Dynamic Wavelength routing in all optical mesh network

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. 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 to maximize the wavelength utilization and reduces the blocking probability in an arbitrary network. This approach contains two sub-algorithms: least congestion with least nodal-degree routing algorithm (LCLNR) and dynamic two-end wavelength routing algorithm (DTWR). We demonstrate that DWR can significantly improve the blocking performance, and the results achieved as good as placing sparse WCs in the networ

A Heuristic Converter Placement Scheme for Wavelength-routed Optical Networks

Absfraci -In optical networks with sparse wavelength conversion, the optimal converter placement (OCP) problem is one of the most important considerations. In this paper, we propose a heuristic O C P algorithm, called the Optimized Utilization Placement (OUP), to determine proper numbers of converters that should he placed at selected nodes. Performances of the OUP are evaluated by simulations when fired routing and fixed-alternate routing are used. The simulations justify that the OUP can significantly increase converter gains

The Scalability and Performance of Common Vector Solution to Generalized Label Continuity Constraint in Hybrid Optical/Packet Networks

Abstract—In hybrid Optical/packet networks, wavelength and VLAN tag continuity along a Label Switched Path are two common constraints. These two types of constraints, referred to as Generalized Label Continuity Constraints, have global significance in a network; namely, the label should appear only in other link- or node- disjoint paths. In considering these constraints, a solution is the common vector approach, which seeks a common available label along the path determined by CSPF without label constraints. In this paper, we provide an estimation method to compute the upper bound of the blocking probability for the above approach. We also address the scalability problem of the existing traffic engineering algorithms. We then present the simulation results corroborating with our analytical model.h

A heuristic for placement of limited range wavelength converters in all-optical networks

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength converters play an important role in enhancing the fiber utilization and reducing the overall call blocking probability of the network. As the distortion of the optical signal increases with the increase in the range of wavelength conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP complete problem [K.C. Lee, V.O.K. Li, IEEE J. Lightwave Technol. 11 (1993) 962-970] in an arbitrary mesh network. In this paper, we investigate heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks. The objective is to achieve near optimal placement of limited range wavelength converters resulting in reduced blocking probabilities and low distortion of the optical signal. The proposed heuristic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion of optical signals is significantly high. We observe that limited range converters at few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength converters placed at all the nodes. Congestion control in the network is brought about by dynamically adjusting the weights of the channels in the link thereby balancing the load and reducing the average delay of the traffic in the entire network. Simulations have been carried out on a 12-node ring network, 14-node NSFNET, 19-node European Optical Network (EON), 28-node US long haul network, hypothetical 30-node INET network and the results agree with the analysis. (C) 2001 Elsevier Science B.V, All rights reserved

Efficient Algorithms for Wavelength Converter Placement

In this paper, we consider the optimal converter placement problem for a given number of converters on a path topology in an all-optical WDM networks. The placement of converters on a path divides the path into segments. A segment is defined as a set of links between two consecutive converters on a path. We first introduce and prove that optimal placement considering end-to-end performance is obtained when segments on a path have equal blocking probability. This result is then used to achieve optimal converter placement using both the link-load independence model and link-load correlation model. It is not always possible to divide a path into segments with equal blocking probability due to the arbitrary values of the load on each link. Three implementation algorithms that approximately achieve minimum blocking probability with linear complexity are then proposed. The algorithms can be readily extended to ring networks

Routing and Spectrum Allocation in Spectrum-Sliced Elastic Optical Path Networks: A Primal-Dual Framework

The recent decade has witnessed a tremendous growth of Internet traffic, which is expected to continue climbing for the foreseeable future. As a new paradigm, Spectrum-sliced Elastic Optical Path (SLICE) networks promise abundant (elastic) bandwidth to address the traffic explosion, while bearing other inherent advantages including enhanced signal quality and extended reachability. The fundamental problem in SLICE networks is to route each traffic demand along a lightpath with continuously and consecutively available sub-carriers, which is known as the Routing and Spectrum Allocation (RSA) problem. Given its NP-Hardness, the solutions to the RSA problem can be classified into two categories: optimal solutions using link-based, path-based, and channel-based Integer Linear Programming (ILP) models, which require extensive computational time; and sub-optimal heuristic and meta-heuristic algorithms, which have no guarantee on the solution quality. In this work, inspired by a channel-based ILP model, we propose a novel primal-dual framework to address the RSA problem, which can obtain a near-optimal solution with guaranteed per-instance closeness to the optimal solution

Performance analysis of WDM optical networks with grooming capabilities

In this paper, we analyze the performance of WDM networks with traffic grooming capabilities supporting low-rate circuit-switched traffic streams. Traffic grooming in WDM networks collectively refers to the multiplexing, demultiplexing and switching of lower-rate traffic streams onto high capacity lightpaths. Networks which perform grooming only at the OADMs present in the nodes are referred to as Constrained Grooming Networks. Networks whose nodes switch traffic streams between wavelengths and perform grooming at the OADMs are referred to as Sparse Grooming Networks. Given the network topology, the traffic matrix and the node locations of grooming and traffic stream switching, we present an analytical model, using link-independence and wavelength-independence assumptions, to calculate the blocking performance. We illustrate the benefits of sparse grooming over constrained grooming in the mesh-torus and ring network topologies, using both simulation and analytical results

Capacity fairness of WDM networks with grooming capabilities

This paper addresses the issue of capacity fairness in WDM networks with traffic grooming capabilities, supporting lower- rate circuit-switched traffic streams. Traffic grooming in WDM networks, is defined as the act of multiplexing, demultiplexing and switching lower rate traffic streams onto higher capacity lightpaths. In such a network, in addition to add/drop and full wavelength switching features, some or all of the network nodes can be provided with the capability to switch lower-rate traffic streams from one wavelength on an input port to another wavelength on an output port. Call requests arrive randomly and can request a lower-rate traffic connection to be established between the node pair. The call requests that ask for capacity nearer to the full wavelength capacity are bound to experience higher blocking than those that ask for a smaller fraction. This difference in loss performance is more pronounced as the traffic switching capability of the network is increased. In this paper, we study the capacity fairness of existing dynamic wavelength assignment algorithms

Blocking performance of fixed‐paths least‐congestion routing in multifibre WDM networks

Wavelength‐routed all‐optical networks have been receiving significant attention for high‐capacity transport applications. Good routing and wavelength assignment (RWA) algorithms are critically important in order to improve the performance of wavelength‐routed WDM networks. Multifibre WDM networks, in which each link consists of multiple fibres and each fibre carries information on multiple wavelengths, offer the advantage of reducing the effect of the wavelength continuity constraint without using wavelength converters. A wavelength that cannot continue on the next hop on the same fibre can be switched to another fibre using an optical cross‐connect (OXC) if the same wavelength is free on one of the other fibres. However, the cost of a multifibre network is likely to be higher than a single‐fibre network with the same capacity, because more amplifiers and multiplexers/demultiplexers may be required. The design goal of a multifibre network is to achieve a high network performance with the minimum number of fibres. In this paper, we study the blocking performance of fixed‐paths least‐congestion (FPLC) routing in multifibre WDM networks. A new analytical model with the consideration of link‐load correlation is developed to evaluate the blocking performance of the FPLC routing. The analytical model is a generalized model that can be used in both regular (e.g. mesh‐torus) and irregular (e.g. NSFnet) networks. It is shown that the analytical results closely match the simulation results, which indicate that the model is adequate in analytically predicting the performance of the FPLC routing in different networks. Two FPLC routing algorithms, wavelength trunk (WT)‐based FPLC and lightpath (LP)‐based FPLC, are developed and studied. Our analytical and simulation results show that the LP‐based FPLC routing algorithm can use multiple fibres more efficiently than the WT‐based FPLC and the alternate path routing. In both the mesh‐torus and NSFnet networks, limited number of fibres is sufficient to guarantee high network performance