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RTP_Presentation by wuyunqing

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									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
   Session setup and teardown implemented
    with SIP (VoIP)
   Streaming media with RTSP
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
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
SSRC + CSRC




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