Elsevier

Computer Communications

Volume 32, Issue 5, 27 March 2009, Pages 1000-1005
Computer Communications

A new heuristic protection algorithm based on survivable integrated auxiliary graph in waveband switching optical networks

https://doi.org/10.1016/j.comcom.2008.12.029Get rights and content

Abstract

In this paper, we study the survivability in waveband switching optical networks and propose a new heuristic algorithm called Protection based on Survivable Integrated Auxiliary Graph (PSIAG) to tolerate the single-link failure. The survivable integrated auxiliary graph (SIAG) is compared of the single virtual topology layer and multiple waveband-plane layers, and it can well solve the problem of routing and waveband assignment. In PSIAG, we can feasible use the waveband sub-path grouping scheme based on SIAG to save the switching ports in MG-OXCs. For each demand, PSIAG first computes the single-hop or multi-hop route-pair including a primary path and a link-disjoint backup path on virtual topology layer. If the route-pair cannot be found on virtual topology layer, PSIAG then computes the hybrid multi-hop route-pair on jointing the virtual topology layer and waveband-plane layers. Simulation results show that PSIAG can obtain better performance than previous algorithm.

Introduction

In Wavelength-Division-Multiplexing (WDM) optical networks, the failures of fiber links may lead to a lot of traffic blocked since each wavelength channel has the transmission rate over several gigabits per second. Therefore, survivability in optical networks is a very important issue and has been studied for many years [1]. Survivable schemes in optical networks mainly include protection scheme and restoration scheme, in which the protection scheme can be simpler configured and also have faster recovery time so that most previous researches are favorite for employing protection scheme. Protection scheme can be further classified into three categories, i.e., path-based protection, link-based protection, and segment-based protection [2], [3], [4], [5]. Generally, path-based protection can perform better resource utilization ratio than the link-based protection and segment-based protection, while link-based protection and segment-based protection can perform faster recovery time than the path-based protection. Most previous researches consider the path-based protection since it is easier to implement in the current phase than the link-based protection and segment-based protection.

At the same time, with the number of wavelengths in each fiber keeps increasing, the number of switching ports and the cost of conventional optical cross-connect (OXC) are greatly enhanced. However, the increased switching ports and cost can be saved by the waveband switching technique [6], [7], which can perform the waveband grouping method to bind several lightpaths of wavelength level into one waveband to be switched by only one port, and then the saved cost can be used for the construction of survivable optical networks. Therefore, survivability in waveband switching optical networks has become a hot research in recent years [8], and some papers have addressed this problem in waveband switching optical networks [9], [10], [11].

Although these papers [9], [10] investigated the protection in waveband switching optical networks with considering the shared backup wavelengths and proposed the ILP formulations, it did not propose efficient heuristic algorithms. The authors in [11] proposed heuristic algorithm, but it is only suitable for the same source-destination waveband grouping which may consume more switching ports in MG-OXCs.

In this paper, in order to improve the performance on saving switching ports in MG-OXCs, we propose a new heuristic routing algorithm called Protection based on Survivable Integrated Auxiliary Graph (PSIAG) to tolerate the single-link failure in waveband switching optical networks. The SIAG is compared of the single virtual topology layer and multiple waveband-plane layers, and it can well solve the problem of routing and waveband assignment. In PSIAG, we can feasible use the waveband sub-path grouping scheme to save the switching ports in MG-OXCs. For each demand, PSIAG first computes the single-hop or multi-hop route-pair including a primary path and a link-disjoint backup path on virtual topology layer. If the route-pair cannot be found on virtual topology layer, PSIAG then computes the hybrid multi-hop route-pair on jointing the virtual topology layer and waveband-plane layers. Compared with previous algorithm, PSIAG not only can save more switching ports but only can obtain lower blocking probability.

The rest of this paper is organized as follows: Section 2 presents the network model and the survivable integrated auxiliary graph; Section 3 proposes the heuristic steps of algorithm; Section 4 presents the simulation results and analysis; Section 5 concludes this paper.

Section snippets

Network model

The physical network is denoted as G (N, L, B, W, T), where N, L, B, W and T represent the set of nodes that are equipped with MG-OXCs, set of links each of which is bidirectional and contains two unidirectional fibers with contrary direction, set of available wavebands on each fiber, set of available wavelengths on each fiber, and set of tunable transceivers that can tune the signal to any wavelength or waveband in fibers. We assume each demand requires the bandwidth of one wavelength channel, and

Algorithm description

The heuristic steps of PSIAG are presented as follows:

  • Step 1: Initialize SIAG according to the physical network topology.

  • Step 2: Update SIAG. Remove the virtual-link if the number of transceivers on the corresponding virtual node is zero. Remove the waveband-route-pair link on VTL if the number of residual available wavelengths on the waveband-route-pair link is zero.

  • Step 3: Wait for the demand arrival. If demand Dn with source node s and destination node d arrives, go to step4; otherwise,

Simulation and analysis

We simulate a dynamic network environment with the assumptions that demands arrive according to an independent Poisson process with arrival rate β and that the demands’ holding times are negatively exponentially distributed 1/μ, i.e., the network load is β/μ Erlang. In simulation, we set μ to 1. The test network is NSFNET shown in Fig. 2, where each link is bidirectional and contains two unidirectional fibers with contrary direction. We assume the required bandwidth of each demand is one

Conclusion

This paper has proposed a novel heuristic algorithm called Protection based on Survivable Integrated Auxiliary Graph (PSIAG) to address the single-link failure in waveband switching optical networks. The SIAG includes the single virtual topology layer and multiple waveband-plane layers for well solve the problem of routing and waveband assignment. In PSIAG, for each demand, we first computed the single-hop or multi-hop route-pair on virtual topology layer. If the route-pair cannot be found on

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