The transmitter MUST begin the license update procedure by sending an ANNOUNCE request to the URL that the receiver intends to play, or is currently playing. The entity-body of the ANNOUNCE request MUST contain a license response message with a leaf license.

The ANNOUNCE request MUST include a "Content-Type: application/vnd.ms-wmdrm-license-response" header to indicate that the body of the ANNOUNCE request contains a license response message.

The license response message in an ANNOUNCE request MUST NOT be Base64 encoded [RFC3548].