Virtual topology design and flow routing in optical networks under multihour traffic demand

Abstract

This paper addresses the problem of finding a static virtual topology design and flow routing in transparent optical WDM networks under a time-varying (multi-hour) traffic demand. Four variants of the problem are considered, using fixed or dynamically adaptable (i.e., variable) flow routing, which can be splittable or unsplittable. Our main objective is to minimize the number of transceivers needed which make up for the main network cost. We formulate the problem variants as exact ILPs (Integer Linear Programs) and MILPs (Mixed ILPs). For larger problem instances, we also propose a family of heuristics based on the concept of domination between traffic matrices. This concept provides the theoretical foundations for a set of techniques proposed to reduce the problem complexity. We present a lower bound to the network cost for the case in which the virtual topology could be dynamically reconfigured along time. This allows us to assess the limit on the maximum possible benefit that could be achieved by using optical reconfigurable equipment. Extensive tests have been conducted, using both synthetically generated and real-traced traffic demands. In the cases studied, results show that combining variable routing with splittable flows obtains a significant, although moderate, cost reduction. The maximum cost reduction achievable with reconfigurable virtual topologies was shown to be negligible compared to the static case in medium and high loads.

Heuristic Approaches for Periodic Reconfiguration of Lightpath-based Networks under Multi-hour Traffic

“…However, in the last decade, the interest of the optical community has shifted to lightpath-based transparent optical networks [3], [8], [11]- [27]. Initial investigations on virtual topology reconfiguration consider solely the case of one-time adaptations.…”

“…Recently, other strategies have been attracting the interest of the research community considering periodicity in transparent optical networks planning [3], [15]- [27]. Most such research efforts have been centered on planning in the lower layer, i.e., finding an RWA for a given sequence of virtual topology designs corresponding to MH traffic.…”

“…In the last years, we have been intensively investigating different MH-VTD problem variants presented in [3], [25]- [27]. In [25] a set of MILP formulations is proposed to solve several MH-VTD-NR and MH-VTD-R problem variants minimizing solely the number of transceivers.…”

“…In [26], a set of Tabu Search based heuristic algorithms solving the previous problems is presented. In [3], we focus on the comparison of a set of variants of the non-reconfigurable problem, with and without flow routing reconfiguration. A set of MILP formulations for the problem and a 3-step algorithm which is based on the concept of traffic domination [28] are proposed.…”

“…Therefore, the traffic demand can be represented as a temporal sequence of matrices, where each matrix is associated to a time slot. This variant is denoted as MultiHour Virtual Topology Design (MH-VTD) [3]. Real traffic traces, such as the Abilene backbone network [4] and GEANT backbone network [5], support this assumption of the periodic nature of traffic.…”