On retransmission-based error control for continuous media traffic in packet-switching networks

Distribution of continuous media traffic such as digital audio and video over packet-switching networks has become increasingly feasible due to a number of technology trends leading to powerful desktop computers and high-speed integrated services networks. Protocols supporting the transmission of continuous media are already available, In these protocols, transmission errors due to packet loss are generally not recovered. Instead existing protocol designs focus on preventive error control techniques that reduce the impact of losses by adding redundancy, e.g., forward error correction, or by preventing loss of important data, e.g., channel coding. The goal of this study is to show that retransmission of continuous media data often is, contrary to conventional wisdom, a viable option in most packet-switching networks. If timely retransmission can be performed with a high probability of success, a retransmission-based approach to error control is attractive because it imposes little overhead on network resources and can be used in conjunction with preventive error control schemes. Since interactive voice has the most stringent delay and error requirements, the study focuses on retransmission in packet voice protocols. An end-to-end model of packet voice transmission is presented and used to investigate the feasibility of retransmission for a wide range of network scenarios, The analytical findings are compared with extrapolations from delay measurements of packet voice transmission over a campus backbone network.