Re: V4 via V6 and IGP routing protocols

[Dave Taht <dave.taht () gmail com>]

On Sun, Apr 3, 2022 at 12:04 PM Mark Tinka <mark@tinka.africa> wrote:
> On 4/3/22 13:55, Dave Taht wrote:
>
> > Periodically I still do some work on routing protocols. 12? years ago I had kind
> > of given up on ospf and isis, and picked the babel protocol as an IGP
> > for meshy networks because I felt link-state had gone as far as it
> > could and somehow unifying BGP DV with an IGP that was also DV
> > (distance vector) seemed like a path forward.
>
> To scale the IGP, we only carry Loopbacks and interfaces (backbone
> infrastructure) in the IGP. Many operators have been doing this, for
> some time now, as a best pratice.
>
> Customer routes as well as the DFZ is carried in iBGP.
>
> The only issue we have hit with this design is hardware that ships with
> limited FIB (you're talking 4,000 slots or less). While this can be
> mitigated with things like 6PE and RFC 3107, there are, now, tons of
> hardware shipping without this physical restriction. For me, the
> simpler, the better.
>
>
> > My question for this list is basically, has anyone noticed or fiddled
> > with babel? It's supported
> > in FRR, bird, and a very small standalone daemon.
>
> Never heard of it as an IGP until now :-).

We'd somewhat foolishly made it a requirement in ietf homenet.

it was how hard adding source specific routing to isis turned out to
be that turned me.
At the time I needed simple means to get ipv6 working on multiple
consumer uplinks.

That later spawned a now mostly dead attempt to unify ipv4 and ipv6
address distribution
called hnet.

I'm fiddling with the new ipv4 over ipv6 stuff now in trying to
interconnect several ipv4
networks over multiple p2p links.

> Googl'ing:
>
>      https://en.wikipedia.org/wiki/Babel_(protocol)
>
>
> > To recap that:
> >
> > "V4-via-v6 routing is a routing technique that allows routers with
> > only IPv6 addresses (including link-locals) to forward IPv4 packets.
> > It doesn't involve encapsulation (tunnelling), it doesn't involve
> > translation (NAT), it just works.  For details, please see
>
> Since around Junos 9 (2007), OSPFv3 shipped with the ability to carry
> IPv4 NLRI over an IPv6-only network. We never did implement that, as
> IS-IS integrated both protocols already. But it's been there for a while
> for OSPFv3.
>
> I don't know when (or if) other vendors implemented the same thing for
> OSPFv3.
>
> That said, nearly any OSPF house I'm aware of still runs both OSPFv2 and
> OSPFv3 side-by-side. I guess folk are probably unprepared to use OSPFv3
> for IPv4 NLRI.

I'm sad to hear that those two still have to co-exist. I'd given up on
how static
both routing protocols had become in light of my wireless requirements way
back then, also memory requirements. Babel had turned out to be the only
way to get teeny routers to route a few thousand ipv6 routes as well
as ipv4 over wifi mesh networks.

I figured it had made zero penetration outside of that world despite
our efforts to get it into frr, bird, etc.

> Mark.



-- 
I tried to build a better future, a few times:
https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org

Dave Täht CEO, TekLibre, LLC