绿色IP over WDM网络研究进展

近年来光网络朝着高速率、大带宽的方向迅猛发展,设备数目快速增加导致网络能耗急剧增长。为了降低网络能耗,提高能量利用率,绿色IP over WDM网络的概念被提出,并成为光网络领域的最新研究热点之一。对现有光网络节能方法的研究状况进行综述,从网络设备入手,讨论业务负载和设备能耗的关系,建立了两种能耗模型。基于IP over WDM网络结构,利用数学表达式描述了网络能耗最小化问题。对当前网络级的节能方法进行分类,分析了其基本原理和节能效果,并选取代表性的节能方法进行比较,得出了现有方法存在的局限性和不足,对进一步的研究方向提出了建议。     

IP over WDM网络结构和生存性研究

对IPoverWDM网络结构和生存性涉及的关键问题进行了阐述 ,并对未来骨干网络发展的趋势进行了预测     

一种面向IP/GMPLS over WDM网络的优化综合路由算法

为了优化利用IP层和WDM层网络资源,在WDM网络集成辅助图模型的基础上,提出了一种面向IP/GMPLS over WDM网络的基于代价的优化综合路由算法,即CIR(Cost-basedIntegrated Routing).该算法将IP层和WDM层资源可用信息以代价函数形式给出,并将因网络拓扑结构和网络负载分布不均衡等产生的瓶颈链路以及带宽碎片问题也统一纳入考虑,由此将LSP建立问题转化为在集成辅助图上找出一条源、目的节点之间的最短通路问题.仿真结果表明:CIR算法有效地实现了IP和WDM两层资源的联合优化,提高了网络资源利用,降低了网络阻塞率.     

IP over WDM城域环网的公平调度接入算法研究

提出了一种公平调度接入算法,适用于由斯坦福大学开发的IPoverWDM城域环网HORNET。该算法充分利用了HORNET提供节点对于信道可用信息的预知能力。仿真显示在不同的网络负载下该算法都能提供较好的公平性和较高的吞吐率。     

基于路径的整数线性规划方法在阻塞IP over WDM网络中能耗优化的应用

针对容量有限的透明IP over WDM网络模型,该文提出一种基于路径的整数线性规划(ILP)方法来优化网络的能耗。相对基于连接的整数线性规划方法,该方法可以在光层提供更多的路径选择组合。仿真结果显示,基于路径的整数线性规划方法能够通过选择更优的光路组合进一步降低网络的能耗。     

采用多层恢复机制的IP over WDM网络生存性研究

IP over WDM网络是下一代网络的核心,生存性则是保证服务质量(QoS)的关键要素.当网络中出现故障时,选择在IP层还是光层进行保护和恢复是非常重要的课题.文章在论述IP层和光层的保护和恢复机制的基础上,提出了多层联合恢复机制的思想,针对多层联合恢复机制中各层之间如何协调进行了仔细的分析,并提出了自己的见解.     

IP over WDM网中的综合选路算法

研究了IP over WDM网中,当节点不具备波长变换能力并且配备有限光收发器对时,如何利用综合选路(IR)算法为到达业务请求建立标签交换路径(LSP)。提出一种新颖的辅助图模型(AGM)表示网络的当前状态,基于AGM提出一种动态IR算法-最小光收发器对法(MTA)。MTA总是选择占用光收发器对最少的通路来建立LSP,仿真结果表明：与已有算法相比,MTA可以降低全网的阻塞率,从而提高业务通过率,并且有利于减少业务连接所经光／电变换的次数。     

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。     

IP over WDM网络中业务持续时间感知的绿色路由算法

研究了IP over WDM网络的低碳路由问题,综合 考虑业务持续时间和利用可再生能源和传统能源供能两个 因素,基于分层图模型,提出一种带有业务持续时间感知的绿色路由(HTAGR)算法。HTAGR 依据节点处太阳能 供能情况以及节点和链路的能耗情况动态调整链路权值,并鼓励选择业务持续时间内需要额 外消耗传统能源最少的 路径建立连接。仿真结果表明,与传统节能路由算法相比,HTAGR 有利于消耗更少的传统能 源和使用更多的可再 生能源,在保持较低阻塞率的同时,进一步降低了业务平均传统能耗和CO₂排放量。     

一种基于多跳光旁路的IP over WDM节能网络设计方法

针对IP over WDM网络,基于多跳光旁路和流量疏导,以减少能耗为目标对网络链路配置进行设计;考虑多跳光旁路会增大业务传输距离的问题,分析了光路建立顺序对业务传输距离的影响;通过优先路由短距离业务和限制最大传输跳数来减少业务的平均传输跳数。仿真结果表明,优先建立短距离光路的启发式算法与Dijkstra算法相比可以减少25%～55%的能耗,业务平均物理跳数与Dijkstra算法相差在1跳之内。     

QoS aware traffic grooming and integrated routing on IP over WDM networks

In this article, we consider traffic grooming and integrated routing in IP over WDM networks. The challenges of this problem come from jointly considering traffic grooming, IP routing, and lightpath routing and wavelength assignment (RWA). Due to the high bandwidth of optical fiber, there exists a mismatch between the capacity needed by an IP flow and that provided by a single lightpath. Traffic grooming is therefore used to increase the network utilization by aggregating multiple IP flows in a single lightpath. However, traffic grooming incurs additional delays that might violate Quality-of-Service (QoS) requirements of IP users. In this work, the tradeoff between traffic grooming and IP QoS routing is well-formulated as a mixed integer and linear optimization problem, in which the revenue from successfully provisioning IP paths is to be maximized. Problem constraints include IP QoS, routing, optical RWA, and the WDM network capacity. We propose a novel Lagrangean relaxation (LGR) algorithm to perform constraint relaxation and derive a set of subproblems. The Lagrangean multipliers are used in the proposed algorithm to obtain a solution in consideration of grooming advantage and resource constraints simultaneously. Through numerical experiments and comparisons between the proposed algorithm and a two-phase approach, LGR outperforms the two-phase approach under all experimental cases. In particular, the improvement ratio becomes even more significant when the ratio of IP flow to the wavelength capacity is smaller.     

An efficient mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks

This paper proposes an efficient overlay multicast provisioning (OMP) mechanism for dynamic multicast traffic grooming in overlay IP/MPLS over WDM networks. To facilitate request provisioning, OMP jointly utilizes a data learning (DL) scheme on the IP/MPLS layer for logical link cost estimation, and a lightpath fragmentation (LPF) based method on the WDM layer for improving resource sharing in grooming process. Extensive simulations are carried out to evaluate the performance of OMP mechanism under different traffic loads, with either limited or unlimited port resources. Simulation results demonstrate that OMP significantly outperforms the existing methods. To evaluate the respective influences of the DL scheme and the LPF method on OMP performance, provisioning mechanisms only utilizing either the IP/MPLS layer DL scheme or the WDM layer LPF method are also devised. Comparison results show that both DL and LPF methods help improve OMP blocking performance, and contribution from the DL scheme is more significant when the fixed routing and first-fit wavelength assignment (RWA) strategy is adopted on the WDM layer. Effects of a few other factors, including definition of connection cost to be reported by the WDM layer to the IP/MPLS layer and WDM-layer routing method, on OMP performance are also evaluated.     

Providing differentiated services for multi-class traffic in IP/MPLS over WDM networks

Providing differentiated services in IP/MPLS over WDM networks has attracted a lot of recent attention. This article extends the Path Inflation Control (PIC) policy recently proposed by us to provide differentiated services in IP/MPLS over WDM networks with traffic grooming. Three different algorithms are considered for provisioning differentiated services. The simulation results show that, with two of the three algorithms, the network cannot only provide differentiated services when the traffic load is high but also gives significantly lower blocking for the lower priority class traffic and for the overall traffic at low traffic loads.

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。     

在IP over WDM中建立直通光路的讨论

IP over WDM是下一代网络的普遍模式,如何建立波长通道是非常重要的问题,本文就静态和动态情况分析讨论了直通光路的建立原则,介绍了相应的算法,并且各自给出例子,最后展望了IP网结合WDM网直通光路的发展前景。     

IP over WDM网中的策略路由算法

业务量工程允许管理者通过赋予业务主干不同的业务量工程属性来体现一定的管理策略,在为业务主干建立标记交换路径(LSP)时也应该考虑这些策略的影响,该文讨论了业务主干具有不同优先权属性时的 LSP建立问题,针对中断 LSP个数最少和中断业务量最小两种指标,分别提出不同的解决策略:最小连接数中断法(MCNIM)和最小连接带宽中断法(MCBIM),并在不同负载的动态业务下对所提算法进行了仿真研究,给出了仿真结果。     

Shared partial path protection in WDM networks with shared risk link groups

For 100% shared risk link group (SRLG) failure protection, conventional full path protection has to satisfy SRLG-disjoint constraints, i.e., its working path and backup path cannot go though the same SRLG. With the increase of size and number of SRLGs, capacity efficiency of conventional shared full path protection becomes poorer due to SRLG-disjoint constraints and the blocking probability becomes much higher due to severe traps. To solve these problems, we present a partial path protection scheme where SRLG-disjoint backup paths may only cover part of the working path. Full path protection becomes a special case of partial path protection, in which the backup path covers the full working path. By choosing the most survivable partial backup path as backup path, we can make the impact of SRLG failures as low as possible and accept as many as possible connection requests. Assuming every SRLG has the same probability to fail, we present a heuristic algorithm to find the most survivable partial backup path by choosing full path protection first, iteratively computing partial backup paths and choosing the most survivable one. The benefit of this heuristic algorithm is that it can find the optimal results within less iteration. Analytical and simulation results show that, compared to conventional full path protection, our proposed scheme can significantly reduce blocking probability with little sacrifice on survivability. The proposed scheme is very useful particularly when the network contains a lot of SRLGs and the blocking probability of conventional full path protection becomes too high.

IP/MPLS over WDM网中的动态选路和波长分配算法

该文研究了IP/MPLS over WDM网中,利用综合路由法为到达的业务流建立标签交换路径(LSP)时,如何选择是在WDM层为它新建一条光路,还是利用现有的逻辑IP链路来满足其要求,提出一种带宽碎片消除的策略,该策略在决定是否利用逻辑IP链路来建立LSP时,总是尽量减少造成带宽碎片,从而可以有效提高全网的资源利用率,仿真结果表明带宽碎片消除策略可以进一步改善综合路由算法的性能。