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Real Time Streaming Protocol

Real Time Streaming Protocol. Sravanthi Swathi. Outline:. Introduction RTP Vs RTSP RTSP methods State Diagram Working of RTSP RTSP message formats Security considerations of RTSP Applications of RTSP. Purpose. Streaming????

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Real Time Streaming Protocol

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  1. Real Time Streaming Protocol Sravanthi Swathi

  2. Outline: • Introduction • RTP Vs RTSP • RTSP methods • State Diagram • Working of RTSP • RTSP message formats • Security considerations of RTSP • Applications of RTSP

  3. Purpose • Streaming???? Streaming breaks the data into packets with size suitable for the transmission between servers and clients. • RTSP establish and controls streams • Client can play the first packet, decompress the second while receiving the third…

  4. Introduction • RTSP is an application level protocol for the control of real-time streaming data with syntax and operations similar to HTTP. • IEFT standard  RFC 2326 • It uses RTP as the underlying data delivery protocol and offers a VCR-like control to the user: Play, Stop Pause, FF, Rew, as well as random access to any part of media clip.

  5. Introduction (contd..) • RTSP helps the server to adjust the media bandwidth to the network congestion in order to suit the available capacity. • Multicast data stream • RTSP is able to choose the optimum delivery channel to the client. For instance, if UDP cannot be used the streaming server has to offer a choice of delivery protocols – multicast UDP or TCP to suit different clients.

  6. RTP Vs RTSP • RTSP allows two-way communication; that is, viewers can communicate with the streaming server and do things like rewind the movie, go to a chapter, and so on. • By contrast, RTP is a one-way protocol used to send live or stored streams from the server to the client.

  7. RTSP methods: Options  Get available methods Setup Establish transport Announce Change description of media objects Describe  Get (low-level) description of media objects Play  start playback, reposition Record Start Recording Redirect Redirect client to new server Pause Halt delivery, but keep state and server resources allocated Set_parameter Device or encoding controls Teardown Removes state

  8. RTSP State Transitions Setup Start an RTSP session and resource allocation for a stream Play and Record Start data transmission of the stream Pause Temporarily halt a stream without freeing server resources Teardown Free resources associated with stream and end of a session

  9. Working of RTSP:

  10. Example: Media On Demand

  11. Example of RTSP message exchange

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  17. RTSP message format • RTSP is a text based protocol and use the same message format as HTTP. • Text-based protocols have the advantage of easy extendibility and human friendly messages. • Suffer from major overhead that text coding brings about. • RTSP text coding is the optimal choice, due to the nature of the protocol, which is prone to extensions and does not burden the network with frequent or high sized messages.

  18. Cont… • General syntax for an RTSP method is {method name} {URL} {protocol version} CRLF {parameters} • Example of an RTSP request DESCRIBE http://foo.com/bar.rm RTSP/1.0 CSeq: 312 Accept: application/sdp, application/mheg

  19. Cont… • General syntax for a method with a body. {method name} {URL} {protocol version} CRLF {MIME header field} CRLF ... {MIME header field} CRLF CRLF {optional body, depending on the presence of a "Content-length"}

  20. RTSP message types

  21. Cont… • A start-line if sent in a request is called Request-line otherwise if in a response, is called Status-line. Start-line = Request-Line | Status-Line • Generic format of request line is • Generic format of status line is

  22. Example of request response pair • C->S: PAUSE rtsp://example.com/foo RTSP/1.0 CSeq: 834 Session: 12345678 • S->C: RTSP/1.0 200 OK CSeq: 834 Date: 23 Jan 1997 15:35:06 GMT

  23. RTSP message fields • Different types of header fields • General-header field • Request-header field • Response-header field • Entity-header field • Generic format for a header field is

  24. Streaming in multimedia environment

  25. Security considerations of RTSP • Concentrated denial of service attack • Session hijacking • Persistently suspicious behavior • Stream securing

  26. RTSP applications • Streaming of multimedia via internet • Video conferencing and lectures • Broadcasting of entertainment • Remote digital editing • Voice mail

  27. Draw backs: • The RTSP protocol says nothing about the problems of recovering state over machine or software failure. • RTSP is a state less protocol

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