Re: [B.A.T.M.A.N.] batman goes looping...

Yang Su
2009-08-13T15:07:06Z

Maybe I miss some thing here. What do you think would prevent A from
choosing via the long route (via B) ?

Cheers,
Yang

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|Marek Lindner <lindner_marek@yahoo.de> |
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|"The list for a Better Approach To Mobile Ad-hoc Networking" <b.a.t.m.a.n@lists.open-mesh.net> |
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| Date: |
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|13.08.2009 11:59 |
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|Re: [B.A.T.M.A.N.] batman goes looping... |
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|b.a.t.m.a.n-bounces@lists.open-mesh.net |
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On Wednesday 12 August 2009 22:34:17 Yang Su wrote:
> Given the DV nature of Batman, current strict dropping policy seems to
make
> sense, because sending known OGMs (as suggested) does introduce
significant
> overhead but does not propagate so much new information.
>
> In addition, loosing the dropping policy may introduce new problems which
> might not be easily predictable at this moment, e.g., stability, looping
> (propagating stale information within the network might cause even more
> nasty looping problems).

I agree that this might introduce new problems which is the reason for
posting
it here. I definitely see the overhead created by that methog. Every better

idea will be accepted immediately. :-)

> Another way (and maybe simpler ) to fix the problem: instead of loosing
the
> OGM dropping policy, loosing the echo cancellation policy.
>
> It is a very simple fix: in addition to the usual echo cancellation
> process, I also check the TQ value contained in the echoed OGM. This TQ
> is announced by the neighbor that broadcasts this echo. If this TQ is
worse
> than my current TQ estimation towards that neighbor, I update the
> estimation with this TQ.

In your testbed it fixed the issue ?
Looking at the example you gave I would expect that the problem is only
solved
partially. You argued the OGMs from E via A would always arrive faster at B

compared to the longer path. Using your method would probably avoid the
loop
between A and B in the event of a packet loss on the longer path but it
would
not let route A via the longer path. Am I mistaken ?

Regards,
Marek
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