Chapter 15 - Multicast and Point-to-Multipoint

Abstract

Multicast services are becoming increasingly popular with the MPLS network providers' customers. VPN services demand multicast support, and IP multicast must be carried across the MPLS backbone. Further, new services, such as video distribution, are entering the market, and the network operator needs efficient, and effective mechanisms to deliver them across an MPLS network. The IETF has recently been working to develop MPLS protocol extensions to facilitate the installation of P2MP LSPs within an MPLS network. MPLS-TE extensions have been completed, with RSVP-TE now able to set up P2MP LSP tunnels. The extensions to LDP are also well advanced, allowing P2MP LSPs to be constructed that follow the routing information within the network.LDP-enabled LSRs learn where to install labels based on the information distributed by the IP routing protocols, and the labels advertised by LDP. Basic LDP LSPs actually have a multipoint-to-point structure in the forwarding plane because traffic that converges on a destination is allocated the same label.The definition of a new Forwarding Equivalence Class (FEC) protocol element encodes a description of the multicast flow as identified by the source node or root of the P2MP tree, and a set of opaque elements that can be used by an application to distinguish different flows, and uses from the same root.