Real Time Streaming Protocol (RTSP)

By : RIGIL TEAM

Shahina Ahmed

Kishwer Jabeen

Shilpa Mayanna

Sowmya Ramarao

Agenda

IntroductionRTP Vs RTSPState DiagramWorking of RTSPRTSP message formatsRTSP methodsRTSP OperationsSecurity Considerations for RTSP

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 …

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.

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.

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.

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

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

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.

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

RTSP State Transitions

Setup: Start an RTSP session and resource allocation for a streamPlay and Record Start data transmission of the streamPause Temporarily halt a stream without freeing server resourcesTeardown Free resources associated with stream and end of a session

RTSP Methods

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->S: DESCRIBE rtsp://server.example.com/fizzle/foo RTSP/1.0 CSeq: 312 Accept: application/sdp, application/rtsl, application/mheg S->C: RTSP/1.0 200 OK CSeq: 312 Date: 23 Jan 1997 15:35:06 GMT Content-Type: application/sdp Content-Length: 376

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

Options Method

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

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->S: TEARDOWN rtsp://example.com/fizzle/foo RTSP/1.0

CSeq: 892

Session: 12345678

S->C: RTSP/1.0 200 OK

Downloads

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

RTSP Operation

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 >= playback rate.

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.

Security Considerations for RTSP

RTSP reuses many of HTTP security features

RTSP presents additional issues

-Denial of service

-Session hijacking

-Authentication

Conclusion

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

Extensible