[Battlemesh] Session about multi-homed IPv6 mesh networks and auto-configuration

Juliusz Chroboczek jch at pps.univ-paris-diderot.fr
Tue Apr 19 17:41:23 CEST 2016

[Adding Henning and Markus to CC.]

> one problem hnetd does not handle at the moment is the concept of
> having a metric ton of prefixes available to choose from and selecting
> an appropriate subset to use and redistribute. Consider a network with
> 1000 routers and 100 exit nodes - you might want 3-5 prefixes per
> router to give you 3-5 possible exits, and rotate around them over
> time. Otherwise you end up carrying a lot of routing traffic for ipv6
> addresses that are mostly unused.

Right.  The HNCP protocol supports doing that (the Delegated-Prefix TLV
has a Preferred Time field, which makes it possible to gracefully
deprecate a prefix), but neither of the implementations make use of the
feature AFAIK. 

Is the amount of routing traffic really a problem in your network?  Can
you provide some figures?

> Hncp also wants to assign those real addresses to itself, and doesn't
> cope with p2p assignment in the spec (tho julius extended it to /128s
> I think)

Right again, although shncpd doesn't yet perform address space
optimisation (optional in the spec).  Henning has provided me with some
patches to do that, but they need more work.  For once, please do hold
your breath (or speak to Henning).

> I am actually not huge on global reachability for internal routers and
> would prefer ULAs, maybe grabbing a real ipv6 address for long enough to
> get an update, that's it.

That's all supported by the protocol, but it's too complex for command-line
options, so it'll only happen when I add a proper config file parser to
shncpd.  It should be a simple matter of porting the parser from babeld,
but I first want to make a stable version of shncpd and push it into Debian.

-- Juliusz

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