Subject: RE: draft-raggarwa-rsvpte-pw-01.txt

From: [email-masked]
Date: Wed, 23 Mar 2005 20:33:39 -0000

Tom....There is a significant difference between a session protocol and
a signalling protocol.  A session protocol only needs to touch the 2 end
node points, a signalling protocol however needs to touch all the nodes
involved in creating the trail.  Why is targeted LDP not used for the
co-cs mode technologies in GMPLS?  Its because they needed a signalling
protocol (one might argue whether RSVP-TE is the best-of-breed
signalling protocol, but that is another matter).  Further, the co-cs
mode forces this to run OOB which is also a good thing for many reasons.

MPLS uses a wrapper to construct hierarchy.  This has some serious arch
issues that I am not going to re-open here.  However, the wrapper
behaviour has been latent to date...MH-PWs however expose it.  In the
case of SH-PWs there was only 1 networked LSP....the top LSP was there
to do little more than than take-on a demerging role as a single hop
entity {But in a proper client/server relationship you don't actually
need 2 stacked server layer trails}.  In such a case targeted LDP
therefore takes on a session-like protocol role and things can be made
to work.  Move to MH PWs however and you have now created a networked PW
entity that lies above (ie is a client of) the lower networked MPLS LSP
entity (or the networked IP/L2tpv3 entity).

There are many things that are wrong with how things have arrived at the
point they are now at. {In a different thread, I also note Dave McDysan
circling round the problem that this new PW layer network needs access
point addresses...and that many other processes, eg in NMS/OSS, may want
to use these IDs}  Indeed, IMO a PW layer network had no need to be
created.....but the reasons for this are now all historical and I doubt
many have the stomach to really address the deeper reasons WHY its ended
up like this.

However, the fact is if you want a signalling protocol then the only one
available in IETF at the present time is RSVP-TE.  And as I have already
noted in a different post, it makes a great deal of sense (looking at
this as an operator) to try and re-use the same signalling solution
(with appropriately tailored messages for the mode) for both the co-cs
and co-ps modes.

Now CR-LDP has been removed from the table there is only RSVP-TE that
fits this role.  That is simply a fact.

regards, Neil

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Thomas D. Nadeau
> Sent: 23 March 2005 15:41
> To: Stewart Bryant
> Cc: pwe3
> Subject: Re: [PWE3] draft-raggarwa-rsvpte-pw-01.txt
> 
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> 
> 	Personally speaking, I don't think that it is useful
> for the WG to spend time and effort re-inventing
> the wheel, so to speak, which is what this draft
> represents. We already have a protocol for
> signaling PWs that works, and is deployed. If
> there were some significant advantage to signaling
> PWs using an alternative means, I would think
> otherwise, but it seems this is just being proposed
> as an alternative means for achieving the same
> end result.
> 
> 	--Tom
> 
> 
> 
> > At IETF62 the authors of
> >
> > Setup and Maintenance of Pseudowires using RSVP-TE 
> > ftp://www.ietf.org/internet-drafts/draft-raggarwa-rsvpte-pw-01.txt
> >
> > asked for the draft to become a WG draft.
> >
> > What is the view of members of the PWE3 WG?
> >
> > Stewart
> >
> > _______________________________________________
> > pwe3 mailing list
> > [email-masked]
> > https://www1.ietf.org/mailman/listinfo/pwe3
> >
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.2.4 (Darwin)
> 
> iD8DBQFCQY4dHwfkLUURkkwRAgbtAJ9Bpc/zSm0TungLQ/LOQOD8VXDr+ACfXkWS
> obq/1BEDNhqeTW+u8DzaYGU=
> =s7XE
> -----END PGP SIGNATURE-----
> 
> _______________________________________________
> pwe3 mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/pwe3
>