RE: TE Requirements Draft - ELSP

[Francois Le Faucheur <flefauch@cisco.com>]

Giovana,

At 10:36 22/11/2001 +0100, Giovanna Piantanida (ERI) wrote:
>Hi Francois,
>
>
> >Great. So I guess you would then agree we should first get SPs to express
> >the need for something before including it in the requirements document and
> >specifying the correponding extensions.
>
>not only I agree, but also I notice that you come exactly to the point ( 
>to my point at
>least) originating this discussion.
>What I think I was misled about , and beg for clarification, is , in fact, 
>not purpose and motivation for E-LSP
>themselves , but for extension of a
>DIFFSERV object for an E-LSP (Ref. section 5.2.1 of 
>draft-ietf-mpls-diff-ext-09), even if
>only optional, in the framework we all agree about.
>
>
> >1) using E-LSPs with traffic from a single OA:
> >==============================================
> >This is already explicitely allowed in the recently posted REQTS draft.
> >As pointed out already, one application for this to allow LSRs to pick
> >queues based on EXP rather than Label.
> >I think everyone agrees this is all fine.
>
>A SP using DIFFSERV object would need LSRs to pick up queues based on (EXP 
>, label)
>couples, and this cancels, in my opinion, advantages of this first point.

But the SP can use "normal" E-LSPs (ie the "E-LSP with default EXP<-->PHB 
mapping as per diff-ext-09). So there is no need to signal the DIFFSERV 
object in that case and the queue can be picked directly from EXP; just 
like SPs actually do today in real life networks.

>
> >2) using E-LSPs with traffic from multiple OAs but using single CSPF
> >=====================================================================
> >Jim Boyle provided a convincing example of how this could be used in his 19
> >Sept message (ie in the case where ratio between voice-sig and
> >voice-payload is known and stable so both traffic can be treated together
> >as a whole from CSPF viewpoint).
> >The important point is that although we have traffic from multiple OAs,
> >those are really treated as a single "traffic trunk" from the DSTE 
> perspective.
>
>At first sight, and here is probably where I am missing something, I would
>have said that having a dynamic establishment of EXP <-> PHB mapping could
>complicate things in this case also.

Again, the SP can use "normal" E-LSPs (ie the "E-LSP with default 
EXP<-->PHB mapping as per diff-ext-09). So there is no need for dynamic 
establishment of EXP<-->PHB mapping in that case either.

>this is why i was induced to think that reason for having DIFFSERV object
>in current extensions was that somebody exists who really wants to follow 
>point #3
>
> >3) using E-LSPs with traffic from multiple OAs each with their own SPF
> >======================================================================
> >In that case, EF and AF1 may be transported on a single E-LSP and would
> >each have their own CSPF (ie own bandwidth, and being constrained by
> >different bandwidth constraints, and then presumably with different
> >restoration requirements, most probably different preemption 
> priorities,...).
>
>and assuming  therefore as hypothesis, not as consequence, that such SPs 
>exists,

We certainly agree that IF there are such SPs, THEN corresponding protocol 
extensions should be specified (BTW I think it would actually require more 
than just per-OA bandwidth eg. also per-OA affinity and per-OA preemption; 
basically per-OA everything; otherwise it would just be halfway there and 
you couldn't really do proper per-OA CSPF).

Based on the top of this message I think we also agree that IF such SPs do 
NOT cleary exist today, THEN we should NOT specify those extensions today.

Cheers

Francois

>per-OA signaling of bandwidth in E-LSP could be aimed to them, and this is why
>it could be worth considering solutions for that,
>
>regards,
>giovanna
>
>

_________________________________________________________
Francois Le Faucheur
Development Engineer, IOS Layer 3 Services
Cisco Systems
Office Phone:          +33 4 97 23 26 19
Mobile :               +33 6 89 108 159
Fax:                   +33 4 97 23 26 26
Email:                 flefauch@cisco.com
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