[Tinyos-help] TOSSIM Problem

Brett Parsons brettmac.parsons at nf.sympatico.ca
Sun Sep 4 15:00:45 PDT 2005


Hi All,

I'm running into an odd problem with TOSSIM and I'm hoping someone can 
help me!

I've created a simple "flooding" application that floods an interest 
from the "Base Station" (node 0) to a destination node (node 6).  Below 
I've given a diagram of my simple network topology:

          2 -- 3
        /           \
0 -- 1            6
        \           /
         4 -- 5

Note that all links are bidirectional and all transmissions are 
broadcast.  My problem is that, when I define this topology in a TOSSIM 
topology file, node 6 never seems to receive the interest.  The interest 
makes it as far as nodes 3 and 5.  Both of these nodes then attempt to 
send the interest to node 6, but it never gets received.

The weird thing is, if I redefine the topology as below, the problem 
disappears and node 6 correctly receives the interest message:

          2 -- 3
        /          
0 -- 1            6
        \           /
         4 -- 5

Notice all I have done is remove the bidirectional link between 3 and 
6.  My guess is that nodes 3 and 5 are attempting to broadcast the 
message at the same time, resulting in corrupted packets.  However, the 
TOSSIM documentation states that this is a very minor possibility.

Does anyone have an idea what is going on here?  I'd appreciate any 
suggestions you could offer!

Thanks,

Brett P


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