Abstract

As networked multimedia applications become widespread, it becomes increasingly important to ensure that these applications can coexist with current TCP-based applications. The TCP protocol is designed to reduce its sending rate when congestion is detected. Networked multimedia applications should exhibit similar behavior, if they wish to co-exist with TCP-based applications [9]. Using TCP for multimedia applications is not practical, since the protocol combines error control and congestion control, an appropriate combination for non-real time reliable data transfer, but inappropriate for loss-tolerant real time applications. In this paper we present a protocol that operates by measuring loss rates and round trip times and then uses them to set the transmission rate to that which TCP would achieve under similar conditions. The analysis in [13] is used to determine this "TCP-friendly" rate. This protocol represents a rst step towards developing a comprehensive protocol for congestion control for time-sensitive multimedia data streams. We evaluate the protocol under various tra c conditions, using simulations and implementation. The simulations are used to study the behavior of the protocol under controlled conditions. The implementation and experimentation involve over 300 experiments over the Internet, using several machines in the US and UK. Our experimental and simulation results show that the protocol is fair to TCP and to other sessions running TFRCP, and that the formula-based approach to achieving TCP-friendliness is indeed practical.

Citations