Real Time Streaming Protocol (RTSP) By : RIGIL TEAM Shahina Ahmed Kishwer Jabeen Shilpa Mayanna Sowmya Ramarao

Agenda Introduction RTP Vs RTSP State Diagram Working of RTSP RTSP message formats RTSP methods RTSP Operations Security 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 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

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 Date: 23 Jan 1997 15:35:06 GMT Content-Type: application/sdp Content-Length: 376

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

Play Method Set-up 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