Constraint-based Dynamic Routing And Wavelength Assignment Algorithms In WDM Optical Networks

With the development of information society and the explosive growth of Internet, there emerges an acute need for very high-bandwidth transport network facilities, whose capabilities are much beyond those that current high-speed networks can provide. Wavelength-division multiplexing (WDM) is a promising approach that can exploit the enormous bandwidth of the optical fiber mismatch by requiring that each end-user's equipment operate only at electronic rate, but multiple WDM channels from different end-users may be multiplexed on the same fiber. All-optical networks based on the concept of WDM and wavelength routing is considered as a candidate for the next generation transport network. The network consists of a photonic switching fabric, comprising "active switches" connected by fiber links to form an arbitrary physical topology. Each end-user is connected to an active switch via a fiber link. Each node has a dynamically configurable optical switch, which supports fiber switching and wavelength switching. The basic mechanism of communication in a wavelength-routed network is a lightpath. A lightpath is an all-optical communication channel between two nodes in the network, and it can span more than one fiber link. In the absence of any wavelength-conversion device, a lightpath is required to be on the same wavelength throughout its path in the network. In this dissertation, we mainly address the following problems: priority-based wavelength assignment algorithm in WDM transport networks, QoS routing algorithm in multi-fiber WDM transport networks, QoS-based routing and wavelength assignment algorithm in survivable WDM transport networks, QoS-based wavelength rerouting algorithms in multi-fiber WDM transport networks, dynamic routing and wavelength assignment in IP over WDM networks, policy-based dynamic routing and wavelength assignment in IP over WDM networks, dynamic routing and wavelength assignment for shared protection in IP over WDM networks.A novel priority-based wavelength assignment algorithm, Dynamic Threshold Method, is proposed in Chapter 2. A set of wavelengths, Preferred Wavelength Set (PWS), is pre-allocated for each priority request. Based on the usage of wavelength in the PWS of a priority request, a threshold is dynamically calculated to decide whether the wavelengths for the higher priority request can be allocated to the lower. By using the algorithm, the blocking rate of the high priority request is guaranteed to be a lower degree, and at the same time performance of the low priority request is improved. So the network's average blocking rate is minimized. Simulation results of the network performance show that the proposed algorithm performs well in different dynamic traffic load situation.Basing on the DOS model's aggregating ability, the client layer's services with different QoS requirement can be mapped directly into the optical channel. Then the different QoS requirement of the client layer's services can be reflected by the different priority of the connection request at the border optical node in a DOS domain. A wavelength graph method is presented in theIVmulti-fiber WDM optical transport network to reduce the blocking probability of the connection request. Two optical QoS routing strategies, concentrating method and equalizing method, are proposed in Chapter 3. The two methods are compared by simulation results of the netw6rk performance in different dynamic traffic load situation.Wavelength continuity constraint leads to inefficient utilization of wavelength channels and results in higher blocking probability in WDM optical transport networks. In order to weaken the inefficiency of the constraint, wavelength rerouting is used. Based on a wavelength graph model, the QoS-based wavelength rerouting strategy, Dynamic selection method, is proposed in Chapter 4. Simulation results of the network performance in different dynamic traffic loads are given. The results show that the method can not only meet the different QoS requirements of the client layer's service, but also u...