QoS Performance of OBS in WDM/TDM Networks

We discuss the requirement of basic quality of service (QoS) in optical burst switched WDM networks considering their delay and loss probability. Low delay and reducing burst overlap in the electronic domain of an ingress node reduces burst loss, and hence improves (QoS). A simplified mathematical model for delay versus traffic loads considering both low and heavy traffic conditions is developed. In optical domain we have studied the delay characteristics for the offset-time-based scheme with fiber delay lines (FDLs). The minimum delay zone is shown considering the variation of channel capacity C, burst size B, offset time depending on degree of isolation, burst overlapping parameters, and token round trip time R in a metropolitan area network (MAN). Finally, numerical calculation and simulations in priority queue management for different class of service (CoS) show the results are very close, thus validating our approximate delay model. The results show the reduction for higher priority packet latency and the conditions so that low priority packets are not severely dropped.