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RTP – Real-time Transport Protocol

RTP – Real-time Transport Protocol. The Five Packeteers ( minus 1  ). Elbert Tsay, Brad Bargabus, Patrick Lim, Henry Quach. Agenda. Introduction RTP Protocol RTCP Protocol RTP Security Summary. RTP - Introduction. Real time video and audio data RFC 1889 in 1996  RFC 3550 in 2003

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RTP – Real-time Transport Protocol

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  1. RTP – Real-time Transport Protocol The Five Packeteers (minus 1 ) Elbert Tsay, Brad Bargabus, Patrick Lim, Henry Quach

  2. Agenda Introduction RTP Protocol RTCP Protocol RTP Security Summary

  3. RTP - Introduction Real time video and audio data RFC 1889 in 1996  RFC 3550 in 2003 Session setup and teardown implemented with SIP (VoIP) Streaming media with RTSP

  4. RTP - Introduction • No standard TCP or UDP ports • Normally runs over UDP (L4) as (L7) app. • Even port for RTP, next odd port RTCP • Ports 16384 – 32767

  5. RTP - Header • Bits Name Description • 0-1 Version Normally version 2 • 2 Padding Padding for fixed length messages • 3 Extension Extension Header follows fixed header • 4-7 CSRC Count CSRC Identifiers that follows fixed header • 8 Marker Used by some Apps to mark a frame • 9-15 Payload Type Encoding of the RTP payload • 16-31 Sequence Number Increments by 1 for each RTP packet

  6. SSRC + CSRC • SSRC is a random identifying number • CSRC is a contributing source (audio conferencing) • Mixer combines SSRC + CSRC in one RTP packet

  7. RTCP • RTCP controls the flow and rate of RTP packets. • Typical types of RTCP header packets: • SR – Sender report. • RR – Receiver report. • SDES – Source description items. • BYE – Termination packet report. • APP – Application specific functions.

  8. RTCP Session • Typical Session: • Initialization: SR or RR packets, with SDES packet. • Continuation: SR or RR packets at timed intervals. • Termination: BYE packet at any given time (can be with SR or RR packets)

  9. RTCP Restrictions • Several defined restrictions for RTCP: • SR and RR are sent out at timed intervals. • CNAME (located in SDES) must be identify ASAP in order to start receiving RTP packets.

  10. RTP Security • Security Concerns: Confidentiality, Integrity, and Authentication. • Confidentiality: • DES-CBC Algorithm • SRTP • Integrity and Authentication: • Not dealt with in original implementation • SHA1 (SRTP) or another layer

  11. RTP - Summary • RTP for audio and video data transmission • RTCP controls RTP • Security is more important now than ever because of the growing popularity of data streaming

  12. References • RTP Header • http://www.geocities.com/intro_to_multimedia/RTP/rtcp.html • SSRC + CSRC Diagram • http://icapeople.epfl.ch/thiran/CoursED/RTP.pdf • General Information • http://en.wikipedia.org/wiki/Real-time_Transport_Protocol • Security • http://www.tml.tkk.fi/Opinnot/Tik-110.501/2000/papers/hallivuori.pdf • RFC 1889 (RTP) • http://www.faqs.org/rfcs/rfc1889.html • RFC 3550 (RTP) • http://www.faqs.org/rfcs/rfc3550.html • RFC 3711 (SRTP) • http://gim.org.pl/rfcs/rfc3711.html

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