2.2.3.3 $D (Data)
The $D (Data) packet is used by the client to transfer an ASF data packet to the server.
The $D packet MUST start with a Framing header (section 2.2.3.1.1) with the following additional details.
PacketID: This field MUST be set to the "D" (0x44) character.
Reason: This field MUST NOT be present.
The variable-size Payload field MUST contain exactly one complete ASF data packet. If the ASF data packet contains a Padding Data field (defined in [ASF] section 5.2.4), that field SHOULD be removed before encapsulating the ASF data packet in the $D packet. If the Padding Data field is removed, the Padding Length field in the ASF payload parsing information section ([ASF] section 5.2.2) MUST be updated to indicate a nonexistent Padding Data field.