RTP Realtime Transport Protocol The Five Packeteers minus

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

Agenda n n n Introduction RTP Protocol RTCP Protocol RTP Security Summary

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

RTP - Introduction n n No standard TCP or UDP ports Normally runs over UDP (L 4) as (L 7) app. Even port for RTP, next odd port RTCP Ports 16384 – 32767

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

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

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

RTCP Session n Typical Session: q q q 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 n Several defined restrictions for RTCP: q q 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 n n Security Concerns: Confidentiality, Integrity, and Authentication. Confidentiality: q q n DES-CBC Algorithm SRTP Integrity and Authentication: q q Not dealt with in original implementation SHA 1 (SRTP) or another layer

RTP - Summary n n n 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 n n n n RTP Header q http: //www. geocities. com/intro_to_multimedia/RTP/rtcp. html SSRC + CSRC Diagram q http: //icapeople. epfl. ch/thiran/Cours. ED/RTP. pdf General Information q http: //en. wikipedia. org/wiki/Real-time_Transport_Protocol Security q http: //www. tml. tkk. fi/Opinnot/Tik-110. 501/2000/papers/hallivuori. pdf RFC 1889 (RTP) q http: //www. faqs. org/rfcs/rfc 1889. html RFC 3550 (RTP) q http: //www. faqs. org/rfcs/rfc 3550. html RFC 3711 (SRTP) q http: //gim. org. pl/rfcs/rfc 3711. html