Channels

A NetShow channel provides clients with the information needed to receive and render ASF streams. The channel specifies the multicast address and port to which clients listen for the stream. The channel also specifies the types and formats of the data in the stream so that the client can play the stream correctly. Channel information is saved as a file with an .nsc extension.

Although the primary use of a channel is to provide address and stream information to clients, channels support additional NetShow features.

Roll Over to Unicast. You can set up a channel so that clients unable to receive the multicast can automatically connect to NetShow Server and receive a unicast of the same information. This feature can be used to reach clients who are behind a firewall.
Stream Distribution. Channels can also be set up to supply secondary NetShow servers with streams, which they can in turn multicast. This feature can be useful on intranets whose routers are not configured for multicast. You can distribute a stream to NetShow servers located on separate LAN segments. Each server can then multicast to clients on its segment.

NetShow uses channels with ASF streams only. A channel is required when multicasting ASF streams. When unicasting ASF streams, using a channel is optional.