In future GMPLS-based wavelength-routed networks (WRNs), lightpaths are set up or torn down dynamically. Blocking probabilities of on-demand requests are an important performance measure. However, the network average blocking probability only indicates the global performance of the network. Due to large resource requirements and wavelength continuity constraint, the blocking probabilities of longer-hop connections are usually much higher than those of shorter-hop connections. This problem is the so-called fairness problem. In this paper, a priority-based control is proposed to improve the fairness between different connections. Connections with high blocking probabilities are assigned high priorities and they are able to preempt low priority connections with a predetermined probability. Both theoretical analyses and simulations are given. It is shown that the proposed control not only improves the fairness, but also ensures that the average blocking probability is not degraded much. Hence, the performance of the GMPLS-based optical networks will be improved greatly.
In next-generation IP over WDM networks, lightpaths are set up or torn down dynamically. Traditionally, OSPF in IP layer and OSPF-TE in optical layer disseminate routing information independently. Obviously, this 2-layer routing mechanism is complex and O&M cost is high. Furthermore, in a dynamic environment, both OSPF-TE and OSPF have very heavy control overheads when lightpaths change frequently. In this paper, an integrated routing protocol is proposed. The link state information of both IP layer and optical layer is disseminated simultaneously using the same routing protocol messages. The proposed protocol also advertises wavelength availability information if necessary in order to reduce the blocking probability of routing and wavelength assignment (RWA) algorithm. This proposed integrated protocol is very simple. Furthermore, its control overhead can be reduced from several to about ten times. In addition, RWA's performance is also improved. Hence, the performance of the IP over WDM networks will be improved greatly and significantly.