Content

| 7.3 |  | Routing Multicast Traffic |
| 7.3.9 |  | Sparse mode routing protocols |

The second approach to multicast routing is based on the assumption that the multicast group members are sparsely distributed throughout the network and bandwidth is not necessarily widely available.

It is important to note that sparse mode does not imply that the group has a few members, just that they are widely dispersed. In this case, flooding would unnecessarily waste network bandwidth and could cause serious performance problems. Therefore, sparse-mode multicast routing protocols must rely on more selective techniques to set up and maintain multicast trees. Sparse-Mode protocols begin with an empty distribution tree and add branches only as the result of explicit requests to join the distribution.

Sparse-mode routing protocols include the following:

- Core-Based Trees (CBT)
- Protocol Independent Multicast Sparse Mode (PIM SM)

Because SM protocols assume that relatively few routers in the network will be involved in each multicast, these protocols are more appropriate in WAN environments.