Wavelength conversion and survivability with multicast sessions in all-optical wavelength-routed networks.

摘要

Wavelength-routed networks can effectively utilize the bandwidth of the optical fibers. We investigate wavelength conversion and survivability problems with multicast sessions in all-optical networks.; In wavelength-routed networks, the wavelength for a connection must be the same on all links. Thus, if a common wavelength is not available on all links, the connection request is blocked. Wavelength converters help to reduce the blocking probability of the network and enhance fiber utilization. First problem we investigate is Wavelength Converter Placement and Routing for Multicast sessions (WCPRM). Given a network topology and a set of multicast sessions, our objective is to realize as many sessions as possible by utilizing a fixed number of wavelength converters. Both static and dynamic traffic are considered. In the case of static traffic, the problem of wavelength converter placement is formulated as an integer linear program (ILP), and solved by CPLEX. The general problem of wavelength converter placement is NP-compete for arbitrary mesh network. Thus, we also developed heuristics to achieve near optimal placement of wavelength converters, which includes a greedy approach and a Tabu Search algorithm. We further studied the limited range wavelength converter placement problem for dynamic traffic.; For network survivability, we mainly study routing and wavelength assignment problem for light-tree protection. We investigate the problem of Preplanned Recovery with Redundant Multicast Trees (PRRMT) and that of Wavelength Assignment for Light-tree Protection (WA-LTP). The redundant trees we generate ensure the source node remains connected to all destination nodes for a multicast session request under single edge or node failures. Our objective is to minimize the total number of links used for both trees. We show that PRRMT can be formulated as an ILP and also develop a heuristic algorithm. We further investigate the wavelength assignment for the multicast protection trees. We propose a mathematical formulation and two heuristics to solve the wavelength assignment problem. The algorithms are evaluated with both static and dynamic traffic.; The performance of the proposed approaches is analyzed on several different network topologies, such as 14-node NSFNET, 21-node Italian network, and 40-node random networks.