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Real Time Transport Protocol

rtp rtcp data session

Definition: Real-Time Transport Protocol (RTP) is a protocol designed for providing end-to- end network transport functions suitable for applications transmitting real-time data, such as audio and video over multicast or unicast network services.

RTP provides services including payload type identification, sequence numbering, time-stamping and delivery monitoring (with RTCP). The sequence numbers included in RTP allow the receiver to reconstruct the sender’s packet sequence and to detect packet loss. Also, the timestamp contained in the RTP header can be used to maintain the original timing sequence of the media stream and perform synchronization with other media streams. However, RTP itself does not provide any mechanism to ensure timely delivery of data and does not guarantee quality-of-service (QoS) for real-time services.

RTP is implemented at the application level and normally run on the top of UDP/IP. In general, RTP is designed to be independent of the underlying protocols. Hence, RTP may also be used with other suitable underlying network or transport protocols. The data encapsulation process of RTP running on the top of UDP/IP is shown in Figure 1. RTP supports any media format. A complete RTP packet contains a RTP common header and a payload field. Different media has different payload formats for packing data into the RTP packet.

The RTP control protocol (RTCP) is designed to monitor the quality of service of the RTP data delivery and to convey information about the participants in an on-going session. For each RTP session, RTCP packets are transmitted by each participant to all other participants in the session (as illustrated in Figure 2). RTCP packets are sent periodically and contain sender and/or receiver reports that announce statistics that are useful to the application. The statistics include number of packets sent, number of packets lost and inter-arrival jitter. For bandwidth scaling, RTCP attempts to limit its traffic to 5% of the session bandwidth.

Real-World Multimedia Systems - Real World Capture, Analysis, Association, Querying and Retrieval, Conclusion [next] [back] Real Time Multimedia - Real-Time Networked Multimedia, Real-time Streaming Media Protocols

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