Name: draft-vasseur-mpls-computation-rsvp-05
Title: RSVP Path computation request and reply messages
State: Active
Authors: Jean Vasseur
Group: Individual Submissions (none)
Date: 2004-07-19
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 Element (PCE), 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 PCE. The PCE 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 PCE may also optionally suggest new constraint values for
which one or several paths could be found. There are many situations where
a PCE may be used. A typical example is in the context of Inter-area MPLS
TE. A head-end LSR could request that a PCE compute one or more paths
obeying a specified set of constraints for a TE LSP spanning multiple
areas. The PCE could be a centralized path computation Element or an LSR
such as an ABR or an ASBR. Another example is the use of a PCE 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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