Streaming with a Streaming Media Server

Posting and Hosting
In the streaming media server approach, the initial steps are similar to the Web server approach, except that the compressed media file is produced and copied to a specialized streaming media server (such as Microsoft Windows Media Services) instead of a Web server. Then a Web page with a reference to the media file is placed on a Web server. Windows Media Services and the Web server may run on the same computer.

Data Delivery
The rest of the streaming media server delivery process differs significantly from the Web server approach. In contrast to the passive burst methodology employed in Web server streaming, the data is actively and intelligently sent to the client, meaning that it delivers the content at the exact data rate associated with the compressed audio and video streams. The server and the client stay in close touch during the delivery process, and the streaming media server can respond to any feedback from the client.

While streaming media servers can use the HTTP/TCP protocols used by Web servers, they can also use specialized protocols such as the User Datagram Protocol (UDP) to greatly improve the streaming experience. Unlike TCP, UDP is a fast, lightweight protocol without any re-transmission or data-rate management functionality. This makes UDP an ideal protocol for transmitting real-time audio and video data, which can tolerate some lost packets. As a bonus, because of the back-off policies implicit in the TCP protocol, UDP traffic gets higher priority than the TCP traffic on the Internet. And instead of the blind retransmission scheme employed by TCP, streaming media servers such as Microsoft's Windows Media Services use an intelligent retransmission scheme on top of UDP. Windows Media Services' UDP Resend feature ensures that the server only retransmits lost packets that can be sent to the client in time to get played.