1.3.2.1.1 Interface Query

An Interface Query is a request/reply exchange. It establishes a new interface ID that can be used as part of a different interface. For example, version 1.0 of the protocol supports messages AA, AB, and AC. These messages are always available for processing on both sides of the connection, and can be called without any explicit query interface exchanges. If a new server or client is introduced with improved interface exchanges, an implementer can add two new messages—BA and BB. These two new messages form a new interface, which is identified by a GUID. To establish whether the remote side of the interface supports these new messages, an Interface Query message is sent as a request, and the interface GUID is specified. If the interface is not supported, the remote side returns a failure message. Otherwise, it returns a new interface ID, which is used in the headers of message BA and message BB packets to identify this new interface.