IP multicast support in MPLS

Multicast support in an MPLS (multiprotocol label switching) network has yet to be defined. An MPLS network consists of label switching devices such as ATM. This document discusses both dense-mode and sparse-mode IP multicast within the context of an MPLS network. Unlike unicast routing, dense-mode multicast routing trees are established in a data-driven manner and it is not possible to topologically aggregate such trees, which are rooted at different sources. In sparse-mode multicast, source-specific trees may coexist with a core/shared tree, and it is not possible to assign a common label to traffic from different sources on a branch of the shared tree. This leads us to suggest a per-source traffic-driven label allocation scheme for supporting all three types of multicast (dense mode, shared tree, source tree) routing trees in an MPLS network.