The MPLS WG Archive

["Cheng-Yin Lee" <leecy@nortelnetworks.com>]

Hello,
Jim Boyle suggested posting a ptr to this draft (available at the ietf
site) on the list.

There are two main aspects to this proposal on using distributed
constraints/route servers.
The first one enables path setup across network boundaries regardless of
whether aggregated constraint routes are available or not.  Since a node
may not have enough information (some constraint information is lost in
route summarization, however not summarizing is not a practical nor
desirable option either) to compute a path across network boundaries,
the proposal allows nodes to request the constraint path from nodes who
knows (eg the transit area border router) instead of computing the
inter-area path themselves. The path request could be recursed to the
transit inter-domain border router. If aggregated constrained routes are
available, the transit border router for the constrained path to the
destination may be queried, otherwise the transit border router for the
'shortest path' to the destination may be queried.

If an area border router could provide the constraint path across area,
then a node could request the area border router for any paths including
intra-area paths as well. If that is the case then it is not necessary
to flood constraint information to all nodes in the network, this is the
second optimization.

The most immediate application of this proposal as quite a number of
people suggested is in inter-area path setup. In addition, the proposal
is also motivated by the issues concerning optical networks eg wrt
flooding constraints out many ports , the feasibility of distributing
optical constraints across network boundaries, especially in the
inter-domain. These aspects may interest the Optical group as well.

The url for the proposal is at

http://ftp.ietf.org/internet-drafts/draft-lee-mpls-te-exchange-00.txt

and a related short draft on the path request message at

http://homepages.go.com/~lcyn/draft-lee-mpls-path-request-00.txt

cheers,
cyl