Dell PowerConnect 7048P User Manual - Page 1138

Applications that often send multicast traffic include video or audio conferencing, Whiteboard tools, stock distribution tickers, and IP-based television (IP/TV). What Is IP Multicast Traffic? IP multicast traffic is traffic that is destined to a host group. Host groups are identified by class D IP addresses, which range from 224.0.0.0 to 239.255.255.255. When a packet with a broadcast or multicast destination IP address is received, the switch will forward a copy into each of the remaining network segments in accordance with the IEEE MAC Bridge standard. Eventually, the packet is made accessible to all nodes connected to the network. This approach works well for broadcast packets that are intended to be seen or processed by all connected nodes. In the case of multicast packets, however, this approach could lead to less efficient use of network bandwidth, particularly when the packet is intended for only a small number of nodes. Packets will be flooded into network segments where no node has any interest in receiving the packet. The L3 multicast features on the switch help to ensure that only the hosts in the multicast group receive the multicast traffic for that group. Multicast applications send one copy of a packet, and address it to a group of receivers (Multicast Group Address) rather than to a single receiver (unicast address). Multicast depends on the network to forward the packets to only those networks and hosts that need to receive them. 1138 Managing IPv4 and IPv6 Multicast