Subject: RE : [Pce] Requirement for less-constrained path indraft-ietf-pce-comm-protocol-gen-reqs-00.txt

From: "LE ROUX Jean-Louis RD-CORE-LAN" <[email-masked]>
Date: Mon, 11 Jul 2005 19:18:17 +0200

Hi Eric,

It seems that this is a well knwow MPLS-TE problem. When one cannot find a path satifying a set of constraints it tries to relax some constraints. IMHO communication of less constrained path is at least a "SHOULD" requirement... This will avoid useless PCC-PCE round trips.

>is very likely to push both the process of coming up with
>any proposed solution that meets this requirement

This is IMHO a simple problem (at least w.r.t the communication protocol, for the algorithm this is another issue but out of the scope of this draft) and we can find simple ways to address it. I don't think that there are so many solutions to address this requirement in the communication protocol. Anyway this is not our problem in a requirement draft...

> - and yet
>remains scalable - and the process of getting agreement for 
>any such proposed solution.

I don't actually see why this should make us renounce to this requirement...

>	I suggest that we might want to better understand the specific 
>customer need - and what the customer is willing to sacrifice in other 
>areas - before we include something like this as a requirement.

Detailed motivations and needs will be addressed in the requirement doc

Best Regards,

JL

>-----Message d'origine-----
>De : [email-masked] 
>[mailto:[email-masked]] De la part de Gray, Eric
>Envoyé : lundi 11 juillet 2005 17:08
>À : 'Ash, Gerald R (Jerry), ALABS'; JP Vasseur
>Cc : [email-masked]
>Objet : RE: [Pce] Requirement for less-constrained path 
>indraft-ietf-pce-comm-protocol-gen-reqs-00.txt
>
>
>Jerry & JP,
>
>	I am not so sure that this should be a requirement.
>
>	Requiring the protocol to support finding alternate
>paths (by a near-arbitrary collections of fuzzy parameters)
>is very likely to push both the process of coming up with 
>any proposed solution that meets this requirement - and yet 
>remains scalable - and the process of getting agreement for 
>any such proposed solution.
>
>	I suggest that we might want to better understand the
>specific customer need - and what the customer is willing 
>to sacrifice in other areas - before we include something 
>like this as a requirement.
>
>	Short of getting that information, simply stating that 
>this might be a preference - or a desirable goal - is about
>as strong as I would put it.
>
>--
>Eric
>
>--> -----Original Message-----
>--> From: [email-masked]
>--> [mailto:[email-masked]]On
>--> Behalf Of Ash, Gerald R (Jerry), ALABS
>--> Sent: Monday, July 11, 2005 7:27 AM
>--> To: JP Vasseur; [email-masked]
>--> Subject: RE: [Pce] Requirement for less-constrained path
>--> indraft-ietf-pce-comm-protocol-gen-reqs-00.txt
>--> 
>--> 
>--> Hi JP,
>--> 
>--> > Quick question ... I do not see any requirement to get less-
>--> > constrained TE LSP path in 
>--> > draft-ietf-pce-comm-protocol-gen-reqs-00.txt.
>--> > In most of the cases, when configuring a TE LSP with specific  
>--> > attributes, one of the most challenging part consists of 
>--> determining
>--> > the attributes values which will not result in the
>--> inability to find
>--> > a path in some circumstances (such as network element
>--> failures). The
>--> > typical case is the bandwidth. The first approach is to try to
>--> > compute the "closest" solutions. Another approach relies on the  
>--> > configuration of multiple set of attributes:
>--> > 1) The preferred set of attributes
>--> > 2) One or more less-preferred set of attributes
>--> > 3) Un-constrained TE LSP
>--> > 
>--> > When a PCE is used for TE LSP path computation, it looks
>--> to me that
>--> > it could be quite useful to be able to specify interest in less-
>--> > constrained path rather than potentially have to 
>--> configure a set of
>--> > attributes (less optimal) which would result in several
>--> > rounds of PCC/ 
>--> > PCE communication.
>--> > 
>--> > Isn't it a requirement that should be listed in
>--> draft-ietf-pce-comm-
>--> > protocol-gen-reqs-00.txt?
>--> 
>--> Sounds OK to me.  It would help if you suggested some
>--> specific text to
>--> insert in the updated draft sent out last Thursday.
>--> 
>--> Thanks,
>--> Jerry
>--> 
>--> _______________________________________________
>--> Pce mailing list
>--> [email-masked] https://www1.ietf.org/mailman/listinfo/pce
>--> 
>
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