A New Survivable Mapping Problem in IP-over-WDM Networks

We introduce a new version of the widely studied survivable mapping problem in IP-over-WDM networks. The new problem allows augmenting the given logical topology and is described as follows: given a physical topology and a logical topology, compute a survivable logical topology that contains the given logical topology such that the minimal survivable mapping cost for the result logical topology is minimized. The problem is significant for two reasons: 1) If there does not exist a survivable mapping for the given logical topology, we can add logical links to the given logical topology to make it survivable; 2) Even if a survivable mapping for the given logical topology can be found, it is still possible to reduce the minimal survivable mapping cost by adding logical links selectively. We first prove the existence of a solution to the problem, then provide a straightforward Integer Linear Program (ILP) formulation for the problem. Moreover, we present a theoretical result that leads to a simple NP-hardness proof of the problem and an improved ILP formulation. Simulation results demonstrate the significance of both the new survivable mapping problem and the theoretical result

Survivability issues in WDM optical networks

WDM optical networks make it possible for the bandwidth of transport networks to reach a level on which any failures would cause tremendous data loss and affect a lot of users. Thus, survivability issues of WDM optical networks have attracted a lot of research work. Within the scope of this dissertation, two categories of problems are studied, one is survivable mapping from IP topology to WDM topology, the other is p-cycle protection schemes in WDM networks.;Survivable mapping problem can be described as routing IP links on the WDM topology such that the IP topology stays connected under any single link failure in the WDM topology. This problem has been proved to be NP-complete [1]. At first, this dissertation provides a heuristic algorithm to compute approximated solutions for input IP/WDM topologies as an approach to ease the hardness of it. Then, it examines the problem with a different view, to augment the IP topology so that a survivable mapping can be easily computed. This new perspective leads to an extended survivable mapping problem that is originally proposed and analyzed in this dissertation. In addition, this dissertation also presents some interesting open problems for the survivable mapping problem as future work.;Various protection schemes in WDM networks have been explored. This dissertation focuses on methods based on the p-cycle technology. p-Cycle protection inherits the merit of fast restoration from the link-based protection technology while yielding higher efficiency on spare capacity usage [2]. In this dissertation, we first propose an efficient heuristic algorithm that generates a small subset of candidate cycles that guarantee 100% restorability and help to achieve an efficient design. Then, we adapt p-cycle design to accommodate the protection of the failure of a shared risk link group (SRLG). At last, we discuss the problem of establishing survivable connections for dynamic traffic demands using flow p-cycle

On Finding Minimal Two-Connected Subgraphs

We present efficient parallel algorithms for the problems of finding a minimal 2-edge-connected spanning subgraph of a 2-edge-connected graph and finding a minimal biconnected spanning sub-graph of a biconnected graph. The parallel algorithms run in polylog time using a linear number of PRAM processors. We also give linear time sequential algorithms for minimally augmenting a spanning tree into a 2-edge-connected or biconnected graph