NetShow uses the term unicast to refer to networking in which computers establish two-way, point-to-point connections. Most network operations today work in this fashion. When streaming multimedia over a network, the advantage of unicasting is that the client computer can communicate with the computer supplying the multimedia stream. If, for example, a server is streaming video to a client, the client can ask the server to pause the stream. The disadvantage of unicasting is that each client that connects to the server receives a separate stream. This rapidly uses up the bandwidth that is available on the network.
NetShow uses the term multicast to refer to networking in which one computer sends a single copy of the data over the network and many computers receive that data. Unlike a broadcast, routers can control where a multicast travels on the network. When streaming multimedia over the network, the advantage to multicasting is that only a single copy of the data is sent across the network. This preserves network bandwidth. The disadvantage of multicasting is that it is connectionless: clients have no control over the streams they receive.
To use multicasting on a network, the network routers must support multicasting. However, whether or not your network routers support multicasts, you can always use NetShow multicasting on the local segment of your LAN. In addition, by setting up NetShow servers on each segment of your network, you can distribute a single stream to the NetShow server on each segment and then use NetShow Server to multicast to clients on that segment.
When you are deciding how to use NetShow, the choice of unicast or multicast affects the types of streams you can use. NetShow can multicast all of the stream types it supports: ASF, RTP audio, and file transfers. If, however, you want to use NetShow for unicasting, you must use ASF streams. NetShow supports ASF unicast streams over UDP, TCP, and HTTP.
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