Subject: I-D ACTION:draft-lee-mpls-te-exchange-02.txt

From: [email-masked]
Date: Fri, 05 Jul 2002 06:34:00 -0400

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

	Title		: Distributed Route Exchangers
	Author(s)	: C. Lee, S. Ghanti, A. Celer, G. Ash
	Filename	: draft-lee-mpls-te-exchange-02.txt
	Pages		: 19
	Date		: 03-Jul-02
	
The  current  link  state  routing protocols flood link states to all
routers so that routers have the information required to compute  the
shortest  paths  to route packets on a hop by hop basis. However, for
the purpose of establishing MPLS paths, constraint  path  computation
is  only  performed at certain nodes, for instance, at the node where
path setup is triggered or  at  the  head-end  of  a  loosely  routed
segment  that  crosses  a network (or area) boundary. In addition, it
not possible to have all required constraints present in all nodes in
a  network,  nor  is it always feasible for nodes setting up paths to
compute the constraint paths themselves, a notable example is when  a
path  traverses  network  or area boundary.  These reasons motivate a
solution using a 'subset' of routers (called  route  exchangers),  to
collect  constraint  information  and  exchange  it  with other route
exchangers. Route exchangers store traffic  engineering  link  states
and  other types of constraint information and compute on demand, the
explicit routes required by routers establishing paths.  Hence,  link
state  information  need  only  be distributed to the subset of nodes
that help compute constraint paths in the network.

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