Grooming of dynamic traffic in WDM star and tree networks using a genetic algorithm

The advances in WDM technology lead to the great interest in traffic grooming problems. As traffic often changes from time to time, the problem of grooming dynamic traffic is of great practical value. In this article, we discuss the dynamic grooming of traffic in star and tree networks. A genetic algorithm (GA) based approach is proposed to support arbitrary dynamic traffic patterns, which minimizes the number of ADMs and wavelengths. To evaluate the algorithm, tighter bounds are derived. Computer simulation results show that our algorithm is efficient in reducing both the number of ADMs and wavelengths in tree and star networks.     

Effective Traffic Grooming Algorithms in SONET/WDM Ring Networks

Much work has focused on traffic grooming in SONET/WDM ring networks. Previous work has considered many aspects of traffic grooming, including minimizing the number of ADMs, minimizing the number of wavelengths, considering different traffic models, using different network architectures, incorporating switching capability and so on. In this work, we study traffic grooming in unidirectional ring networks with no switching capability under both uniform traffic and non-uniform traffic models to reduce electronic multiplexing costs. Based on the clustering notion, we derive a general and tighter lower bound for the number of ADMs required in traffic grooming under the uniform all-to-all traffic model. This bound reduces to special cases obtained in previous work. We also derive general, tighter, and closed form lower bounds for the number of ADMs required under two non-uniform traffic models: the distance-dependent traffic model and the non-uniform symmetric traffic model. Cost-effective multi-phase algorithms that exploit traffic characteristics are then designed and studied to efficiently groom traffic streams under different traffic models. Our numerical and simulation results show that the proposed multi-phase algorithms outperform existing traffic grooming algorithms by using a fewer number of ADMs. Our algorithms in several cases also achieve the lower bounds derived.     

Improved Approaches for Cost-Effective Traffic Grooming in WDM Ring Networks: Uniform-Traffic Case*

To fully utilize the capabilities of a SONET/ADM network, traffic grooming is needed to multiplex a number of lower-rate traffic streams into a higher-rate stream, and vice versa. Although the capacity of a SONET ring network can be upgraded by operating it over multiple wavelengths, the corresponding network design may be costly if it employs a large number of ADMs. A cost-effective design attempts to minimize the total number of ADMs used in the network while carrying the offered traffic. We introduce and evaluate the performance characteristics of two new traffic-grooming approaches for WDM ring networks, called single-hop and multihop. Our single-hop implementation uses the simulated-annealing heuristic. After placing all the traffic on virtual circles, we group the circles in order to reduce the number of ADMs in the network. Our multihop implementation places an ADM at each node based on the requested traffic in the traffic-demand matrix; then, it tries to groom the wavelengths which can be groomed. We select one of the nodes to be the hub node which has an ADM for each wavelength. The hub node, therefore, can bridge traffic between all of the wavelengths. Each algorithm is specified and illustrated by a simple example. Our results demonstrate that it is beneficial to use a single-hop approach based on simulated annealing for a small grooming ratio, but for a large grooming ratio and node number, we advocate the use of the multihop approach.     

A heuristic solution to SONET ADM minimization for static traffic grooming in WDM uni-directional ring networks

In recent years, minimization of add-drop multiplexers (ADMs) in wavelength division multiplexing (WDM) optical networks has gained lots of attention in both the research and commercial areas. This motivates the research presented in this paper. A heuristic algorithm is formulated for static traffic grooming in WDM uni-directional ring networks with an eye to minimize the number of required ADMs. The distinguished feature of the proposed heuristic is that it pairs up the calls of a given static traffic to approach the solution. The proposed heuristic is compared with the previous approach with same network configuration and traffic matrix to establish its effectiveness.     

Design and Performance Evaluation of Traffic Grooming Algorithms in WDM Multi-Ring Networks

In this paper, we propose novel traffic grooming algorithms to reduce the cost of the entire system in WDM multi-ring networks. In order to achieve this goal, it is important to construct a virtual topology and groom the traffic in these networks. We consider four kinds of virtual topologies of WDM multi-ring networks according to the way in which traffic is transmitted among rings. Accordingly, we design four kinds of traffic grooming (TG) algorithms depending on the considered virtual topologies: mixed (MTG), partially mixed (PMTG), separate (STG), and independent (ITG) traffic grooming algorithms. Each algorithm consists of a separation, a connection-ring construction, and a grooming procedure. In the separation procedure, all traffic connections are classified into intra and inter-connections. The connection-ring construction procedure makes full connection-rings from traffic connections. The grooming procedure groups connection-rings onto a wavelength in order to reduce the number of SONET add/drop multiplexers (SADMs) and wavelengths and to improve the utilization of network resources. To analyze the performance of each algorithm, a circular multi-ring architecture with uniform traffic is considered. The simulation results show that ITG and PMTG are more efficient in terms of wavelengths. STG and PMTG require a smaller number of SADMs.     

Heuristic Algorithms for Grooming of Arbitrary Traffic in WDM Ring Networks

In a wavelength division multiplexing (WDM) network, sub-wavelength traffic streams can be elaborately arranged in wavelength channels to minimize the number of required electronic end systems, known as the traffic grooming problem. In this paper, a modified genetic algorithm without crossover operation is proposed to solve the problem using a permutation-based chromosome representation and using a selection strategy of reproducing the best chromosomes, thereby minimizing the number of electronic devices and requiring less wavelengths. Then, three methods are developed to improve the performance of the algorithm and a hill-climbing algorithm is proposed for the same purpose. Computer simulations were performed with plenty of randomly generated traffic patterns in unidirectional rings. The results show that these methods can improve the algorithm considerably. The relationships between the minimized network cost and the number of nodes are also presented.     

Simulation-based SONET ADM optimization approach for dynamic traffic grooming in WDM optical networks

The article addresses a simulation-based optimization approach for allocation of ADMs in WDM optical networks with stochastic dynamic traffic. Since ADMs are expensive, it is desirable that if each node in WDM optical networks can use a minimum number of ADMs to achieve a near-ideal performance. In this article, first, the utilization statistics of ADMs are gathered by simulation. Then, ADMs are allocated based on the utilization statistics. In this respect, a simple sorting mechanism is used. The distinguished feature of the proposed approach is that it shows the way to allocate ADMs at the nodes of WDM optical networks with stochastic dynamic traffic. The experimental results ensure that the proposed approach can solve the problem of allocating ADMs in practical WDM optical networks considering stochastic dynamic traffic.

Traffic grooming in WDM ring networks to minimize the maximum electronic port cost

We consider the problem of traffic grooming in WDM ring networks. Traffic grooming is a variant of the well-known logical topology design problem, and is concerned with the development of techniques for combining low speed traffic components onto high speed channels in order to minimize network cost. Previous studies have focused on aggregate representations of the network cost. In this work, we consider a Min-Max objective, in which it is desirable to minimize the cost at the node where this cost is maximum. Such an objective is of high practical value when dimensioning a network for unknown future traffic demands and/or for dynamic traffic scenarios. We present new theoretical results which demonstrate that traffic grooming with the Min-Max objective is NP-complete even when wavelength assignment is not an issue. We also present new polynomial-time traffic grooming algorithms for minimizing the maximum electronic port cost in both unidirectional and bidirectional rings. We evaluate our algorithms through experiments with a wide range of problem instances, by varying the network size, number of wavelengths, traffic load, and traffic pattern. Our results indicate that our algorithms produce solutions which are always close to the optimal and/or the lower bound, and which scale well to large network sizes, large number of wavelengths, and high loads. We also demonstrate that, despite the focus on minimizing the maximum cost, our algorithms also perform well in terms of the aggregate electronic port cost over all ring nodes.     

Reducing electronic multiplexing costs in SONET/WDM rings with dynamically changing traffic

In this paper, we consider traffic grooming in WDM/SONET ring networks when the offered traffic is characterized by a set of traffic matrices. Our objective is to minimize the cost of electronic add/drop multiplexers (ADMs) in the network, while being able to support any offered traffic matrix in a rearrangeably nonblocking manner. We provide several methods for reducing the required number of ADMs for an arbitrary class of traffic matrices. We then consider the special case where the only restriction on the offered traffic is a constraint on the number of circuits a node may source at any given time. For this case, we provide a lower bound on the number of ADMs required and give conditions that a network must satisfy in order for it to support the desired set of traffic patterns. Circuit assignment and ADM placement algorithms with performance close to this lower bound are provided. These algorithms are shown to reduce the electronic costs of a network by up to 27%. Finally, we discuss extensions of this work for supporting dynamic traffic in a wide-sense or strict sense nonblocking manner as well as the benefits of using a hub node and tunable transceivers. Much of this work relies on showing that these grooming problems can often be formulated as standard combinatorial optimization problems.     

一种新型动态流量疏导策略

在WDM光网络中业务流量疏导能够有效地降低网络建设成本.为了疏导网络中的动态业务,提出动态业务流量的可重构疏导方案,并给出相应快速在线算法.此算法通过动态调整网络的虚拟拓扑结构,可使网络适应各种动态业务.计算机模拟结果表明,该算法能得到较优的疏导结果.     

Strategy for Dynamic Routing and Grooming of Data Flows into Lightpaths in New Generation Network Based on the GMPLS Paradigm

This paper reports on a novel strategy and related algorithm for realizing dynamic routing and grooming into wavelengths of data flows (label switched paths, LSPs) in new generation optical networks based on generalized MPLS (GMPLS). The method allows arbitrary granularities of LSPs. The new generation network is modeled as a multi-layer network consisting of an IP/MPLS layer and an optical layer. In particular, the proposed solution adopts a dynamic routing algorithm based on the Dijkstra algorithm, that makes use of a weight system, integrated with a suitable method for grooming LSPs into wavelengths based on the packing criterion, thus harmonizing the features of MPLS packet flows whose bandwidth vary in a continuous range of values, with the optical world, where the wavelength bandwidth ranges according to discrete values. The weight system is based on the concepts of least resistance routing that allows to evenly distribute the traffic at the MPLS layer, while packing improves the use of optical resources by favoring more filled wavelengths with respect to the emptier ones. To assess the validity of the proposed solution a simulation model has been realized. The results obtained by simulation show that the packing criterion allows reducing the refused bandwidth from two down to about four times, for a network load of 70% and 55%, respectively, when compared with the alternative method named spreading. The dependence of the proposed solution on bandwidth granularity has been also investigated. Moreover, in order to demonstrate the superior performance of the proposed routing solution, a comparison between the proposed strategy with relevant solutions known in the literature, based on either a single or multi-layer approach, is also reported. In order to perform the comparison, all the reference routing solutions that have been considered adopt the packing method for LSP grooming into the lightpaths. The results show that our solution outperforms the others in terms of amount of traffic that can be on-line accommodated. For instance, assuming a blocking probability of 10^–3, the proposed solution is able to further reduce the refused bandwidth of the best routing algorithm considered in the analysis by a factor of three times, thanks to the knowledge of optical resource availability.     

一种用于光网络的高效业务疏导辅助图及动态业务疏导算法

利用辅助图,研究了光网络中的业务疏导技术。为解决传统的辅助图存在着模型复杂、波长通道的带宽利用率不高等问题,提出一种新的业务疏导辅助图,能够更有效地利用已有波长通道,避免低效的路由;为了降低动态业务疏导算法的复杂度,提出了一种简化的k最短路径算法,并以此为基础提出了多种疏导策略。仿真结果表明,本文提出的辅助图及其业务疏导算法,可以有效地减少阻塞率。     

光网络中基于组播树的静态业务疏导算法

为了减少波分复用(WDM)网络中波长资源消耗,将组播路由算法的思想运用于静态业务疏导的计算,通过建立业务疏导树来实现静态业务疏导.为了减少疏导树的数量,从而减少网络中波长资源的消耗,将节点间的业务请求分组归并,利用装包算法使业务分组的数量最少,并通过构建最小生成树实现传输路径共享.仿真结果表明,本文的算法可以有效地减少...     

WDM网络中动态流量的资源效率疏导策略

为了解决波分复用(WDM)网状网络中的动态流量疏导问题,基于收发器节约辅助图模型,提出了一种资源效率疏导策略.它同时考虑收发器和波长链路两种网络资源的有效利用,根据当前的网络状态动态改变疏导策略,使网络不会由于某一种资源的缺乏而导致阻塞所有流量,避免了另一种资源因富余而造成的浪费,从而两种资源都能得到充分利用.在辅助图模型中,根据两种资源的可用数目比值,对各条边设置不同的权值函数,可轻易地实现该策略.仿真结果证明,不管是收发器资源受限还是波长资源受限,该策略都能取得较好的性能,降低了网络的阻塞率.     

基于分簇的动态业务量疏导区分保护策略

To make dynamic traffic grooming faster and more efficient,and achieve an intelligent differentiated protection,a differentiated protection strategy with dynamic traffic grooming based on clustering(DPS-DTGC)was proposed.The whole network topology was allocated some clusters based on maximal independent set,in order to reduce the routing time consumption.Meanwhile,by the cooperation of layered auxiliary graph,residual capacity matrix and cluster aggregation layer,the traffic in inter- and intra- clusters would been groomed to realize the reasonable planning of resources and the higher efficiency of grooming.Furthermore,according to the proportion of different priority traffic in one wavelength ,the link importance was evaluated and a smart P-cycle was designed to give differentiated protection to the link.The simulation results show this strategy can make a better utilization of network resource.And with the increase of network load,it will gain a good performance in blocking rate.     

Multiobjective evolutionary approach to cost-effective traffic grooming in unidirectional SONET/WDM rings

Traffic grooming in optical networks is the process of multiplexing and demultiplexing low-speed traffic streams onto high-speed wavelengths. The research in the domain of traffic grooming mainly focuses on minimizing number of SONET add/drop multiplexers (SADMs) in SONET/WDM rings and it has been shown that they can potentially be reduced by careful assignment of low-speed traffic streams onto high-speed wavelengths. However, the cost of the network not only depends on the number of SADMs, but also the number of wavelengths and the grooming ratio. It is often the case that all of them cannot be minimized simultaneously. In this article, the problem of minimization of cost of a SONET/WDM unidirectional ring has been modeled as a multiobjective optimization problem which simultaneously minimizes the number of SADMs, the number of wavelengths, and the grooming ratio. A popular multiobjective genetic algorithm (NSGA-II) has been used as the underlying optimization tool. The resultant set of near-Pareto-optimal solutions contains a number of nondominated solutions, which the user can judge relatively and pick up the most promising one according to the problem requirements. Performance of the proposed algorithm has been demonstrated on different network topologies.

一种新的动态流量疏导算法

文章主要研究WDM(波分复用)光网络中动态业务流量疏导的选路算法,提出了基于拓扑融合的动态流量疏导算法。该算法的最大特点在于融合了物理拓扑及其抽象出来的虚拓扑,利用最小权重优先方法进行选路。仿真结果表明,该算法在不增大建路时延的基础上,可以有效提高资源利用率,降低阻塞率,尤其是在高负载情况下,效果显著。     

Dynamic Grooming Algorithms for Survivable WDM Mesh Networks

Within a WDM grooming mesh network and under the constraints of the number of transceivers per node and wavelength continuity, we propose a novel dynamic grooming graph which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources. Based on the grooming graph, we first propose a dynamic traffic-grooming algorithm called integrated grooming algorithm (IGA). And we also propose two dynamic survivable traffic-grooming algorithms, which are called protection per lightpath traffic-grooming algorithm (PPL) and protection per connection traffic-grooming algorithm (PPC). These algorithms are evaluated via simulations.     

WDM疏导网络中一种新的多播业务路由算法

研究了波分复用(WDM)网状网中动态多播业务量疏导,提出一种新的辅助疏导模型,其可以描述当前网络资源状况和节点分光特点,并动态更新.进而提出一种有效的多播业务量疏导启发式算法(MGA),将业务的多播选路和波长分配同时完成.仿真表明,该算法在波长连续性限制、网络波长和节点收发器数目有限的情况下,具有较低网络阻塞率.     

静态波带交换中的一种波带粒度取值算法

波带交换可以有效地减少波长交换的交换端口数量,本文研究节点间业务量已知时静态波带交换中的波带粒度取值算法,提出了基于k均值聚类的波带粒度取值算法。算法将业务量相近的业务分为一组,一组内的业务用相同粒度的波带装载,以提高波带的利用率。研究表明,在没有业务疏导的环境下,与其他方法相比,算法使用的波带数量和波带内的空闲波长数量都比较少。本文还研究了静态疏导环境下不同波带粒度取值算法的性能,提出了多波带粒度下的业务装载策略。对于大粒度的波带,使用向下装载,而对于小粒度的波带,使用向上装载,意在减少波带的使用数量的同时提高波带利用率。仿真结果表明,使用静态业务疏导后,本文算法与其他方法相比,依然可以有效地减少波带数量,提高波带利用率。与基于组播路由的静态波带疏导算法相结合,使波带利用率可以达到98%以上。