Quanta Cloud Technology QuantaMesh QNOS5, Configuration Manual

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8. Configuring Multicast Routing
8.1. L3 Multicast Overview
IP Multicasting enables a network host (or multiple hosts) to send an IP datagram to multiple destinations
simultaneously. The initiating host sends each multicast datagram only once to a destination multicast group
address, and multicast routers forward the datagram only to hosts who are members of the multicast group.
Multicast enables efficient use of network bandwidth because each multicast datagram needs to be
transmitted only once on each network link, regardless of the number of destination hosts. Multicasting
contrasts with IP unicasting, which sends a separate datagram to each recipient host. The IP routing protocols
can route multicast traffic, but the IP multicast protocols handle the multicast traffic more efficiently with
better use of network bandwidth.
Applications that often send multicast traffic include video or audio conferencing, Whiteboard tools, stock
distribution tickers, and IP-based television (IP/TV).
8.1.1. 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.
8.1.2. Multicast Protocol Switch Support
Multicast protocols are used to deliver Multicast packets from one source to multiple receivers. Table 22
summarizes the multicast protocols that the switch supports.
Table 8-1: Multicast Protocol Support Summary