Research On Grooming Algorihtms In WDM Multi-Domain Optical Networks

With the rapid growth of Internet traffic, the Wavelength Division Multiplexing (WDM) technology to carry the IP services has become the core technology of the next-generation backbone network. However, in practical applications, the required transmission rate of each connection demand is much lower than that of each wavelength. Accommodating such kind of low-rate connection demands with one dedicated lightpath will lead to inefficient resource utilization and high blocking probability. Therefore, grooming technology in WDM optical network has become a challenging issue.At the same time, with the growing size of optical network, today’s backbone optical network is primarily hybrid and it has been divided into several independent domains. Each domain is an independent routing and recovery area in which different network operators manipulate and manage the own networks alone by using different techniques. In order to satisfy the network security, the scalability and the network operators interest considerations, only the aggregated routing information can be exchanged amongst multi-domains. The lack of complete and global knowledge of the network information makes it much chanllenging to calculate the optimal routing for the cross-domain connection demands. The division of domains of the optical network makes it impossible to directly apply the grooming algorithms in single-domain optical network to multi-domain optical network. Therefore, considering the inter-domain routing and intra-domain routing, this thesis focused on the grooming problems in WDM multi-domain network and studied the waveband grooming, the multi-granularity grooming and the survivable grooming in multi-domain network.With the increasing number of wavelengths in each fiber, the OXC port number and the management cost keep enlarging. This brings a lot of issues to the design and the stability of the OXC. In order to reduce the high cost and complexity of switches, current works proposed WaveBand Switching (WBS) technology that allows several wavelengths to be grouped into a waveband through a port to switch, thus the switching ports and the expense can be saved. Most previous research literatures about waveband switching are in the single-domain network. But with the rapid growing size of the network, the control cost and the management complexity of switching node in multi-domain network are also increased significantly. Therefore, in chapter two, this thesis studied the problem of waveband grooming in WDM multi-domain network and proposed a novel heuristic algorithm called Hierarchical Multi-domain Waveband Grooming (HMWG). The algorithm can not only solve the routing problem for the cross-domain connection demands, but also can decrease the transmitting port consumption of the whole network. Through simulation, the results showed that the HMWG algorithm can obtain better resource utilization and lower blocking probability than the previous algorithm.With the increasing of the network multimedia services, multicast connection demands are becoming more and more popular. Most previous research literatures about multicast grooming algorithms are in the single-domain network. However, in multi-domain optical network, due to the limited nature of the information exchange amongst multi-domains, it brings new challenges to cross-domain multicast grooming. To support the multicast grooming in multi-domain network, in chapter three, this thesis studied the problem of multicast grooming in WDM multi-domain network and proposed three heuristic algorithms called Fixed Routing Multicast Grooming (FRMG), Virtual Topology Multicast Grooming (VTMG) and Hierarchical Topology Multicast Grooming (HTMG), respectively. The main difference of these algorithms was that the inter-domain routings are performed by different manners; that is, the routings in FRMG, VTMG and HTMG are computed based on the domain-by-domain fixed routing table, on the high-layer aggregative virtual topology of multi-domains, and on the Inter-domain Virtual Topology Graph (Inter-VTG), respectively. Finally, this thesis compared the performance of the three algorithms through simulation. It can be seen from the results that the blocking probability and the average port-cost of the HTMG are all the lowest while its cost is the high time complexity.Because of diverse trends of users’bandwidth requirements, optical network has been 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 network to dynamically allocate bandwidth on connection demand. Most previous research literatures are focusing on the single-granularity and in the single-domain. Therefore, in chapter four, this thesis investigated the problem of multi-granularity grooming and proposed a new heuristic algorithm called Hierarchical Multi-domain Multi-granularity Grooming (HMMG). The algorithm can combine the traffic grooming with the waveband grooming. For each connection demand, the HMMG first classified the size of the connection demand, and then according to the size of the demand the HMMG groomed it into the existing waveband-or wavelength-tuunel links. Through simulation, the results showed that the HMMG algorithm can obtain better resource utilization and lower blocking probability than the previous algorithm.In optical network, since each optical channel has the transmission rate over several gigabits per second, the failures of fiber links or nodes may lead a lot of connection demands to be blocked. Therefore, the survivable grooming has emerged as one of important issues in the design of optical network. Combining with the waveband grooming, most previous research literatures studied the problem of survivable waveband grooming in single-domain network, but they did not consider the multi-domain network; Therefore, in chapter five, this thesis investigated the problem of survivable waveband grooming in multi-domain network and proposed two mixed shared path survivable grooming algorithms, called Intra-domain Sub-path Survivable Grooming (ISSG) and Inter-domain End-to-end Survivable Grooming (IESG), respectively. The main difference between the two algorithms is in the computation on the inter-domain protection path. The simulation results show that the blocking probability of IESG algorithm is lower than ISSG algorithm, but its cost is to spend more average port-cost.To verify and evaluate the proposed algorithms in this thesis, the simulation platform software has been developed. Based on this platform, the performances of all proposed algorithms are evaluated. The platform and important data structure are given in chapter six. Finally, the chapter seven gave the summary and prospects.