From: Janet Davis (jlnd_at_cs.washington.edu)
Date: Tue Feb 03 2004 - 12:28:55 PST
Hi all,
Abhinav and I just discovered an important interoperability issue with
neighbor discovery and link state routing.
The scenario is this:
* For neighbor discovery, node 1 sends a ping with a special message and
TTL=1, and expects to receive a ping with the same message back.
* Node 2 receives this ping, discovers it has no route to node 1, and
consequently does not send a reply.
* As a result, node 1 never recognizes node 2 as its neighbor, and since
we only use bidirectional links in our Dijkstra computation, node 2 never
does compute a route to node 1.
For interoperability, we all need to agree on one method of recognizing
your neighbors. The most efficient approach is to use the 'from' argument
of the onReceive method -- it's guaranteed that this is the address of one
of your neighbors, regardless of the packet contents.
Note that if you use this method, you can eliminate the special neighbor
discovery ping packets entirely! (Why?)
So, for this assignment you should decide who your neighbors are based on
the 'from' argument of the onReceive method, not on the contents of
neighbor discovery ping packets.
Cheers,
Janet
-- Janet Davis jlnd_at_cs.washington.edu http://www.cs.washington.edu/homes/jlnd/ _______________________________________________ Cse461 mailing list Cse461_at_cs.washington.edu http://mailman.cs.washington.edu/mailman/listinfo/cse461
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