TCP-like flow control algorithm for real-time applications

This paper proposes an efficient flow control algorithm for RTP/RTCP which has been employed as a transport layer protocol for real-time applications over the Internet. As the Internet becomes a common transport vehicle for various applications, some of them require a new flow control different from TCP since they do not need the expensive error recovery inseparable from the current TCP. The new flow control algorithm for real-time applications should efficiently utilize network bandwidth and also minimize the delay jitter while not hampering the performance of the existing TCP applications. This paper introduces a flow control algorithm which dynamically adjusts the sending rate similarly to TCP based on the network status evaluated by two network parameters; packet loss and round trip time (RTT) reported by RTP/RTCP. For the reduction of delay jitters, the algorithm tries to maintain RTTs periodically reported by RTCP within a predetermined range by either additively increasing or multiplicatively decreasing the sending rate as much aggressively as TCP. For evaluation, we compare the behavior of our algorithm to that of RAP, one of representative flow control algorithms for real-time applications. The simulation experiments show that our algorithm achieves the same degree of performance for TCP as RAP but without overloading the network with ack packets like RAP.