The MPLS WG Archive

[Bora Akyol <akyol@pluris.com>]

Markus Jork wrote:

> Bora,
>
> > When filling in the ERO, there are three options:
> >
> > 1) Put in the router ID of the routers. This does not work for cases
> > when routers have multiple links and for unnumbered interfaces.
> >
> > 2) Put in the egress interface of the routers on the path and finish it
> > with the router ID of the final router. So that from router A to router
> > B, we represent the hop as the IP address/interface index of the
> > interface from A to B on router A.
> >
> > 3) Put in the ingress interface of the routers on the path starting with
> > the router ID of ingress and finishing with the router ID of the egress
> > LSRs. This is kind of opposite of (2).
> >
> > I believe that (2) is the only option that works with unnumbered
> > interfaces.
> >
> > Does anyone think otherwise?
>
> your option (1) will work when you only have a single link (which may
> be unnumbered) between the routers. Using router IDs in the
> ERO may also be useful in the presence of multiple links when you
> don't care which of the multiple links between a pair of routers will
> be used.
>

Thanks for pointing out the obvious which I have already stated in my previous
email. Next time, you may want to actually read the message before jumping on
the trigger ;-)

>
> I'm kind of confused about your option (2). Have you read
> draft-kompella-mpls-unnum or are you trying to reinvent it here?
>

Yes, and this is exactly why I think only option (2) would work, since only
the local router has information about its ifindex to interface mapping.

Bora