Research On Key Techniques In OBS Networks With Limited Wavelength Conversion Capabilities

Nowadays, traditional core switching networks are performing poorly because of the increasing traffic volumes, the growing diversity of services and burstiness of data transmissions in the Internet. The next-generation backbones will be constructed based on the all-optical network (AON) with the abilities of fast-speed switching and terabit data transmission. Optical Burst Switching (OBS) combining high-speed optical transmission/switching technology and flexible electronic processing, has been proposed as a promising switching paradigm for next-generation of all-optical Internet backbones.In the dissertation, the current situation of optical switching techniques and the future development of next-generation networks are investigated, and particular attention is paid to the commercial OBS networks with limited wavelength conversion capabilities (OBS-LWCC). Firstly, the analytical models are built for OBS-LWCC network architectures; the solutions to the burst contention problem are developed from three aspects, involving signaling protocol, routing and wavelength assignment; and then the systematical and scalable mathematical frameworks are provided for the OBS-LWCC switching nodes with various configurations. Secondly, the mature control technologies of general multi-protocol label switching (GMPLS) system are introduced into OBS networks. The main achievements are summarized as follows:1) The concept of'leg'is proposed to establish the clear analysis model for the valuable OBS-LWCC network architecture. A general and practical OBS-LWCC network can be decomposed into multiple wavelength continuous segments according to the positions of wavelength converters in the network topology. Taking into account of the important role of convertible nodes in the network operations and significant effect on the overall blocking performance, the proposed leg-based analysis method is more adaptable to proactive congestion avoidance approaches, such as control signaling protocols, routing and wavelength assignment algorithms.2) Based on the leg analysis model, two control signaling mechanisms, that is Wavelength-Amend-on-Demand (WAoD) and contention-based limited signaling protocol (CLSP), are proposed respectively. Utilizing the feedback scheme on the leg scales in the signaling protocol, WAoD can adaptively support wavelength reconfiguration during a burst transmission period. Combining the advantages of DoD and the proposed WAoD, CLSP can accomplish the burst time-slot and carrier-wavelength reconfiguration simultaneously. By applying the WAoD and CLSP, the switching nodes in an OBS-LWCC network can be cooperated closely with each other when the contention arises, which overcomes the drawbacks in the existing protocols. Extensive simulation results indicate that, both the proposed WAoD and the compound CLSP perform better in avoiding burst contention in advance and obtain lower overall burst loss probability in the OBS-LWCC networks than the previous signaling mechanisms. Furthermore, since more detailed fields on service levels are added in the control formats, the proposed signaling protocols can support the expansion of multiple services in the future and the guaranteed QoS transmissions.3) The dynamic and static wavelength assignment algorithms, named PWA-leg and limited conversion graph algorithm (LCGA) are proposed for the OBS networks with sparse wavelength conversion capabilities (SWCC). Combining the conventional priority calculation and the new leg structures, the PWA-leg achieves overall optimality through local optimal selection on the burst carrier-wavelengths, and consequently, better adapts to the changes of dynamic burst traffics and network topology. Moreover, regarding more practical network configurations with the limited-range and limited number of wavelength converters, LCGA uses the auxiliary graph constructed with groups of available leg-lambdas and the classical Dijkstra algorithm to simplify the complex problem-solving process. The simulation experiments have verified that, in the OBS-SWCC networks, the proposed wavelength selection algorithms can intelligently assign the optimal wavelengths to diverse burst traffics at the wavelength convertible switches and have better performance in reducing blocking compared with the homologous algorithms.4) The asynchronous OBS switching systems with limited-range and limited number of wavelength converters (WCs) deployed by a share-per-fiber (SPF) mode are investigated. An analytical framework and the relevant blocking probability formulas are designed by combining the calculation of discouraged arrival rate in a birth-death process and two-dimensional Markov chain model. Compared with existing works, the main advantages of our work are to provide precise theoretical estimates for the general configuration cases of optical nodes and effectively predict the system blocking performance in a fraction of the computational time demanded by the repeated simulations. Furthermore, some results of the mathematical analyses and numerical computations will provide important instructions for the preliminary design and network dimensioning of next-generation commercial OBS backbones.5) A versatile overall routing scheme is presented, in which the solvable integer linear programming (ILP) problems are designed for the OBS networks with different wavelength conversion capabilities. Based on the above mathematical frameworks and analysis of various OBS-LWCC switching systems and the traffic engineering approaches, this routing algorithm can easily obtain a group of optimal transmission paths for an appointed OBS-LWCC network. The experiment results have indicated that, the expanded routing algorithm gains lower overall burst blocking probabilities than classical shortest-path routing algorithm, and moreover, always performs well in balancing payloads throughout the whole network under the different network topologies and traffic patterns.6) A novel peer-to-peer general label optical burst switching (GLOBS) system is proposed, in which the hierarchical model and the relevant functional modules are described in detail. Furthermore, the important issues of network applications in this system, such as packet-based integrated service provision, resource scheduling and traffic engineering, and label space reduction, are addressed and the corresponding solutions are presented respectively. Based on the investigations of next-generation commercial OBS network protocols and GMPLS-related control standards, the proposed GLOBS system which combines GMPLS technology with the OBS transport network as an organic whole, can satisfy the requirements of multiple-traffic developments and integrated service provisions. Both the general system infrastructure and detailed programming set an example for the future optical networks.