A practical approach to operating survivable WDM networks

Abstract

Several methods have been developed for joint working and spare capacity planning in survivable wavelength-division-multiplexing (WDM) networks. These methods have considered a static traffic demand and optimized the network cost assuming various cost models and survivability paradigms. Our interest primarily lies in network operation under dynamic traffic. We formulate various operational phases in survivable WDM networks as a single integer linear programming (ILP) optimization problem. This common framework avoids service disruption to the existing connections. However, the complexity of the optimization problem makes the formulation applicable only for network provisioning and offline reconfiguration. The direct use of this method for online reconfiguration remains limited to small networks with few tens of wavelengths.Our goal in this paper is to develop an algorithm for fast online reconfiguration. We propose a heuristic algorithm based on LP relaxation technique to solve this problem. Since the ILP variables are relaxed, we provide a way to derive a feasible solution from the relaxed problem. The algorithm consists of two steps. In the first step, the network topology is processed based on the demand set to be provisioned. This preprocessing step is done to ensure that the LP yields a feasible solution. The preprocessing step in our algorithm is based on: a) the assumption that in a network, two routes between any given node pair are sufficient to provide effective fault tolerance and b) an observation on the working of the ILP for such networks. In the second step, using the processed topology as input, we formulate and solve the LP problem. Interestingly, the LP relaxation heuristic yielded a feasible solution to the ILP in all our experiments. We provide insights into why the LP formulation yields a feasible solution to the ILP. We demonstrate the use of our algorithm on practical size backbone networks with hundreds of wavelengths per link. The results indicate that the run time of our heuristic algorithm is fast enough (in order of seconds) to be used for online reconfiguration.

Performance Implications of Meshing Degree for Optical Burst Switched Networks Using One-Way Resource Reservation Protocols

“…In this study, we consider OBS networks with the following mesh topologies: chordal rings with nodal degrees between 3 and 6, mesh-torus with 16 and 20 nodes, the NSFNET with 14-node and 21 links [11], the NSFNET with 16 nodes and 25 links [9], the ARPANET with 20 nodes and 32 links [6,11], and the European Optical Network (EON) with 19 nodes and 37 links [7]. For comparison purposes bi-directional ring topologies are also considered.…”

“…This result is confirmed in fig. 6, that presents the performance comparison of the nodal degree gain for the best (D5T (1,19,3,7,11)) and the worst (EON) of the topologies showed in figures 1 to 5. Figure 6 shows the nodal degree gain due to the increase of the nodal degree from 2 (D2T(1,19)) to: 3.89 (EON), and 6 (D6T (1,19,3,5,11,15)), as a function of λ/µ, in the last hop of each topology, for JIT, JET, Horizon, JIT + , and JumpStart signaling protocols (F = 64).…”

“…Figures 7-11 plot, respectively for JIT, JumpStart, JIT + , JET, and Horizon, the nodal degree gain in the last hop of each topology, as a function of the nodal degree, due to the increase of the nodal degree from 2 (D2T (1,14)) to 3 (NSFNET (N = 14)), from 2 (D2T(1,15)) to: 3 (D3T (1,15,5)), 3.125 (NSFNET (N = 16)), 4 (D4T (1,15,5,13) and Mesh-Torus (N = 16)), and 5 (D5T (1,15,7,3,9)), from 2 (D2T (1,18)) to 3.89 (EON (N = 19)), from 2 (D2T(1,19)) to: 3 (D3T (1,19,7)), 3.2 (ARPANET (N = 20)), 4 (D4T (1,19,3,9)), 5 (D5T (1,19,3,7,11)), 6 (D6T (1,19,3,5,11, 15)), from 2 (D2T(1,24)) to 4 (Mesh-Torus (N = 25)), and from 2 (D2T(1,29)) to 6 (D6T (1,29,3,7,11,13)). As may be seen, when the nodal degree increases from 2 to around 3, the largest gain is observed for degree-three chordal rings (slightly less than three orders of magnitude) and the smallest gain is observed for the ARPANET (less than one order of magnitude).…”

Optimizing multi-layered networks towards a transparently optical internet

“…This limitation is also applicable to some heuristics that have been proposed (e.g. [2], [3]), that are not scalable to large problems. Furthermore, when a large number of technologies are considered simultaneously, formulation of the design problem as a mathematical program is a task of massive complexity, and its solution, if it can be obtained, cannot be intuitively understood.…”

Design and operation of mesh-restorable WDM networks

“…Our goal in Chapter 5 ( [33]) is to develop an algorithm for fast online reconfiguration. We propose a heuristic algorithm based on LP relaxation technique to solve this problem.…”