Real%20Time%20Streaming%20Protocol

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Real Time Streaming Protocol

• Sravanthi
• Swathi

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Outline

• Introduction
• RTP Vs RTSP
• RTSP methods
• State Diagram
• Working of RTSP
• RTSP message formats
• Security considerations of RTSP
• Applications of RTSP

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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

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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.

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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.

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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.

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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

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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

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Working of RTSP
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Example Media On Demand
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Example of RTSP message exchange
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Cont
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Cont
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Cont.
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Cont
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(No Transcript)
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Cont
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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.

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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

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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"

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RTSP message types
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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

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Example of request response pair

• C-gtS
• PAUSE rtsp//example.com/foo RTSP/1.0
• CSeq 834
• Session 12345678
• S-gtC
• RTSP/1.0 200 OK
• CSeq 834
• Date 23 Jan 1997 153506 GMT

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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

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Streaming in multimedia environment
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Security considerations of RTSP

• Concentrated denial of service attack
• Session hijacking
• Persistently suspicious behavior
• Stream securing

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RTSP applications

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

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Draw backs

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