Valid inequalities and a branch-and-cut algorithm for the routing and spectrum allocation problem

TL;DR

This paper introduces new valid inequalities and a branch-and-cut algorithm to efficiently solve the NP-hard routing and spectrum allocation problem in flexible optical networks, improving solution methods for this critical networking challenge.

Contribution

The paper develops novel valid inequalities and a branch-and-cut algorithm specifically tailored for the RSA problem in flexgrid optical networks, advancing solution techniques.

Findings

The proposed method effectively solves RSA instances.

The approach outperforms existing methods in computational experiments.

The algorithm demonstrates scalability for large network instances.

Abstract

One of the most promising solutions to deal with huge data traffic demands in large communication networks is given by flexible optical networking, in particular the flexible grid (flexgrid) technology specified in the ITU-T standard G.694.1. In this specification, the frequency spectrum of an optical fiber link is divided into narrow frequency slots. Any sequence of consecutive slots can be used as a simple channel, and such a channel can be switched in the network nodes to create a lightpath. In this kind of networks, the problem of establishing lightpaths for a set of end-to-end demands that compete for spectrum resources is called the routing and spectrum allocation problem (RSA). Due to its relevance, RSA has been intensively studied in the last years. It has been shown to be NP-hard and different solution approaches have been proposed for this problem. In this paper we present several families of valid inequalities, valid equations, and optimality cuts for a natural integer programming formulation of RSA and, based on these results, we develop a branch-and-cut algorithm for this problem. Our computational experiments suggest that such an approach is effective at tackling this problem.