PF-OBS: A proportionally fair congestion avoidance algorithm for Optical Burst Switching networks

Abstract

Optical Burst Switching (OBS) is an optical switching technique which eliminates the electronic bottleneck by keeping transmitted data in the optical domain. Therefore, it can effectively utilize the large bandwidth available in optical fibres. For these reasons, OBS is considered the future of optical networks. However, burst loss caused by congestion is a significant problem in OBS because flexible, practical optical buffers currently do not exist. This thesis proposes a rate-based congestion control method, called PF-OBS, which limits the blocking probability in OBS networks. PF-OBS uses a utility maximization approach to congestion control. The method assigns prices to congested links. Ingress nodes receive bandwidth proportionally to the price they are willing to pay. The resulting rate allocation is proportionally fair. The method can keep the traffic load on all links under a predefined level. Simulations show that PF-OBS maintains the overall blocking probability at lower levels as compared with plain OBS. In addition, PF-OBS achieves higher total throughput than existing OBS flow control methods. The method remains stable in the presence of propagation delays.