Research On Traffic Grooming In Multi-layer Communication Networks

Optical transport networks(OTNs)include the first generation SDH networks and the second generation WDM/DWDM networks,which have evolved into the backbone for communication networks due to their enormous capacity.IP/MPLS over OTNs represents an evolution direction of Next Generation Networks,which is characterized by the framework involving multilayer transport networks.It is noted that the switching techniques in today's SDH and WDM networks still employ circuit switching,i.e.,the bandwidth is allocated to services according to some fixed granularities.However,the bandwidth of IP traffic flows is various.This results in traffic grooming becoming a research hotspot in IP over OTNs.The research on traffic grooming greatly influences the optimal utilization of network resource, network throughput and quality of service.In this dissertation,traffic grooming in IP/MPLS over WDM and/or IP/MPLS over SDH over WDM networks are researched thoroughly.Our work focus on the presentation of a novel multilayer network framework,the mathematic model for traffic grooming in multilayer networks,routing algorithm and resource allocation strategy.The main outcomes are depicted as follows.1.Dynamic routing optimal model and routing algorithm in IP/MPLS over WDM networksLabel switched paths(LSP)with various bandwidth granularities in an IP/MPLS over WDM network are earried by lightpaths that are offered by WDM layer through routing and wavelength assignment(RWA)algorithm.A series of lightpaths between the same node pair at IP/MPLS layer have different paths or wavelengths at WDM layer.A lightpath's path at WDM layer,which is composed of a series of wavelength links,actually reflects the wavelength consumption in the fiber links passed by the lightpath.Additionally,the available bandwidth of a lightpath varies with the dynamic traffic flows which cause the LSP's establishing or tearing down dynamically.Thus,the cost of a lightpath should be determined by the number of wavelength links and the lightpath's available bandwidth.In chapter 2,a dynamic routing optimal model-minimizing the total cost of lightpaths(MTCLP)is proposed.Correspondingly,an integrated routing algorithm also called as MTCLP is developed on the basis of this kind of optimal model and layered graph.Compared with two representative routing algorithms in optical networks,MTCLP has lower blocking probability and less consumption to the wavelength links.2.Routing algorithms for multi-priority label switched path in optical-transceiver-constraint MPLS over WDM networksOriginal layered graph that must guarantee wavelength consistency is used to solve RWA problems in all-optical networks.As it is used in MPLS over WDM networks,there exist two shortcomings.Firstly,all wavelength planes in a layered graph are isolated each other.This case requires the multi-hop lightpaths to carry a LSP must have the same wavelength,whereas these lightpaths can have various wavelength through O-E-O conversion.Additionally,wavelength is viewed as a kind of label in GMPLS paradigm,which means it could be switched.As a result,the blocking probability of LSP establishment arises sharply when employing original layered graph.Secondly,optical transceiver is not considered in original layered graph,but the number of optical transceiver is limited in practical networks and sometimes optical transceiver is perhaps the main bottleneck when routing a LSP.The extended layered graph is proposed in Chapter 3 to solve these problems,in which optical transceiver is processed as a kind of link resources.Furthmore,a LSP's priority is evaluated according to its QoS request,thus differentiating integrated routing algorithm(DIRA)is proposed for establishing multi-priority LSPs. DIRA takes into account a LSP's QoS and the optimal network resource usage comprehensively by the method that converts a LSP's end-to-end delay to the hop bound of lightpaths that carry this LSP,thus DIRA can reduce the blocking probability of delay-constraint LSP and improve network throughput.3.Algorithms for traffic grooming in three-layer networks involving IP,SDH, and WDM networksFor most of telecom service providers,the development of WDM networks doesn't mean SDH networks should be abandoned because their important revenue-generating voice business and/or other services are still operated by SDH networks.In addition,the capacity of SDH networks can be expanded through SDH over WDM.For this case,a three-layer network framework that involves IP over SDH,IP over WDM,and SDH over WDM is proposed in chapter 4.An optimal model for traffic grooming in three-layer networks is presented on the basis of integer linear programming.Validity of the proposed optimal model is proved by employing the optimal software to get the model's solution in a small size network. Since our optimal model for traffic grooming in three-layer networks is NP-Complete,three kinds of heuristics-RS-IRAMN,MAF-IRAMN and LCBRF-IRAMN are developed.4.Virtual topology reconfiguration in three-layer networksIn three-layer networks the topology of SDH and IP layer,which are constructed by a specific algorithm for traffic grooming according to some traffic matrices,are both reconfigurable.Some greedy algorithms make the utilization of network resource(wavelength in fiber link,the interface equipment between layers,etc.) limited to some status which are corresponding to local optimization.Strategy of global path provision(StraGPP)which is used for virtual topology reconfiguration is proposed in Chapter 5.StraGPP utilizes tabu-search heuristic to optimize network resource utilization on the condition of no loss of traffic flows.