TE-WG draft-lee-mpls-path-request-00.txt

[Cheng-Yin Lee <clee@paragon-networks.com>]

NAME OF I-D: 
http://search.ietf.org/internet-drafts/draft-lee-mpls-path-request-00.txt


SUMMARY
The draft describes a scalable approach, using a path query
message/signalling
to obtain constrained routes (including diverse routes) in a flat
network(eg single area) or multiple hierarchy networks (e.g multiple
areas in OSPF). 
Without a similar approach, in order to compute diverse routes
spanning multiple areas, either TE LSAs are flooded in the whole AS (all
areas) or all the TE LSAs must be downloaded from all areas. The
approach describes in this draft allows a router to query routers (e.g.
Area Border Routers), which have the TE link state information necessary
to compute the disjoint route. A router may also query another router
within an area if it is not capable of doing certain path computation or
if it does not have the required information to compute a constrained
route within an area.

RELATED DOCUMENTS


http://www.ietf.org/internet-drafts/draft-ash-ccamp-multi-area-te-reqmts
-00.txt

http://search.ietf.org/internet-drafts/draft-kompella-mpls-multiarea-te-
01.txt
draft-dharanikota-interarea-mpls-te-ext-01.txt
draft-venkatachalam-interarea-mpls-te-00.txt
http://search.ietf.org/internet-drafts/draft-lee-mpls-te-exchange-01.txt

WHERE DOES IT FIT IN THE PICTURE OF THE SUB-IP WORK

It fits in the TE-WG.

  Applications         +-------+  +-------+        (new) Hour glass
  that use CCAMP: \    | TE-WG |  | PPVPN |  ...           /
                   \   +-------+  +-------+               /
                    \     +----------------------+       /
                     \    |         CCAMP        |      /
                      \   |-----------+----------|     /  
                      /   |   C       |    M   --|------ IGP LSA ext
                     /    | control   | measure  |     \  
                    /     +----------------------+      \
  Technologies to  / +----+ +----+ +----+ +----+ +----+  \
  measure/control:/  |MPLS| |OPT | |RPR | |ATM | | FR |...\
                     +----+ +----+ +----+ +----+ +----+


WHY IS IT TARGETED AT THIS WG

>From the charter of TE-WG:
"The working group also serves as a general forum for discussing
improvements to IETF protocols to advance the traffic engineering
function. 

The working group may also consider the problems of traffic engineering
across autonomous systems boundaries."

The draft provides a means to obtain constrained route in a scalable
manner within an area and in multiple areas, enabling diverse route
computation in multiple areas and improving the scalability of the TE
function, in general. The approach is also applicable to TE across
AS.


JUSTIFICATION

There were discussions in the TE WG about this draft. The consensus was
such a mechanism is required. Some suggestions on the list were to
modify existing protocols (e.g SNMP, COPS, RSVP-TE, CR-LDP, BGP) for
this mechanism. The authors have looked into some of the suggested
protocols and is updating the draft on this issue.
In addition,
http://www.ietf.org/internet-drafts/draft-ash-ccamp-multi-area-te-reqmts-00.
txt describes initial requirements for protocol support of multi-area TE
of which a query functionality such as the one described in this draft
is required.