The Multi-granularity Switching Optical Network Dynamic Routing Algorithm

In recent years,optical networks using wavelength division multiplexing (WDM) have become promising candidates for wide area backbone networks.Since low-rate traffic services(e.g.IP services) are widely in use,traffic services not only entail the strong demand for network bandwidth.Because traffic services(e.g.IP services) are uncertain and unpredictable,optical networks are required to rapidly provide high quality multi-granularity bandwidth services and applications to users.That is to say,it is more and more urgent for optical networks to dynamically allocate bandwidth on demand.Within optical networks,each wavelength can be operated at very high speed,e.g.OC-48,OC-192 and OC-768 (the corresponding rates are 2.5Gb/s,10Gb/s and 40Gb/s,respectively),the bandwidth provided by the optical networks is coarse granularity.However,in operational networks,there is a huge bandwidth gap between the capacity of a wavelength and the low-rate traffic streams,e.g.OC-1,OC-3 and OC-12.To accommodate such kind of low-rate traffic streams(or called connections) with one lightpath will lead to inefficient resource utilization.At the same time,it is impossible to establish end-to-end lightpaths for all the connection requests,due to the limits of the number of wavelengths per fiber and the number of wavelength add/drop ports per node.So it is necessary to investigate how to efficiently set up connections for these traffic streams.Traffic grooming,which can also be called grooming,routing and wavelength assignment(GRWA),can meet this problem.With the explosive increase in Internet and Multi-media traffic,traffic services are carried by more and more wavelengths.It brings about a tremendous increase in the size(e.g.,number of ports) of optical cross-connects(OXC),as well as the cost and difficulty associated with controlling and management of such large cross connects.Hence,despite the remarkable technological advances in building photonic cross-connect systems and associated switch fabrics,the high cost and unproven reliability of huge switches have hindered their deployment.Recently,a new traffic grooming method has been considered,that is several wavelengths can be grouped into a waveband and waveband switching(WBS) has been paid more attention to in academic because of its actual advantages in reducing total number of ports in optical switch fabric at a node,the associated control complexity,and deployment cost of OXC nodes.To provide traffic grooming,optical switcher should be capable of multi- granularity switching.Optical networks composed of multi-granularity optical switcher are called multi-granularity switching optical networks.The main subject of this paper is multi-granularity switching optical networks,and the focus is Routing and Wavelength Assignment(RWA) algorithms for IP+Optical networks and waveband switching optical networks.In the first chapter,the concept of traffic grooming is given,and then the background and advances of multi-granularity switching technology are introduced. Most of previous works on grooming studies of static traffic streams for SDH/SONET WDM ring networks.But in the operational networks,connection requests dynamically arrive and hold for a period,then leave.With the constraints of the number of wavelength add/drop ports per node,the number of wavelengths per fiber and wavelength continuty in optical domain,dynamic traffic grooming problem is investigated in chapter 2.At first,three grooming policies are proposed,two routing graphs for traffic grooming are presented,and then an adaptive traffic-grooming algorithm,i.e.TLRA,is proposed.Finally,based on the simulation platform software developed,the performances of the proposed algorithm are evaluated.In chapter 3,three types of multi-granularity optical cross-connect(MG-OXC) architectures are analyzed.Various WBS schemes and lightpath grouping strategies are presented,and issues related to routing,waveband conversion and failure recovery techniques in WBS networks are discussed.Multi-granularity optical cross-connect(MG-OXC) has been proposed to reduce the size of optical switch for large capacity optical networks.With MG-OXC,fiber switching,waveband switching and wavelength switching can be introduced into optical network,Chapter 4 studies routing technology for waveband switching optical networks based on two-stage(wavelength and waveband) multiplexing scheme under dynamic traffic conditions.The characteristics in waveband switching(WBS) optical network are analyzed,and a new dynamic routing and wavelength assignment algorithm suitable for waveband switching optical networks is proposed.In this chapter,the blocking performances of WBS networks are compared with different node switching ratios,different waveband granularity and different routing methods using this algorithm.Moreover the optimal switching ratios of multi-granularity optical cross connect(MG-OXC) are analyzed.These results are instructive for the design of WBS network.To verify and evaluate the proposed algorithms in this paper,simulation platform software using discrete event simulating methods is developed.And based on the platform,the performances of all proposed algorithms are evaluated.The platform and some pseudo codes are given in chapter 5.Conclusions follow at the end of this dissertation.