Cisco Systems 78-11741-02 manual IPC-434

Configuring IP Multicast Routing

Configuring IP Multicast over ATM Point-to-Multipoint Virtual Circuits

In order for the Express RTP Header Compression feature to work, the following conditions must exist:

•CEF switching or fast switching must be enabled on the interface.

•HDLC, PPP, or Frame Relay encapsulation must be configured.

•RTP header compression must be enabled.

The Express RTP Header Compression feature supports the following RFCs:

•RFC 1144, Compressing TCP/IP Headers for Low-Speed Serial Links

•RFC 2507, IP Header Compression

•RFC 2508, Compressing IP/UDP/RTP Headers for Low-Speed Serial Links

Configuring IP Multicast over ATM Point-to-Multipoint Virtual Circuits

IP multicast over ATM point-to-multipoint virtual circuits (VCs) is a feature that dynamically creates ATM point-to-multipoint switched virtual circuits (SVCs) to handle IP multicast traffic more efficiently.

The feature can enhance router performance and link utilization because packets are not replicated and sent multiple times over the ATM interface.

Traditionally, over NBMA networks, Cisco routers would perform a pseudobroadcast to get broadcast or multicast packets to all neighbors on a multiaccess network. For example, assume in Figure 71 that routers A, B, C, D, and E were running the Open Shortest Path First (OSPF) protocol. Router A must deliver to Routers D and E. When Router A sends an OSPF hello packet, the data link layer replicates the hello packet and sends one to each neighbor (this procedure is known as pseudobroadcast), which results in four copies being sent over the link from Router A to the multiaccess WAN.

Cisco IOS IP Configuration Guide

IPC-434