Subject: RE: loop in AODV?

From: Dan Iregren <[email-masked]>
Date: Thu, 1 Nov 2001 09:42:39 +0100 (CET)

On Wed, 31 Oct 2001, Sasuta Mike-CSM001 wrote:

> Dan,
>
> It seems to me there has been some confusion of recording routes.
> In the discussion of your example of [c] needing a route to [d], you
> correctly reflect that [a] has a route path to [d] via [b] from a
> previous message attempt.

So, [a] has a route towards [d], and [d] does not (which you seem to agree
is the case here). That is the actual problem. [a] is further away from [d]
than [b] is not allowed to have fresher info about [d] than [b] if we want
to avoid loops.

> However [b] will receive the packet from
> [a], originally from [c], seeking [d] which [b] no longer has in its
> route table. In processing this, [b] creates a backward route path to
> [c] via [a], not to [d] via [a].     [b] will then forwards the request,
> finding [d].

This is not what will happen if the nodes process route requests as
described in draft 8.

I assume the packet you are talking about here is the request that [c]
sent, asking for route to [d].

[a] will not forward that request since [a] has a route towards [d] and
hence will send a route reply instead. That route reply will be received
by [b] and cause the loop as I described earlier.

/Dan