2.2.7.14 UdpPacketPair

The purpose of the UdpPacketPair request is to request packet-pair data delivered as RTP packets over UDP, using the RTP payload format for packet-pair data, as specified in section 2.2.3. The server's response to this request contains an empty message body because the packet-pair data is transmitted over UDP. By measuring the time it takes for the second RTP packet to arrive, the client can estimate the bottleneck bandwidth in the network path between the server and the client.

The client needs to have sent a SelectStream request to establish an RTP session for a retransmission stream before it sends the UdpPacketPair request because the RTP packets with packet-pair data will be transmitted over that RTP session. For information on how to determine if a stream is a retransmission stream, see section 2.2.5.2.5.

The UdpPacketPair request is defined as the SET_PARAMETER request method (sent by the client to the server), as specified in [RFC2326] section 10.9, with the following additional constraints:

The syntax of the message body of the SET_PARAMETER request is defined as follows, with all characters in ASCII:

 message-body       = "type:" SP "high-entropy-packetpair"
                      [ SP "variable-size" ]

The following example shows a UdpPacketPair request:

  
  
 SET_PARAMETER rtsp://myserver.com/mycontent.wmv RTSP/1.0
 Content-Length: 43
 User-Agent: WMPlayer/9.0.0.2833 guid/B64345F5-8C45-4818-8A1A-4775F0923FAC
 Accept-Charset: UTF-8, *;q=0.1
 X-Accept-Authentication: Negotiate, NTLM, Digest
 Accept-Language: en-US, *;q=0.1
 Content-Type: application/x-rtsp-udp-packetpair
 CSeq: 3
  
 type: high-entropy-packetpair variable-size