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Published byDarcy Jacobs Modified over 9 years ago
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RTP – Real-time Transport Protocol Elbert Tsay, Brad Bargabus, Patrick Lim, Henry Quach The Five Packeteers (minus 1 )
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Agenda Introduction RTP Protocol RTCP Protocol RTP Security Summary
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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
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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
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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
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SSRC + CSRC SSRC is a random identifying number CSRC is a contributing source (audio conferencing) Mixer combines SSRC + CSRC in one RTP packet
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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.
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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)
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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.
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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
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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
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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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