replaced
"retransmit" by the slightly more accurate term "regenerate".
</t>
<t>
Issues were resolved as discussed on the mailing list.
</t>
<t>
Changed definition of LoopFree as suggested by Kedar Namjoshi
and Richard Trefler to avoid the failure condition that they
have described.
In order to make understanding easier, replaced abstract
parameters R1 by RteMsg and R2 by Route to reduce the
level of abstraction when the function LoopFree is discussed.
</t>
<t>
Added text to clarify that different metrics may have
different data types and different ranges of acceptable values.
</t>
<t>
Added text to section "RteMsg Structure" to emphasize the
proper use of RFC 5444.
</t>
<t>
Included within the main body of the specification the
mandatory setting of the TLV flag thassingleindex
for TLVs OrigSeqNum and TargSeqNum.
</t>
<t>
Made more extensive use of the AdvRte terminology, in
order to better distinguish between the incoming RREQ
or RREP message (i.e., RteMsg) versus the route advertised
by the RteMsg (i.e., AdvRte).
</t>
<!--
<t>
xxxxx
xxxxx
</t>
<t>
xxxxx
</t>
<t>
xxxxx
</t>
<t>
xxxxx
xxxxx
</t>
-->
</list>
</t>
</section>
<section anchor="changes-03" title="Changes since revision ...-03.txt">
<t> This section lists the changes since AODVv2 revision ...-03.txt
</t>
<t><list style="symbols">
<t>
An appendix was added to exhibit algorithmic code
for implementation of AODVv2 functions.
</t>
<t>
Numerous editorial improvements and improvements to
consistent terminology were made. Terminology related
to prefix lengths was made consistent. Some items listed
in "Notational Conventions" were no longer used, and so
deleted.
</t>
<t>
Issues were resolved as discussed on the mailing list.
</t>
<t>
Appropriate instances of "may" were changed to "MAY".
</t>
<t>
Definition inserted for "upstream".
</t>
<t>
Route.Precursors included as an *optional* route table field
</t>
<t>
Reworded text to avoid use of "relevant".
</t>
<t>
Deleted references to "DestOnly" flag.
</t>
<t>
Refined statements about Metric Type TLV to allow for
omission when Metric Type == HopCount.
</t>
<t>
Bulletized list in section 8.1
</t>
<t>
ENABLE_IDLE_UNREACHABLE renamed to be ENABLE_IDLE_IN_RERR
</t>
<t>
Transmission and subscription to LL-MANET-Routers converted
to MUST from SHOULD.
</t>
</list>
</t>
</section> <!-- End "Changes since revision ...-03.txt" -->
<section anchor="changes-02" title="Changes since revision ...-02.txt">
<t> This section lists the changes since AODVv2 revision ...-02.txt
</t>
<t><list style="symbols">
<t>
The "Added Node" feature was removed. This feature was
intended to enable additional routing information to be
carried within a RREQ or a RREP message, thus increasing the
amount of topological information available to nodes along
a routing path. However, enlarging the packet size to include
information which might never be used can increase congestion
of the wireless medium. The feature can be included as an
optional feature at a later date when better algorithms are
understood for determining when the inclusion of additional
routing information might be worthwhile.
</t>
<t>
Numerous editorial improvements and improvements to
consistent terminology were made. Instances of OrigNodeNdx
and TargNodeNdx were replaced by OrigNdx and TargNdx,
to be consistent with the terminology shown in
<xref target="notational-conventions"/>.
</t>
<t>
Example RREQ and RREP message formats shown in the Appendices
were changed to use OrigSeqNum and TargSeqNum message TLVs
instead of using the SeqNum message TLV.
</t>
<t>
Inclusion of the OrigNode's SeqNum in the RREP message
is not specified. The processing rules for the OrigNode's
SeqNum were incompletely specified in previous versions
of the draft, and very little benefit is foreseen for
including that information, since reverse path forwarding
is used for the RREP.
</t>
<t>
Additional acknowledgements were included, and contributors
names were alphabetized.
</t>
<t>
Definitions in the Terminology section capitalize the term to
be defined.
</t>
<t>
Uncited bibliographic entries deleted.
</t>
<t>
Ancient "Changes" sections were deleted.
</t>
</list>
</t>
</section>
<!--
<section anchor="prop_changes"
title="Proposed additional changes for LOADng conformance">
<t><list style="symbols">
</list>
</t>
-->
<!-- Issue #28 -->
<section anchor="multihome" title="Multi-homing Considerations">
<t>Multi-homing is not supported by the AODVv2 specification.
There has been previous work indicating that it can be supported by
expanding the sequence number to include the AODVv2 router's IP
address as a parsable field of the SeqNum. Otherwise, comparing
sequence numbers would not work to evaluate freshness. Even when the
IP address is included, there isn't a good way to compare sequence
numbers from different IP addresses, but at least a handling node can
determine whether the two given sequence numbers are comparable. If the
route table can store multiple routes for the same destination, then
multi-homing can work with sequence numbers augmented by IP addresses.</t>
<t>This non-normative information is provided simply to document
the results of previous efforts to enable multi-homing.
The intention is to simplify the task of future specification if
multihoming becomes needed for reactive protocol operation.
</t>
</section>
<section anchor="change_address_location"
title="Shifting Network Prefix Advertisement Between AODVv2 Routers">
<t>Only one AODVv2 router within a MANET SHOULD be
responsible for a particular address at any time. If two AODVv2
routers dynamically shift the advertisement of a network prefix, correct
AODVv2 routing behavior must be observed. The AODVv2 router adding
the new network prefix must wait for any existing routing information
about this network prefix to be purged from the network. Therefore, it
must wait at least ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the
previous AODVv2 router for this address stopped
advertising routing information on its behalf.</t>
</section>
</back>
</rfc>
<!-- ====================================================================== -->
<!--
<msg-header> := <msg-type>
<msg-size:16> /* up to 65,545 bytes */
<msg-orig-addr>?
<msg-hop-limit:8>?
<msg-hop-count:8>?
<msg-seq-num:16>?
<tlv-block>
(<addr-block><tlv-block>)*
<address-block> := <num-addr:8>
<addr-flags:8>
(<head-length><head>?)?
(<tail-length><tail>?)?
<mid>*
<prefix-length>*
<tlv-block> := <tlvs-length:16> /* Aggregate length of <tlv>* */
<tlv>*
<tlv> := <tlv-type:8>
<tlv-flags:8>
<tlv-type-ext>?
(<index-start><index-stop>?)?
(<length><value>?)?
-->
Mobile Ad hoc Networks Working Group C. Perkins
Internet-Draft Futurewei
Intended status: Standards Track S. Ratliff
Expires: July 2, 2015 Idirect
J. Dowdell
Airbus Defence and Space
L. Steenbrink
Hamburg University of Applied Sciences
December 29, 2014
Dynamic MANET On-demand (AODVv2) Routing
draft-ietf-manet-aodvv2-06
Abstract
The revised 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 rapid
convergence in dynamic topologies.
Status of This Memo
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This Internet-Draft will expire on July 2, 2015.
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Data Elements and Notational Conventions . . . . . . . . . . 8
4. Applicability Statement . . . . . . . . . . . . . . . . . . . 8
5. AODVv2 Message Transmission . . . . . . . . . . . . . . . . . 10
6. Data Structures . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Route Table Entry . . . . . . . . . . . . . . . . . . . . 10
6.2. Bidirectional Connectivity and Blacklists . . . . . . . . 12
6.3. Router Clients and Client Networks . . . . . . . . . . . 13
6.4. Sequence Numbers . . . . . . . . . . . . . . . . . . . . 13
6.5. Metrics . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.5.1. The Cost() function . . . . . . . . . . . . . . . . . 15
6.5.2. The LoopFree() function . . . . . . . . . . . . . . . 15
6.5.3. Default Metric type . . . . . . . . . . . . . . . . . 15
6.5.4. Alternate Metrics . . . . . . . . . . . . . . . . . . 16
6.6. RREQ Table: Received RREQ Messages . . . . . . . . . . . 16
7. AODVv2 Operations on Route Table Entries . . . . . . . . . . 17
7.1. Evaluating Incoming Routing Information . . . . . . . . . 17
7.2. Applying Route Updates To Route Table Entries . . . . . . 19
7.3. Route Table Entry Timeouts . . . . . . . . . . . . . . . 20
8. Routing Messages RREQ and RREP (RteMsgs) . . . . . . . . . . 20
8.1. Route Discovery Retries and Buffering . . . . . . . . . . 21
8.2. RteMsg Structure . . . . . . . . . . . . . . . . . . . . 21
8.3. RREQ Generation . . . . . . . . . . . . . . . . . . . . . 23
8.4. RREP Generation . . . . . . . . . . . . . . . . . . . . . 23
8.5. Handling a Received RteMsg . . . . . . . . . . . . . . . 24
8.5.1. Additional Handling for Incoming RREQ . . . . . . . . 25
8.5.2. Additional Handling for Incoming RREP . . . . . . . . 26
8.6. Suppressing Redundant RREQ messages . . . . . . . . . . . 26
9. Route Maintenance and RERR Messages . . . . . . . . . . . . . 27
9.1. Maintaining Route Lifetimes During Packet Forwarding . . 27
9.2. Next-hop Router Adjacency Monitoring . . . . . . . . . . 27
9.3. RERR Generation . . . . . . . . . . . . . . . . . . . . . 28
9.3.1. Case 1: Undeliverable Packet . . . . . . . . . . . . 29
9.3.2. Case 2: Broken Link . . . . . . . . . . . . . . . . . 30
9.4. Receiving and Handling RERR Messages . . . . . . . . . . 30
10. Representing AODVv2 data elements using RFC 5444 . . . . . . 31
11. Simple Internet Attachment . . . . . . . . . . . . . . . . . 33
12. Multiple Interfaces . . . . . . . . . . . . . . . . . . . . . 34
13. AODVv2 Control Message Generation Limits . . . . . . . . . . 35
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14. Optional Features . . . . . . . . . . . . . . . . . . . . . . 35
14.1. Expanding Rings Multicast . . . . . . . . . . . . . . . 35
14.2. Intermediate RREP . . . . . . . . . . . . . . . . . . . 35
14.3. Precursor Lists and Notifications . . . . . . . . . . . 35
14.3.1. Overview . . . . . . . . . . . . . . . . . . . . . . 36
14.3.2. Precursor Notification Details . . . . . . . . . . . 36
14.4. Multicast RREP Response to RREQ . . . . . . . . . . . . 37
14.5. RREP_ACK . . . . . . . . . . . . . . . . . . . . . . . . 37
14.6. Message Aggregation . . . . . . . . . . . . . . . . . . 37
15. Administratively Configurable Parameters and Timer Values . . 38
15.1. Timers . . . . . . . . . . . . . . . . . . . . . . . . . 38
15.2. Protocol constants . . . . . . . . . . . . . . . . . . . 39
15.3. Administrative (functional) controls . . . . . . . . . . 39
15.4. Other administrative parameters and lists . . . . . . . 39
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
16.1. AODVv2 Message Types Specification . . . . . . . . . . . 40
16.2. Message TLV Type Specification . . . . . . . . . . . . . 40
16.3. Address Block TLV Specification . . . . . . . . . . . . 41
16.4. Metric Type Number Allocation . . . . . . . . . . . . . 41
17. Security Considerations . . . . . . . . . . . . . . . . . . . 41
18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 43
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
19.1. Normative References . . . . . . . . . . . . . . . . . . 43
19.2. Informative References . . . . . . . . . . . . . . . . . 44
Appendix A. Example Algorithms for AODVv2 Protocol Operations . 45
A.1. Subroutines for AODVv2 Protocol Operations . . . . . . . 47
A.2. Example Algorithms for AODVv2 RREQ Operations . . . . . . 48
A.2.1. Generate_RREQ . . . . . . . . . . . . . . . . . . . . 48
A.2.2. Receive_RREQ . . . . . . . . . . . . . . . . . . . . 49
A.2.3. Regenerate_RREQ . . . . . . . . . . . . . . . . . . . 50
A.3. Example Algorithms for AODVv2 RREP Operations . . . . . . 51
A.3.1. Generate_RREP . . . . . . . . . . . . . . . . . . . . 52
A.3.2. Receive_RREP . . . . . . . . . . . . . . . . . . . . 53
A.3.3. Regenerate_RREP . . . . . . . . . . . . . . . . . . . 54
A.3.4. Consume_RREP . . . . . . . . . . . . . . . . . . . . 55
A.4. Example Algorithms for AODVv2 RERR Operations . . . . . . 55
A.4.1. Generate_RERR . . . . . . . . . . . . . . . . . . . . 55
A.4.2. Receive_RERR . . . . . . . . . . . . . . . . . . . . 56
A.4.3. Regenerate_RERR . . . . . . . . . . . . . . . . . . . 57
A.5. Example Algorithms for AODVv2 RREP-Ack Operations . . . . 59
A.5.1. Generate_RREP_Ack . . . . . . . . . . . . . . . . . . 59
A.5.2. Consume_RREP_Ack . . . . . . . . . . . . . . . . . . 59
A.5.3. Timeout_RREP_Ack . . . . . . . . . . . . . . . . . . 59
Appendix B. Example RFC 5444-compliant packet formats . . . . . 59
B.1. RREQ Message Format . . . . . . . . . . . . . . . . . . . 60
B.2. RREP Message Format . . . . . . . . . . . . . . . . . . . 62
B.3. RERR Message Format . . . . . . . . . . . . . . . . . . . 64
B.4. RREP_ACK Message Format . . . . . . . . . . . . . . . . . 65
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Appendix C. Changes since revision ...-05.txt . . . . . . . . . 65
Appendix D. Changes since revision ...-04.txt . . . . . . . . . 66
Appendix E. Changes since revision ...-03.txt . . . . . . . . . 66
Appendix F. Changes since revision ...-02.txt . . . . . . . . . 67
Appendix G. Multi-homing Considerations . . . . . . . . . . . . 68
Appendix H. Shifting Network Prefix Advertisement Between AODVv2
Routers . . . . . . . . . . . . . . . . . . . . . . 68
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 68
1. Overview
The revised Ad Hoc On-demand Distance Vector (AODVv2) routing
protocol [formerly named DYMO] enables on-demand, multihop unicast
routing among AODVv2 routers in mobile ad hod networks
[MANETs][RFC2501]. The basic operations of the AODVv2 protocol are
route discovery and route maintenance. Route discovery is performed
when an AODVv2 router must transmit a packet towards a destination
for which it does not have a route. Route maintenance is performed
to avoid prematurely expunging routes from the route table, and to
avoid dropping packets when a route breaks.
During route discovery, the originating AODVv2 router (RREQ_Gen)
multicasts a Route Request message (RREQ) to find a route toward some
target destination. Using a hop-by-hop regeneration algorithm, each
AODVv2 router receiving the RREQ message records a route toward the
originator. When the target's AODVv2 router (RREP_Gen) receives the
RREQ, it records a route toward RREQ_Gen and generates a Route Reply
(RREP) unicast toward RREQ_Gen. Each AODVv2 router that receives the
RREP stores a route toward the target, and again unicasts the RREP
toward the originator. When RREQ_Gen receives the RREP, routes have
then been established between RREQ_Gen (the originating AODVv2
router) and RREP_Gen (the target's AODVv2 router) in both directions.
Route maintenance consists of two operations. In order to maintain
routes, AODVv2 routers extend route lifetimes upon successfully
forwarding a packet. When a data packet is received to be forwarded
but there is no valid route for the destination, then the AODVv2
router of the source of the packet is notified via a Route Error
(RERR) message. Each upstream router that receives the RERR marks
the route as broken. Before such an upstream AODVv2 router could
forward a packet to the same destination, it would have to perform
route discovery again for that destination. RERR messages are also
used to notify upstream routers when routes break (say, due to loss
of a link to a neighbor).
AODVv2 uses sequence numbers to assure loop freedom [Perkins99],
similarly to AODV. Sequence numbers enable AODVv2 routers to
determine the temporal order of AODVv2 route discovery messages,
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thereby avoiding use of stale routing information. See Section 10
for the mapping of AODVv2 data elements to RFC 5444 Address Block,
Address TLV, and Message TLV formats.
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].
This document uses terminology from [RFC5444].
This document defines the following terms:
Adjacency
A bi-directional relationship between neighboring AODVv2 routers
for the purpose of exchanging routing information. Not every pair
of neighboring routers will necessarily form an adjacency.
Monitoring of adjacencies where packets are being forwarded is
required (see Section 9.2).
AODVv2 Router
An IP addressable device in the ad-hoc network that performs the
AODVv2 protocol operations specified in this document.
AODVv2 Sequence Number (SeqNum)
Same as Sequence Number.
Client Interface
An interface that directly connects Router Clients to the Router.
Current_Time
The current time as maintained by the AODVv2 router.
Data Element
A named object used within AODVv2 protocol messages
Disregard
Ignore for further processing (see Section 5).
Handling Router (HandlingRtr)
HandlingRtr denotes the AODVv2 router receiving and handling an
AODVv2 message.
Incoming Link
A link over which an AODVv2 Router has received a message from an
adjacent router.
MANET
A Mobile Ad Hoc Network as defined in [RFC2501].
MetricList
A MetricList is a list of Metrics associated with the addresses in
an AddressList.
Node
An IP addressable device in the ad-hoc network. A node may be an
AODVv2 router, or it may be a device in the network that does not
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perform any AODVv2 protocol operations. All nodes in this
document are either AODVv2 Routers or else Router Clients.
OrigAddr
The IP address of the Originating Node used as a data element
within AODVv2 messages.
Originating Node (OrigNode)
The Originating Node is the node that launched the application
requiring communication with the Target Address. If OrigNode is a
Router Client, its AODVv2 router (RREQ_Gen) has the responsibility
to generate a AODVv2 RREQ message on behalf of OrigNode as
necessary to discover a route.
PrefixLengthList
A PrefixLengthList is the list of prefix lengths associated with
the addresses in an AddressList.
Reactive
A protocol operation is called "reactive" if it is performed only
in reaction to specific events. As used in this document,
"reactive" is synonymous with "on-demand".
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
unicast IP addresses and Unique Local Addresses (ULAs) [RFC4193]
are examples of routable unicast IP addresses.
Route Error (RERR)
A RERR message is used to indicate that an AODVv2 router does not
have a route toward one or more particular destinations.
Route Reply (RREP)
A RREP message is used to establish a route between the Target
Address and the Originating Address, at all the AODVv2 routers
between them.
Route Request (RREQ)
An AODVv2 router uses a RREQ message to discover a valid route to
a particular destination address, called the Target Address. An
AODVv2 router processing a RREQ receives routing information for
the Originating Address.
Router Client
A node that requires the services of an AODVv2 router for route
discovery and maintenance. An AODVv2 router is always its own
client, so that its list of client IP addresses is never empty.
Router Interface
An interface supporting the transmission or reception of Router
Messages.
RREP Generating Router (RREP_Gen)
The RREP Generating Router is the AODVv2 router that serves
TargNode. RREP_Gen generates the RREP message to advertise a
route towards TargAddr from OrigAddr.
RREQ Generating Router (RREQ_Gen)
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The RREQ Generating Router is the AODVv2 router that serves
OrigNode. RREQ_Gen generates the RREQ message to discover a route
for TargAddr.
Sequence Number (SeqNum)
A Sequence Number is an unsigned integer maintained by an AODVv2
router to avoid re-use of stale messages. The router associates
SeqNum with the IP address of its network interface. If the
router has multiple network interfaces, it can use the same SeqNum
for the IP addresses of all of them, or it can assign different
SeqNums for use with different IP addresses. However, the router
MUST NOT use multiple SeqNums for any particular IP address. A
Router Client has the same SeqNum as the IP address of the network
interface that the AODVv2 router uses to forward packets to that
Router Client. Similarly, a route to a subnet has the same SeqNum
as the IP address of the network interface that the AODVv2 router
uses to forward packets to that subnet. The Sequence Number
guarantees the temporal order of routing information to maintain
loop-free routes, and fulfills the same role as the "Destination
Sequence Number" of DSDV [Perkins94], and as the AODV Sequence
Number in RFC 3561[RFC3561]. The value zero (0) is reserved to
indicate that the Sequence Number for an address is unknown.
SeqNumList
A SeqNumList is the list of Sequence Numbers associated with the
addresses in an AddressList.
TargAddr
The IP address of the Target Node used as a data element within
AODVv2 messages.
Target Node (TargNode)
The Target Node denotes the node hosting the IP address towards
which a route is needed.
Unreachable Addr (UnreachableAddr)
An UnreachableAddr is an address for which a valid route is not
known.
upstream
In the direction from TargAddr to OrigAddr.
Valid route
A route that can be used for forwarding; in other words a route
that is not Broken or Expired.
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3. Data Elements and Notational Conventions
This document uses the Data Elements and conventions found in Table 1
and Table 2.
+---------------+-------------------------------------------------+
| Data Elements | Meaning |
+---------------+-------------------------------------------------+
| msg_hop_limit | Number of hops allowable for the message. |
| msg_hop_count | Number of hops traversed so far by the message. |
| AckReq | Acknowledgement Requested for RREP |
| MetricType | Metric Type for Metric data element |
| PktSource | The IP address which is unreachable. |
| AddressList | A list of IP addresses |
| SeqNum | Sequence Number |
| SeqNumList | Sequence Number List |
| Metric | Metric value for route to associated IP address |
| OrigSeqNum | Originating Node Sequence Number |
| TargSeqNum | Target Node Sequence Number |
+---------------+-------------------------------------------------+
Table 1
+------------------------+------------------------------------------+
| Notation | Meaning |
+------------------------+------------------------------------------+
| Route[Address] | A route table entry towards Address |
| Route[Address].{field} | A field in a route table entry |
| -- | -- |
| RREQ_Gen | AODVv2 router originating an RREQ |
| RREP_Gen | AODVv2 router responding to an RREQ |
| RteMsg | Either RREQ or RREP |
| RteMsg.{field} | Field in RREQ or RREP |
| AdvRte | a route advertised in an incoming RteMsg |
| HandlingRtr | Handling Router |
| UnreachableAddr | Unreachable Addr |
+------------------------+------------------------------------------+
Table 2
4. Applicability Statement
The AODVv2 routing protocol is a reactive routing protocol designed
for stub (i.e., non-transit) or disconnected (i.e., from the
Internet) mobile ad hoc networks (MANETs). AODVv2 handles a wide
variety of mobility patterns by determining routes on-demand. AODVv2
also handles a wide variety of traffic patterns. In networks with a
large number of routers, AODVv2 is best suited for relatively sparse
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traffic scenarios where any particular router forwards packets to
only a small percentage of the AODVv2 routers in the network, due to
the on-demand nature of route discovery and route maintenance.
AODVv2 supports routers with multiple interfaces, as long as each
interface has its own (unicast routeable) IP address; the set of all
network interfaces supporting AODVv2 is administratively configured
in a list (namely, AODVv2_INTERFACES).
Although AODVv2 is closely related to AODV [RFC3561], and shares some
features of DSR [RFC4728], AODVv2 is not interoperable with either of
those other two protocols.
AODVv2 is applicable to memory constrained devices, since only a
little routing state is maintained in each AODVv2 router. Routes
that are not needed for forwarding data do not have to be maintained,
in contrast to proactive routing protocols that require routing
information to all routers within the MANET be maintained.
In addition to routing for its own local applications, each AODVv2
router can also route on behalf of other non-routing nodes (in this
document, "Router Clients"), reachable via Client Interfaces. Each
AODVv2 router, if serving router clients other than itself, SHOULD be
configured with information about the IP addresses of its clients,
using any suitable method. In the initial state, no AODVv2 router is
required to have information about the relationship between any other
AODVv2 router and its Router Clients (see Section 6.3).
The coordination among multiple AODVv2 routers to distribute routing
information correctly for a shared address (i.e. an address that is
advertised and can be reached via multiple AODVv2 routers) is not
described in this document. The AODVv2 router operation of shifting
responsibility for a routing client from one AODVv2 router to another
is described in Appendix H. Address assignment procedures are
entirely out of scope for AODVv2. A Router Client SHOULD NOT be
served by more than one AODVv2 router at any one time.
AODVv2 routers perform route discovery to find a route toward a
particular destination. AODVv2 routers MUST must be configured to
respond to RREQs for themselves and their clients. When AODVv2 is
the only protocol interacting with the forwarding table, AODVv2 MAY
be configured to perform route discovery for all unknown unicast
destinations.
AODVv2 only supports bidirectional links. In the case of possible
unidirectional links, blacklists (see Section 6.2) SHOULD be used, or
other means (e.g. adjacency establishment with only neighboring
routers that have bidirectional communication as indicated by NHDP
[RFC6130]) of assuring and monitoring bi-directionality are
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recommended. Otherwise, persistent packet loss or persistent
protocol failures could occur. The cost of bidirectional link L
(denoted Cost(L)) may depend upon the direction across the link for
which the cost is measured. If received over a link that is
unidirectional, metric information from incoming AODVv2 messages MUST
NOT be used for route table updates.
The routing algorithm in AODVv2 may be operated at layers other than
the network layer, using layer-appropriate addresses. The routing
algorithm makes use of some persistent state; if there is no
persistent storage available for this state, recovery can impose a
performance penalty (e.g., in case of AODVv2 router reboots).
5. AODVv2 Message Transmission
In its default mode of operation, AODVv2 sends messages using the
parameters for port number and IP protocol specified in [RFC5498].
By default, AODVv2 messages are sent with the IP destination address
set to the link-local multicast address LL-MANET-Routers [RFC5498]
unless otherwise specified. Therefore, all AODVv2 routers MUST
subscribe to LL-MANET-Routers [RFC5498] to receive AODVv2 messages.
In order to reduce multicast overhead, regenerated multicast packets
in MANETs SHOULD be done according to methods specified in [RFC6621].
AODVv2 does not specify which method should be used to restrict the
set of AODVv2 routers that have the responsibility to regenerate
multicast packets. Note that multicast packets 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.
The IPv4 TTL (IPv6 Hop Limit) field for all packets containing AODVv2
messages is set to 255. If a packet is received with a value other
than 255, any AODVv2 message contained in the packet MUST be
disregarded by AODVv2. This mechanism, known as "The Generalized TTL
Security Mechanism" (GTSM) [RFC5082] helps to assure that packets
have not traversed any intermediate routers.
IP packets containing AODVv2 protocol messages SHOULD be given
priority queuing and channel access.
6. Data Structures
6.1. Route Table Entry
The route table entry is a conceptual data structure.
Implementations MAY use any internal representation so long as it
provides access to the information specified below.
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A route table entry has the following fields:
Route.Address
An address or address prefix of a node
Route.PrefixLength
The length of the address or prefix. If the value of
Route.PrefixLength is less than the length of addresses in the
address family used by the AODVv2 routers, the associated address
is a routing prefix, rather than an address. A PrefixLength is
stored for every route in the route table.
Route.SeqNum
The Sequence Number associated with Route.Address, as obtained
from the last packet that successfully updated this route table
entry.
Route.NextHopAddress
The IP address of the adjacent AODVv2 router used for the path
toward the Route.Address
Route.NextHopInterface
The interface used to send packets toward Route.Address
Route.LastUsed
The time that this route was last used
Route.ExpirationTime
The time at which this route must expire
Route.MetricType
The type of the metric for the route towards Route.Address
Route.Metric
The cost of the route towards Route.Address expressed in units
consistent with Route.MetricType
Route.State
The last *known* state of the route. Route.State is one of the
following: Active, Idle, Expired, or Broken.
Route.Timed
The Route.Timed flag is true if the route was specified to have a
specific lifetime for use.
Route.Precursors (optional)
A list of upstream nodes using the route.
A route table entry (i.e., a route) is in one of the following
states:
Active
An Active route is in current use for forwarding packets. An
Active route is maintained continuously by AODVv2 and is
considered to remain active as long as it is used at least once
during every ACTIVE_INTERVAL, or if the Route.Timed flag is true.
When a route that is not a timed route is no longer active the
route becomes an Idle route.
Idle
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An Idle route can be used for forwarding packets, even though it
is not in current use. If an Idle route is used to forward a
packet, it becomes an Active route once again. After an Idle
route remains idle for MAX_IDLETIME, it becomes an Expired route.
Expired
After a route has been idle for too long, it expires, and may no
longer be used for forwarding packets. An Expired route is not
used for forwarding, but the sequence number information can be
maintained until the destination sequence number has had no
updates for MAX_SEQNUM_LIFETIME; after that time, old sequence
number information is considered no longer valuable and the
Expired route MUST BE expunged.
Broken
A route marked as Broken cannot be used for forwarding packets but
still has valid destination sequence number information. When the
link to a route's next hop is broken, the route is marked as being
Broken, and afterwards the route MAY NOT be used.
Timed
The expiration of a Timed route is controlled by the
Route.ExpirationTime time of the route table entry (instead of
MAX_IDLETIME). Until that time, a Timed route can be used for
forwarding packets. A route is indicated to be a Timed route by
the setting of the Route.Timed flag in the route table entry.
Afterwards, the route MAY be expunged; otherwise the route must be
must be marked as Expired.
MAX_SEQNUM_LIFETIME is the time after a reboot during which an AODVv2
router MUST NOT transmit any routing messages. Thus, if all other
AODVv2 routers expunge routes to the rebooted router after that time
interval, the rebooted AODVv2 router's sequence number will not be
considered stale by any other AODVv2 router in the MANET.
6.2. Bidirectional Connectivity and Blacklists
To avoid repeated failure of Route Discovery, an AODVv2 router
(HandlingRtr) handling a RREP message MUST attempt to verify
connectivity towards RREQ_Gen. This MAY be done by including the
Acknowledgement Request (AckReq) data element in the RREP. In reply
to an AckReq, an RREP_ACK message message MUST be sent. If the
verification is not received within UNICAST_MESSAGE_SENT_TIMEOUT,
HandlingRtr MUST put the upstream neighbor in the blacklist. RREQs
received from a blacklisted router, or any router over a link that is
known to be incoming-only, MUST NOT be regenerated by HandlingRtr.
However, the upstream neighbor SHOULD NOT be permanently blacklisted;
after a certain time (MAX_BLACKLIST_TIME), it SHOULD once again be
considered as a viable upstream neighbor for route discovery
operations.
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For this purpose, a list of blacklisted routers along with their time
of removal SHOULD be maintained:
Blacklist.Router
The IP address of the router that did not verify bidirectional
connectivity.
Blacklist.RemoveTime
The time at which Blacklist.Router MAY be removed from the
blacklist.
6.3. Router Clients and Client Networks
An AODVv2 router may offer routing services to other nodes that are
not AODVv2 routers; such nodes are defined as Router Clients in this
document.
For this purpose, CLIENT_ADDRESSES must be configured on each AODVv2
router with the following information:
Client IP address
The IP address of the node that requires routing service from the
AODVv2 router.
Client Prefix Length
The length of the routing prefix associated with the client IP
address.
If the Client Prefix Length is not the full length of the Client IP
address, then the prefix defines a Client Network. If an AODVv2
router is configured to serve a Client Network, then the AODVv2
router MUST serve every node that has an address within the range
defined by the routing prefix of the Client Network. The list of
Routing Clients for an AODVv2 router is never empty, since an AODVv2
router is always its own client as well.
6.4. Sequence Numbers
Sequence Numbers allow AODVv2 routers to evaluate the freshness of
routing information. Each AODVv2 router in the network MUST maintain
its own sequence number. Each RREQ and RREP generated by an AODVv2
router includes that sequence number. Each AODVv2 router MUST make
sure that its sequence number is unique and monotonically increasing.
This can be achieved by incrementing it with every RREQ or RREP it
generates.
Every router receiving a RREQ or RREP can thus use the Sequence
Number of a RREQ or RREP as information concerning the freshness of
the packet's route update: if the new packet's Sequence Number is
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lower than the one already stored in the route table, its information
is considered stale.
As a consequence, loop freedom is assured.
An AODVv2 router increments its SeqNum as follows. Most of the time,
SeqNum is incremented by simply adding one (1). But when the SeqNum
has the value of the largest possible number representable as a
16-bit unsigned integer (i.e., 65,535), it MUST be incremented by
setting to one (1). In other words, the sequence number after 65,535
is 1.
An AODVv2 router SHOULD maintain its SeqNum in persistent storage.
If an AODVv2 router's SeqNum is lost, it MUST take the following
actions to avoid the danger of routing loops. First, the AODVv2
router MUST set Route.State = Broken for each entry. Furthermore the
AODVv2 router MUST wait for at least MAX_SEQNUM_LIFETIME before
transmitting or regenerating any AODVv2 RREQ or RREP messages. If an
AODVv2 protocol message is received during this waiting period, the
AODVv2 router SHOULD perform normal route table entry updates, but
not forward the message to other nodes. If a data packet is received
for forwarding to another destination during this waiting period, the
AODVv2 router MUST transmit a RERR message indicating that no route
is available. At the end of the waiting period the AODVv2 router
sets its SeqNum to one (1) and begins performing AODVv2 protocol
operations again.
6.5. Metrics
Metrics describe the quality of a route or a link. They can take
various aspects into account, such as latency, delay, financial,
energy, etc. Whenever an AODV router receives metric information in
an incoming message, the value of the metric is as measured by the
transmitting router, and does not reflect the cost of traversing the
incoming link.
Each routing table entry is associated with metric information. When
presented with information which may update a route, deciding whether
to use the information involves evaluating the metric. For some
metrics, a maximum value is defined, namely MAX_METRIC[i] where 'i'
is the Metric Type. AODVv2 does not store routes in its route table
that cost more than MAX_METRIC[i].
Each metric has to have a Metric Type, and the Metric Type is
allocated by IANA as specified in [RFC6551]. Apart from its default
metric type, which is detailed in Section 6.5.3, AODVv2 enables the
use of generic metrics, whose data type depends on the metric used.
The Metric Type is specified by the MetricType TLV of each RteMsg.
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As a natural result of the way routes are looked up according to
conformant metric type, all intermediate routers handling a RteMsg
will assign the same metric type to all metric information in the
RteMsg.
6.5.1. The Cost() function
In order to simplify the description of storing accumulated route
costs in the route table, a Cost() function is defined. This
function returns the Cost of traversing a Route ('Cost(R)') or a Link
('Cost(L)'). The specification of Cost(L) for metric types other
than DEFAULT_METRIC_TYPE is beyond the scope of this document.
6.5.2. The LoopFree() function
Since determining loop freedom is known to depend on comparing the
Cost(R) of route update information to the Cost(R) of an existing
stored route using the same metric, AODVv2 must also be able to
invoke an abstract routine which in this document is called
"LoopFree(R1, R2)". LoopFree(R1, R2) returns TRUE when, (under the
assumption of nondecreasing SeqNum during Route Discovery) given that
R2 is loop-free and Cost(R2) is the cost of route R2, Cost(R1) is
known to guarantee loop freedom of the route R1. In this document,
an AODVv2 router will only invoke LoopFree (AdvRte, Route), for
routes AdvRte and Route which use the same metric to the same
destination. AdvRte is the route advertised in an incoming RREQ or
RREP, and is used as parameter R1 for LoopFree. Route is a route
already existing in the AODVv2 router's route table, and is used as
parameter R2 for LoopFree.
6.5.3. Default Metric type
HopCount is still the default metric for use in MANETs,
notwithstanding the above objections. Therefore, the default Metric
Type DEFAULT_METRIC_TYPE is Hop Count. It is also the only metric
described in detail by this protocol. With this metric, Cost(L) is
always 1, and Cost(R) is simply the hop count between the router and
the destination.
MAX_METRIC[DEFAULT_METRIC_TYPE] is defined to be MAX_HOPCOUNT.
MAX_HOPCOUNT MUST be larger than the AODVv2 network diameter.
Otherwise, AODVv2 protocol messages may not reach their intended
destinations.
Using Metric Type DEFAULT_METRIC_TYPE, LoopFree (AdvRte, Route) is
TRUE when Cost(AdvRte) <= Cost(Route). The specification of Cost(R)
and LoopFree(AdvRte, Route) for metric types other than
DEFAULT_METRIC_TYPE is beyond the scope of this document.
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6.5.4. Alternate Metrics
Some applications may require metric information other than Hop
Count, which has traditionally been the default metric associated
with routes in MANET. It is well known that reliance on Hop Count
can cause selection of the worst possible route in many situations.
For this reason, it is important to enable route selection based on
metric information other than Hop Count -- in other words, based on
"alternate metrics".
The range and data type of each such alternate metric may be
different. For instance, the data type might be integers, or
floating point numbers, or restricted subsets thereof. It is out of
the scope of this document to specify for alternate metrics the
Cost(L) and Cost(R) functions, or their return type.
6.6. RREQ Table: Received RREQ Messages
Two incoming RREQ messages are considered to be "comparable" if they
were generated by the same AODVv2 router in order to discover a route
for the same destination with the same metric type. According to
that notion of comparability, when RREQ messages are flooded in a
MANET, an AODVv2 router may well receive comparable RREQ messages
from more than one of its neighbors. A router, after receiving an
RREQ message, MUST check against previous RREQs to assure that its
response message would contain information that is not redundant (see
Section 8.6 regarding suppression of redundant RREQ messages).
Otherwise, multicast RREQs are likely to be regenerated again and
again with almost no additional benefit, but generating a great deal
of unnecessary signaling traffic and interference.
To avoid transmission of redundant RREQ messages, while still
enabling the proper handling of earlier RREQ messages that may have
somehow been delayed in the network, it is needed for each AODVv2
router to keep a list of the certain information about RREQ messages
which it has recently received.
This list is called the AODVv2 Received RREQ Table -- or, more
briefly, the RREQ Table. Two AODVv2 RREQ messages are comparable if:
o they have the same metric type
o they have the same OrigAddr and TargAddr
Each entry in the RREQ Table has the following fields:
o OrigAddr
o TargAddr
o OrigNode Sequence Number
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o TargNode Sequence Number (if present in RREQ)
o Metric Type
o Metric
o Timestamp
The RREQ Table is maintained so that no two entries in the RREQ
Table are comparable -- that is, all RREQs represented in the RREQ
Table either have a different OrigAddr, different TargAddr, or
different metric types. If two RREQs have the same metric type,
OrigAddr, and TargAddr, the information from the one with the older
Sequence Number is not needed in the table; in case they have the
same Sequence Number, the one with the greater Metric value is not
needed; in case they have the same Metric as well, it does not matter
which table entry is maintained. Whenever a RREQ Table entry is
updated, its Timestamp field should also be updated to reflect the
Current_Time.
When optional multicast RREP (see Section 14.4) is used to enable
selection from among multiple possible return routes, an AODVv2
router can eliminate redundant RREP messages using the analogous
mechanism along with a RREP Table. The description in this section
only refers to RREQ multicast messages.
Protocol handling of RERR messages eliminates the need for tracking
RERR messages, since the rules for RERR regeneration prevent the
phenomenon of redundant retansmission that affects RREQ and RREP
multicast.
7. AODVv2 Operations on Route Table Entries
In this section, operations are specified for updating the route
table due to timeouts and route updates within AODVv2 messages.
Route update information in AODVv2 messages includes IP addresses,
along with the SeqNum and prefix length associated with each IP
address, and including the Metric measured from the node transmitting
the AODVv2 message to the IP address in the route update. A RREQ
message advertises a route to OrigAddr, and a RREP message
analogously advertises a route to TargAddr. In this section, RteMsg
is either RREQ or RREP, and AdvRte is the route advertised by the
RteMsg. All SeqNum comparisons use signed 16-bit arithmetic.
7.1. Evaluating Incoming Routing Information
If the incoming RteMsg does not have a Metric Type data element, then
the metric information contained by AdvRte is considered to be of
type DEFAULT_METRIC_TYPE -- in other words, 3 (for HopCount) unless
changed by administrative action. The AODVv2 router (HandlingRtr)
checks the advertised route (AdvRte) to see whether the AdvRte should
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be used to update an existing route table entry. HandlingRtr
searches its route table to see if there is a route table entry with
the same Metric Type as the AdvRte, matching AdvRte.Address. If not,
HandlingRtr creates a route table entry for AdvRte.Address as
described in Section 7.2. Otherwise, HandlingRtr compares the
incoming routing information for AdvRte against the already stored
routing information in the route table entry (Route) for
AdvRte.Address, as described next.
Route[AdvRte.Address] uses the same metric type as the incoming
routing information, and the route entry contains Route.SeqNum,
Route.Metric, and Route.State. Define AdvRte.SeqNum and
AdvRte.Metric to be the corresponding routing information for
Route.Address in the incoming RteMsg. Define AdvRte.Cost to be
(AdvRte.Metric + Cost(L)), where L is the link from which the
incoming message was received. The incoming routing information is
classified as follows:
1. Stale:: AdvRte.SeqNum < Route.SeqNum :
If AdvRte.SeqNum < Route.SeqNum the incoming information is stale.
Using stale routing information is not allowed, since that might
result in routing loops. In this case, HandlingRtr MUST NOT
update the route table entry using the routing information for
AdvRte.Address.
2. Unsafe against loops:: (TRUE != LoopFree (AdvRte, Route)) :
If AdvRte is not Stale (as in (1) above), AdvRte.Cost is next
considered to insure loop freedom. If (TRUE != LoopFree (AdvRte,
Route)) (see Section 6.5), then the incoming AdvRte information is
not guaranteed to prevent routing loops, and it MUST NOT be used
to update any route table entry.
3. More costly::
(AdvRte.Cost >= Route.Metric) && (Route.State != Broken)
When AdvRte.SeqNum is the same as in a valid route table entry,
and LoopFree (AdvRte, Route) assures loop freedom, incoming
information still does not offer any improvement over the existing
route table information if AdvRte.Cost >= Route.Metric. Using
such incoming routing information to update a route table entry is
not recommended.
4. Offers improvement::
Advertised routing information that does not match any of the
above criteria is better than existing route table information and
SHOULD be used to improve the route table. The following pseudo-
code illustrates whether advertised routing information should be
used to update an existing route table entry as described in
Section 7.2.
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(AdvRte.SeqNum > Route.SeqNum) OR
((AdvRte.SeqNum == Route.SeqNum) AND
[(AdvRte.Cost < Route.Metric) OR
((Route.State == Broken) && LoopFree (AdvRte, Route))])
The above logic corresponds to placing the following conditions
(compared to the existing route table entry) on the advertised
route update before it can be used:
* it is more recent, or
* it is not stale and is less costly, or
* it can safely repair a broken route.
7.2. Applying Route Updates To Route Table Entries
To apply the route update, a route table entry for AdvRte.Address is
either found to already exist in the route table, or else a new route
table entry for AdvRte.Address is created and inserted into the route
table. If the route table entry already exists, and the state is
Expired or Broken, then the state is reset to be Idle. If the route
table entry had to be created, the state is set to be Active. The
route table entry is populated with the following information:
o If AdvRte.PrefixLength exists, then Route.PrefixLength :=
AdvRte.PrefixLength. Otherwise, Route.PrefixLength := maximum
length for address family (either 32 or 128).
o Route.SeqNum := AdvRte.SeqNum
o Route.NextHopAddress := IP.SourceAddress (i.e., an address of the
node from which the RteMsg was received)
o Route.NextHopInterface is set to the interface on which RteMsg was
received
o Route.MetricType := AdvRte.MetricType
o Route.Metric := AdvRte.Cost
o Route.LastUsed := Current_Time
o If RteMsg.VALIDITY_TIME is included, then
Route.Timed := TRUE and Route.ExpirationTime := Current_Time +
RteMsg.VALIDITY_TIME. Otherwise, Route.ExpirationTime :=
Current_Time + (ACTIVE_INTERVAL + MAX_IDLETIME).
With these assignments to the route table entry, a route has been
made available, and the route can be used to send any buffered data
packets and subsequently to forward any incoming data packets for
Route.Address. An updated route entry also fulfills any outstanding
route discovery (RREQ) attempts for Route.Address.
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7.3. Route Table Entry Timeouts
During normal operation, AODVv2 does not require any explicit
timeouts to manage the lifetime of a route. However, the route table
entry MUST be examined before using it to forward a packet, as
discussed in Section 9.1. Any required expiry or deletion can occur
at that time. Alternatively, timers and timeouts MAY be implemented
to achieve the same effect.
At any time, the route table can be examined and route table entries
can be expunged according to their current state at the time of
examination, as follows.
o An Active route MUST NOT be expunged.
o An Idle route SHOULD NOT be expunged.
o An Expired route MAY be expunged (least recently used first).
o A route MUST be expunged if (Current_Time - Route.LastUsed) >=
MAX_SEQNUM_LIFETIME.
o A route MUST be expunged if Current_Time >= Route.ExpirationTime
If precursor lists are maintained for the route (as described in
Section 14.3) then the precursor lists must also be expunged at the
same time that the route itself is expunged.
8. Routing Messages RREQ and RREP (RteMsgs)
AODVv2 message types RREQ and RREP are together known as Routing
Messages (RteMsgs) and are used to discover a route between an
Originating and Target Addr, denoted by OrigAddr and TargAddr. The
constructed route is bidirectional, enabling packets to flow between
OrigAddr and TargAddr. RREQ and RREP have similar information and
function, but have some differences in their rules for handling.
When a node receives a RREQ or a RREP, the node then creates or
updates a route to the OrigAddr or the TargAddr respectively. The
main difference between the two messages is that RREQ messages are
typically multicast to solicit a RREP, whereas RREP is typically
unicast as a response to RREQ.
When an AODVv2 router needs to forward a data packet from a node
(with IP address OrigAddr) in its set of router clients, and it does
not have a forwarding route toward the packet's IP destination
address (TargAddr), the AODVv2 router (RREQ_Gen) generates a RREQ (as
described in Section 8.3) to discover a route toward TargAddr.
Subsequently RREQ_Gen awaits reception of an RREP message (see
Section 8.4) or other route table update (see Section 7.2) to
establish a route toward TargAddr. The RREQ message contains routing
information to enable RREQ recipients to route packets back to
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OrigAddr, and the RREP message contains routing information enabling
RREP recipients to route packets to TargAddr.
8.1. Route Discovery Retries and Buffering
After issuing a RREQ, as described above RREQ_Gen awaits a RREP
providing a bidirectional route toward the Target Address. If the
RREP is not received within RREQ_WAIT_TIME, RREQ_Gen MAY retry the
Route Discovery by generating another RREQ. Route Discovery SHOULD
be considered to have failed after DISCOVERY_ATTEMPTS_MAX and the
corresponding wait time for a RREP response to the final RREQ. After
the attempted Route Discovery has failed, RREQ_Gen MUST wait at least
RREQ_HOLDDOWN_TIME before attempting another Route Discovery to the
same destination.
To reduce congestion in a network, repeated attempts at route
discovery for a particular Target Address SHOULD utilize a binary
exponential backoff.
Data packets awaiting a route SHOULD be buffered by RREQ_Gen. This
buffer SHOULD have a fixed limited size (BUFFER_SIZE_PACKETS or
BUFFER_SIZE_BYTES). Determining which packets to discard first is a
matter of policy at each AODVv2 router; in the absence of policy
constraints, by default older data packets SHOULD be discarded first.
Buffering of data packets can have both positive and negative effects
(albeit usually positive). Nodes without sufficient memory available
for buffering SHOULD be configured to disable buffering by
configuring BUFFER_SIZE_PACKETS == 0 and BUFFER_SIZE_BYTES == 0.
Doing so will affect the latency required for launching TCP
applications to new destinations.
If a route discovery attempt has failed (i.e., DISCOVERY_ATTEMPTS_MAX
attempts have been made without receiving a RREP) to find a route
toward the Target Address, any data packets buffered for the
corresponding Target Address MUST BE dropped and a Destination
Unreachable ICMP message (Type 3) SHOULD be delivered to the source
of the data packet. The code for the ICMP message is 1 (Host
unreachable error). If RREQ_Gen is not the source (OrigNode), then
the ICMP is sent to OrigAddr.
8.2. RteMsg Structure
RteMsgs have the following general format:
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+---------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+---------------------------------------------------------------+
| AckReq, MetricType |
+---------------------------------------------------------------+
| AddressList := {OrigAddr,TargAddr} |
+---------------------------------------------------------------+
| Address Prefix Length for OrigAddr OR TargAddr |
+---------------------------------------------------------------+
| SeqNumList (OrigSeqNum AND/OR TargSeqNum) |
+---------------------------------------------------------------+
| MetricList (Metric for OrigAddr OR TargAddr) |
+---------------------------------------------------------------+
Figure 1: RREQ and RREP (RteMsg) message structure
RteMsg Data Elements
msg_hop_limit
The remaining number of hops allowed for dissemination of the
RteMsg message.
msg_hop_count
The number of hops already traversed during dissemination of
the RteMsg message.
AckReq
(RREP Only) Acknowledgement Requested by sender (optional).
MetricType
If MetricType != DEFAULT_METRIC_TYPE, the MetricType associated
with route to OrigAddr or TargAddr.
AddressList
AddressList contains OrigAddr and TargAddr.
OrigSeqNum AND/OR TargSeqNum
At least one of OrigSeqNum or TargSeqNum is REQUIRED and
carries the destination sequence number(s) associated with
OrigNode or TargNode respectively.
MetricList
The MetricList data element is REQUIRED, and carries the route
metric information associated with either OrigAddr or TargAddr
(but not both).
RteMsgs carry information about OrigAddr and TargAddr, as identified
in the context of the RREQ_Gen. Either the OrigSeqNum or TargSeqNum
MUST appear. Both MAY appear in the same RteMsg when SeqNum is
available for both OrigAddr and TargAddr.
If the OrigSeqNum data element appears, then it MUST apply only to
OrigAddr. The other address in the Address List is TargAddr.
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If the TargSeqNum data element appears, then it MUST apply only to
TargAddr. The other address in the AddressList is OrigAddr.
8.3. RREQ Generation
RREQ_Gen (the AODVv2 router generating the RREQ and associated data
elements on behalf of its client OrigNode) follows the steps in this
section. OrigAddr MUST be a unicast address. The order of data
elements is illustrated schematically in Figure 1. RREQ_Gen SHOULD
include TargSeqNum, if a previous value of the TargNode's SeqNum is
known (e.g., from an invalid route table entry using longest-prefix
matching). If TargSeqNum is not included, AODVv2 routers handling
the RREQ assume that RREQ_Gen does not have that information.
1. RREQ_Gen MUST increment the SeqNum for OrigAddr by one (1)
according to the rules specified in Section 6.4. This assures
that each node receiving the RREQ will update its route table
using the information in the RREQ.
2. msg_hop_limit SHOULD be set to MAX_HOPCOUNT.
3. msg_hop_count, if included, MUST be set to 0.
* This RFC 5444 constraint causes certain RREQ payloads to incur
additional enlargement (otherwise, msg_hop_count could often
be used as the metric).
4. AddressList := {OrigAddr, TargAddr}
5. If Route[OrigAddr].PrefixLength is equal to the number of bits in
the addresses of the RREQ (32 for IPv4, 128 for IPv6), then no
PrefixLengthList is included. Otherwise, PrefixLengthList :=
{Route[OrigAddr].PrefixLength, null}.
6. OrigSeqNum := OrigAddr's SeqNum number
7. If known, TargSeqNum := Route[TargAddr].SeqNum
8. RREQ.MetricList := {Route[OrigAddr].Metric, null}
By default, the RREQ message is multicast to LL-MANET-Routers. An
example RREQ message format is illustrated in Appendix B.1.
8.4. RREP Generation
This section specifies the generation of an RREP by an AODVv2 router
(RREP_Gen) that provides connectivity for TargAddr, thus enabling the
establishment of a route between OrigAddr and TargAddr. If TargAddr
is not a unicast IP address, the RREP MUST NOT be generated, and
processing for the RREQ is complete. Before transmitting a RREP, the
routing information of the RREQ is processed as specified in
Section 7.2; after such processing, RREP_Gen has an updated route to
OrigAddr as well as TargAddr. The basic format of an RREP conforms
to the structure for RteMsgs as shown in Figure 1.
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RREP_Gen creates data elements and generates the RREP as follows:
1. RREP_Gen checks the RREQ against recently received RREQ messages
as specified in Section 8.6. If a previously received RREQ has
made the information in the incoming RREQ to be redundant, no
RREP is generated and processing is complete.
2. RREP_Gen MUST increment TargAddr's SeqNum by one (1) according to
the rules specified in Section 6.4.
3. msg_hop_count, if included, MUST be set to 0.
4. msg_hop_limit SHOULD be set to RREQ.msg_hop_count.
5. If (DEFAULT_METRIC_TYPE != Route[TargAddr].MetricType) then
include the MetricType data element and set MetricType :=
Route[TargAddr].MetricType
6. AddressList := {OrigAddr, TargAddr}
7. TargSeqNum := Route[TargAddr].SeqNum
8. If Route[TargAddr].PrefixLength is equal to the number of bits in
the addresses of the RREQ (32 for IPv4, 128 for IPv6), then no
PrefixLengthList is included in the RREP. Otherwise,
PrefixLengthList := {null, Route[TargAddr].PrefixLength}
9. MetricList := {null, Route[TargAddr].Metric}}
By default, the RREP message is unicast to OrigAddr. An example
message format for RREP is illustrated in Appendix B.2.
8.5. Handling a Received RteMsg
Before an AODVv2 router can make use of a received RteMsg (i.e., RREQ
or RREP), the router must verify that the RteMsg is valid according
to the following steps. First the router extracts the data elements
from the message (see Section 10). RteMsg_Metric is the single
Metric. In this section (unless qualified by additional description)
all occurrences of the term "router" refer to the AODVv2 router
handling the received RteMsg.
1. A router MUST handle RteMsgs only from neighbors as specified in
Section 5. RteMsgs from other sources MUST be disregarded.
2. The router verifies that the RteMsg contains the required data
elements: msg_hop_limit, OrigAddr, TargAddr, RteMsg_Metric, and
either OrigSeqNum or TargSeqNum. If the required data elements
are absent, the message is disregarded.
3. The router checks that OrigAddr and TargAddr are routable unicast
addresses. If not, the message is disregarded.
4. If the MetricType is absent, the router uses DEFAULT_METRIC_TYPE
for the metric type. Otherwise the router verifies that the
MetricType is known; if not, the message is disregarded.
* DISCUSSION: or, can change Metric data element to use
HopCount, e.g., measured from msg_hop_count.
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5. If (MAX_METRIC[MetricType] - Cost(L)) <= RteMsg_Metric, where L
denotes the incoming link, the RteMsg is disregarded.
An AODVv2 router handles a valid RteMsg as follows:
1. The router MUST process the advertised route for OrigAddr or
TargAddr contained in the RteMsg as specified in Section 7.1.
2. If msg_hop_limit is zero (0), no further action is taken, and the
RteMsg is not regenerated. Otherwise, the router MUST decrement
msg_hop_limit.
3. If the RteMsg.msg_hop_count is present, and MAX_HOPCOUNT <=
msg_hop_count, then no further action is taken. Otherwise, the
router MUST increment msg_hop_count.
Further actions to regenerate an updated RteMsg depend upon whether
the incoming RteMsg is an RREP or an RREQ.
8.5.1. Additional Handling for Incoming RREQ
o By sending a RREQ, a router advertises that it will forward
packets to the OrigAddr contained in the RteMsg according to the
information enclosed. The router MAY choose not to regenerate the
RREQ, though not regenerating the RREQ could decrease connectivity
in the network or result in nonoptimal paths. The circumstances
under which a router might choose not to re-transmit a RREQ are
not specified in this document. Some examples might include the
following:
* The router is already heavily loaded and does not want to
advertise routing for more traffic
* The router recently transmitted the same routing information
(e.g. in a RREQ advertising the same metric) Section 8.6
* The router is low on energy and has to reduce energy expended
for sending protocol messages or packet forwarding
Unless the router is prepared to advertise the new route, it halts
processing.
o If the upstream router sending a RREQ is in the Blacklist, and
Current_Time < Blacklist.RemoveTime, then the router receiving
that RREQ MUST NOT transmit any outgoing RteMsg, and processing is
complete.
o Otherwise, if the upstream router is in the Blacklist, and
Current_Time >= Blacklist.RemoveTime, then the upstream router
SHOULD be removed from the Blacklist, and message processing
continued.
o The incoming RREQ MUST be checked against previously received
information from the RREQ Table (Section 8.6). If the information
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in the incoming RteMsg is redundant, then then no further action
is taken.
o If TargNode is a client of the router receiving the RREQ, then the
router generates a RREP message as specified in Section 8.4, and
subsequently processing for the RREQ is complete. Otherwise,
processing continues as follows.
o If (DEFAULT_METRIC_TYPE != Route[OrigAddr].MetricType) then
include the MetricType data element and assign MetricType :=
Route[OrigAddr].MetricType
o Metric := Route[OrigAddr].Metric
o The RREQ (with updated fields as specified above>) SHOULD be
multicast the IP address LL-MANET-Routers [RFC5498]. If the RREQ
is unicast, the IP.DestinationAddress is set to
Route[RREQ.TargAddr].NextHopAddress.
8.5.2. Additional Handling for Incoming RREP
The OrigAddr and TargAddr data elements are extracted from the
AddressList of the incoming RREP, for instance according to the
format of message elements as shown in Section 10.
o If no forwarding route exists to OrigAddr, then a RERR SHOULD be
transmitted to TargAddr. Otherwise, if HandlingRtr is not
RREQ_Gen then the outgoing RREP is sent to the
Route.NextHopAddress for OrigAddr.
o If HandlingRtr is RREQ_Gen then the RREP satisfies RREQ_Gen's
earlier RREQ, and RREP processing is completed. Any packets
buffered for OrigAddr should be transmitted.
8.6. Suppressing Redundant RREQ messages
Since RREQ messages are multicast, there are common circumstances
under which an AODVv2 router might transmit a redundant response
(RREQ or RREP), duplicating the information transmitted in response
to some other recent RREQ (see Section 6.6). Before responding, an
AODVv2 router MUST suppress such RREQ messages. This is done by
checking the list of recently received RREQs to determine whether the
incoming RREQ is redundant, as follows:
o The AODVv2 router searches the RREQ Table for recent entries with
the same OrigAddr, TargAddr, and MetricType. If not, the incoming
RREQ message is not suppressed, and a new entry for the incoming
RREQ is created in the RREQ Table.
o If there is such an entry, and the incoming RREQ has a newer
sequence number, the incoming RREQ is not suppressed, and the
existing table entry MUST be updated to reflect the new Sequence
Number and Metric.
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o Similarly, if the Sequence Numbers are the same, and the incoming
RREQ offers a better Metric, the incoming RREQ is not suppressed,
and the RREQ Table entry MUST be updated to reflect the new
Metric.
o Otherwise, the incoming RREQ is suppressed.
9. Route Maintenance and RERR Messages
AODVv2 routers attempt to maintain active routes. When a routing
problem is encountered, an AODVv2 router (denoted RERR_Gen) sends the
RERR to quickly notify upstream routers. Two kinds of routing
problems can trigger generation of a RERR message. The first case
happens when the router receives a packet but does not have a route
for the destination of the packet. The second case happens
immediately upon detection of a broken link (see Section 9.2) for an
Active route.
9.1. Maintaining Route Lifetimes During Packet Forwarding
Before using a route to forward a packet, an AODVv2 router MUST check
the status of the route as follows.
o If the route is marked has been marked as Broken, it cannot be
used for forwarding.
o If Current_Time > Route.ExpirationTime, the route table entry has
expired, and cannot be used for forwarding.
o Similarly, if (Route.ExpirationTime == MAXTIME), and if
(Current_Time - Route.LastUsed) > (ACTIVE_INTERVAL +
MAX_IDLETIME), the route has expired, and cannot be used for
forwarding.
o Furthermore, if Current_Time - Route.LastUsed >
MAX_SEQNUM_LIFETIME, the route table entry MUST be expunged.
If any of the above route error conditions hold true, the route
cannot be used to forward the packet, and an RERR message MUST be
generated (see Section 9.3).
Otherwise, Route.LastUsed := Current_Time, and the packet is
forwarded to the route's next hop.
Optionally, if a precursor list is maintained for the route, see
Section 14.3 for precursor lifetime operations.
9.2. Next-hop Router Adjacency Monitoring
Neighboring routers MAY form an adjacency based on AODVv2 messages,
other protocols (e.g. NDP [RFC4861] or NHDP [RFC6130]), or manual
configuration. Loss of a routing adjacency may also be indicated by
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similar information. AODVv2 routers SHOULD monitor connectivity to
adjacent routers along active routes. This monitoring can be
accomplished by one or several mechanisms, including:
o Neighborhood discovery [RFC6130]
o Route timeout
o Lower layer trigger that a link is broken
o TCP timeouts
o Promiscuous listening
o Other monitoring mechanisms or heuristics
If a next-hop AODVv2 router has become unreachable, RERR_Gen follows
the procedures in Section 9.3.2.
9.3. RERR Generation
An RERR message is generated by a AODVv2 router (i.e., RERR_Gen) in
order to notify upstream routers that packets cannot be delivered to
one or more destinations. An RERR message has the following general
structure:
+---------------------------------------------------------------+
| msg_hop_limit, msg_hop_count |
+---------------------------------------------------------------+
| PktSource, MetricType |
+---------------------------------------------------------------+
| Unreachable Address List |
+---------------------------------------------------------------+
| Unreachable Address PrefixLength List |
+---------------------------------------------------------------+
| Unreachable Address Sequence Number List |
+---------------------------------------------------------------+
Figure 2: RERR message structure
RERR Data Elements
msg_hop_limit
The remaining number of hops allowed for dissemination of the
RERR message.
msg_hop_count
The number of hops already traversed during dissemination of
the RERR message.
PktSource
The IP address of the unreachable destination triggering RERR
generation.
MetricType
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If MetricType != DEFAULT_METRIC_TYPE, the MetricType associated
with routes affected by a broken link.
AddressList
A list of IP addresses not reachable by the AODVv2 router
transmitting the RERR.
PrefixLengthList
The list of prefix lengths associated with the addresses in the
Unreachable Address List.
SeqNumList
The list of destination sequence numbers associated with the
Unreachable Address List.
There are two kinds of events indicating that packets cannot be
delivered to certain destinations. The two cases differ in the way
that the neighboring IP destination address for the RERR is chosen,
and in the way that the set of UnreachableAddrs is identified.
In both cases, the msg_hop_limit MUST be included and SHOULD be set
to MAX_HOPCOUNT. msg_hop_count SHOULD be included and set to 0, to
facilitate use of various route repair strategies including expanding
rings multicast and Intermediate RREP [I-D.perkins-irrep].
9.3.1. Case 1: Undeliverable Packet
The first case happens when the router receives a packet from another
AODVv2 router but does not have a valid route for the destination of
the packet. In this case, there is exactly one UnreachableAddr to be
included in the RERR's AddressList (either the Destination Address of
the IP header from a data packet, or the OrigAddr found in the
AddressList of an RREP message). The RERR SHOULD be sent to the
multicast address LL-MANET-Routers, but RERR_Gen MAY instead send the
RERR to the next hop towards the source IP address of the packet
which was undeliverable. For unicast RERR, the PktSource data
element MUST be included, containing the the source IP address of the
undeliverable packet, or TargAddr in case the undeliverable packet
was an RREP message for a route to TargAddr. If a Sequence Number
for UnreachableAddr is known, that Sequence Number SHOULD be included
in a Seqnum data element the RERR. Otherwise all nodes handling the
RERR will assume their route through RERR_Gen towards the
UnreachableAddr is no longer valid and mark those routes as broken,
regardless of the Sequence Number information for those routes.
RERR_Gen MUST discard the packet or message that triggered generation
of the RERR.
If an AODVv2 router receives an ICMP packet from the address of one
of its client nodes, it simply relays the packet to the ICMP packet's
destination address, and does not generate any RERR message.
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9.3.2. Case 2: Broken Link
The second case happens when the link breaks to an active adjacent
AODVv2 router (i.e., the next hop of an active route). In this case,
the RERR MUST be sent to the multicast address LL-MANET-Routers,
except when the optional feature of maintaining precursor lists is
used as specified in Section 14.3. All routes (Active, Idle and
Expired) that use the broken link MUST be marked as Broken. The
AddressList (which will contain the Unreachable Addresses) is
initialized by first identifying those Active routes which use the
broken link. For each such Active Route, Route.Dest is added to the
AddressList. After the Active Routes using the broken link have all
been indicated in the AddressList, Idle routes MAY also be included,
if allowed by the setting of ENABLE_IDLE_IN_RERR, as long as the
packet size of the RERR does not exceed the MTU (interface "Maximum
Transfer Unit") of the physical medium.
If there are no Unreachable Addresses in the AddressList, no RERR is
generated. Otherwise, RERR_Gen generates a new RERR using the
AddressList. If any Unreachable Address is associated with a routing
prefix (i.e., a prefix length shorter than the maximum length for the
address family), then the AddressList MUST be accompanied by a
PrefixLengthList; otherwise, if no such entry, the PrefixLengthList
SHOULD NOT be included. The value (from the route table) for each
Unreachable Address's SeqNum MUST be placed in the SeqNum data
element.
Every broken route reported in the RERR MUST have the same
MetricType. If the MetricType is not DEFAULT_METRIC_TYPE, then the
RERR message MUST contain a MetricType data element indicating the
MetricType of the broken route(s).
9.4. Receiving and Handling RERR Messages
When an AODVv2 router (HandlingRtr) receives a RERR message, it uses
the information provided to mark affected routes as broken. If
HandlingRtr has neighbors that are using the affected routes, then
HandlingRtr subsequently sends an RERR message to those neighbors.
This regeneration of the RERR message is counted as another "hop" for
purposes of properly modifying msg_hop_limit and msg_hop_count in the
RERR message header.
HandlingRtr examines the incoming RERR to assure that it contains
msg_hop_limit and at least one Unreachable Address; otherwise, the
incoming RERR message is disregarded and further processing stopped.
For each UnreachableAddr, HandlingRtr searches its route table for a
route using longest prefix matching. If no such Route is found,
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processing is complete for that UnreachableAddr. Otherwise,
HandlingRtr verifies the following:
1. The UnreachableAddr is a routable unicast address.
2. Route.NextHopAddress is the same as the SourceAddress in the IP
header of the RERR packet.
3. Route.NextHopInterface is the same as the interface on which the
RERR was received.
4. The UnreachableAddr.SeqNum is unknown, OR Route.SeqNum <=
UnreachableAddr.SeqNum (using signed 16-bit arithmetic).
If the Route satisfies all of the above conditions, HandlingRtr
checks whether Route.PrefixLength is the same as the prefix length
for UnreachableAddr. If so, HandlingRtr simply sets the state for
that Route to be Broken. Otherwise, HandlingRtr creates a new route
(call it BrokenRoute) with the same PrefixLength as the prefix length
for UnreachableAddr, and sets Route.State == Broken for BrokenRoute.
If the prefix length for the new route is shorter than
Route.PrefixLength, then Route MUST be expunged from the route table
(since it is a subroute of the larger route which is reported to be
broken). If msg_hop_limit is 0, then HandlingRtr takes no further
action on the RERR message.
If there are no UnreachableAddrs to be transmitted in an RERR to
upstream routers, HandlingRtr takes no further action on the RERR
message.
Otherwise, msg_hop_limit is decremented by one (1) and processing
continues as follows:
o The UnreachableAddrs data element is included in the RERR.
o msg_hop_limit is decremented by one (1).
o (Optional) If precursor lists are maintained, the outgoing RERR
SHOULD be sent to the active precursors of the broken route as
specified in Section 14.3.
o Otherwise, if the incoming RERR message was received at the LL-
MANET-Routers [RFC5498] multicast address, the outgoing RERR
SHOULD be sent to LL-MANET-Routers.
o Otherwise, if the PktSource data element is present, and
HandlingRtr has a Route to PktSource.Addr, then HandlingRtr MUST
send the outgoing RERR to Route[PktSource.Addr].NextHop.
o Otherwise, the outgoing RERR MUST be sent to LL-MANET-Routers.
10. Representing AODVv2 data elements using RFC 5444
AODVv2 specifies that all control plane messages between Routers
SHOULD use the Generalised Mobile Ad-hoc Network Packet and Message
Format [RFC5444], which provides a multiplexed transport for multiple
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protocols. AODVv2 therefore specifies Route Messages comprising data
elements that map to message elements in RFC5444 but, in line with
the concept of use, does not specify which order the messages should
be arranged in an RFC5444 packet. An implementation of an RFC5444
parser may choose to optimise the content of certain message elements
to reduce control plane overhead.
Here is a brief summary of the RFC 5444 format.
A packet formatted according to RFC 5444 contains zero or more
messages.
A message contains a message header, message TLV block, and zero
or more address blocks.
Each address block MAY also have an associated TLV block; this TLV
block MAY encode multiple TLVs. Each such TLV may include an
array of values. The list of TLV values may be associated with
various subsets of the addresses in the address block.
If a packet contains only a single AODVv2 message and no packet TLVs,
it need only include a minimal Packet-Header [RFC5444]. The length
of an address (32 bits for IPv4 and 128 bits for IPv6) inside an
AODVv2 message is indicated by the msg-addr-length (MAL) in the msg-
header, as specified in [RFC5444].
This section specifies a way to represent the data elements specified
by AODVv2 within RFC 5444 message format.
Type-Length-Value structure (TLV)
A generic way to represent information, conformant to use in
[RFC5444].
AODVv2 uses the following RFC5444 message elements:
o Message Hop Count, <msg-hop-count>, which should be mapped to the
<msg-hop-count> element in <msg-header>.
o Message Hop Limit, <msg-hop-limit>, which should be mapped to the
<msg-hop-limit> element in <msg-header>.
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+---------------------+---------------------------------------------+
| Data Element | RFC 5444 Message Representation |
+---------------------+---------------------------------------------+
| msg_hop_limit | RFC 5444 Message Header <msg-hop-count> |
| msg_hop_count | RFC 5444 Message Header <msg-hop-limit> |
| AckReq | Acknowledgement Requested Message TLV |
| MetricType | Metric Type Message TLV |
| AddressList | RFC 5444 Address TLV Block |
| PrefixLengthsList | Included in RFC 5444 Address TLV Block |
| MetricList | Metric Address Block TLV |
| SeqNumList | Sequence Number Address Block TLV |
| OrigSeqNum | Originating Node Sequence Number Address |
| | Block TLV |
| TargSeqNum | Target Node Sequence Number Address Block |
| | TLV |
| OrigAddr | Included in AddressList |
| TargAddr | Included in AddressList |
| UnreachableAddr | Included in AddressList |
| SeqNum | Included in SeqNumList |
| Metric | Included in MetricList |
+---------------------+---------------------------------------------+
Table 3
For handling of messages that contain unknown TLV types, ignore the
information for processing, but preserve it unmodified for
forwarding.
11. Simple Internet Attachment
Simple Internet attachment means attachment of a stub (i.e., non-
transit) network of AODVv2 routers to the Internet via a single
Internet AODVv2 router (called IAR).
As in any Internet-attached network, AODVv2 routers, and their
clients, wishing to be reachable from hosts on the Internet MUST have
IP addresses within the IAR's routable and topologically correct
prefix (e.g. 191.0.2.0/24).
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/-------------------------\
/ +----------------+ \
/ | AODVv2 Router | \
| | 191.0.2.2/32 | |
| +----------------+ | Routable
| +-----+--------+ Prefix
| | Internet | /191.0.2/24
| | AODVv2 Router| /
| | 191.0.2.1 |/ /---------------\
| | serving net +------+ Internet \
| | 191.0.2/24 | \ /
| +-----+--------+ \---------------/
| +----------------+ |
| | AODVv2 Router | |
| | 191.0.2.3/32 | |
\ +----------------+ /
\ /
\-------------------------/
Figure 3: Simple Internet Attachment Example
When an AODVv2 router within the AODVv2 MANET wants to discover a
route toward a node on the Internet, it uses the normal AODVv2 route
discovery for that IP Destination Address. The IAR MUST respond to
RREQ on behalf of all Internet destinations.
When a packet from a node on the Internet destined for a node in the
AODVv2 MANET reaches the IAR, if the IAR does not have a route toward
that destination it will perform normal AODVv2 route discovery for
that destination.
12. Multiple Interfaces
AODVv2 MAY be used with multiple interfaces; therefore, the
particular interface over which packets arrive MUST be known whenever
a packet is received. Whenever a new route is created, the interface
through which the route's destination can be reached is also recorded
in the route table entry.
When multiple interfaces are available, a node transmitting a
multicast packet to LL-MANET-Routers MUST send the packet on all
interfaces that have been configured for AODVv2 operation.
Similarly, AODVv2 routers MUST subscribe to LL-MANET-Routers on all
their AODVv2 interfaces.
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13. AODVv2 Control Message Generation Limits
To avoid congestion, each AODVv2 router's rate of packet/message
generation SHOULD be limited. The rate and algorithm for limiting
messages (CONTROL_TRAFFIC_LIMITS) is left to the implementor and
should be administratively configurable. AODVv2 messages SHOULD be
discarded in the following order of preference: RREQ, RREP, and
finally RERR.
14. Optional Features
Some optional features of AODVv2, associated with AODV, are not
required by minimal implementations. These features are expected to
apply in networks with greater mobility, or larger node populations,
or requiring reduced latency for application launches. The optional
features are as follows:
o Expanding Rings Multicast
o Intermediate RREPs (iRREPs): Without iRREP, only the destination
can respond to a RREQ.
o Precursor lists.
o Reporting Multiple Unreachable Addresses: a RERR message can carry
more than one Unreachable Destination Address for cases when a
single link breakage causes multiple destinations to become
unreachable from an intermediate router.
o RREP_ACK.
o Message Aggregation.
14.1. Expanding Rings Multicast
For multicast RREQ, msg_hop_limit MAY be set in accordance with an
expanding ring search as described in [RFC3561] to limit the RREQ
propagation to a subset of the local network and possibly reduce
route discovery overhead.
14.2. Intermediate RREP
This specification has been published as a separate Internet Draft
[I-D.perkins-irrep].
14.3. Precursor Lists and Notifications
This section specifies an interoperable enhancement to AODVv2 (and
possibly other reactive routing protocols) enabling more economical
notifications to traffic sources upon determination that a route
needed to forward such traffic to its destination has become Broken.
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14.3.1. Overview
In many circumstances, there can be several sources of traffic for a
certain destination. Each such source of traffic is known as a
"precursor" for the destination, as well as all upstream routers
between the forwarding AODVv2 router and the traffic source. For
each destination, an AODVv2 router MAY choose to keep track of the
upstream neighbors that have provided traffic for that destination;
there is no need to keep track of upstream routers any farther away
than the next hop.
Moreover, any particular link to an adjacent AODVv2 router may be a
path component of multiple routes towards various destinations. The
precursors for all destinations using the next hop across any link
are collectively known as the precursors for that next hop.
When an AODVv2 router determines that an link to one of its neighbors
has broken, the AODVv2 router detecting the broken link must mark
multiple routes as Broken, for each of the newly unreachable
destinations, as described in Section 9.3. Each route that relies on
the newly broken link is no longer valid. Furthermore, the
precursors of the broken link should be notified (using RERR) about
the change in status of their route to a destination relying upon the
broken next hop.
14.3.2. Precursor Notification Details
During normal operation, each AODVv2 router wishing to maintain
precursor lists as described above, maintains a precursor table and
updates the table whenever the node forwards traffic to one of the
destinations in its route table. For each precursor in the precursor
list, a record must be maintained to indicate whether the precursor
has been used for recent traffic (in other words, whether the
precursor is an Active precursor). So, when traffic arrives from a
precursor, the Current_Time is used to mark the time of last use for
the precursor list element associated with that precursor.
When an AODVv2 router detects that a link is broken, then for each
precursor using that next hop, the node MAY notify the precursor
using either unicast or multicast RERR:
unicast RERR to each Active precursor
This option is applicable when there are few Active precursors
compared to the number of neighboring AODVv2 routers.
multicast RERR to RERR_PRECURSORS
RERR_PRECURSORS is, by default, LL-MANET-Routers [RFC5498]. This
option is typically preferable when there are many precursors,
since fewer packet transmissions are required.
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Each upstream neighbor (i.e., precursor) MAY then execute the same
procedure until all upstream routers have received the RERR
notification.
14.4. Multicast RREP Response to RREQ
The RREQ Target Router (RREP_Gen) MAY, as an alternative to
unicasting a RREP, be configured to distribute routing information
about the route toward TargAddr. That is, RREP_Gen MAY be configured
respond to a route discovery by generating a RREP, using the
procedure in Section 8.4, but multicasting the RREP to LL-MANET-
Routers [RFC5498] (subject to similar suppression algorithm for
redundant RREP multicasts as described in Section 8.6). The
redundant message suppression must occur at every router handling the
multicast RREP. Afterwards, RREP_Gen processing for the incoming
RREQ is complete.
Broadcast RREP response to incoming RREQ was originally specified to
handle unidirectional links, but it is expensive. Due to the
significant overhead, AODVv2 routers MUST NOT use multicast RREP
unless configured to do so by setting the administrative parameter
USE_MULTICAST_RREP.
14.5. RREP_ACK
Instead of relying on existing mechanisms for requesting verification
of link bidirectionality during Route Discovery, RREP_Ack is provided
as an optional feature and modeled on the RREP_Ack message type from
AODV [RFC3561].
Since the RREP_ACK is simply echoed back to the node from which the
RREP was received, there is no need for other data elements.
Considerations of packet TTL are as specified in Section 5. An
example message format is illustrated in section Appendix B.4.
14.6. Message Aggregation
The aggregation of multiple messages into a packet is specified in
RFC 5444 [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].
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15. Administratively Configurable Parameters and Timer Values
AODVv2 uses various configurable parameters of various types:
o Timers
o Protocol constants
o Administrative (functional) controls
o Other administrative parameters and lists
The tables in the following sections show the parameters along their
definitions and default values (if any).
Note: several fields have limited size (bits or bytes). These sizes
and their encoding may place specific limitations on the values that
can be set. For example, <msg-hop-count> is a 8-bit field and
therefore MAX_HOPCOUNT cannot be larger than 255.
15.1. Timers
AODVv2 requires certain timing information to be associated with
route table entries. The default values are as follows, subject to
future experience:
+------------------------------+---------------+
| Name | Default Value |
+------------------------------+---------------+
| ACTIVE_INTERVAL | 5 second |
| MAX_IDLETIME | 200 seconds |
| MAX_BLACKLIST_TIME | 200 seconds |
| MAX_SEQNUM_LIFETIME | 300 seconds |
| RREQ_WAIT_TIME | 2 seconds |
| UNICAST_MESSAGE_SENT_TIMEOUT | 1 second |
| RREQ_HOLDDOWN_TIME | 10 seconds |
+------------------------------+---------------+
Table 4: 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 for the
network where AODVv2 is used. Ideally, for networks with frequent
topology changes the AODVv2 parameters should be adjusted using
either experimentally determined values or dynamic adaptation. For
example, in networks with infrequent topology changes MAX_IDLETIME
may be set to a much larger value.
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15.2. 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 specification describing their use.
+------------------------+--------------------+---------------------+
| Name | Default Value | Description |
+------------------------+--------------------+---------------------+
| DISCOVERY_ATTEMPTS_MAX | 3 | Section 8.1 |
| MAX_HOPCOUNT | 20 hops | Section 6.5 |
| MAX_METRIC[i] | Specified only for | Section 6.5 |
| | HopCount | |
| MAXTIME | [TBD] | Maximum expressible |
| | | clock time |
+------------------------+--------------------+---------------------+
Table 5: Parameter Values
15.3. Administrative (functional) controls
The following administrative controls may be used to change the
operation of the network, by enabling optional behaviors. These
options are not required for correct routing behavior, although they
may potentially reduce AODVv2 protocol messaging in certain
situations. The default behavior is to NOT enable most such options,
options. Packet buffering is enabled by default.
+------------------------+------------------------------------+
| Name | Description |
+------------------------+------------------------------------+
| DEFAULT_METRIC_TYPE | 3 (i.e, Hop Count (see [RFC6551])) |
| ENABLE_IDLE_IN_RERR | Section 9.3.2 |
| ENABLE_IRREP | Section 8.3 |
| USE_MULTICAST_RREP | Section 14.4 |
+------------------------+------------------------------------+
Table 6: Administratively Configured Controls
15.4. Other administrative parameters and lists
The following table lists contains AODVv2 parameters which should be
administratively configured for each specific network.
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+-----------------------+-----------------------+-----------------+
| Name | Default Value | Cross Reference |
+-----------------------+-----------------------+-----------------+
| AODVv2_INTERFACES | | Section 4 |
| BUFFER_SIZE_PACKETS | 2 | Section 8.1 |
| BUFFER_SIZE_BYTES | MAX_PACKET_SIZE [TBD] | Section 8.1 |
| CLIENT_ADDRESSES | AODVv2_INTERFACES | Section 6.3 |
| CONTROL_TRAFFIC_LIMIT | TBD [50 packets/sec?] | Section 13 |
+-----------------------+-----------------------+-----------------+
Table 7: Other Administrative Parameters
16. IANA Considerations
This section specifies several RFC 5444 message types, message tlv-
types, and address tlv-types. Also, a new registry of 16-bit
alternate metric types is specified.
16.1. AODVv2 Message Types Specification
+----------------------------------------+------------+
| Name | Type (TBD) |
+----------------------------------------+------------+
| Route Request (RREQ) | 10 |
| Route Reply (RREP) | 11 |
| Route Error (RERR) | 12 |
| Route Reply Acknowledgement (RREP_ACK) | 13 |
+----------------------------------------+------------+
Table 8: AODVv2 Message Types
16.2. Message TLV Type Specification
+-----------------------------------+-------+---------+-------------+
| Name | Type | Length | Cross |
| | (TBD) | in | Reference |
| | | octets | |
+-----------------------------------+-------+---------+-------------+
| AckReq (Acknowledgment Request) | 10 | 0 | Section 6.2 |
| PktSource (Packet Source) | 11 | 4 or 16 | Section 9.3 |
| MetricType | 12 | 1 | Section 8.2 |
+-----------------------------------+-------+---------+-------------+
Table 9: Message TLV Types
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16.3. Address Block TLV Specification
+-----------------------------+--------+--------------+-------------+
| Name | Type | Length | Value |
| | (TBD) | | |
+-----------------------------+--------+--------------+-------------+
| Metric | 10 | depends on | Section 8.2 |
| | | Metric Type | |
| Sequence Number (SeqNum) | 11 | 2 octets | Section 8.2 |
| Originating Node Sequence | 12 | 2 octets | Section 8.2 |
| Number (OrigSeqNum) | | | |
| Target Node Sequence Number | 13 | 2 octets | Section 8.2 |
| (TargSeqNum) | | | |
| VALIDITY_TIME | 1 | 1 octet | [RFC5497] |
+-----------------------------+--------+--------------+-------------+
Table 10: Address Block TLV (AddrTLV) Types
16.4. Metric Type Number Allocation
Metric types are identified according to the assignments as specified
in [RFC6551]. The metric type of the Hop Count metric is assigned to
be 3, in order to maintain compatibility with that existing table of
values from RFC 6551. Non-addititve metrics are not supported in
this draft.
+-----------------------+----------+-------------+
| Name | Type | Metric Size |
+-----------------------+----------+-------------+
| Unallocated | 0 -- 2 | TBD |
| Hop Count | 3 - TBD | 1 octet |
| Unallocated | 4 -- 254 | TBD |
| Reserved | 255 | Undefined |
+-----------------------+----------+-------------+
Table 11: Metric Types
17. Security Considerations
The objective of the AODVv2 protocol is for each router to
communicate reachability information about addresses for which it is
responsible. Positive routing information (i.e. a route exists) is
distributed via RREQ and RREP messages. Negative routing information
(i.e. a route does not exist) is distributed via RERRs. AODVv2
routers store the information contained in these messages in order to
properly forward data packets, and they generally provide this
information to other AODVv2 routers.
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This section does not mandate any specific security measures.
Instead, this section describes various security considerations and
potential avenues to secure AODVv2 routing.
The most important security mechanisms for AODVv2 routing are
integrity/authentication and confidentiality.
In situations where routing information or router identity are
suspect, integrity and authentication techniques SHOULD be applied to
AODVv2 messages. In these situations, routing information that is
distributed over multiple hops SHOULD also verify the integrity and
identity of information based on originator of the routing
information.
A digital signature could be used to identify the source of AODVv2
messages and information, along with its authenticity. A nonce or
timestamp SHOULD also be used to protect against replay attacks. S/
MIME and OpenPGP are two authentication/integrity protocols that
could be adapted for this purpose.
In situations where confidentiality of AODVv2 messages is important,
cryptographic techniques can be applied.
In certain situations, for example sending a RREP or RERR, an AODVv2
router could include proof that it has previously received valid
routing information to reach the destination, at one point of time in
the past. In situations where routers are suspected of transmitting
maliciously erroneous information, the original routing information
along with its security credentials SHOULD be included.
Note that if multicast is used, any confidentiality and integrity
algorithms used MUST permit multiple receivers to handle the message.
Routing protocols, however, are prime targets for impersonation
attacks. In networks where the node membership is not known, it is
difficult to determine the occurrence of impersonation attacks, and
security prevention techniques are difficult at best. However, when
the network membership is known and there is a danger of such
attacks, AODVv2 messages must be protected by the use of
authentication techniques, such as those involving generation of
unforgeable and cryptographically strong message digests or digital
signatures. While AODVv2 does not place restrictions on the
authentication mechanism used for this purpose, IPsec Authentication
Message (AH) is an appropriate choice for cases where the nodes share
an appropriate security association that enables the use of AH.
In particular, routing messages SHOULD be authenticated to avoid
creation of spurious routes to a destination. Otherwise, an attacker
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could masquerade as that destination and maliciously deny service to
the destination and/or maliciously inspect and consume traffic
intended for delivery to the destination. RERR messages SHOULD be
authenticated in order to prevent malicious nodes from disrupting
routes between communicating nodes.
If the mobile nodes in the ad hoc network have pre-established
security associations, the purposes for which the security
associations are created should include that of authorizing the
processing of AODVv2 control packets. Given this understanding, the
mobile nodes should be able to use the same authentication mechanisms
based on their IP addresses as they would have used otherwise.
If the mobile nodes in the ad hoc network have pre-established
security associations, the purposes for which the security
associations Most AODVv2 messages are transmitted to the multicast
address LL-MANET-Routers [RFC5498]. It is therefore required for
security that AODVv2 neighbors exchange security information that can
be used to insert an ICV [RFC6621] into the AODVv2 message block
[RFC5444]. This enables hop-by-hop security. For destination-only
RREP discovery procedures, AODVv2 routers that share a security
association SHOULD use the appropriate mechanisms as specified in RFC
6621. The establishment of these security associations is out of
scope for this document.
18. 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-Royer for
her long time authorship of AODV. Additional thanks to Derek Atkins,
Emmanuel Baccelli, Abdussalam Baryun, Ramon Caceres, Thomas Clausen,
Christopher Dearlove, Ulrich Herberg, Henner Jakob, Luke Klein-
Berndt, Lars Kristensen, Tronje Krop, Koojana Kuladinithi, Kedar
Namjoshi, Alexandru Petrescu, Henning Rogge, Fransisco Ros, Pedro
Ruiz, Christoph Sommer, Lotte Steenbrink, Romain Thouvenin, Richard
Trefler, Jiazi Yi, Seung Yi, and Cong Yuan, for their reviews AODVv2
and DYMO, as well as numerous specification suggestions.
19. References
19.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized Mobile Ad Hoc Network (MANET) Packet/Message
Format", RFC 5444, February 2009.
[RFC5497] Clausen, T. and C. Dearlove, "Representing Multi-Value
Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497, March
2009.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network
(MANET) Protocols", RFC 5498, March 2009.
[RFC6551] Vasseur, JP., Kim, M., Pister, K., Dejean, N., and D.
Barthel, "Routing Metrics Used for Path Calculation in
Low-Power and Lossy Networks", RFC 6551, March 2012.
19.2. Informative References
[I-D.perkins-irrep]
Perkins, C. and I. Chakeres, "Intermediate RREP for
dynamic MANET On-demand (AODVv2) Routing", draft-perkins-
irrep-02 (work in progress), November 2012.
[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, M. and J. Macker, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
[RFC3561] Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
Demand Distance Vector (AODV) Routing", RFC 3561, July
2003.
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[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[RFC4728] Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
Routing Protocol (DSR) for Mobile Ad Hoc Networks for
IPv4", RFC 4728, February 2007.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
Considerations in Mobile Ad Hoc Networks (MANETs)", RFC
5148, February 2008.
[RFC6130] Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, April 2011.
[RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621,
May 2012.
Appendix A. Example Algorithms for AODVv2 Protocol Operations
The following subsections show example algorithms for protocol
operations required by AODVv2, including RREQ, RREP, RERR, and RREP-
ACK.
Processing for RREQ, RREP, and RERR messages follows the following
general outline:
1. Receive incoming message.
2. Update route table as appropriate.
3. Respond as needed, often regenerating the incoming message with
updated information.
Once the route table has been updated, the information contained
there is known to be the most recent available information for any
fields in the outgoing message. For this reason, the algorithms are
written as if outgoing message field values are assigned from the
route table information, even though it is often equally appropriate
to use fields from the incoming message.
AODVv2_algorithms:
o Process_Routing_Info
o Generate_RREQ
o Receive_RREQ
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o Regenerate_RREQ
o Generate_RREP
o Receive_RREP
o Regenerate_RREP
o Generate_RERR
o Receive_RERR
o Regenerate_RERR
o Generate_RREP_Ack
o Consume_RREP_Ack()
o Timeout RREP_Ack()
The following lists indicate the meaning of the field names used in
subsequent sections to describe message processing for the above
algorithms.
Incoming RREQ message parameters:
inRREQ.origIP := originator IP address
inRREQ.origSeq := originator IP sequence #
inRREQ.metType := metric type
inRREQ.origMet := metric to originator
inRREQ.targIP := target IP address
inRREQ.targSeq := target sequence # (if known)
inRREQ.hopLim := msg-hop-limit /* from RFC 5444 header */
inRREQ.nbrIP := IP address of the neighbor that sent the RREQ
Outgoing RREQ message parameters:
outRREQ.origIP := originator IP address
outRREQ.origSeq := originator IP sequence #
outRREQ.metType := metric type
outRREQ.origMet := metric to origNode {initially
MIN_METRIC[MetType]}
outRREQ.targIP := target IP address
outRREQ.targSeq := target sequence # (if known)
outRREQ.hopLim /* initially MAX_HOPCOUNT at originator */
Incoming RREP message parameters:
inRREP.hoplim /* msg-hop-limit from RFC 5444 header */
inRREP.origIP := originator's IP address
inRREP.metType := metric type
inRREP.targIP := target IP address
inRREP.targSeq := target sequence #
inRREP.targMet := target's metric {initially MIN_METRIC[MetType]}
inRREP.PfxLen
Outgoing RREP message parameters:
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outRREP.origIP := originator's IP address
outRREP.metType := metric type
outRREP.targIP := target IP address
outRREP.targSeq := target sequence #
outRREP.targMet := target's metric {starting with zero}
outRREP.PfxLen
outRREP.hopLim /* initially MAX_HOPCOUNT at originator */
Incoming RERR message parameters:
inRERR.PktSrc := source IP of unforwardable packet (if present)
inRERR.metType := metric type for routes to unreachable
destinations
inRERR.PfxLen[] := prefix lengths for unreachable destinations
inRERR.LostDest[] := unreachable destinations
inRERR.LostSeq[] := sequence #s for unreachable destinations
Outgoing RERR message parameters:
outRERR.PktSrc := source IP of unforwardable packet (if present)
outRERR.metType := metric type for routes to unreachable
destinations
outRERR.PfxLen[] := prefix lengths for unreachable destinations
outRERR.LostDest[] := unreachable destinations
outRERR.LostSeq[] := sequence #s for unreachable destinations
A.1. Subroutines for AODVv2 Protocol Operations
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/* Compare incoming route information to current route, maybe use */
Process_Routing_Info (dest, seq#, metric_type, metric,
last_hop_metric)
/* last_hop_metric: either Cost(inRREQ.netif) or (inRREP.netif) */
{
new_metric := metric + last_hop_metric;
rte := Fetch_Route_Table_Entry (dest, seq#, metric_type);
if (NULL == rte) {
rte := Create_Route_Table_Entry
(dest, seq#, metric_type, new_metric);
} else if (seq# > rte.seq#) { /* stale rte route entry */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else if (seq# < rte.seq#) { /* stale incoming route infor */
return(NULL);
} else if (rte.state == broken) { /* when (seq# == rte.seq#) */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else if (rte.metric > (new_metric) { /* and (seq# == rte.seq#) */
Update_Route_Table_Entry (rte, seq#, metric_type, new_metric);
} else { /* incoming route information is not useful */
return(NULL);
}
return (rte);
}
A.2. Example Algorithms for AODVv2 RREQ Operations
A.2.1. Generate_RREQ
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Generate_RREQ {
/* Marshall parameters */
outRREQ.origIP := IP address used by application
outRREQ.origSeq := originating router's sequence #
outRREQ.metType := (if included) metric type needed by application
outRREQ.origMet := 0 (default) or MIN_METRIC(Metric_type)
outRREQ.targIP := target IP address
outRREQ.targSeq := target sequence # /* if known from route table */
outRREQ.hopLim := msg-hop-limit /* RFC 5444 */
/* build RFC 5444 message header fields */
{
msg-type=RREQ (message is of type RREQ)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_HOPCOUNT
if (Metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* Include each available Sequence Number in appropriate AddrTLV */
/* put outRREQ.origSeq in OrigSeqNum AddrTLV */
if (NULL != targSeq) {
/* put outRREQ.targSeq in TargSeqNum AddrTLV */
}
/* Build Metric AddrTLV containing OrigAddr metric */
/* use MIN_METRIC(metric type) [==0 for default metric type */
}
A.2.2. Receive_RREQ
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Receive_RREQ (inRREQ) {
/* Extract inRREQ values */
origRTE = Process_Routing_Info (inRREQ.origIP, inRREQ.origSeq, ...)
if (inRREQ.targIP belongs to me or my client subnet) {
Generate_RREP()
} else if (inRREQ present in RREQ_table) {
return; /* don't regenerate RREQ... */
} else if (inRREQ.nbrIP not present in blacklist) {
Regenerate_RREQ(origRTE, inRREQ)
} else if (blacklist_expiration_time > current_time) {
return; /* don't regenerate RREQ... */
} else {
Remove nbrIP from blacklist;
Regenerate_RREQ(origRTE, inRREQ)
}
}
A.2.3. Regenerate_RREQ
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Regenerate_RREQ (origRTE, inRREQ) { /* called from receive_RREQ() */
outRREQ.hopLim := inRREQ.hopLim - 1
if (outRREQ.hopLim == 0) { /* don't regenerate */
return()
}
/* Marshall parameters */
outRREQ.origIP := origRTE.origIP
outRREQ.origSeq := origRTE.origSeq
outRREQ.origMet := origRTE.origMet
outRREQ.metType := origRTE.metType
outRREQ.targIP := inRREQ.targIP
outRREQ.targSeq := inRREQ.targSeq /* if present */
/* build RFC 5444 message header fields */
{
msg-type=RREQ (message is of type RREQ)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_METRIC(Metric Type) (default, MAX_HOPCOUNT)
if (Metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* Include each available Sequence Number in its proper AddrTLV */
/* put outRREQ.origSeq in OrigSeqNum AddrTLV */
if (NULL != targSeq) {
/* put outRREQ.targSeq in TargSeqNum AddrTLV */
}
/* Build Metric AddrTLV to contain outRREQ.origMet */
}
A.3. Example Algorithms for AODVv2 RREP Operations
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A.3.1. Generate_RREP
Generate_RREP {
/* Marshall parameters */
outRREP.origIP := origRTE.origIP
metric_type := origRTE.metType /* if not default */
if (DEFAULT != metric_type)
outRREP.metType := metric_type
outRREP.targIP := inRREQ.targIP
outRREP.targMet := MIN_METRIC(outRREP.metType) (0 by default)
my_sequence_# := (1 + my_sequence_#) /* from nonvolatile storage */
outRREP.targSeq := my_sequence_#
/* build RFC 5444 message header fields */
{
msg-type=RREP
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := MAX_HOPCOUNT
/* Include the AckReq TLV when:
- previous RREP does not seem to enable any data flow, OR
- when RREQ is received from same OrigAddr after RREP was
unicast to targRTE.nextHop
*/
if (DEFAULT != metric_type) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* put outRREP.TargSeq in TargSeqNum AddrTLV */
/* Build Metric AddrTLV containing TargAddr metric */
/* use MIN_METRIC(origRTE.metType) */
}
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A.3.2. Receive_RREP
Receive_RREP (inRREP)
{
If (RREP includes AckReq data element) {
Generate_RREP_Ack()
}
/* Extract inRREP values */
targRTE := Process_Routing_Info (inRREP.targIP, inRREP.targSeq, ...)
if (inRREP.targIP belongs to me, a client, or a client subnet) {
Consume_RREP(inRREP)
} else {
Regenerate_RREP(targRTE, inRREP)
}
}
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A.3.3. Regenerate_RREP
Regenerate_RREP(targRTE, inRREP) {
outRREP.hopLim := inRREP.hopLim - 1
if (outRREP.hopLim == 0) { /* don't regenerate */
return()
}
/* Marshall parameters */
outRREP.targIP := targRTE.targIP
outRREP.targSeq := targRTE.targSeq
outRREP.targMet := targRTE.targMet
metric_type := origRTE.metType /* if not default */
if (DEFAULT != metric_type)
outRREP.metType := metric_type
outRREP.origIP := inRREP.origIP
outRREP.nextHop := targRTE.nextHop
/* build RFC 5444 message header fields */
{
msg-type=RREP (message is of type RREP)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
/* Include the AckReq data element when:
- previous RREP does not seem to enable any data flow, OR
- when RREQ is received from same OrigAddr after RREP was
unicast to targRTE.nextHop
*/
msg-hop-limit := outRREP.hopLim;
if (metric_type == DEFAULT) {
msg.tlvs-length=0
} else { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := 2
AddrBlk := {outRREQ.origIP and outRREQ.targIP addresses}
/* put outRREP.targSeq in TargSeqNum AddrTLV */
/* Build Metric AddrTLV containing TargAddr metric */
}
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A.3.4. Consume_RREP
/* executed by RREQ_Gen */
/* TargAddr route table entry was updated by Receive_RREP() */
Consume_RREP() {
/* Transmit buffered packet(s) (if any) to TargAddr */
}
A.4. Example Algorithms for AODVv2 RERR Operations
A.4.1. Generate_RERR
Generate_RERR()
{
metric_type := DEFAULT;
switch (error_type) in {
case (broken_link):
num-broken-addr=0
/* find unreachable destinations, seqNums, prefixes */
for (every rte (route table entry) in route table) {
if (broken_link == rte.next_hop) {
rte.state := broken;
outRERR.LostDest[num-broken-addr] := rte.dest
outRERR.LostSeq[num-broken-addr] := rte.seq#
outRERR.PfxLen[num-broken-addr] := rte.pfx
metric_type := rte.metType
num-broken-addr := (num-broken-addr+1)
}
}
/* No offending-src for this case */
case (undeliverable packet):
offending-src := undeliverable_packet.srcIP
outRERR.LostDest[] := undeliverable_packet.destIP
outRERR.LostPfxSiz[] := MAX_PFX_SIZE /* 31 or 127 */
num-broken-addr=1
}
/* build RFC 5444 message header fields */
{
msg-type=RERR (message is of type RERR)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
msg-hop-limit := outRERR.hopLim;
if (NULL != offending-src) {
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/* Build PktSource Message TLV */
}
if (metric_type != DEFAULT) { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := num-broken-addr;
AddrBlk := outRERR.LostDest[];
/* Add AddrBlk Seq# TLV */
Seq#TLV := outRERR.LostSeq[]
/* only add AddrBlk PfxSiz TLV if prefixes are nondefault */
for (pfx in outRERR.LostPfx[]) {
if (pfx != Max_Prefix_Size) { /* 31 for IPv4, 127 for IPv6 */
PfxSizTLV := outRERR.LostPfx[]
return;
}
}
}
A.4.2. Receive_RERR
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Receive_RERR (inERR)
{
/* Extract inERR values */
next_hop := inRERR.nbrIP
offending-src := inRERR.offending-src; /* NULL if not present */
precursors[] := NULL;
num-broken-addr := 0;
in-broken-addr := 0;
for (IPaddr := inRERR.LostDest[in-broken-addr]) {
rte := Fetch_Route_Table_Entry (dest, metric_type);
if (NULL == rte) {
continue;
} else if (rte.nextHop != inRERR.fromIP) {
continue;
} else if (NULL != rte.precursors) {
/* add rte.precursors to precursors */
} else if (rte.PfxSiz < inRERR.PfxSiz) {
/***********************************************************
If the reported prefix from the incoming RERR is *longer*
than the prefix from Route Table, then create a new route
with the longer prefix.
The newly created route will be marked as broken, and used
to regenerate RERR, NOT using shorter the routing prefix.
This avoids unnecessarily invalidating the larger subnet.
**********************************************************/
rte := Create_Route_Table_Entry (IPaddr, seq#,
metric_type, new_metric, inRERR.PfxSiz);
}
LostDest[num-broken-addr] := rte.Dest;
Seq#[num-broken-addr] := rte.Seq#;
PfxSiz[num-broken-addr] := rte.PfxSiz;
rte.state = broken;
num-broken-addr := (num-broken-addr + 1);
in-broken-addr := (in-broken-addr + 1);
}
if (num-broken-addr > 0) {
Regenerate_RERR (offending-src, precursors,
LostDest[], Seq#[], PfxSiz[])
}
}
A.4.3. Regenerate_RERR
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Regenerate_RERR (offending-src, precursors,
LostDest[], LostSeq#[], PfxSiz[])
{
/* build RFC 5444 message header fields */
{
msg-type=RERR (message is of type RERR)
MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
MAL=3 or 15 (Message Address Length [3 for IPv4, 15 for IPv6])
msg-size=NN (octets -- counting MsgHdr, AddrBlk, and AddrTLVs)
outRERR.hopLim := inRERR.hopLim - 1
msg-hop-limit := outRERR.hopLim;
if (NULL != offending-src) {
/* Build PktSource Message TLV */
}
if (metric_type != DEFAULT) { /* Metric_type != HopCount */
/* Build Metric_type Message TLV */
}
}
/* build AddrBlk */
num-addr := num-broken-addr;
AddrBlk := LostDest[];
/* Add AddrBlk Seq# TLV */
Seq#TLV := LostSeq[]
/* only add AddrBlk PfxSiz TLV if prefixes are nondefault */
for (pfx in PfxSiz[]) {
if (pfx != Max_Prefix_Size) { /* 31 for IPv4, 127 for IPv6 */
PfxSizTLV := PfxSiz[]
}
} /* If all are default, don't include PfxSize AddrTLV */
if (#precursors == 1) {
unicast RERR to precursor[0];
} else if (#precursors > 1) {
multicast RERR to RERR_PRECURSORS;
} else if (offending-src != NULL) {
unicast RERR to offending-src;
} else {
multicast RERR to RERR_PRECURSORS;
}
}
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A.5. Example Algorithms for AODVv2 RREP-Ack Operations
A.5.1. Generate_RREP_Ack
/* To be sent when RREP includes the AckReq TLV */
Generate_RREP_Ack()
{
/* assign RFC 5444 fields */
msgtype := RREPAck
MF := 0
MAL := 3
msg-size := 4
}
A.5.2. Consume_RREP_Ack
Consume_RREP_Ack()
{
/* turn off timeout event for the node sending RREP_Ack */
}
A.5.3. Timeout_RREP_Ack
Timeout_RREP_Ack()
{
/* insert unresponsive node into blacklist */
}
Appendix B. Example RFC 5444-compliant packet formats
The following subsections show example RFC 5444-compliant packets for
AODVv2 message types RREQ, RREP, RERR, and RREP-Ack. These proposed
message formats are designed based on expected savings from IPv6
addressable MANET nodes, and a layout for the Address TLVs that may
be viewed as natural, even if perhaps not the absolute most compact
possible encoding.
For RteMsgs, the msg-hdr fields are followed by at least one and
optionally two Address Blocks. The first AddrBlk contains OrigAddr
and TargAddr. For each AddrBlk, there must be AddrTLVs of type
Metric and one of the SeqNum types (i.e, OrigSeqNum, TargSeqNum, or
Seqnum).
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There is no Metric Type Message TLV present, so the Metric AddrTLV
measures HopCount. The Metric AddrTLV also provides a way for the
AODV router generating the RREQ or RREP to supply an initial nonzero
cost for the route to its client node (OrigAddr or TargAddr, for RREQ
or RREP respectively).
In all cases, the length of an address (32 bits for IPv4 and 128 bits
for IPv6) inside an AODVv2 message is indicated by the msg-addr-
length (MAL) in the msg-header, as specified in [RFC5444].
The RFC 5444 header preceding AODVv2 messages in this document has
the format illustrated in Figure 4.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| PV=0 | PF=0 |
+-+-+-+-+-+-+-+-+
Figure 4: RFC 5444 Packet Header
The fields in Figure 4 are to be interpreted as follows:
o PV=0 (Packet Header Version = 0)
o PF=0 (Packet Flags = 0)
B.1. RREQ Message Format
Figure 5 illustrates an example RREQ message format.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RREQ | MF=4 | MAL=3 | msg-size=28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (bytes for Orig & Target):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head(Orig&Targ)| Orig.Mid | Target.Mid |addr.TLV.len=11:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=11|type=OrigSeqNum|0|1|0|1|0|0|Rsv| Index-start=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| tlv-length=2 | Orig.Node Sequence # | type=Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|0|1|0|0|Rsv| Index-start=0 | tlv-length=1 | OrigAddrHopCt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Example IPv4 RREQ, with OrigSeqNum and Metric AddrTLVs
The fields in Figure 5 are to be interpreted as follows:
o msg-type=RREQ (first [and only] message is of type RREQ)
o MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
o MAL=3 (Message Address Length indicator [3 for IPv4, 15 for IPv6])
o msg-size=28 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)
o msg-hop-limit (initially MAX_HOPCOUNT by default)
o msg.tlvs-length=0 (no Message TLVs)
o num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)
o AddrBlk flags:
* bit 0 (ahashead): 1
* bit 1 (ahasfulltail): 0
* bit 2 (ahaszerotail): 0
* bit 3 (ahassingleprelen): 0
* bit 4 (ahasmultiprelen): 0
* bits 5-7: RESERVED
o head-length=3 (length of head part of each address is 3 octets)
o Head (3 initial bytes for both Originating & Target addresses)
o Orig.Mid (4th byte of Originating Address)
o Target.Mid (4th byte of Target Address)
o addr.TLV.len = 11 (length in bytes for OrigSeqNum and Metric TLVs
o type=OrigSeqNum (type of first AddrBlk TLV, value 2 octets)
o AddrTLV flags for the OrigSeqNum TLV:
* bit 0 (thastypeext): 0
* bit 1 (thassingleindex): 1
* bit 2 (thasmultiindex): 0
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* bit 3 (thasvalue): 1
* bit 4 (thasextlen): 0
* bit 5 (tismultivalue): 0
* bits 6-7: RESERVED
o Index-start=0 (OrigSeqNum TLV value applies at index 0)
o tlv-length=2 (so there is only one TLV value, [1 = 2/2])
o Orig.Node Sequence # (TLV value for the OrigSeqNum TLV
o type=Metric (AddrTLV type of second AddrBlk TLV, values 1 octet)
o AddrTLV flags for Metric_TLV:
* bit 0 (thastypeext): 0
* bit 1 (thassingleindex): 1
* bit 2 (thasmultiindex): 0
* bit 3 (thasvalue): 1
* bit 4 (thasextlen): 0
* bit 5 (tismultivalue): 0
* bits 6-7: RESERVED
o Index-start=0 (Metric TLV values start at index 0)
o tlv-length=1 (so there is only one TLV value, [1 = 1/1])
o OrigAddrHopCt (first [and only] TLV value for the Metric TLV)
B.2. RREP Message Format
Figure 6 illustrates a packet format for an example RREP message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RREP | MF=4 | MAL=3 | msg-size=28 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (bytes for Orig & Target):
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head(Orig&Targ)| Orig.Mid | Target.Mid |addr.TLV.len=11:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=11|type=TargSeqNum|0|1|0|1|0|0|Rsv| Index-start=1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| tlv-length=2 | Targ.Node Sequence # | type=Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|1|0|1|0|0|Rsv| Index-start=1 | tlv-length=1 | TargAddrHopCt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Example IPv4 RREP, with TargSeqNum TLV and 1 Metric
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The fields in Figure 6 are to be interpreted as follows:
o msg-type=RREP (first [and only] message is of type RREP)
o MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
o MAL=3 (Message Address Length indicator [3 for IPv4, 15 for IPv6])
o msg-size=28 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)
o msg-hop-limit (initially MAX_HOPCOUNT by default)
o msg.tlvs-length=0 (no Message TLVs)
o num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)
o AddrBlk flags:
* bit 0 (ahashead): 1
* bit 1 (ahasfulltail): 0
* bit 2 (ahaszerotail): 0
* bit 3 (ahassingleprelen): 0
* bit 4 (ahasmultiprelen): 0
* bits 5-7: RESERVED
o head-length=3 (length of head part of each address is 3 octets)
o Head (3 initial bytes for both Originating & Target addresses)
o Orig.Mid (4th byte of Originating Address)
o Target.Mid (4th byte of Target Address)
o addr.TLV.len = 11 (length in bytes for TargSeqNum TLV and Metric
TLV
o type=TargSeqNum (type of first AddrBlk TLV, value 2 octets)
o AddrTLV flags for the TargSeqNum TLV:
* bit 0 (thastypeext): 0
* bit 1 (thassingleindex): 1
* bit 2 (thasmultiindex): 0
* bit 3 (thasvalue): 1
* bit 4 (thasextlen): 0
* bit 5 (tismultivalue): 0
* bits 6-7: RESERVED
o Index-start=1 (TargSeqNum TLV value applies to address at index 1)
o tlv-length=2 (there is one TLV value, 2 bytes in length)
o Targ.Node Sequence # (value for the TargSeqNum TLV)
o type=Metric (AddrTLV type of second AddrBlk TLV, value 1 octet)
o AddrTLV flags for the Metric TLV [01010000, same as for TargSeqNum
TLV]
o Index-start=1 (Metric TLV values start at index 1)
o tlv-length=1 (there is one TLV value, 1 byte in length)
o TargAddrHopCt (first [and only] TLV value for Metric TLV)
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B.3. RERR Message Format
Figure 7 illustrates an example RERR message format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type=RERR | MF=4 | MAL=3 | msg-size=24 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-hop-limit | msg.tlvs-length=0 | num-addr=2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|0|0|0|0| Rsv | head-length=3 | Head (for both destinations) :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:Head (3rd byte)| Mid (Dest_1) | Mid (Dest_2) | addr.TLV.len=7:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:addr.TLV.len=7 | type=SeqNum |0|0|1|1|0|1|Rsv| tlv-length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dest_1 Sequence # | Dest_2 Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Example IPv4 RERR with Two Unreachable Addresses
The fields in Figure 7 are to be interpreted as follows:
o msg-type=RERR (first [and only] message is of type RERR)
o MF=4 (Message Flags = 4 [only msg-hop-limit field is present])
o MAL=3 (Message Address Length indicator [3 for IPv4, 15 for IPv6])
o msg-size=24 (octets -- counting MsgHdr, MsgTLVs, and AddrBlks)
o msg-hop-limit (initially MAX_HOPCOUNT by default)
o msg.tlvs-length=0 (no Message TLVs)
o num-addr=2 (OrigAddr and TargAddr in RteMsg AddrBlock)
o AddrBlk flags == 10000000 [same as RREQ and RREP AddrBlk examples]
o head-length=3 (length of head part of each address is 3 octets)
o Head (3 initial bytes for both Unreachable Addresses, Dest_1 and
Dest_2)
o Dest_1.Mid (4th byte of Dest_1 IP address)
o Dest_2.Mid (4th byte of Dest_2 IP address)
o addr.TLV.len = 7 (length in bytes for SeqNum TLV
o type=SeqNum (AddrTLV type of AddrBlk TLV, values 2 octets each)
o AddrTLV flags for SeqNum TLV:
* bit 0 (thastypeext): 0
* bit 1 (thassingleindex): 0
* bit 2 (thasmultiindex): 1
* bit 3 (thasvalue): 1
* bit 4 (thasextlen): 0
* bit 5 (tismultivalue): 1
* bits 6-7: RESERVED
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o tlv-length=4 (so there are two TLV values, [2 = 4/2])
o Dest_1 Sequence # (first of two TLV values for the SeqNum TLV)
o Dest_2 Sequence # (second of two TLV values for the SeqNum TLV)
B.4. RREP_ACK Message Format
The figure below illustrates a packet format for an example RREP_ACK
message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|msgtype=RREPAck| MF=0 | MAL=3 | msg-size=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Example IPv4 RREP_ACK
Appendix C. Changes since revision ...-05.txt
This section lists the changes since AODVv2 revision ...-05.txt
o Added Lotte Steenbrink as co-author.
o Reorganized section on Metrics to improve readability by putting
specific topics into subsections.
o Introduced concept of data element, which is used to clarify the
method of enabling RFC 5444 representation for AODVv2 data
elements. A list of Data Elements was introduced in section 3,
which provides a better understanding of their role than was
previously supplied by the table of notational devices.
o Replaced instances of OrigNode by OrigAddr whenever the more
specific meaning is appropriate. Similarly for instances of other
node versus address terminology.
o Introduced concepts of PrefixLengthList and MetricList in order to
avoid use of index-based terminology such as OrigNdx and TargNdx.
o Added section 5, "AODVv2 Message Transmission", describing the
intended interface to RFC 5444.
o Included within the main body of the specification the mandatory
setting of the TLV flag thassingleindex for TLVs OrigSeqNum and
TargSeqNum.
o Removed the Route.Timed state. Created a new flag for route table
entries known as Route.Timed. This flag can be set when the route
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is in the active state. Previous description would require that
the route table entry be in two states at the same time, which
seems to be misleading. The new flag is used to clarify other
specification details for Timed routes.
o Created table 3 to show the correspondence between AODVv2 data
elements and RFC 5444 message components.
o Replaced "invalid" terminology by the more specific terms "broken"
or "expired" where appropriate.
o Eliminated the instance of duplicate specification for inclusion
of OrigNode (now, OrigAddr) in the message.
o Corrected the terminology to be Mid instead of Tail for the
trailing address bits of OrigAddr and TargAddr for the example
message formats in the appendices.
Appendix D. Changes since revision ...-04.txt
This section lists the changes since AODVv2 revision ...-04.txt
o Normative text moved out of definitions into the relevant section
of the body of the specification.
o Editorial improvements and improvements to consistent terminology
were made. Replaced "retransmit" by the slightly more accurate
term "regenerate".
o Issues were resolved as discussed on the mailing list.
o Changed definition of LoopFree as suggested by Kedar Namjoshi and
Richard Trefler to avoid the failure condition that they have
described. In order to make understanding easier, replaced
abstract parameters R1 by RteMsg and R2 by Route to reduce the
level of abstraction when the function LoopFree is discussed.
o Added text to clarify that different metrics may have different
data types and different ranges of acceptable values.
o Added text to section "RteMsg Structure" to emphasize the proper
use of RFC 5444.
o Included within the main body of the specification the mandatory
setting of the TLV flag thassingleindex for TLVs OrigSeqNum and
TargSeqNum.
o Made more extensive use of the AdvRte terminology, in order to
better distinguish between the incoming RREQ or RREP message
(i.e., RteMsg) versus the route advertised by the RteMsg (i.e.,
AdvRte).
Appendix E. Changes since revision ...-03.txt
This section lists the changes since AODVv2 revision ...-03.txt
o An appendix was added to exhibit algorithmic code for
implementation of AODVv2 functions.
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o Numerous editorial improvements and improvements to consistent
terminology were made. Terminology related to prefix lengths was
made consistent. Some items listed in "Notational Conventions"
were no longer used, and so deleted.
o Issues were resolved as discussed on the mailing list.
o Appropriate instances of "may" were changed to "MAY".
o Definition inserted for "upstream".
o Route.Precursors included as an *optional* route table field
o Reworded text to avoid use of "relevant".
o Deleted references to "DestOnly" flag.
o Refined statements about Metric Type TLV to allow for omission
when Metric Type == HopCount.
o Bulletized list in section 8.1
o ENABLE_IDLE_UNREACHABLE renamed to be ENABLE_IDLE_IN_RERR
o Transmission and subscription to LL-MANET-Routers converted to
MUST from SHOULD.
Appendix F. Changes since revision ...-02.txt
This section lists the changes since AODVv2 revision ...-02.txt
o The "Added Node" feature was removed. This feature was intended
to enable additional routing information to be carried within a
RREQ or a RREP message, thus increasing the amount of topological
information available to nodes along a routing path. However,
enlarging the packet size to include information which might never
be used can increase congestion of the wireless medium. The
feature can be included as an optional feature at a later date
when better algorithms are understood for determining when the
inclusion of additional routing information might be worthwhile.
o Numerous editorial improvements and improvements to consistent
terminology were made. Instances of OrigNodeNdx and TargNodeNdx
were replaced by OrigNdx and TargNdx, to be consistent with the
terminology shown in Table 2.
o Example RREQ and RREP message formats shown in the Appendices were
changed to use OrigSeqNum and TargSeqNum message TLVs instead of
using the SeqNum message TLV.
o Inclusion of the OrigNode's SeqNum in the RREP message is not
specified. The processing rules for the OrigNode's SeqNum were
incompletely specified in previous versions of the draft, and very
little benefit is foreseen for including that information, since
reverse path forwarding is used for the RREP.
o Additional acknowledgements were included, and contributors names
were alphabetized.
o Definitions in the Terminology section capitalize the term to be
defined.
o Uncited bibliographic entries deleted.
o Ancient "Changes" sections were deleted.
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Appendix G. Multi-homing Considerations
Multi-homing is not supported by the AODVv2 specification. There has
been previous work indicating that it can be supported by expanding
the sequence number to include the AODVv2 router's IP address as a
parsable field of the SeqNum. Otherwise, comparing sequence numbers
would not work to evaluate freshness. Even when the IP address is
included, there isn't a good way to compare sequence numbers from
different IP addresses, but at least a handling node can determine
whether the two given sequence numbers are comparable. If the route
table can store multiple routes for the same destination, then multi-
homing can work with sequence numbers augmented by IP addresses.
This non-normative information is provided simply to document the
results of previous efforts to enable multi-homing. The intention is
to simplify the task of future specification if multihoming becomes
needed for reactive protocol operation.
Appendix H. Shifting Network Prefix Advertisement Between AODVv2
Routers
Only one AODVv2 router within a MANET SHOULD be responsible for a
particular address at any time. If two AODVv2 routers dynamically
shift the advertisement of a network prefix, correct AODVv2 routing
behavior must be observed. The AODVv2 router adding the new network
prefix must wait for any existing routing information about this
network prefix to be purged from the network. Therefore, it must
wait at least ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the previous AODVv2
router for this address stopped advertising routing information on
its behalf.
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.dowdell486@xxxxxxxxx
Lotte Steenbrink
Hamburg University of Applied Sciences
Berliner Tor 5
Hamburg 20099
Germany
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Perkins, et al. Expires July 2, 2015 [Page 69]
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