How multicast works

Multicasting is a method of transmitting a single stream of data to multiple clients. Multicasting is connectionless; clients receive a multicast by monitoring a specific multicast IP address and port that receives the content stream from the server.

To successfully use multicast delivery with your server, your network must use multicast-enabled routers. Multicast-enabled routers are routers that are able to interpret class-D IP addresses use the Internet Group Management Protocol (IGMP) to route clients to the multicast IP address.

All multicast content must have a specified time-to-live value that limits the number of routers that the multicast can traverse before it expires.

The WMS Multicast Data Writer plug-in controls how the server uses multicast delivery with your publishing point. This plug-in is disabled by default and can only be enabled on broadcast publishing points.

This section contains the following topics:

• About multicast IP addresses and ports
• About time-to-live values

Note

• Multicast streaming and the WMS Multicast Data Writer plug-in are available only if Windows Media Services 9 Series is running on the following editions of the operating system: Windows Server 2003, Enterprise Edition and Windows Server 2003, Datacenter Edition. If you are running Windows Server 2003, Standard Edition, these features are not supported.

Related topics

• Understanding protocols