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Dynamic Wavelength Routing in All Optical Mesh Network CORE Metadata, citation and similar papers at core.ac.uk Provided by Research Online @ ECU Edith Cowan University Research Online ECU Publications Pre. 2011 2005 Dynamic Wavelength routing in all optical mesh network Kungmang Lo Edith Cowan University Daryoush Habibi Edith Cowan University Quoc Viet Phung Edith Cowan University Hoang Nghia Nguyen Edith Cowan University Follow this and additional works at: https://ro.ecu.edu.au/ecuworks Part of the Engineering Commons 10.1109/APCC.2005.1554043 This is an Author's Accepted Manuscript of: Lo, K. , Habibi, D. , Phung, Q.V. , & Nguyen, H. N. (2005). Dynamic Wavelength routing in all optical mesh network. Proceedings of Asia Pacific Conference on Communications. (pp. 178-182). Perth, WA. IEEE. Available here © 2005 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This Conference Proceeding is posted at Research Online. https://ro.ecu.edu.au/ecuworks/2918 2005 Asia-Pacific Conference on Communications, Perth, Western Australia, 3 - 5 October 2005. Dynamic Wavelength Routing in All-Optical Mesh Networks Kungmeng Lo, Daryoush Habibi, Senior Member, IEEE, Quoc Viet Phung, and Hoang Nghia Nguyen SCHOOL OF ENGINEERING AND MATHEMATICS EDITH COWAN UNIVERSITY PERTH, AUSTRALIA Abstract— Wavelength-division multiplexing (WDM) offers the capability to handle the increasing demand of network traffic in a manner that takes advantage of already deployed optical fibers. Lightpaths are optical connections carried end-to-end over a wavelength on each intermediate link. Wavelengths are the main resource in WDM networks. Due to the inherent channel constraints, a dynamic control mechanism is required to efficiently utilize the resource to maximize lightpath connections. Fig. 1. A 6 nodes and 9 links topology In this paper, we investigate a class of adaptive routing called Dynamic Wavelength Routing (DWR), in which wavelength converters (WCs) are not utilized in the network. The objective is constraint is removed, thus reducing network blocking. WCs, to maximize the wavelength utilization and reduces the blocking probability in an arbitrary network. This approach contains two however, are costly devices. It is not cost-efficient to set up sub-algorithms: Least Congestion with Least Nodal-degree Routing WC at each routing node. Therefore, one possible scheme to algorithm (LCLNR) and Dynamic Two-end Wavelength Routing address this issue is to set up a sparse number of WCs at algorithm (DTWR). We demonstrate that DWR can significantly some specific selected nodes to achieve adequate cost-effective improve the blocking performance, and the results achieved as performance [7]. Alternatively, call requests need to be as- good as placing sparse WCs in the network. signed appropriate routes and wavelengths over the lightpaths I. INTRODUCTION to maximize throughput of traffic pattern. This consideration The relentless need and continuously increasing demand is known as the routing and wavelength assignment (RWA) for telecommunication leads to wavelength-routed all-optical problem [8] [9]. WDM networks as the broadband backbone data transport The study of RWA algorithms is based on traffic load networks [1]. In WDM, the optical spectrum is divided into assumptions. If the traffic patterns in the network are organized many non-overlapping wavelength channels. Multiple kinds in advance, the traffic variations can be formulated as a of traffic are multiplexed onto a fiber by using different mixed-integer linear program (MILP) to yield an optimum wavelength channels. Wavelength routers can switch the input solution [10]. However, with dynamic traffic, each lightpath optical signals according to their wavelengths. Lightpath is an request between source and destination (s-d) pair arrives at optical channel, which is carried end-to-end optical connection random, and has a random holding time; after which it is from a source node to a destination node without any interme- tore down and the resources are set free. The objective in the diate electronics, created by the allocation of the wavelength dynamic traffic case is to efficiently select routes and assign throughout each intermediate link [2] [3]. Thus, lightpath is wavelengths to connections in the network at any time so as a direct communication path’ between any two nodes. If no to minimize the connection blocking, or maximize the number wavelength conversion is available in networks, lightpath must of call connections. Both static and dynamic traffic problems use the same wavelength on all the links along its path from the are NP-complete [10]. source to the destination edge node. In Figure 1, for example, RWA problem can be decoupled into the routing sub- ¡ if a call request on a route 1-2-4-6 is assigned wavelength problem and the wavelength assignment sub-problem. Among to establish a lightpath, then the links 1-2, 2-4 and 4-6 need proposed wavelength assignment algorithms, the first-fit as- ¡ to have free to support this connection. This restriction is signment (FF) [11] is the most popular and easy to implement called the wavelength continuity constraint. algorithm. This algorithm selects wavelength according to an Wavelength continuity constraint can lead to the inefficient ascending order from the available wavelengths along the utilization of wavelength channels and high blocking proba- path. In general, the first-fit assignment achieves a lower call bility. Thus, the task of efficient utilization of wavelengths in blocking probability than the random assignment especially optical networks becomes an important issue. when the number of wavelength channels per link is small. An idea that employs wavelength converters (WCs) in all- Routing strategy can be classified into two types: fixed and optical WDM networks to increase wavelength utilization adaptive. In fixed routing, the routing path between any two has been proposed [4] [5] [6]. The wavelength continuity end-nodes is pre-defined. The candidate path number can be 0-7803-9132-2/05/$20.00 ©2005 IEEE. 178 one or more. Normally, paths are chosen for the shortest paths II. DYNAMIC WAVELENGTH ROUTING or the minimum cost paths. Adaptive routing determines routes A. Assumptions after considering the current network state when a connection The objective of DWR is to minimize blocking probability request arrives. This sort of routing is more efficient than and maximize wavelength utilization. DWR requires extensive the fixed routing. Thus, recent studies on routing strategies support from the control and management protocols to con- mostly focus on adaptive routing [12]. One of the earliest tinuously update the current network state information. The proposed adaptive routing strategies is Least Loaded Routing link state routing algorithm is considered in our study. Our (LLR) [5]. LLR chooses the least congested path and assigns analytical model is designed under the following assumptions: a wavelength among the available wavelengths over a set of k A call (connection) request of each s-d pair is based on shortest paths. However, LLR may introduce a longer route, a Poisson distribution with arrival rate . The average thus wasting the network resources and resulting in a higher service holding time is exponentially distributed with blocking rate. © mean . The offered load (Erlangs) per node is ¥ © In [13], Hsu et al. propose a weighted-shortest path strategy . (WSP) to select a route. Their objective is to minimize the The mesh network is a set of nodes interconnected by network resource cost and balance the traffic load among each single-fiber links. Each fiber link is bidirectional. link as much as possible. Their analytical model, however, No queuing of connection requests is allowed. If a only considers that all nodes are equipped with a full-range connection can not be made, it is immediately discarded. of wavelength converters. Chu et al. proposed a weighted Each node has the same array of transmitters and re- least-congestion routing and first-fit wavelength assignment ceivers. algorithm (WLCR) [14]. Their algorithm focuses on a route for There is no multicasting. Call request is an end-to-end both the distribution of free wavelengths (F) and the lengths model. of the routes (h) jointly. The weight function is defined as Each fiber link can support each wavelength in either ¥ § © ¤ . Their routes are chosen from a set of routes that direction. have been pre-computed for each s-d pair. Their objective is to Each link is bidirectional, and each link has W wave- carry more traffic while keeping the blocking probability low. length channels. Without using WCs in the networks, their algorithms perform B. Notations better than the shortest path first-fit routing (SP-FF) and fixed- To solve the routing problem, a physical topology can be alternate first-fit routing (FA-FF), but close to LLR algorithm. modeled as a connected graph G(N,L),whereN is the set of In this paper, we study the RWA problem in single- network wavelength routing nodes and L is the set of network fiber circuit switched wavelength routing networks where the single-fiber links. The parameters of the model are functions of same set of wavelengths provided on each link. To our best the nodes, wavelength converters, fiber links and the number knowledge, most proposed adaptive routing algorithms select of wavelengths in a fiber link, where candidate routes from a pre-computed set of alternate paths. is the set of wavelength routing nodes (e.g OXCs or OADMs). Normally, routes are pre-computed by the edge-disjoint k- s denotes a source node. shortest paths for each s-d pair [4]. A route is determined d denotes a destination node. denotes the neighbour nodes of s. by calculating their cost or weight function, which is related denotes the neighbour nodes of d.
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