[Babel-users] FW: Loose ends with Babel

[Juliusz Chroboczek]

> From my point of view, it would be nice to have shorter massages,
> because I am using protocol on very limited bandwidth link,

Speaking about that, Robert, perhaps you could tell us more about your
setup?  You appear to be doing unusual stuff (I have trouble imagining
why you'd prefer PPP over serial to an Ethernet link).

> also is better to have shorter messages anyway.

I'll expand about that a little.

In Babel, I distinguish between messages and packets.  A message is
always 24 bytes long, and can carry one route, IPv4 or IPv6.

A packet consists of an 8-byte header followed with an arbitrary
number of messages followed by an optional cryptographic signature
(not implemented at the current time).

Now 24 bytes for an IPv4 route is overkill; it could fit in 8 bytes.
If you're compressing your PPP link, you don't care -- the extra data
are mostly zeroes, and will compress beautifully.  What's more, Babel
sends reachability data at very large intervals (there are other
mechanisms that ensure that the routing is mostly up-to-date usually,
and that even when it isn't, the network keeps working, although not
optimally).

The alternative would be to encode the Babel protocol as
``type-length-value'' triples.  This would make it more complex, more
difficult to parse, but would save quite a bit of space for IPv4
routes.  I'm not sure if it's worth my while; we'll only know when we
deploy larger Babel networks.

Regards,

                                        Juliusz