engleski

Rapid Synchronization of RTP Multicast Sessions in Case of Link Failure

Quality of Service (QoS) is still one of the major challenges for emerging services based on the Real-Time Transport Protocol (RTP) to deliver multimedia content. In order to synchronize audio and video components of multimedia content, RTP timestamps have to be related. Periodic Real- Time Transport Control Protocol (RTCP) Sender Report (SR) packets, which associate the RTP timestamps in the stream with a common clock at the transmitter, are associated with each stream. Thus, the frequency and the timing of the RTCP SR packets often contribute to the delay before audio and video are rendered, not just to their synchronization, because many clients will not render anything before the synchronization has been established. This paper investigates synchronization delay problem for RTP multicast sessions caused by link failure and packet losses before retained by retransmission server (RS) which disables it to continuously cache all RTP/RTCP packets as they are sent in the session and to act as a feedback target (FT) for the session. The concept of isolation of the RTCP from the RTP packets sent from source to the RS by assigning them to higher priority class is evaluated. It ensures the synchronization delay of the multicast multimedia sessions sufficient for lip-synchronization without excessive delay regardless of network congestion, with accurate statistics measured by RTCP.

IP; QoS; RTP; RTCP; synchronization; multicast

nije evidentirano