Real%20Time%20Streaming%20Protocol%20(RTSP)

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Real Time Streaming Protocol (RTSP)

• By RIGIL TEAM
• Shahina Ahmed
• Kishwer Jabeen
• Shilpa Mayanna
• Sowmya Ramarao

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Agenda

• Introduction
• RTP Vs RTSP
• State Diagram
• Working of RTSP
• RTSP message formats
• RTSP methods
• RTSP Operations
• Security Considerations for 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, Rewind, 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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RTSP Vs RTP

• 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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Features of RTSP

• Retrieval and control of media from media server
• Invitation of a media server to a conference
• Addition of media to an existing presentation

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Properties of RTSP

• Extendibility
• Secure
• Transport independent
• Multi-server capable Control of recording devices
• Separation of stream control and conference
  invitation
• Presentation description neutral
• Proxy and firewall friendly

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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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RTSP Message Type

• 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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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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RTSP Methods
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Describe Method

• Phase of session establishment
• Fetch the description of a media object or a
  presentation
• Reply of the server contains a complete
  description of the requested resource.
• C-gtS DESCRIBE rtsp//server.example.com/fizz
  le/foo RTSP/1.0
• CSeq 312
• Accept application/sdp, application/rtsl,
  application/mheg
• S-gtC RTSP/1.0 200 OK
• CSeq 312
• Date 23 Jan 1997 153506 GMT
• Content-Type application/sdp
• Content-Length 376

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Options Method

• Borrowed from HTTP 1.1
• Represents a request for the options associated
  to a resource or the capabilities of a server
• Pause Method
• Request the server to interrupt momentarily the
  delivery of the stream
• If client does not resume the state before
  timeout expiration all resources are released

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Play Method

• Clients to begin or resume the play of a media
• Specifying a desired retrieval range
• Play requests can be pipelined
• Set-up Method
• Initializes, or modifies, the transport mechanism
  to be used between client and server

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Tear-down Method

• Permanently stops the delivery of a media
  stream, or a presentation
• Implies releasing the state associated to the
  session and freeing the associated resources.
• C-gtS TEARDOWN rtsp//example.com/fizzle/foo
  RTSP/1.0
• CSeq 892
• Session 12345678
• S-gtC RTSP/1.0 200 OK

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Downloads

• browser GETs metafile
• browser launches player, passing metafile
• player contacts server
• server downloads audio/video to player

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RTSP Operation
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Streaming Vs Downloading

• Download Receive entire content before playback
  begins
• High start-up delay as media
• file can be large
• Streaming Play the media file while it is being
  received
• Reasonable start-up delays
• Reception Rate gt playback rate.

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What RTSP does not do?

• Does not define how audio/video is encapsulated
  for streaming over network.
• Does not restrict how streamed media is
  transported it can be transported over UDP or
  TCP.
• Does not specify how the media player buffers
  audio/video.

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Security Considerations for RTSP

• RTSP reuses many of HTTP security features
• RTSP presents additional issues
• -Denial of service
• -Session hijacking
• -Authentication

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Conclusion

• RTSP provides a efficient protocol which can be
  used in streaming system to remotely control a
  media server
• Extensible