The Supported header is used for specifying features of the protocol that are supported and that are allowed to be used in the current session. Different features can apply to different entries in a server-side playlist.

If a feature is listed in the Supported header, the feature is supported, and the feature SHOULD be used, if appropriate. If a feature has been defined for use on the Supported header, but it is not listed on the Supported header, that feature MUST NOT be used.<9>

A missing Supported header (from either a request or response) MUST NOT be interpreted as changing the list of features that are currently supported.

The syntax of the Supported header is as follows.

 WMCfeat   = "com.microsoft.wm.eosmsg"
             | "com.microsoft.wm.fastcache" 
             | "com.microsoft.wm.locid"
             | "com.microsoft.wm.packetpairssrc"
             | "com.microsoft.wm.predstrm"
             | "com.microsoft.wm.srvppair"
             | "com.microsoft.wm.sswitch"
             | "com.microsoft.wm.startupprofile" 
 Supported = "Supported: " WMCfeat *7["," [SP] WMCfeat]

For example:

 Supported: com.microsoft.wm.srvppair, com.microsoft.wm.sswitch,
    com.microsoft.wm.predstrm, com.microsoft.wm.startupprofile

The tokens that can be used on the Supported header are defined in the following sections.