Rtp
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The Real-time Transport Protocol (RTP) provides end-to-end delivery services for real-time data like audio and video. It identifies payload types, numbers sequences, timestamps packets, and monitors delivery. RTP is designed to be lightweight, flexible, scalable, and works with various transport protocols like UDP. It is used with the RTP Control Protocol (RTCP) for quality of service feedback.
Rtp
- 1. Real-time Transport Protocol (RTP) Emil Diaz VoIP Security COMS 4995 – 03 Dept. of Computer Science Henning Schulzrinne Columbia University Fall 2008
- 2. Overview Protocol goals & background Real-time Transport Protocol (RTP) RTP Control Protocol (RTCP) Use Scenarios 12/04/12 Real-time Transport Protocol 2
- 3. Real-Time Transport Protocol End-to-end delivery services for applications transmitting real-time data, such as audio and video Payload type identification Sequence numbering Time stamping Delivery monitoring Goals lightweight flexible scalable 12/04/12 Real-time Transport Protocol 3
- 4. Origin of Protocol Developed by the Audio-Video Transport Working Group of the IETF: H. Schulzrinne (Columbia University) S. Casner (Packet Design) R. Frederick (Blue Coat Systems Inc.) V. Jacobson (Packet Design) First published as RFC 1889 in the year 1996 Superseded by RFC 3550 in the year 2003 12/04/12 Real-time Transport Protocol 4
- 5. Protocol Structure Application layer protocol Typically used on top of IP and UDP Applications that use RTP are: Less sensitive to packet loss Very sensitive to packet delays UDP provides key services: Multiplexing Checksum 12/04/12 Real-time Transport Protocol 5
- 6. RTP Does NOT Define media data formats or encodings Need media specific profiles Handle connection setups or tear-downs Need other protocols like SIP or H.323 Handle resource reservation Need other protocols like RSVP Guarantee timely delivery or Quality of Service However, it does provide necessary data to application to order packets and adjust signal quality 12/04/12 Real-time Transport Protocol 6
- 7. RTP Sample Packet http://www.codeproject.com/KB/IP/Video_Voice_Conferencing.aspx 12/04/12 Real-time Transport Protocol 7
- 8. RTCP Sample Packet 5 main types: Sender Report (SR) Receiver Report (RR) Source Description (SDES) Bye Message (BYE) Application-defined (APP) http://developer.apple.com/documentation/QuickTime/QTSS/Concepts/chapter_2_section_13.html 12/04/12 Real-time Transport Protocol 8
- 9. Use Scenarios 12/04/12 Real-time Transport Protocol 9
- 10. Simple Multicast Audio Conference 1. Call connection established 2. Audio sampled at 20ms durations 3. Each data chunk is packaged with an RTP header 4. RTP packet is wrapped around UDP packet 5. Sent through network 6. Receiver receives and parses RTP header 7. Based on payload type, application reconstructs audio stream in 20ms chunks 12/04/12 Real-time Transport Protocol 10
- 11. Audio and Video Conference Audio and Video has separate RTP/RTCP sessions Receiver can choose media type to use Encodings can change independently Network resource allocations per media basis 12/04/12 Real-time Transport Protocol 11
- 12. Mixers and Translators Accommodate participant network resources Mixer – Low Bandwidth Mixer – Combining media streams Translator – Forward RTP packets to private networks 12/04/12 Real-time Transport Protocol 12
- 13. Quality & Data Distribution Feedback Packet loss, congestion, jitter, delivery times Directly useful for control of adaptive encodings Identify if problems are local or global Short-term and long-term statistical analysis Self-adjusting network Each participant eventually knows about the other members Source description dynamically identifies who is sending Active senders get more bandwidth Session bandwidth kept constant by adjusting transmission rate based on the number of participants 12/04/12 Real-time Transport Protocol 13
- 14. Source Description Information CNAME – Conical name (joe@example.com) NAME – Display Name (Joe Smith) EMAIL – Email (different than CNAME) PHONE – International phone number LOC – Location information (City, Building, Room?) TOOL – Application (VideoView 2.0) 12/04/12 Real-time Transport Protocol 14
- 15. References RFC 3550 - http://tools.ietf.org/html/rfc1889 RFC 3551 - http://tools.ietf.org/html/rfc3551 RTP News - http://www.cs.columbia.edu/~hgs/rtp/ Wikepedia: RTP - http://en.wikipedia.org/wiki/Real-time_Transport_Protocol RTCP - http://en.wikipedia.org/wiki/RTCP 12/04/12 Real-time Transport Protocol 15
- 16. Summary Services: payload type identification sequence numbering time stamping delivery monitoring mixers & translators Goals : lightweight flexible protocol-neutral scalable separate control/data secure 12/04/12 Real-time Transport Protocol 16