Integrated IP/WDM routing in GMPLS-based optical networks

Future transport networks will have to cope with the continuous growth of IP traffic. Furthermore, transport networks need to evolve so as to drastically reduce both deployment costs and operating expenses. A reasonable strategy to achieve this goal consists of simplifying the network architecture by reducing the number of layers. Assuming a peer model IP over optical network, we propose an integrated routing strategy that takes into account constraints and dynamic occupancy of both the IP and optical layers. The collaboration of both layers in the routing process leads to optimization of network performance. The main emphasis is on the implementation requirements of this grooming functionality using GMPLS-TE mechanisms. Simulation results show the benefits obtained by applying this strategy.     

On-line integrated routing in dynamic multifiber IP/WDM networks

This paper focuses on dynamic integrated routing in multifiber Internet protocol/wavelength-division multiplexing (IP/WDM) networks, which can be implemented through either one-step routing (OSR) or two-step routing (TSR) approach. Based on an extended layered-graph, two resource assignment strategies, termed channel-level balance (CLB) and link-level balance (LLB), are proposed to balance the traffic in the network at different levels. To further improve the performance, a parameter K is introduced to make a dynamic tradeoff between the logical-layer links and the optical-layer links. Simulation studies are carried out for various topologies. The results show that LLB is better than CLB in most cases, and LLB combined with OSR has the optimal performance. Also, we find that the routing approach and the resource assignment strategy individually play different roles with different values of r/sub l/ that is introduced to indicate the resource richness of the network. As a multifiber network is functionally equivalent to a single-fiber network with limited wavelength conversion, we investigate the effects of wavelength conversion by studying the multifiber IP/WDM networks. The analysis shows that, when the granularity of each connection request is much smaller than the wavelength granularity, wavelength conversion may increase the request blocking probability in the network.     

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。     

跨越不同容量设置DWDM网络的动态IP/DWDM综合路由算法研究

IP/DWDM网络的综合路由中的一个重要的研究问题就是如何对跨越不同DWDM网络的IP路由进行综合路由,特别是当两个DWDM网络的容量设置不同时。本文着重解决的就是如何对从单波长带宽大的网络进入单波长带宽小的网络传输的IP业务的综合路由问题。根据尽量鼓励对波长链路的带宽进行完全使用,以减小波长链路带宽碎片的原则,我们提出了两种解决算法:1 n 算法和 m n算法。仿真结果对两种算法的效率和性能进行了测试。     

IP/WDM网络中的链路保护路由算法研究

基于IP/WDM网络的对等模型,在联合路由的基础上,对SRLG约束的联合共享链路保护机制的路由选择与资源分配算法进行了研究,并提出了一种新的MI-APF-ISLP算法.为了验证该算法的有效性,以自相似和Poisson模型两种业务模型为基础,将连接阻塞概率CBP和带宽吞吐率BTP作为性能指标,在不同参数条件下进行动态仿真,结果表明MI-APF-ISLP算法要优于传统算法.     

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。     

SLEA: a novel scheme for routing in overlay IP/WDM networks

This paper studies the routing problems in Internet protocol/wavelength-division-multiplexing (IP/WDM) networks based on the overlay routing algorithm (ORA) and the integrated routing algorithm (IRA), respectively. Although IRA usually outperforms ORA in terms of blocking performance, IRA exhibits disadvantages in control information exchange, network privacy issue, and wavelength port efficiency. In this paper, a new mechanism called the short lightpath establishment approach (SLEA) is proposed for ORA in order to tackle the problems in IRA and achieve similar (or even better) network performance at the same time. The main idea of SLEA is to ensure that each new lightpath created by ORA is restricted by an optical hop constraint when a subwavelength-granularity connection is routed in the optical layer. It follows that SLEA essentially avoids per-connection-based greedy treatment and improves network wide resource utilization by eliminating inefficient long optical bypasses. To implement SLEA in ORA, the Dijsktra's algorithm has been modified based on an extended layered graph model. SLEA does not introduce any additional signaling and computational complexity. The analysis and simulation in this paper show that there exists an optimal optical hop constraint for each particular network configuration such that SLEA-based ORA (SLEA-ORA) can efficiently utilize the network resource of concern. As a result, with the optimal optical hop constraint, SLEA-ORA could outperform ORA and IRA in terms of the bandwidth-blocking ratio (BBR) and the average number of IP hops of label-switched paths (LSPs).     

基于GMPLS的动态分布式WDM网状网恢复路由选择算法研究

提出了一种在GMPLS体系下的分布式业务路径和恢复路径在线选路算法，以使光网络在动态业务请求下能有效的利用波长资源。由于该算法对业务路径和恢复路径的选择进行了联合优化，其性能更优于独立业务路径恢复算法(SSPR)。仿真结果表明，利用该算法时业务路径和恢复路径占用的网络总资源明显小于SSPR算法，而恢复时间只比SSPR算法略有增加。     

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。     

Historical data learning based dynamic LSP routing for overlay IP/MPLS over WDM networks

Overlay IP/MPLS over WDM network is a promising network architecture starting to gain wide deployments recently. A desirable feature of such a network is to achieve efficient routing with limited information exchanges between the IP/MPLS and the WDM layers. This paper studies dynamic label switched path (LSP) routing in the overlay IP/MPLS over WDM networks. To enhance network performance while maintaining its simplicity, we propose to learn from the historical data of lightpath setup costs maintained by the IP-layer integrated service provider (ISP) when making routing decisions. Using a novel historical data learning scheme for logical link cost estimation, we develop a new dynamic LSP routing method named Existing Link First (ELF) algorithm. Simulation results show that the proposed algorithm significantly outperforms the existing ones under different traffic loads, with either limited or unlimited numbers of optical ports. Effects of the number of candidate routes, add/drop ratio and the amount of historical data are also evaluated.     

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.     

Multisource multicasting in IP/MPLS over WDM networks

Multicasting applications such as multimedia conferencing, online multiplayer interactive games, and distance learning are becoming increasingly popular. With multiprotocol label switching, Internet protocol networks can offer quality of service and traffic engineering capabilities. This article introduces several approaches for multisource multicast sessions in the context of IP over WDM networks and evaluates their performance in terms of blocking probability, time complexity, and memory consumption. Our simulation study shows that among all the approaches, the newly proposed approach, known as one Bidirectional Tree with Just enough bandwidth reserved on each link of the tree, achieves the best overall performance.     

On routing in large WDM networks

An important problem in WDM network design is to construct a logical topology and determine an optimal routing over that topology. Mixed Integer Linear Program (MILP) formulations to generate optimal solutions for this problem have been presented. Such formulations are computationally intractable, even for moderate sized networks. A standard approach is to decouple the problem of logical topology design and the problem of routing the traffic on this logical topology. Heuristics for finding the logical topology exist and a straight-forward linear program (LP), based on the node-arc formulation can be used to solve the routing problem over a given logical topology. We have found that such LP formulations become computationally infeasible for large networks. In this paper, we present a new formulation, based on the arc-chain representation, for optimally routing the specified traffic over a given logical topology to minimize the congestion of the network. We have used the revised simplex method incorporating an implicit column generation technique, and exploited the special Generalized Upper Bounding structure as well as the possibility of eta-factorization for efficiently updating the dual variables and finding the solution. Experimental results on a number of networks demonstrate the suitability of this approach.     

基于IP over WDM的光城域网

提出了基于IP over WDM的光城域网方案,详细阐述了波长选路WDM光城域网的多级网络拓扑及波长配置方式,并分析了波长配置方式对波长选路由策略的影响。     

IP over WDM网络联合恢复策略的研究

文章对动态自相似业务在多纤IP over WDM 网中的联合恢复问题进行了系统的研究,提出了3种联合恢复策略,算法的实现基于一种扩展的多纤分层图模型.通过大量的动态仿真实验,以业务中断率和恢复效率为性能指标,研究了上述3种恢复策略在不同自相似参数(突发度、均值和方差)中的性能,最后通过分析和比较得出联合通道恢复策略是最优的.     

All-optical multipoint-to-point routing in WDM mesh networks

In this article, the routing and wavelength assignment (RWA) problem for supporting multipoint-to-point communications in all-optical WDM mesh networks is investigated. Two efficient algorithms, namely reverse shortest path tree routing (RSPT) and k-bounded edge disjoint path routing (EDPR), are proposed. We proved that the problem of minimizing the total cost while establishing a multipoint-to-point session can be solved in polynomial time of O(|V|log|V|?+?|V|?+?|E|) by the RSPT algorithm, where |V| and |E| denote the number of nodes and the number of edges in the network, respectively. Nevertheless, the solution provided by the EDPR algorithm produces a significant reduction in the maximum number of wavelengths required per link (i.e., the link stress) for a multipoint-to-point session compared to RSPT algorithm. EDPR algorithm can also approximate to the optimal total cost with a ratio of k. Simulations are done to assess these two algorithms. Numerical results demonstrate their efficiencies in supporting multipoint-to-point communications in all-optical WDM networks.     

Deflection routing in IP optical networks

This paper deals with optical packet switching in a full-IP transport network scenario. Given the technological limits of accomplishing packet buffering in the optical domain, deflection routing is here explored as an alternative technique for resolving packet contentions without buffering packets. Two different network topologies have been considered here, that is a regular six-node network with different connectivity factors and the classical NSF network. A limited amount of optical buffering is considered in the switching nodes that performs both input queuing and shared queuing of packets to be switched. The performance improvements that can be obtained by deflection routing have been evaluated considering different methods for choosing the alternative paths where to deflect packets that cannot be transmitted onto the shortest path to the addressed destination.     

Integrated design of fault localization and survivable mapping in IP over transparent WDM networks

Lightpaths play multiple critical roles in cross-layer fault management of IP over transparent optical networks. While the roles of lightpaths have been discussed specifically in fault localization as well as fault recovery phases, these existing works only take a sporadic, piecemeal view of these roles by studying each of them individually as a separate lightpath routing problem. In this paper, we instead take an integrated, systematic view by considering these multiple roles jointly as one single lightpath routing problem. In particular, we propose a new design model to fulfill the lightpath layout requirements in both identifying fiber link failures for fault localization and ensuring IP topology connectivity for fault recovery. With a much smaller formulation size, our new model significantly outperforms the existing counterpart in computational efficiency, scalability, and solution quality.     

Dynamic connection provisioning with shared protection in IP/WDM networks

Internet protocol (IP) traffic connections arrive dynamically at wavelength‐division multiplexing (WDM) network edges with low data rates compared with the wavelength capacity, availability, and quality‐of‐service (QoS) constraints. This paper introduces a scheme to be integrated into the control and management plane of IP/WDM networks to satisfy the availability and QoS required for IP traffic connections bundled onto a single wavelength (lightpath) in WDM networks protected by shared‐backup path protection (SBPP). This scheme consists of two main operations: (i) routing multi‐granular connections and traffic grooming policies, and (ii) providing appropriate shared protection on the basis of subscribers’ service‐level agreements in terms of data rate, availability, and blocking probability. Using the Markov chain process, a probabilistic approach is developed to conceive connection blocking probability models, which can quantify the blocking probability and service utilization of M:N and 1:N SBPP schemes. The proposed scheme and developed mathematical models have been evaluated in terms of bandwidth blocking ratio, availability satisfaction rate, network utilization, and connection blocking probability performance metrics. The obtained research results in this paper provide network operators an operational setting parameter, which controls the allocation of working and backup resources to dynamic IP traffic connections on the basis of their priority and data rate while satisfying their requirements in terms of bandwidth and availability. Copyright © 2013 John Wiley & Sons, Ltd.     

On managing optical services in future control-plane-enabled IP/WDM networks

This paper presents the design and experimental implementation of a service-oriented Internet Protocol (IP)/wavelength division multiplexing (WDM) management plane. In the proposed approach, compliant with International Telecommunication Union Telecommunication Standardization Sector (ITU-T)'s automatic-switched optical network (ASON), a distributed control plane performs signaling, routing, and discovery functions, and a decentralized management plane, both at information and architectural levels, performs cross-plane actions to enforce service establishment and monitoring with a view to guarantee service level agreements (SLAs). In-service monitoring provides status of optical resources and services by using spectral- and time-domain information. Some performance aspects of the approach are evaluated in a real testbed featuring dense wavelength multiplexing and a control plane based on the Internet Engineering Task Force (IETF)'s generalized multiprotocol label switching (GMPLS).