Ip Multicasting - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

IP multicasting allows hosts to send messages to multiple hosts simulta-
neously. Hosts join multicast host groups to be become eligible to receive
specific multicasts. The ProCurve Secure Router supports the routing of such
multicasts using either PIM-SM or IGMP proxy.

IP Multicasting

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 10-1.)
Network 1
192.168.1.0/24
Figure 10-1. Broadcasting
It is not hard to imagine the challenges broadcast messages pose for packet
containment. A malfunctioning or misconfigured device can congest an entire
network. Even properly functioning devices must flood all hosts with unnec-
essary information just to send a message to the hosts that do need it.
IP multicasting addresses these problems by allowing a host to send a message
to a select group.
Configuring Multicast Support for a Stub Network
Packet destination
192.45.1.255
Switch
Router
Switch
Overview
10-3