[Babel-users] A Babel experiment at funkfeuer.at

Harald Geyer harald at lefant.net
Sun Dec 14 17:31:05 UTC 2008

> > Perhaps we should take this discussion to some public place...
> You're very much welcome on babel-users at lists.alioth.debian.org.

Ok, Ccing that list ...

> > I want to build an as big as possible babel network quite soon and 
> > I'd like to get your input and perhaps also your help.
> That'd be great.
> > After discussing babel with other people from funkfeuer I belive
> > our main concern is if babel will scale to big networks with
> > jumpy metric values - especially if the metric values are distributed
> > over a wide range.
> If it doesn't, we'll fix it.


> > Unfortunately we can't deploy babel on enough routers in our network
> > to have one big connected mesh, therefore I plan to connect several
> > small babel blobs via tunnels. I think you have a babel network at
> > your site too. I suggest that you participate in the experiment by
> > setting up some tunnels between your network and funkfeuer.
> Agreed.
> > There are some other constraints that we have to meet: Most of our
> > devices lack any support for IPv6 so for the purpose of the
> > experiment we are restricted to some subnet of or some
> > similiar setup.
> Hmm... the current implementation of Babel requires IPv6 in the kernel.
> (It does not require global IPv6 addresses, but IPv6 must be compiled into
> the kernel.)

So on an openwrt router you need kmod_ipv6 installed ... we have such
a setup (using 6to4 and radvd) on some experimental nodes and it works
very well - even on freifunkfirmware based nodes, but of course it
takes some RAM.

With olsrd and ipv6 and babel and openvpn or vtun and $monitor_tool
running on the same mesh node we will most likely hit the RAM limit.
It sure can be done, but it might take some extra work to save the RAM

OTOH if we need IPv6 support in the kernel anyway, then I don't see
a reason not to do the whole experiment in IPv6 space - but perhaps
I miss something.

> > * Make some packages at least for openwrt kamikaze and freifunkfirmware
>  >  (used on most of our devices) which implement the above
> I finally got commit rights into OpenWRT, so expect a fixed Babel package
> really soon.

That would be nice. Anyway I guess I'll compile a custom babel-0xff
package with everything setup specifically for the experiment to
make it easier for $random_node_admin to participate.
> My experimental net uses the range, so please don't use that.

At Funkfeuer we consider anything in to be reserved for
whatever the local admin wants to do in the network behind his node
so that shouldn't be a problem. And if we really can/must use IPv6 space
then there won't a problem anyway ...

> > would setup babel to write to it's own routing table and have some
> > policy rules to select this table for the ip range we select but nothing
> > else.
> What about simply making sure that Babel only installs route in this range?
> Assuming your prefix is, ust put something like this in
> /etc/babel.conf:
>   in ip allow
>   in deny

That's a possibility too and as long as babel uses a different proto tag
than olsrd its routes should be save but still there would be strange
effects if somebody announced some ip in olsr - which
we can't prohibit. AFAICS babel already provides everything required so I 
guess it is easier to set up some policy rules than to debug the
cartesian product of the bugs of two routing daemons. 


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