The hop-limit approach for spare-capacity assignment in survivable networks

Abstract

This paper presents a new approach for sparecapacity assignment in mesh-type self-healing networks which use reconfigurable network elements as transmission hubs. Under this approach the process of reducing total weighted cost of spare capacity is obtained by taking into account all network's eligible restoration routes which do not violate a predetermined hop-limit value. The process derived considers a given set of possible failure scenarios, which include single-link, multi-link and node failures, and is adaptive to accommodate several practical considerations such as integrality of spare channels and modularity of transmission systems. This process is generally composed of two parts: Part 1 relies on a linear-programming formulation (Min-Max) from which a lower bound solution of spare cost is found; Part 2 rounds-up the solution of Part 1 to a feasible solution and uses a series of Max-Flow tests aimed at tightening the rounded-up assignment to a practical optimum. For small and moderate size networks a Mixed-Integer-Programming formulation of Part 1 can be used to obtain optimal results. A network, which has already been studied in the literature, is analyzed to illustrate the approach developed and to demonstrate, for cases where hop limits can feasibly be kept low, its superiority over other algorithms published in this area.Index Terms-Self-healing survivable networks, network flow, linear programming.

A New Approach to Survivability of Connection Oriented Networks

“…Without loss of generality we assume that sets containing proposals of primary routes that conform the LDR strategy are known. The hop-limit approach proposed in [6] can be used in order to calculate such sets. It means that we do not process all possible routes, but only a subset of them.…”

A comparative study of restoration schemes and spare capacity assignments in mesh networks

“…Note that in NSF restoration, if the traffic flows on primary paths are integers then the working and spare capacities on the links and the traffic flows on restoration paths will be integers. Our ILP formulation is similar to the one reported in [6], [9], [10], [14]. Therefore, only the methodology of defining the eligible path set is presented.…”

“…To achieve the global minimum spare capacity cost, all the possible distinct routes between the target node pair must be represented in the constraint system. The number of all possible distinct routes in networks of moderate size is very large and has been restricted in practice [3], [6], [9], [10], [14]. We have chosen the minimum of K successively shortest loopless paths and all possible loopless paths between the target node pair to form the eligible path set.…”

“…The (offline) spare capacity assignment problem has been formulated as an integer linear program using multicommodity flow model in [3], [6], [8]- [10], [14]- [18]. These models use pre-defined eligible path sets for all the demand pairs to formulate the search space.…”

“…The objective is to minimize the cost of spare capacity assignment. The hop limit approach to restrict the path length has been proposed in [14]. The K successively shortest paths approach to restrict the size of the eligible path set is used in [3], [6], [9], [10].…”