6.3.1 Protocol Overview

# 6.3 Multicast Protocol Statements

## 6.3.1 Protocol Overview

## 6.3.2 Intra-Domain Routing Protocols

Intra-Domain Routing protocols are used to exchange reachability information within an autonomous system (AS). They are referred to as a class by the acronym igp. There are two intra-domain routing protocols currently supported by this version of GateD:

DVMRP
  Distance Vector Multicast Routing Protocol (DVMRP) is the original IP Multicast routing protocol. It was designed to run over both multicast capable lans (like Ethernet) as well as through non-multicast capable routers. In this case, the IP Multicast packets are "tunneled" through the routers as unicast packets. This replicates the packets and has an effect on performance, but has provided an intermediate solution for IP Multicast routing on the Internet while router vendors decide to support native IP Multicast routing.

PIM-DM

> PIM Dense Mode provides multicast routing for a densely populated group. A PIM Dense Mode implementation is planned for Gated, but not yet implemented.

PIM-SM
  PIM Sparse Mode (PIM-SM) provides efficient routing for a group distributed sparsely across a wide area.

CBT
  Core Based Trees (CBT) like PIM-SM provides a mechanism for creating shared delivery trees for multicast groups. Shared trees allow for a single tree per multicast group (*,G) instead of trees based in each source-group pair (S,G). CBT depends on existing multicast routing to provide a route to do the Reverse Path Forwarding. In contrast, DVMRP passes this set of routes within the protocol.

## 6.3.3 Inter-Domain Routing Protocol

BGP for Multicast - protocol not ready yet

## 6.3.4 Other Routing Protocols

## 6.3.5 Other Support

IGMP
Internet Group Management Protocol (IGMP) was primarily designed for hosts on multi-access networks to inform locally attached routers of their group membership information. This is performed by hosts multicasting IGMP Host Membership Reports. Multicast routers listen for these messages and can then exchange group membership information with other multicast routers. This allows distribution trees to be formed to deliver multicast datagrams.

Last updated April 26, 1997 (11:59AM)

gated@gated.merit.edu