This section and its subsections focuses on Multicast in IP VPN functionality. Refer to the 7450 ESS, 7750 SR, 7950 XRS, and VSR Multicast Routing Protocols Guide for information about multicast protocols.
Applications for this feature include enterprise customer implementing a VPRN solution for their WAN networking needs, customer applications including stock-ticker information, financial institutions for stock and other types of trading data and video delivery systems.
Implementation of multicast in IP VPNs entails the support and separation of the providers core multicast domain from the various customer multicast domains and the various customer multicast domains from each other.
Figure 1 depicts an example of multicast in an IP-VPN application. The provider’s domain encompasses the core routers (1 through 4) and the edge routers (5 through 10). The various IP-VPN customers each have their own multicast domain, VPN-1 (CE routers 12, 13 and 16) and VPN-2 (CE Routers 11, 14, 15, 17 and 18). Multicast in this VPRN example, the VPN-1 data generated by the customer behind router 16 will be multicast only by PE 9 to PE routers 6 and 7 for delivery to CE routers 12 and 13 respectively. Data generated for VPN-2 generated by the customer behind router 15 will be forwarded by PE 8 to PE routers 5, 7 and 10 for delivery to CE routers 18, 11, 14 and 17 respectively.
The demarcation of these domains is in the PE’s (routers 5 through 10). The PE router participates in both the customer multicast domain and the provider’s multicast domain. The customer’s CEs are limited to a multicast adjacency with the multicast instance on the PE specifically created to support that specific customer’s IP-VPN. This way, customers are isolated from the provider’s core multicast domain and other customer multicast domains while the provider’s core routers only participate in the provider’s multicast domain and are isolated from all customers’ multicast domains.
The PE for a given customer’s multicast domain becomes adjacent to the CE routers attached to that PE and to all other PE’s that participate in the IP-VPN (or customer) multicast domain. This is achieved by the PE who encapsulates the customer multicast control data and multicast streams inside the provider’s multicast packets. These encapsulated packets are forwarded only to the PE nodes that are attached to the same customer’s edge routers as the originating stream and are part of the same customer VPRN. This prunes the distribution of the multicast control and data traffic to the PEs that participate in the customer’s multicast domain. The Rosen draft refers to this as the default multicast domain for this multicast domain; the multicast domain is associated with a unique multicast group address within the provider’s network.