The receiver MUST encode the binary registration request message to Base64 format [RFC3548]. The Base64-encoded data block MUST then be sent to the transmitter through the UPnP RegisterDevice action of the X_MS_MediaReceiverRegistrar:1 service.

After the receiver retrieves the Base64-encoded data block in the RegisterDevice response from the transmitter, it MUST decode the data block from Base64 to binary [RFC3548]. The resulting Binary large object (BLOB) is the registration response message.

The registration request and registration response messages are defined in sections and, respectively.