Selecting data transfer protocols
Updated: October 4, 2007
Applies To: Windows Server 2008, Windows Server 2008 R2
A data transfer protocol is a standardized format for transmitting data between two devices. The type of protocol used can determine such variables as the error checking method, the data compression method, and end-of-file acknowledgements. If all networks were constructed in the same manner and all networking software and equipment behaved similarly, only one protocol would be necessary to handle all of our data transmission needs. In reality, the Internet is comprised of millions of different networks running a wide array of hardware and software combinations. As a result, the ability to stream digital media content reliably to clients depends on a set of several well-engineered protocols. The protocols used to stream Windows Media-based content are Real Time Streaming Protocol (RTSP) and Hypertext Transfer Protocol (HTTP).
Windows Media Services manages the use of these protocols by using control protocol plug-ins. The control protocol plug-in receives the incoming client request, determines what action is indicated by the request (for example, to start or stop streaming), translates the request into a command form, and then passes the command to the server. Control protocol plug-ins can also return notification information to clients if there is an error condition or a change of status. Windows Media Services includes the WMS RTSP Control Protocol plug-in and the WMS HTTP Control Protocol plug-in.
While the control protocol plug-ins handle the high-level exchange of data, basic networking protocols such as User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) are used to manage more fundamental tasks such as network connectivity and packet error correction. The RTSP protocol is used in combination with both the UDP or TCP protocols.
The following diagram depicts how Windows Media Services uses different protocols to negotiate connections between a Windows Media server, encoders, content sources, and clients.