A novel auxiliary graph model for effective dynamic traffic grooming in light-trail optical WDM mesh networks

Photonic Network Communications - The SDN paradigm profoundly affects the architecture of networks in favor of more adaptability to the needs for new value-added services. This article examines the...     

Algorithms for multicast traffic grooming in WDM mesh networks

Several of the new applications in high-performance networks are of the multicast traffic type. Since such networks employ an optical network infrastructure, and since most of these applications require subwavelength bandwidth, several streams are usually groomed on the same wavelength. This article presents an account of recent advances in the design of optical networks for multicast traffic grooming in WDM mesh networks. The article addresses network design and session provisioning under both static and dynamic multicast traffic. Under static traffic conditions, the objective is to accommodate a given set of multicast traffic demands, while minimizing the implementation cost. Optimal and heuristic solution techniques for mesh network topologies are presented. Under dynamic traffic conditions, techniques for dynamic routing and session provisioning of multicast sessions whose objective is to minimize session blocking probabilities are explained. The article also presents a number of open research issues     

支持不同可靠性要求的WDM网状网业务量疏导算法

WDM光网络中不同的业务流具有不同的可靠性要求，本文研究动态业务下如何解决此类业务量疏导问题，提出了一种在WDM网状网中支持多种可靠要求的业务量疏导算法(MRTG)。仿真结果表明该算法具有很好的性能。     

Traffic engineering in multigranularity heterogeneous optical WDM mesh networks through dynamic traffic grooming

In this article we investigate the problem of efficiently provisioning connections of different bandwidth granularities in a heterogeneous WDM mesh network through dynamic traffic grooming schemes under traffic engineering principles. Due to the huge amount of traffic a WDM backbone network can support and the large geographic area it can cover, constructing and upgrading such an optical WDM network can be costly. Hence, it is extremely important for network operators to apply traffic engineering strategies to cost-effectively support different bandwidth granularity services using only the appropriate amount of network resources. This requires an optical WDM network to have multigranularity switching capability, and such a network tends to be a multivendor heterogeneous network. However, WDM network heterogeneity increases the difficulty and challenge of efficient traffic provisioning. In this article we present different TE issues that need to be carefully considered in such an optical WDM network, and propose possible solutions and extensions for the generalized multiprotocol label switching optical network control plane. We extend an existing generic graph model to perform efficient traffic grooming and achieve different TE objectives through simple shortest path computation algorithms. We show that our approach is very practical and very suitable for traffic engineering in a heterogeneous multigranularity optical WDM mesh network.     

Light-tree configuration for multicast traffic grooming in WDM mesh networks

Recent advances in wavelength-division multiplexing (WDM) technology will provide bandwidth intensive multicast applications with large transmit capacities. This article provides two new grooming schemes that lead to efficient resource utilization in WDM networks. They are called Light-Tree Division-Destination Branch Node-based Grooming scheme (LTD-DBNG) and Light-Tree Division-Adjacent Node Component-based Grooming scheme (LTD-ANCG). These schemes are based on the idea of dividing a light-tree into smaller sub-light-trees. They improve the efficiency of resource utilization and also lower the optical-electronic-optical conversion overhead. We use computer simulations to evaluate the performance of these schemes. Our simulations demonstrate that compared with existing algorithms, these schemes significantly reduce the request blocking probability (BP) but can be implemented with very reasonable electronic processing, with LTD-ANCG performing better than LTD-DBNG but with greater complexity. We also evaluate the BP of these schemes considering variations in the add/drop ratio and demonstrate that a proper choice of this ratio will provide target BP with low network costs.     

Analysis of multi-hop traffic grooming in WDM mesh networks

Traffic grooming is an essential functionality of WDM optical networks to provision multi-granularity subwavelength connections. Depending on the number of lightpaths allowed in a connection route, traffic grooming can be classified as single-hop traffic grooming (SH-TG) and multi-hop traffic grooming (MH-TG). MH-TG is more general and resource-efficient than SH-TG, because it allows connections from different source-destination pairs to share the bandwidth of a lightpath. In this paper, we propose a MH-TG algorithm, namely the fixed-order multi-hop (FOMH) grooming algorithm, based on the fixed-alternate routing approach. We introduce the grooming node selection (GNS) problem in MH-TG and propose three grooming policies, namely exhaustive sequential (ES), limited-hop sequential (LHS) and load sharing (LS) policies, to address the GNS problem. These policies represent different trade-offs among blocking probability, computational complexity and transceiver requirements. Given that the analysis of MH-TG is a relatively unexplored area, we propose an analytical model to evaluate the blocking performance of MH-TG using FOMH and the LS grooming policy. To address the multi-layered routing and multi-rate connection characteristics of traffic grooming, we introduce a novel multi-level decomposition approach in our analytical model which decomposes traffic at four different levels, namely alternate path, connection route, lightpath and link levels. The model also addresses various factors that affect connection blocking probability. These factors include wavelength continuity constraint, channel continuity constraint and route dependence. The Erlang fixed-point approximation method is used to solve the analytical model. Numerical results show that analytical results match well with simulation results. We also evaluate the effect of the grooming policies, the number of virtual hops (lightpaths) within a connection route and the number of alternate paths on the performance of the grooming algorithm.     

WDM中基于业务带宽的业务量疏导算法

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,极大地增加了网络中电层和光层设备的处理负担,加大了网络成本.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技术成为目前光网络研究的一个热点.文章提出了一种基于带宽优先级的启发式算法,将业务的选路与波长分配同时完成.仿真表明,该算法在波长连续性限制,网络波长数目有限的情况下具有较低的阻塞率.     

Constrained light-tree design for WDM mesh networks with multicast traffic grooming

Multicast applications such as IPTV, video conferencing, telemedicine and online multiplayer gaming are expected to be major drivers of Internet traffic growth. The disparity between the bandwidth offered by a wavelength and the bandwidth requirement of a multicast connection can be tackled by grooming multiple low bandwidth multicast connections into a high bandwidth wavelength channel or light-tree. Light-trees are known to be especially suited for networks that carry ample multicast traffic. In this paper, we propose new algorithms to address the problem of multicast traffic grooming. In particular, an Integer Linear Programming (ILP) formulation is proposed for optimal assignments of hop constrained light-trees for multicast connections so that network throughput can be maximized. Hop constrained light-trees improve the scalability of the approach by reducing the search space of the ILP formulation. Since solving the ILP problem is very time consuming for realistically large networks, we are motivated to propose a heuristic algorithm with a polynomial complexity, called Dividable Light-Tree Grooming (DLTG) algorithm. This algorithm is based on grooming traffic to constrained light-trees and also divides a light-tree to smaller constrained light-trees on which traffic is groomed for better resource utilization. Simulations show that the proposed DLTG heuristic performs better than other algorithms. It achieves network throughputs which are very close to the ILP formulation results, but with far lower running times.     

WDM网状网中基于光连接抗毁业务量疏导保护算法

研究了WDM网状网中基于光连接(connection)的抗毁业务量疏导通道(path)保护问题,以最大化网络的吞吐量为目标,提出了新的基于共享风险链路组(Shared Risk Link Group,SRL G)的共享保护算法和专用保护算法.并以NSFNET为仿真网络,比较说明了这两种算法在网络拥塞率和波长利用率方面的性能优劣.     

WDM网状网中动态多播流量疏导的结构与算法

回顾了近期WDM网状网中动态多播流量疏导问题的研究成果.讨论和比较了文献中动态多播会话的动态路由和会话供应的技术,还提出了几个关于此问题的未来研究方向.     

WDM光网络中的动态流量疏导

针对波分复用光网络中的业务疏导问题,文章基于通道组交换网络模型,采用波分复用网络中的相对容量算法来解决业务疏导的路由、波长分配和时隙分配问题.基于该模型的算法能够将波长和时隙分配这两个通常分开解决的问题一步解决,因此比现有方法具有更好的效能,仿真也验证了这一点.     

WDM网络中基于分簇的静态业务量疏导算法

针对大多数文献中报道的静态业务量疏导技术不适用于大型光网络的问题,文章基于分簇思想提出了一种有效的静态业务量疏导算法.该方法将大型光网络划分为若干个相互独立的簇,并在每个簇中选择一个节点作为簇头节点采负责簇内和簇间的业务量疏导.仿真结果表明:该算法与已知的静态业务量疏导算法相比具有更好的性能.     

WDM抗毁网状网络中的业务量疏导算法

研究具有抗毁能力的WDM网状网中的业务量疏导设计问题，提出几种以网络吞吐量为优化目标的启发式算法，并通过计算机仿真分析，证实了基于最大化资源利用率的算法具有很好的性能。     

Survivable traffic grooming with path protection at the connection level in WDM mesh networks

Survivable traffic grooming (STG) is a promising approach to provide reliable and resource-efficient multigranularity connection services in wavelength-division-multiplexing (WDM) optical networks. In this paper, we study the STG problem in WDM mesh optical networks employing path protection at the connection level. Both dedicated-protection and shared-protection schemes are considered. Given network resources, the objective of the STG problem is to maximize network throughput. To enable survivability under various kinds of single failures, such as fiber cut and duct cut, we consider the general shared-risk-link-group (SRLG) diverse routing constraints. We first resort to the integer-linear-programming (ILP) approach to obtain optimal solutions. To address its high computational complexity, we then propose three efficient heuristics, namely separated survivable grooming algorithm (SSGA), integrated survivable grooming algorithm (ISGA), and tabu-search survivable grooming algorithm (TSGA). While SSGA and ISGA correspond to an overlay network model and a peer network model, respectively, TSGA further improves the grooming results from SSGA and ISGA by incorporating the effective tabu-search (TS) method. Numerical results show that the heuristics achieve comparable solutions to the ILP approach, which uses significantly longer running times than the heuristics.     

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.     

Dynamic traffic grooming algorithms for reconfigurable SONET over WDM networks

The emergence of wavelength-division multiplexing (WDM) technology provides the capability for increasing the bandwidth of synchronous optical network (SONET) rings by grooming low-speed traffic streams onto different high-speed wavelength channels. Since the cost of SONET add-drop multiplexers (SADM) at each node dominates the total cost of these networks, how to assign the wavelength, groom the traffic, and bypass the traffic through the intermediate nodes has received a lot of attention from researchers recently. Moreover, the traffic pattern of the optical network changes from time to time. How to develop dynamic reconfiguration algorithms for traffic grooming is an important issue. In this paper, two cases (best fit and full fit) for handling reconfigurable SONET over WDM networks are proposed. For each approach, an integer linear programming model and heuristic algorithms (TS-1 and TS-2, based on the tabu search method) are given. The results demonstrate that the TS-1 algorithm can yield better solutions but has a greater running time than the greedy algorithm for the best fit case. For the full fit case, the tabu search heuristic yields competitive results compared with an earlier simulated annealing based method and it is more stable for the dynamic case.     

A novel dynamic Multiple Ring-based Local Restoration for point-to-multipoint multicast traffic in WDM mesh networks

Optical networks with DWDM (Dense Wavelength Division Multiplex) can provide multiple data channels to supply high speed, high capacity to perform bandwidth-intensive multicast transmission service. Light-tree is a popular technique applied to support point-to-multipoint multicast services. Any failure during a multicast session would cause severe service loss or disruptions, especially when the faults occur near the source node. A novel ring-based local fault recovery mechanism, Multiple Ring-based Local Restoration (MRLR), for point-to-multipoint multicast traffic based on the minimum spanning tree (MST) in WDM mesh networks is proposed in this article. The MRLR mechanism dismembers the multicast tree into several disjoint segment-blocks (sub-trees) and reserves preplanned spare capacity to set up multiple protection rings in each segment-block for providing rapid local recovery. The MRLR scheme outperforms other methodologies in terms of the blocking probability, recovery time, and average hop count of protection path per session for different network topologies.     

Logical topology design for dynamic traffic grooming in WDM optical networks

Traffic grooming in optical networks refers to consolidation of subwavelength client connections onto lightpaths. Depending on whether client connections are given in advance or randomly arrive/depart, traffic grooming is classified as static and dynamic. Dynamic traffic grooming has been traditionally performed through establishing/releasing lightpaths online. In this paper, the authors propose an alternate approach to design a static logical topology a priori and then route randomly arriving client connections on it to avoid frequent lightpath setup/teardown. Two problems are considered: 1) minimize resource usage constrained by traffic blocking requirements and 2) maximize performance constrained by given resources. These are formulated as integer linear-programming (ILP) problems. The numerical results show that the resource usage dramatically decreases when the blocking requirement is relaxed, and the grooming performance slowly increases when given more resources. In addition, the number of ports at client nodes has more profound impact on traffic grooming than the number of wavelengths.     

Traffic grooming in mesh WDM optical networks - performance analysis

Traffic grooming is an important task in interworking between the wavelength-division multiplexing (WDM) optical network that supplies "pipes" at the wavelength granularity, and the attached client networks that usually require connections of subwavelength granularity. The focus of this paper is to conduct performance analysis of grooming dynamic client traffic in WDM optical networks with a mesh topology. This paper first briefly introduces the traffic grooming problem in WDM optical networks and the issues related to performance analysis. It then develops two link blocking models, an exact model based on the stochastic knapsack problem and an approximation model based on an approximate continuous time Markov chain (CTMC). The end-to-end performance analysis is conducted using the reduced load approximation. The result obtained from analysis is shown to be accurate compared with the numerical result obtained from simulation.     

WDM网状网络中一种动态多播自适应业务疏导算法

光多播业务需要消耗大量的WDM光网络带宽资源,业务疏导是光多播网络降低业务请求阻塞率和提高带宽资源利用率的有效方法。提出了一种新型光多播疏导节点结构,研究了疏导端口优先的多播业务疏导算法(TGPFA)和新建光树优先的多播业务疏导算法(TCLFA),进而提出了一种能够适应网络资源变化的动态多播业务疏导算法(ADMGA)。结果表明,在网络资源有限的情况下,ADMGA算法能取得较低的请求阻塞率和带宽阻塞率,获得较好的网络性能。