Subject: [homenet] Stub-only Babel revisited

From: Juliusz Chroboczek <[email-masked]>
Date: Tue, 18 Nov 2014 16:27:43 +0100

[This is cross-posted between babel-users and Homenet@IETF, please choose
 your followups wisely.]

You might remember the stub-only implementation of Babel that I published
last week-end:

  https://github.com/jech/sbabeld

After playing some more with it, I've come to the conclusion that it could
be useful under some circumstances.  Apologies to anyone who tried to
convince me otherwise -- you were right, I was wrong.

I have therefore spent part of yesterday evening debugging and improving
it.  It's still 12kB text, but it now performs better route selection,
times out unreachable neighbours in a timely manner, and uses the
link-quality estimates published by neighbours (but doesn't measure its
own).  Convergence time is still slow (10s on average), but I don't see
a good way to improve it without maintaining a set of alternate routes

If you decide to use this in production (which is not completely
unreasonable now), please let me know, since I'd like to know how it
should evolve.  There are two possible directions:

  - smaller: remove reverse reachablity detection and route selection
    (just pick whichever neighbour sends an update first);

  - larger: maintain a table of alternate routes, which would dramatically
    improve convergence speed.

Thanks for your help,

-- Juliusz