We study the problem of maximizing path availability in mesh networks against simultaneous failures of multiple links without using protection schemes. The links belong to shared risk link groups (SRLGs) that have arbitrary failure probabilities. This problem is NP-hard, so we propose heuristic algorithms for networks with large numbers of SRLGs, as well as optimal solutions for networks with smaller numbers of SRLGs. The solutions are evaluated through simulations.

In this work, we study the problems of finding the path of maximum survivability between two end nodes. Multiple network devices and connections may fail simultaneously due to either deliberate attacks or components failures. The problem is NP-hard and we propose a novel algorithm to find the optimal paths with semi-polynomial running time and prove its correctness.

In this work, we study the NP-hard problem of finding the path of maximum reliability between two end nodes in mesh networks against simultaneous failures of multiple links. The links belong to shared risk link groups (SRLGs) that have arbitrary failure probabilities. We propose a novel algorithm to find the optimal path with semi-polynomial running time and prove its correctness.

In this work, we study the problem of maximizing lightpath reliability in optical mesh networks against simultaneous failures of multiple fiber links without using protection schemes. The fiber links belong to shared risk link groups (SRLGs) that have arbitrary failure probabilities. This problem is NP-hard and we propose heuristic algorithms for networks with large numbers of SRLGs as well as optimal solutions for networks with smaller numbers of SRLGs. The solutions are evaluated through simulations.

In this work, we investigate the routing problems of minimizing the number of distinct transmission mediums or carrier domains for multimedia communications. We consider the problems of two-party connection as well as three-or-more-party connections. By minimizing the number of distinct transmission mediums or carrier domains on the connections, rather than minimizing bandwidth, length or hop counts, the network carriers may achieve higher cost savings on connection provisioning and management. These problems are proven to be NP-hard. Heuristic algorithms are proposed for larger instances of the problems and evaluated through simulations.

In this work, we consider the problem of maximizing the reliability of connections in mesh networks against failure scenarios in which multiple links may fail simultaneously. We consider the single-path connection problem as well as multiple-path (protected) connection problems. The problems are formulated as minimum-color path problems, where each link is associated with one or more colors, and each color corresponds to a given failure event Thus, when a certain color fails, all links which include that color will fail. In a single-path problem, by minimizing the number of colors on the path, the failure probability of the path can be minimized if all colors have the same probability of causing failures. In the case of two paths, where one path is a protection path, if all colors have the same probability of causing failures, the problem becomes that of finding two link-disjoint paths which either have a minimum total number of colors, or which have a minimum number of overlapping colors. By minimizing the total number of colors, the probability that a failure will occur on either of the paths is minimized. On the other hand, by minimizing the number of overlapping colors, the probability that a single failure event will cause both paths to fail simultaneously is minimized. The problems are proved to be NP-complete, and ILP formulations are developed. Heuristic algorithms are proposed for larger instances of the problems, and the heuristics are evaluated through simulation.

In this paper, we provide a new analytical model for evaluating the blocking performance of dynamic lightpath establishment in multifiber wavelength-routed networks. By adopting the simple link-independent model together with the wavelength correlation assumptions, we manage to achieve a good balance between analytical accuracy and computational complexity. Extensive numerical results show that the proposed model can quickly produce accurate analytical results under different traffic loads and in different networks.

Path protection requires finding a working path and a protection path that are link disjoint. We consider the dynamic lightpath protection problem in WDM mesh networks where a single risk factor may cause multiple links to fail simultaneously. The objective is to find link-disjoint lightpaths that are also risk disjoint. A similar problem has recently been proven to be NP-complete. We give an alternative proof of the NP-completeness, and formulate the problem as an integer linear program. We then develop heuristic algorithms and evaluate the performance of the algorithms through computer simulation. We show that we can achieve satisfactory performance using the heuristic techniques.

Path protection requires finding a working path and a protection path that are link disjoint. In this paper, we consider the dynamic lightpath protection problem in WDM mesh networks under the wavelength continuity constraint. Existing polynomial time algorithms can be applied to find a pair of link-disjoint lightpaths on a single wavelength; however, such algorithms fail if the working and protection lightpaths are on two different wavelengths. We prove the problem is NP-complete for both dedicated protection and shared protection. We develop an integer linear programming (ILP) formulation and heuristic solutions for the problem. Computer simulations are conducted to evaluate the performance of the heuristic algorithms.