What is the difference between unicast and multicast streams?

A Unicast transmission/stream sends IP packets to a single recipient on a network. A Multicast transmission sends IP packets to a group of hosts on a network. If the streaming video is to be distributed to a single destination, then you would start a Unicast stream by setting the destination IP address and port on the AVN equal to the destination’s values. If you want to view the stream at multiple concurrent locations, then you would set the AVN’s destination IP address to a valid Multicast IP address ( –

Note that while the Multicast IP address range is from –, the first octet (224.xxx.xxx.xxx) is generally reserved for administration. VSI recommends setting the first octet to 225 and the remaining three octets to the AVN’s IP address. For example, if the AVN’s IP address is, then set the destination IP address to for Multicast streaming.

Since Multicasting is a relatively new technology, some legacy devices that are part of your network might not support Multicasting.

Before using the AVN encoder in Multicast streaming mode, check the functional specifications of your network infrastructure to ensure that the Multicast stream will not create major traffic on your network. Verify that your backbone switch supports Internet Group Messaging Protocol (IGMP) snooping, which allows the core of your network to ignore the traffic streams that Multicasting may generate.

For more information on IGMP querying and snooping please refer to an AVN encoder’s user manual, available on our website by product, in the chapter titled “Connecting to the Network”.