Subject: Unnumbered links in non-GMPLS scenario

From: [email-masked]
Date: Fri, 08 Feb 2002 15:03:22 +200

Hi,
I have two questions regarding usage of unnumbered links in plain MPLS (non-GMPLS) scenario:

1) Draft draft-ietf-mpls-rsvp-unnum-03.txt assumes that LSRs exchange local identifiers assigned to their unnumbered links. Why is it necessary in non-GMPLS scenario ? By non-GMPLS scenario I mean the case when RSVP messages are exchanged on the unnumbered links (data channel is the same as control channel).

2) How LSRs can exchange local ids assigned to their unnumbered not using LMP? In my opinion, OSPF is unsufficient because it does not allow to match identifiers assigned to many parallel unnumbered links (i.e. connecting the same two LSRs).  

Thanks,

Ania

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From: Yakov Rekhter <[email-masked]>
Date: Sun, 10 Feb 2002 11:58:41 -0800

Ania,

> I have two questions regarding usage of unnumbered links in plain
> MPLS (non-G MPLS) scenario:
> 
> 1) Draft draft-ietf-mpls-rsvp-unnum-03.txt assumes that LSRs exchange
> local identifiers assigned to their unnumbered links. Why is it
> necessary in non-GMPLS scenario ? By non-GMPLS scenario I mean the
> case when RSVP messages are exchanged on the unnumbered links
> (data channel is the same as control channel).

It was agreed that one always use the IF_ID HOP object on an
unnumbered link (see e-mail to the MPLS mailing list on 11/2/2001).
And if you use the IF_ID HOP object, then the choice of the data
interface is indicated by the upstream node using addresses and
identifiers used by the upstream node.

> 2) How LSRs can exchange local ids assigned to their unnumbered
> not using LMP ? In my opinion, OSPF is unsufficient because it does
> not allow to match identifiers assigned to many parallel unnumbered
> links (i.e. connecting the same two LSRs).

I think that saying that OSPF is "unsufficient" may be a bit strong.
It would be fair to say though that we don't have yet an OSPF
mechanism to do this. But it doesn't mean that such a mechanism
can't exist - it means that we just haven't specified it.

Yakov.