Standards Track A. Rao Netscap - RFC Editor

RFC 2326 Real Time Streaming Protocol April 1998In this example, the media server was previously invited to theconference indicated.C->S: RECORD rtsp://example.com/meeting/audio.en RTSP/1.0CSeq: 954Session: 12345678Conference: 128.16.64.19/3249237410.12 Embedded (Interleaved) Binary DataCertain firewall designs and other circumstances may force a serverto interleave RTSP methods and stream data. This interleaving shouldgenerally be avoided unless necessary since it complicates client andserver operation and imposes additional overhead. Interleaved binarydata SHOULD only be used if RTSP is carried over TCP.Stream data such as RTP packets is encapsulated by an ASCII dollarsign (24 hexadecimal), followed by a one-byte channel identifier,followed by the length of the encapsulated binary data as a binary,two-byte integer in network byte order. The stream data followsimmediately afterwards, without a CRLF, but including the upper-layerprotocol headers. Each $ block contains exactly one upper-layerprotocol data unit, e.g., one RTP packet.The channel identifier is defined in the Transport header with theinterleaved parameter(Section 12.39).When the transport choice is RTP, RTCP messages are also interleavedby the server over the TCP connection. As a default, RTCP packets aresent on the first available channel higher than the RTP channel. Theclient MAY explicitly request RTCP packets on another channel. Thisis done by specifying two channels in the interleaved parameter ofthe Transport header(Section 12.39).RTCP is needed for synchronization when two or more streams areinterleaved in such a fashion. Also, this provides a convenient wayto tunnel RTP/RTCP packets through the TCP control connection whenrequired by the network configuration and transfer them onto UDPwhen possible.C->S: SETUP rtsp://foo.com/bar.file RTSP/1.0CSeq: 2Transport: RTP/AVP/TCP;interleaved=0-1S->C: RTSP/1.0 200 OKCSeq: 2Date: 05 Jun 1997 18:57:18 GMTTransport: RTP/AVP/TCP;interleaved=0-1Schulzrinne, et. al. Standards Track [Page 40]