Research On Hierarchical Routing In Automatically Switched Optical Network

As automatically switched optical network (ASON) has been defined as the next generation universal transport network, the theoretical and technological research on hierarchical ASON becomes one of the key topics recently. This kind of research includes the structural design of large scale ASON as well as the intelligent controlling techniques in hierarchical ASON. In this dissertation, the performance of the routing protocol in hierarchical ASON is addressed in terms of several features through theoretical analysis and simulation. A kind of topology aggregation algorithm suitable for hierarchical wavelength routing optical networks is proposed. Simulations with randomly-generated networks show that topology information compression can be achieved with a little loss of its accuracy. Results also indicate that the advantage of this algorithm is also behaved on reducing the amount of link-state-advertisement messages and making networks less vulnerable to the propagation delay of these messages over communication links. In this dissertation, several different routing and connection management schemes are implemented and their performance compared in the environment of hierarchical ASON. Both the advantage of hierarchical routing over source routing and the advantage of local information based connection management scheme over global link-state-information based connection management scheme in terms of the connection acceptance capability are illustrated. Analytical model and approximation method are developed for analyzing end to end call blocking probability in hierarchical wavelength routing optical networks. By comparing theoretical results and results obtained from discrete event simulation, it is demonstrated that this model provides reasonable estimate of end to end call blocking probability in hierarchical wavelength routing optical networks, with the correlation model giving much more accurate estimate than the independent model. Based on the above achievements, hierarchical routing protocol (HRP) in ASON has been devised in this dissertation. The protocol validation is fulfilled in two different ways. Firstly, the procedure of this hierarchical routing protocol is modeled in the simulation environment of OPNET. Secondly, a hierarchical ASON test-bed is set up and the hierarchical routing software is developed in Linux platform in accordance to the devised protocol. By conducting both simulations and field experiments, the applicability and scalability of HRP is validated. The research on fast connection setup procedures in ASON is also addressed in this dissertation. i An intra-domain parallel signaling scheme is implemented and results from field experiments and simulation show that its performance is superior to the traditional serial signaling in terms of connection setup time and call blocking probability. ii Distributed inter-domain parallel signaling scheme in source routing paradigm is proposed. By conducting experiments in the emulated hierarchical network, it is illustrated that the average connection setup time decreases greatly when this new scheme is adopted instead of the traditional scheme. iii A new connection management scheme called Multi-Path Routing with Abundant-Information-Collecting Probing is proposed. Simulation results show that the advantage of this scheme is behaved in achieving faster connection setup, lighter signaling overhead as well as lower call blocking probability concurrently.