Subject: AODV: remarks about the version 9 of the draft

From: Yves Prelot <[email-masked]>
Date: Tue, 20 Nov 2001 09:59:41 +0100

My remarks about the draft 9 of the AODV protocol after implementation
in our routing daemon:

8.1 This section doesn't clearly state that a seuence number can never
decrease. Is this an omission, or this voluntary ? In the second case,
it seems to imply that sequence numbers can indeed decrease, but I fail
to clearly see the circumstances where this should happen.
Can someone enlighten me on that point ?

8.3 When a data packet is forwarded, shouldn't the routes to
- the destination,
- the next hop,
- the previous hop,
- the source
be updated so that their Lifetime be no less than the current time plus
ACTIVE_ROUTE_TIMEOUT ?

8.3 Why not simply not process any RREQ with Source IP equal to one of
the node's IP address instead of using the FLOOD_RECORD_TIME timer ?

8.5 "the node silently discards the newly received RREQ..." could
contradict
- 8.1 "it receives an AODV message with new information about the
sequence number for some
other destination node..."
- 8.5 "Under all circumstances whenever a RREQ message is received..."

8.5 "MinimalLifetime = (current time + REV_ROUTE_LIFE
-HopCount*NODE_TRAVERSAL_TIME)"
doesn't indicate which HopCount is used.

8.6.3 "Destination Sequence Number: The Source Sequence Number from the
RREQ" doesn't seem correct because the intermediate node may know about
a higher sequence number.

8.6.3 "Hop Count: The Hop Count as received in the RREQ" doesn't seem
correct; it should be "The Hop Count as received in the RREQ plus one".

8.6 To correct the two problems above, I believe it would be more
straightforward to read the information to fill in the gratuitous RREP
from the updated routing table.

8.9 It seems curious that a Hello message Lifetime is set to
ALLOWED_HELLO_LOSS * HELLO_INTERVAL, but that "If a route already
exists, then the Lifetime for the route should be increased if necessary
to be at least ACTIVE_ROUTE_TIMEOUT" ; why is not the Hello Lifetime
used in that case ?

8.11 This paragraph is still quite confusing. The management of the
sequence number is unclear, especially if one accounts for the new 8.1
paragraph (e.g. one copies the sequence number from the received RERR;
does one also increment it as would suggest 8.1 when invalidating a node
? Does one really copy the sequence numbers from the received RERR, and
what happens should one actually decrease an existing sequence number).
It seems that this paragraph could be clarified if separated into three
distinct cases:
- RERR emission due to the reception of a RERR,
- RERR emission due to the detection of a broken link,
- RERR emission due to the reception of a data packet for which no route
is available.

8.11 Why is broadcast 255.255.255.255 ? isn't this a little general and
couldn't one use a less generic broadcast address mask ?

Thanks!

Yves

---

From: David Lundberg <[email-masked]>
Date: Tue, 20 Nov 2001 19:33:55 +0100 (CET)

Hi!

> couldn't one use a less generic broadcast address mask ?

Since the nodes around is not requiered to be on the same
subnetwork. 

Regards,

// David //

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