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The DLNA Guidelines define a concept called Device Class. A Device Class is a role assumed by an implementation of the DLNA Guidelines. The Microsoft Extensions to the DLNA Guidelines specify extensions to the Digital Media Player (DMP) role, the Digital Media Renderer (DMR) role, and the Digital Media Server (DMS) role.
The DLNA Guidelines define additional Device Classes, such as the Digital Media Controller (DMC), but because there are no Microsoft Extensions to the DMC role, these classes are not covered in this document.
An implementation of the DMS role includes an implementation of the UPnP MediaServer V1.0 Device Control Protocol as defined in [UPnP] with the extensions defined in the DLNA Guidelines.
The DMS uses the UPnP Device Architecture [UPNPARCH1] with the extensions defined in DLNA Guidelines to discover DMR implementations.
DMP implementations use the UPnP Device Architecture [UPNPARCH1] with the extensions defined in DLNA Guidelines to discover DMS implementations.
DMP implementations also use the UPnP MediaServer V1.0 Device Control Protocol with the extensions defined in [DLNA] to request a list of multimedia content that is available for streaming from the server. The request and response use SOAP.
A DMR differs from a DMP in that the DMR does not itself request a list of multimedia content from a DMS. Instead, the DMR receives the list from a DMC. The DMR implements the UPnP MediaRenderer V1.0 Device Control Protocol as defined in [UPnP] with the extensions defined in the DLNA Guidelines to receive instructions from the DMC.
The Microsoft Extensions to the DLNA Guidelines extend the HTTP protocol used in the SOAP requests received by the DMS. An HTTP header extension is defined in this document that allows the requestor to specify parameters that can alter the SOAP response. For example, the requestor can use the HTTP header extension to specify that the size of the SOAP response cannot exceed a certain number of bytes.
Once the DMP or DMR has obtained a URL to content that is available for streaming, the DMP or DMR then uses either HTTP, with extensions defined in [DLNA] or RTSP, with extensions defined in [DLNA], to initiate streaming of the multimedia content.
The Microsoft Extensions to the DLNA Guidelines extend the HTTP protocol used for streaming. An HTTP header extension is defined in this document, which allows the client to determine the available range for seeking, in time units, without having to request that the server seek through the content to a particular time.