A simulation study of forward error correction in ATM networks

Abstract

If the packet loss rate in a network is higher than the loss rate requested by an application, the transport protocol must make up for the difference in loss rate. In high bandwidth delay-product networks the latency introduced by retransmission-based error recovery schemes may be too high for applications with latency constraints. In this case, Forward Error Correction (FEC) can be used. FEC allows recovery from loss without retransmission. The amount of loss recovered strongly depends on the loss behavior of the network. FEC works best if losses are dispersed.We use simulation to study the loss behavior of an output buffered multiplexer for three different traffic scenarios. Our results show how the loss behavior of the multiplexer is affected by the traffic mix and the statistics of the sources. The more bursty the sources are the larger the loss rate and the higher the probability that losses will occur in bursts. We then investigate the effectiveness of an FEC scheme that can recover a fixed number of lost packets within a block of consecutive packets. For a heterogeneous traffic scenario consisting of video and burst sources, this scheme reduces the loss rate for the video sources by several orders of magnitude.