[Ninux-Wireless] Esperimento BGP

[Juliusz Chroboczek]

(Sono il principale sviluppatore di Babel.)

> A Cosenza stiamo per riattivare il link verso le isole e pensavamo di usare
> BGP ma da quello che ho capito è un pochino lentuccio ad aggiornare le
> rotte rispetto a Babel, che può funzionare sia su reti mesh che wired.

That's interesting.  Whatever you decide to do, please tell me about
your experiences (you can write in Italian).

While both BGP and Babel are loop-free distance vector protocols, they
have very different designs.  BGP is really designed for carrying huge
numbers of stable networks over a stable link -- it only sends deltas
(differences between updates), so on a completely stable network it is
almost completely silent.  Babel, on the other hand, is designed for
carrying moderate numbers of unstable routes over potentially unstable
links -- hence link quality estimation, fairly frequent hellos, and
periodic full updates (but Babel can also send deltas).

Another important difference is that BGP is designed to give great
flexibility to the operator -- there are no metrics in BGP, instead
the operator is expected to carefully tweak filtering rules until the
traffic flows over the right path.  Babel, on the other hand, is
designed to be fully automatic -- metrics are determined
automatically, so that the operator doesn't need to tweak anything in
the config file.  (Should babeld fail to determine the best route, you
can still do some tweaking, but nothing as extensive as can be done
with BGP.)

Since you're using tunnels, you'll want to know that the current
release of babeld is not very smart about tunnels.  Baptiste Jonglez
has recently implemented an extension to Babel that automatically
measures tunnels' latencies and chooses the fastest one:

  http://www.pps.univ-paris-diderot.fr/~jch/research/rapport-jonglez-2013.pdf
  
You'll find the code in the babel-rtt branch of the babeld repository.
(Note however that we're going to change the details of the
on-the-wire protocol in the next weeks, so expect the final version to
be incompatible with this protocol.)

-- Juliusz

P.S. Giuseppe, if this mail doesn't get through, could you please
     forward it to the list?