1. Real Time Streaming Protocol
Sirisha Yenigalla
Vishal Marda
Dushyant Vipradas

2. Real Time Streaming Protocol
Contents
Introduction
RTSP and Streaming
Role of RTSP
RTP and RTSP
Working of RTSP
RTSP Methods
Applications of RTSP
RTSP Vulnerabilities
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3. Real Time Streaming Protocol
Introduction
RTSP is an application-level protocol for the control of real-time streaming data.
IETF 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 and REW, as well as random access to any part of the media clip.
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4. (Introduction…contd)
RTSP also helps the server to adjust the media bandwidth to the network congestion in order to suit the available capacity.
Another important function of RTSP is its ability to choose the optimum delivery channel to the client. For instance, if UDP cannot be used (some corporate firewalls will not pass UDP), the streaming server has to offer a choice of delivery protocols – multicast UDP or TCP to suit different clients.
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5. Real Time Streaming Protocol
RTSP and HTTP
RTSP is similar to HTTP/1.1 in terms of syntax and operation but differs in several important aspects.
With RTSP, both the client and the server can issue requests during interaction, as opposed to HTTP where the client always issues the requests (for documents).
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6. Real Time Streaming Protocol
(RTSP and HTTP…contd)
RTSP maintains a state by default which happens to be very important in streaming media files.
The HTTP protocol is a stateless protocol. This simply means that HTTP is unable to retain a memory of the identity of each client that connects to a web site and therefore treats each request for a web page as a unique and independent connection, with no relationship whatsoever to the connections that preceded it.
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7. Real Time Streaming Protocol
RTSP and Streaming
RTSP is the central protocol of a streaming framework.
Streaming is the process of playing a file while it is still downloading.
The innovation of streaming
 No need to entirely store it locally before playing
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8. Real Time Streaming Protocol
(…contd)
Large audio and video files need not be downloaded to your computer .
Streaming media technology allows the client to see or hear the content in just a few seconds instead of waiting.
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9. Streaming media will usually take the form of:
pre-stored media Its already been recorded and archived somewhere, when the user wants to access it we serve it as a stream
live broadcast media The content is streamed as its produced (there may be a small editing / safety delay, as with traditional broadcasting) straight to the user
live interactive media Such as videoconferencing - each user might produce their own stream, and there isn't control by one broadcaster
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10. Real Time Streaming Protocol
The transmission of the stream can be:
one-to-one or point to point - in networking terms, unicast. The stream travels directly from the source (server) to the user (client).
one-to-many or multicast. One stream will be (literally) broadcast to many users.
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11. Kinds of streaming audio or video available
Real Networks (with RealMedia, Real Video and RealAudio)
Microsoft (with Windows Media - audio and video)
Apple (with QuickTime)
Null soft Streaming Video (.nsv) and Shoutcast, IceCast (GNU GPL/Open Source version of Shoutcast), Live365 streaming audio
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12. Protocols used in Streaming Technology
 Session Description Protocol (SDP)
 Real Time Transport Protocol (RTP)  Real-time Control Protocol (RTCP)
 Hypertext Transfer Protocol (HTTP)
 Real Time Streaming Protocol (RTSP)
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14. Real Time Streaming Protocol
Role of RTSP
Controlling and processing the interactive control functions such as pause/resume, fast forward, rewind is an important aspect of streaming and RTSP takes up this major role.
Delivery mechanisms are based solely on RTP.
RTSP is designed to be on top of RTP to both control and deliver real-time content.
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15. Real Time Streaming Protocol
RTP and RTSP
It’s important to distinguish between RTP and Real-Time Streaming Protocol (RTSP), another transfer protocol. RTSP is used when viewers communicate with a unicast server.
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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16. Streaming from a streaming server to a media player
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17. Real Time Streaming Protocol
Working of RTSP
FIGURE
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18. RTSP Media Player-Server Sequence Chart
User
Interface
RTSP
Player
RTSP
Server
OpenURL
SETUP
response1
PLAY
Activate
RTP
response2
Activate
RTP
audio
PAUSE
response3
Quit
TEARDOWN
response10

19. Explanation – Working of RTSP
Before a client can establish the streaming session it some how has to get the session description from the web server using the HTTP protocol.
According to the information in the session description the client sends a RTSP SETUP request to the streaming server.
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20. (working of RTSP …contd)
The server informs the client with an OK (ack) response to indicate that the stream has been prepared successfully.
The client starts the streaming with a RTSP PLAY request and ends the streaming session with a RTSP TEARDOWN request.
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21. Real Time Streaming Protocol
Client State Machine
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22. Real Time Streaming Protocol
Server State Machine
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23. Example of a RTSP Description File
<title>Twister/title>
<session>
<group language=en lipsync>
<switch>
<track type=audio
e=”PCMU/8000/1”
src= ”rtsp://audio.example.com/twister/
audio.en/lofi”>
e=”DVI4/16000/2” pt=”90 DVI4/8000/1”
scr=”rtsp://audio.example.com/twister/
audio.en/hifi”>
</switch>
<track type=”video/jpeg”
scr=”rtsp://video.example.com/twister/video”>
</group>
</session>
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24. Explanation of the Description File
The RTSP Content Markup Language document can be defined using an XML DTD (Document Type Definition), and is HTML-like. Most of it is self-explanatory. The ’group’ includes two audio tracks and a video track, and the ’group’ tag includes the language parameter (en =English) and a requirement that the sound shall be lip-synchronised with the video. The ’swich’ tag indicates that we can swich between two sound tracks. The coding schemes for the audio are given by the parameters ’e’ and ’pt’. To locate resources, RTSP defines a variant of URL, see ’src’. The parameter ’lofi’ indicates ’low fidelity’ sound. The RTSP URL may include a port number.
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25. RTSP Message Format
The RTSP message formats share a similar syntax to HTTP The general syntax for an RTSP method is:
{method name} {URL} {protocol version}CRLF {parameters}
An example of an RTSP request follows:
DESCRIBE RTSP/1.0
CSeq: 312
Accept: application/sdp, application/mheg
This is a request for an RTSP server to send a description of the media
content, using either Session Description Protocol
(SDP) or Multimedia and Hypermedia Experts Group (MHEG) formats.
An RTSP message may also contain a body. The general syntax for a method with a body is:
{method name} {URL} {protocol version}CRLF
{MIME header field}CRLF
...
CRLF
{optional body, depending on the presence of a "Content-length"}
The following example contains a description of the media referenced by the request URL, rtsp://foo.bar.com/bar.rm, using the SDP format.
ANNOUNCE rtsp://foo.bar.com/bar.rm RTSP/1.0
CSeq: 312
Date: 9 Sep :00:00 GMT
Session:
Content-Type: application/sdp
Content-Length: 332
v=0
o=efutz IN IP
s=A Short Story
i=A short narrative depicting the early days of the Internet u=
(Elmer Futz)
c=IN IP /127 t=
a=recvonly
m=audio 8756 RTP/AVP 0
m=video 3487 RTP/AVP 31
Each RTSP request is followed by a response message. Syntax: {protocol version} {status code} {reason-phrase}CRLF
{parameters}
A typical response message may look like the following:
RTSP/ OK

26. Real Time Streaming Protocol
RTSP message types
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27. Real Time Streaming Protocol
(…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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28. Real Time Streaming Protocol
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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29. Streaming in Mobile Environments
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30. Real Time Streaming Protocol
RTSP Methods
Method
DESCRIBE
ANNOUNCE
GET_PARAMETER
OPTIONS
PAUSE
PLAY
RECORD
REDIRECT
SETUP
SET_ PARAMETER
TEARDOWN
Description
Retrieves the description of a presentation
Posts the description of a presentation
Retrieves the value of a parameter
Queries the available methods
Streams delivery is halted temporarily
Starts sending data
Starts receiving data
Informs to connect another server location
Specifies the transport mechanism
Requests to set the value of a parameter
Stops the stream delivery and frees the resources
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31. Real Time Streaming Protocol
RTSP Applications
Streaming of multi-media via Internet
Video conferencing & lectures.
Broadcasting of entertainment.
Remote digital editing
Voice mail
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32. Real Time Streaming Protocol
RTSP Vulnerabilities
Vulnerability VU#329561
Real Networks Helix Universal server Vulnerable to buffer overflow when supplied an overly long string within the "Transport" field of a SETUP RTSP request.
Impact
A remote attacker may be able to execute arbitrary code on the vulnerable system. This attacker-supplied code would be run with the privileges of the user running the Helix Server.
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33. Real Time Streaming Protocol
Vulnerability Note VU#934932
Real Networks media server RTSP protocol parser buffer overflow.
Impact
A remote attacker can either execute arbitrary code with privileges of the running service or cause it to crash.
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34. Real Time Streaming Protocol
Vulnerability Note VU#485057
Real Networks Helix Universal Server vulnerable to buffer overflow when supplied an overly long string for the "Describe" field
Impact
A remote attacker may be able to execute arbitrary code on the vulnerable system. This attacker-supplied code would be run with the privileges of the user running the Helix Server.
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35. Real Time Streaming Protocol
Vulnerability Note VU#460350
Apple QuickTime/Darwin Streaming Server fails to properly parse DESCRIBE requests.
Impact
An unauthenticated, remote attacker could prevent legitimate users from accessing the streamed content.
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36. Solution to the Vulnerabilities
Here all the problems can be resolved by applying a patch from the vendor.
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37. Real Time Streaming Protocol
References
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38. Real Time Streaming Protocol
Questions
#1. What is the transport protocol being used by RTSP?
Ans. An RTSP client may use reliable transport connection such as TCP or alternatively use UDP.(So could be on top of UDP/IP or TCP/IP)
#2. Where is RTSP used?
Ans. It is used by streaming media players ,to control the media streams.
#3. What is main difference between RTSP and HTTP?
Ans. HTTP is a stateless protocol ,where as RTSP maintains the state through out.
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39. Real Time Streaming Protocol
THANK YOU
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