2.2.6.10.7 com.microsoft.wm.sswitch

The com.microsoft.wm.sswitch token specifies support for the SelectStream (section 2.2.7.10) message body.

If a server never sends the Supported header, or if a server does not specify the com.microsoft.wm.sswitch token on the Supported header, clients SHOULD assume that the server does not support receiving a SelectStream request that includes a nonempty message body.<15>

If a client never sends the Supported header, or if a client does not specify the com.microsoft.wm.sswitch token on the Supported header, servers SHOULD assume that the client does not support sending a SelectStream request with a non-empty message body.