Dear Ms. Yousefi,
Am 08.03.2016 um 21:03 schrieb Behnaz yousefi <behyousefi@xxxxxxxxx>:
Dear Mr. Lotte Steenbrink
Again sorry for the delay, we were busy revising our paper. You can publish
our finding in the MANET group since our paper is under revision we will
upload its revised version near a week on the arXiv.
We really appreciate it if you answer our previous question that whether the
scenario we have found can happen in reality. As we mentioned before, your
answer will effect on our theorem since as we explained before we found that
scenario based on some assumptions. If our assumptions don’t hold we need to
change our paper and that’s why we would really like to get a feedback from
you.
·n0 attempts to resend the “rreq” message when it doesn’t receive an “ack”
from n1
·The resending procedure of the “rreq” message by n0 takes long enough that
the “rreq” message passes through two nodes and be processed by them.
In addition, we found another loop scenario which involves resending the
“rreq” messages and is given for a network of four nodes with the network
topologies shown in Fig.1.
<network.jpg>
At first nodes are connected to each other as shown in Fig1.a.
n0 initiates a route discovery procedure for destination n3 by multicasting a
“rreq” message to n2 with sq=2.
n2 after updating its routing table, multicast the “rreq” to its neighbors,
n1 and n3.
n1 upon receiving the “rreq” message sent by n2 updates its routing table and
adds a route with hop-count=2, sq=2 and next-hope=2
Consider that topology changes at this point and n1 moves into communication
range of n0, gets connected to n0, and n2 leaves n0 communication range, gets
disconnected from n0, which leads to network topology shown in Fig1.b.
n0, which hasn’t received an “rrep” yet, resend the “rreq” message after
increasing its sequence number to 3.
n1 receives the new “rreq” message, with sq=3, next-hop=0 and hop-count=1,
since it’s a better route it would be added to the routing table. Then n1
multicast the “rreq” message to its neighbors, n2 and n3.
n2 evaluate the received message sent by n1 and adds a new route to its
routing table with sq=3, next-hop=1 and hop-count=2 since the sequence number
of the received message is greater than the stored one.
At this point a loop has been formed between nodes n1 and n2. This loop
scenario and the one we mentioned before occur because the existing route has
not been replaced by the better route, the received one. Instead the new
route is added to the table. The new route replaces the existing one only
when the route state of the existing route is “invalid” or the route state of
the new route is “confirmed”. It is been said in the protocol that when the
route state of the existing route is “unconfirmed” and the neighbor state of
the next-hop of the new route is “unknown”, the new route should be added to
the table, if it’s a better route and loop free, not replace the existing one.
We believe, these loop scenarios won’t happen if the routing table only keeps
the best and freshest routes. In other words, whenever a better route is
discovered the existing routes which are worse than the new route are
expunged from the routing table.
We hope are findings would be helpful.
We are looking forward to receive your feedback especially about our question
as I explained earlier it means a lot to us.
Best regards
Behnaz Yousefi
<network.jpg>
