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

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 BitsNameDescription 0-1VersionNormally version 2 2PaddingPadding for fixed length messages 3ExtensionExtension Header follows fixed header 4-7CSRC CountCSRC Identifiers that follows fixed header 8MarkerUsed by some Apps to mark a frame 9-15Payload TypeEncoding of the RTP payload 16-31Sequence NumberIncrements by 1 for each RTP packet

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

8. 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.

9. 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)

10. 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.

11. 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

12. 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

13. 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