Combining GA with Splitting Methods for Rearrangeably Nonblocking Grooming of Dynamic Traffic in SONET Ring Networks

SONET/WDM rings are widely deployed in today’s networks. To reduce the total cost of such a network, an efficient way is using the traffic grooming technique to minimize the number of add/drop multiplexers (ADMs) on the ring. Since traffic often changes frequently, the problem of supporting dynamic traffic patterns with minimum number of ADMs and wavelengths becomes incresingly important, which is referred to as grooming of dynamic traffic. In this paper, we will deal with rearrangeably nonblocking grooming of arbitrary dynamic traffic in such ring networks. We will discuss in detail the benefit of splitting methods to such a grooming way and apply them to this kind of grooming. A novel genetic algorithm (GA) approach with a hierarchical chromosome structure for each individual is proposed in combination with splitting methods to address such grooming problems. Computer simulation results under different conditions show that our algorithm is efficient in reducing both the numbers of ADMs and wavelengths.     

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.     

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.     

业务疏导技术在WDM网络及OPS网络中的应用

在波分复用(WDM)光网络中,可使用业务疏导(Traffic Grooming)技术来提高网络性能,降低网络成本.详细阐述了WDM光网络中业务疏导的基本概念及主要目标,并对国内外研究现状进行了总结.最后介绍了OPS光交换网络中使用的业务疏导技术.     

多播格状WDM光网络中流量疏导的一种启发性算法

波分复用技术的开发应用及网络业务信息的多样化促进了多播技术的应用和发展.由于网络中波长带宽与节点间业务信息需求之间的巨大反差,使流量疏导成为必要,以节约网络资源和成本.但多播的出现使流量疏导算法变得更复杂多样.本文提出了对多播格状网络中的静态流量进行有效疏导的一种启发性算法,并取得较为优化的结果.     

WDM光网络动态业务流量的可重构疏导

流量疏导是当今光网络研究中一个学术与商业价值并重的研究热点。在WDM(波分复用)光网络中使用流量疏导技术不仅能够有效地降低网络成本，也能够使网络性能得到必要的优化。为了适应当前网络中普遍存在的突发多变的业务分布，引入了一种称为网络可重构动态流量疏导的新型流量疏导概念，并对疏导进行了分类，较全面地论述和评价了近年来这方面的研究，最后对今后的研究作了一番展望。     

Grooming of Arbitrary Traffic in Optical WDM Mesh Networks Using a Genetic Algorithm

In this paper, a genetic algorithm is proposed for grooming of arbitrary traffic in optical mesh networks. Traffic streams are routed in the wavelength division multiplexing (WDM) grooming networks that comprise both fiber links and established lightpaths. Chromosomes are split into multiple versions when multiple shortest routes are found. The selection strategy is based on a comparison between chromosomes. A variety of cost functions are proposed for the routing algorithm and two comparison methods are considered in the selection procedure. Computer simulations are performed with randomly generated traffic patterns. The results show that the algorithm is effective for traffic grooming (TG) problems, and also for routing and wavelength assignment problems.     

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光网络的多优先级业务疏导机制

IP over WDM网络中,业务疏导能有效提高波长带宽利用率.然而,单一化的业务疏导机制难以满足不同业务的QoS要求,也很难做到经济合理地使用光路.提出了一种支持多优先级业务的疏导机制,该机制根据光路传输的时延和丢包特性来选择恰当的疏导路径,同时,该机制结合了抢占和流量分割技术,能有效地实现流量分割和多路抢占,降低了业务的阻塞概率.仿真结果显示,该疏导机制在保证业务QoS的同时,降低了高优先级业务的阻塞概率;在业务负载低时,能有效减少抢占.     

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.     

WDM网络中基于阻塞公平性的业务疏导和波长分配

在具有多速率级别连接请求的WDM网络中，通过为较高速率的请求预留更多的波长集合，结合网络节点对较低速率业务更强的输导能力，解决网络的阻塞公平性和全网的流量问题。在中国教育科研网的仿真实验，本文的策略比First-fit算法取得了更好的阻塞公平性能，并接纳了更多的网络流量。当负载为170Erlang时，多接纳的流量约为12％。     

Minimal Delay Traffic Grooming in WDM Optical Star Networks

All-optical networks face the challenge of reducing slower opto-electronic conversions by managing assignment of traffic streams to wavelengths in an intelligent manner, while maximizing the bandwidth resources utilization. This challenge becomes harder in networks closer to the end users that have insufficient data to saturate single wavelengths as well as traffic streams outnumbering the usable wavelengths. Traffic grooming has been proposed as a possible solution in the network closer to the end users. However, it requires costly traffic analysis at access nodes. We study the problem of traffic grooming that reduces the need to analyze traffic, for a class of network architecture mostly used by Metropolitan Area Networks; the star network. We first prove that the problem is NP-hard, then provide an efficient greedy heuristics that can be used to intelligently groom traffics at the LANs to reduce latency at the access nodes. Simulation results show that our greedy heuristics achieves a near-optimal solution.     

WDM光网络多跳业务量疏导算法

针对具有多跳疏导能力的WDM光网络进行了研究,提出了一种基于固定备选路由的多跳业务量疏导算法（FO-HC-MH）。该算法对备选路由的跳数进行限制,因而可以节约使用网络的收发器资源。仿真实验表明,与FO-MH算法相比,在网络负载较低的情况下该算法节约效果明显。     

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.

WDM光网络中动态流量的疏导

流量疏导是当今光网络研究中的一个前沿和热点问题,在波分复用(WDM)光网络中使用流量疏导技术能有效降低网络的成本,减少网络节点中业务信息的处理量.文章讨论了动态流量疏导的意义及其分类,分析了关于在各种网络结构中动态流量疏导的研究近况,最后对今后的发展方向做了一番展望.     

Optimal Wavelength Assignment Algorithms for Permutation Traffic in Multi-Fiber WDM Ring Networks*

Permutation traffic occurs in a number of networking applications. In this paper, the problem of wavelength assignment for permutation traffic in multi-fiber WDM rings with and without wavelength conversion is considered. We focus on a special class of permutation traffic and analyze the bounds on the number of wavelengths required to establish the connections. Lower bounds and optimal algorithms are presented for all the cases. The results indicate that a small number of fibers is sufficient to provide most of the benefits that wavelength conversion provides for this class of permutation traffic.     

一种WDM网状网中基于共享保护的业务量疏导算法

在WDM网络中业务的带宽需求远低于一个波长所提供的带宽,业务量疏导可以聚集低速业务到大容量的光路中从而有效地利用波长带宽资源.目前大多数业务量疏导的研究限于环形网,考虑对WDM网状网中低速业务可靠疏导的文献更少.该文综合考虑WDM网状网生存性及业务量疏导,提出了基于波长分层图的共享保护业务量疏导算法(SPTG-LG,Shared Protection Traffic Grooming algorithm ba,sed on wavelength Layered-Graph),并对算法进行了仿真和分析.     

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.     

WDM光网络中的业务疏导

目前WDM光网络普通用户大量的一般业务请求数目及波长通道带宽的不断增加极大的增加了网络中电层和光层设备的处理负担,增加了网络成本。对低速电信号复用到高速光通道进行优化,减少网络电层设备的使用,降低网络成本的业务疏导(TrafficGrooming)技术成为目前光网络研究的一个热点。本文主要介绍了WDM光网络中的业务疏导问题的基本概念、技术特点、国内外研究现状进行了总结。     

Dynamic Routing in WDM Grooming Networks

Traffic grooming in optical networks has gained significant importance in recent years due to the prevailing sub-wavelength traffic requirement of end-users. In this paper, a methodology for dynamic routing of fractional-wavelength traffic in WDM grooming networks is developed. To evaluate the performance of routing algorithms, a new performance metric that reflects the network utilization is also proposed. The performances of shortest-widest path, widest-shortest path, and available shortest path routing algorithms are evaluated on a class of WDM grooming networks by considering traffic of different capacity requirements. The effect of dispersity routing, where higher capacity requests are broken into multiple unit capacity requests, is also investigated. The most interesting counter-intuitive result that is observed is that increasing the grooming capability in a network could result in degrading the performance of the widest-shortest path algorithm.