Chapter 6. Providing IPv6 Multicast Services

A wide range of applications used over all types of networks rely on delivering the same data from one source to multiple destinations. Examples of such applications are listed here, grouped together based on the network environments in which they are typically used:

• On enterprise networks Distribution of financial information such as stock quotes, distribution of news, videoconferencing, distance learning, delivery of content such as software updates

• On service provider networks Content delivery such as video and audio streaming, collaborative applications such as conferencing for enterprise customers, multiplayer gaming and chat for residential customers

Source replication of unicast streams for all destinations clearly is not a scalable approach from the source or network resources perspective. The proper solution to support such applications is to enable a network that can replicate the traffic as physically close as possible to the destinations, a multicast-enabled network. The growing number of multicast-based applications, and their increased importance to businesses and users, drives the demand for multicast services.

IPv4 multicast has evolved over a number of years. Multiple features and protocols were developed for it, and many of them were shelved based on the experience gained through deploying and operating the service. With the benefit of hindsight, IPv6 multicast builds on this experience. Features or protocols that were not deemed useful to IPv4 multicast were completely ignored in IPv6, as shown in Table 6-1. On the other hand, IPv6 leverages its address size and structure through new, specific features. The implementation is also cleaner or simpler at times because multicast was part of the IPv6 development from day one and avoided some constraints introduced by unicast features or concepts. In Table 6-1, IPv4 multicast features that are explicitly not considered in IPv6 are marked NC.

Table 6-1. Taxonomy of Multicast Protocols and Their Availability in IPv6

Protocol Function	Multicast Protocol	IPv4	IPv6
Group membership management	Internet Group Management Protocol (IGMP) v1, v2, v3	X
	Multicast Listener Discovery (MLD) v1, v2		X
Multicast support at layer 2	Snooping (IGMP or MLD)	X	X
	Cisco Group Management Protocol (CGMP)	X	NC
	Router Group Management Protocol (RGMP)	X
	GARP (Generalized Attribute Registration Protocol) Multicast Registration Protocol	X
Multicast routing	Protocol Independent Multicast-Dense Mode (PIM-DM)	X	NC
	Protocol Independent Multicast-Sparse Mode (PIM-SM)	X	X
	Protocol Independent Multicast-Source Specific Multicast (PIM-SSM)	X	X
	Protocol Independent Multicast-Bidirectional (PIM-Bidir)	X	X
	Pragmatic General Multicast (PGM)	X
Rendezvous point management	Static-RP	X	X
	Auto-RP	X
	Bootstrap router (BSR)	X	X
	Embedded RP		X
	Multicast Source Discovery Protocol	X	NC

Table 6-1 is not meant to be complete from a historical perspective. It intends only to summarize the most relevant multicast protocols of both IPv4 and IPv6. The IPv6-specific ones are discussed in the remainder of this chapter. It is assumed that the reader is familiar with the IPv4 multicast concepts. Some of these concepts are briefly described here, but for a complete and detailed presentation, refer to the Cisco Press book Developing IP Multicast Networks, Volume 1.

This chapter covers the following topics:

• A review of IP multicast concepts and their implementation in IPv6

• IPv6 multicast deployment considerations

• Examples of configuring IPv6 multicast

By the end of the chapter, you will most likely conclude that, for the most part, IPv6 multicast is not dramatically different from its predecessor, but it enables cleaner service deployments.