Multipoint LDP (mLDP) In-Band Signaling with Wildcards
This RFC 7438 was published in 2015
There are scenarios in which an IP multicast tree traverses an MPLS domain.
In these scenarios, it can be desirable to convert the IP multicast tree "seamlessly" into an MPLS Multipoint Label Switched Path (MP-LSP) when it enters the MPLS domain, and then to convert it back to an IP multicast tree when it exits the MPLS domain.
Previous documents specify procedures that allow certain kinds of IP multicast trees (either Source-Specific Multicast trees or Bidirectional Multicast trees) to be attached to an MPLS Multipoint Label Switched Path (MP-LSP).
However, the previous documents do not specify procedures for attaching IP Any-Source Multicast trees to MP-LSPs, nor do they specify procedures for aggregating multiple IP multicast trees onto a single MP-LSP.
This document specifies the procedures to support these functions.
It does so by defining "wildcard" encodings that make it possible to specify, when setting up an MP- LSP, that a set of IP multicast trees, or a shared IP multicast tree, should be attached to that MP-LSP.
Support for non-bidirectional IP Any-Source Multicast trees is subject to certain applicability restrictions that are discussed in this document.
This document updates RFCs 6826 and 7246.
RFC 7438 introduction
[RFC6826] and [RFC7246] specify procedures for mLDP (Multipoint LDP) that allow an IP multicast tree (either a Source-Specific Multicast tree or a Bidirectional Multicast tree) to be attached "seamlessly" to an MPLS Multipoint Label Switched Path (MP-LSP).
This can be useful, for example, when there is multicast data that originates in a domain that supports IP multicast, which then has to be forwarded across a domain that supports MPLS multicast and then has to forwarded across another domain that supports IP multicast.
By attaching an IP multicast tree to an MP-LSP, data that is traveling along the IP multicast tree can be moved seamlessly to the MP-LSP when it enters the MPLS multicast domain.
The data then travels along the MP-LSP through the MPLS domain.
When the data reaches the boundary of the MPLS domain, it can be moved seamlessly to an IP multicast tree.
This ability to attach IP multicast trees to MPLS MP-LSPs can be useful in either VPN context or global context.
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