Subject: AODV draft (05) addresses looping potential

From: Elizabeth Royer <[email-masked]>
Date: Tue, 14 Mar 2000 12:40:57 -0800 (PST)

Hello everyone,

Previously Charlie had sent a message to the group reporting
the potential for routing loops in AODV which were found by 
Carl Gunter and his group at UPenn.  A few people have asked 
if we have fixed this looping potential in the latest version
(05) of our draft.  

The latest draft does address all of the situations indicated
to us where loops may occur.  Specifically, we have changed the
format of the RERR message so that the sequence number (incremented
by 1) of each listed destination is also included in the message.
Additionally, we have added 2 new sections, "Actions After Reboot"
for both unicast and multicast, which specify exactly that - actions
nodes should take after booting/rebooting in order to prevent
the formation of loops from stale routing information.  Finally,
we have added another section, "Route Expiry and Deletion", which
specifies the conditions under which a route may be deleted from
the route table.  This section introduces a DELETE_PERIOD (as
suggested by Gunter, et al) for which an invalidated route entry 
must be maintained before it can be completely deleted.  

These solutions should prevent the formation of routing loops
within AODV.  If anyone detects additional scenarios which could 
cause loops, please send us that information so we can continue 
to improve the protocol.

Thanks,
Elizabeth