Subject: I-D ACTION:draft-vasseur-mpls-ospf-pcsd-discovery-00.txt

From: [email-masked]
Date: Mon, 24 Jun 2002 07:47:53 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: RSVP Path computation request and reply messages
	Author(s)	: J. Vasseur, P. Psenak
	Filename	: draft-vasseur-mpls-ospf-pcsd-discovery-00.txt
	Pages		: 29
	Date		: 21-Jun-02
	
This document describes extensions to RSVP-TE to support a new 
message type called a 'Path computation' message.  This message is to 
be used between an LSR and a Path Computation Server, which may be an 
LSR or a centralized path computation tool. An RSVP Path Computation 
Request message is used by the head-end LSR to send its request to 
the Path Computation Server. The Path Computation Server in turn 
sends an RSVP Path Computation Reply message containing either: 
- a positive reply, containing one or more paths, if the request 
can be satisfied. 
- a negative reply if no path obeying the requested constraints 
can be found. The Path Computation Server may also optionally 
suggest new constraint values for which one or several paths 
could be found. 
There are many situations where a Path Computation Server may be 
used. A typical example is in the context of Inter-area MPLS TE. A 
head-end LSR could request that a Path Computation Server compute one 
or more paths obeying a specified set of constraints for a TE LSP 
spanning multiple areas. The path computation server could be a 
centralized path computation server or an ABR. Another example is the 
use of a Path Computation Server to compute diversely routed paths 
between two end points.  This may be useful in the context of MPLS TE 
LSP Path protection or GMPLS LSP Path protection. The computation of 
Multi-constraints paths requires intensive CPU resources, and may be 
yet another usage example. Lastly, those protocol extensions could be 
used as a 'UNI' like protocol between a CE (Customer Edge equipment) 
and a PE (Provider Edge equipment) where the CE is not part of the 
PE's IGP domain.

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