TMS zl Management and Configuration Guide ST.1.0.090213

9-55

Routing

Multicast

Many emerging applications rely on delivering the same information to many

hosts. LAN TV, video conferencing, collaborative computing, and desktop

conferencing all involve transmitting a great deal of information from a source,

or many sources, to many hosts. Email systems can more efficiently deliver

mail to multiple servers simultaneously rather than one by one. Increasingly,

such technologies are turning from delivering information through multiple

point-to-point sessions to delivering it through multipoint communication.

IP multicasting allows hosts to send messages to multiple hosts simultane-

ously. Hosts join multicast host groups to be become eligible to receive

specific multicasts. The TMS zl Module supports the routing of such multicasts

using Protocol Independent Multicast-Sparse Mode (PIM-SM) supported by

Internet Group Multicast Protocol (IGMP).

LANs, which are often Ethernet networks, are usually broadcast networks:

hosts can transmit messages to every other host on the network. When a host

sends a broadcast message to all other hosts in the subnet, the destination

address in the packet’s IP header is the subnet’s broadcast address—typically,

the network address with all ones for the host bits. The host can send a

broadcast message to all subnets by sending a broadcast to 255.255.255.255.

(See Figure 9-20.)

Figure 9-20. Broadcasting