Constructing protection paths for inter-AS, inter-sub-AS P2MP TE-LSPs

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Last updated 2013-07-29 (latest revision 2013-01-25)
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Constructing primary and backup explicit path Point-to-Multipoint Label Switched Paths is important from the point of view of providing protection switching in case the primary fails. It is absolutely essential that the backup P2MP LSPs constructed do not share risk with any of the links and nodes of the primary path. In the case of inter-AS P2MP TE-LSPs or in the case of inter-sub-AS (in the case of BGP-Confederations being deployed) P2MP TE-LSPs where BGP confederations are deployed within an AS, such protection switching can be provided by calculating primary and backup multicast distribution trees (read P2MP TE-LSPs) that dont intersect with each other. In this paper we propose a method by which inter-sub-AS P2MP TE-LSPs (hence even inter-AS P2MP TE-LSPs) can be constructed by first finding the AS level topology of the network (be it inter-AS or inter-sub-AS within a single AS) in question and secondly to compute the paths in such a way that they dont intersect or if necessary in the worst case partially intersect each other. The proposed scheme is explained with an example and subsequent discussion is done to elucidate its benefits to multicast in particular.


Shankar Raman (
Balaji Venkat (
Gaurav Raina (

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