智能光网中的联合路由

在IP／MPLS智能光网络中的LSP路由分为独立路由和联合路由两类。由于综合考虑了光层和IP层的可用资源信息和拓扑信息，联合路由能够提供比独立路由方案更高的资源利用率。文中提出了联合路由算法的设计目标，综述了联合路由算法的研究现状，并给出了下一步的研究方向。     

WDM网络链路负载平衡综合路由算法

要在光因特网(IP over WDM)网络中获得较好的负载分布平衡性能?有必要将IP层和WDM层的路由选择结合考虑。本文提出了将路由选择成本和光路传输距离折衷考虑的综合路由算法。由于算法对路由成本的计算仔细考虑了IP层和WDM层的资源信息?极大的降低了带宽碎片;并且选择的路由也不会太长。因此?极大地改善了业务丢失率和网络负载分布的平衡度。仿真结果表明?本文算法取得了较满意的效果。     

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网络集成动态路由算法研究

提出一种 IP over WDM网络中有带宽保证的集成动态路由算法 ,称之为最大开放容量路由算法。它充分考虑了 IP层和光层的拓扑和资源利用信息 ,能保证路径的带宽。算法可以决定 :(1)是否将一个到达的请求路由到已经存在的拓扑上 ,还是重新创建一条波长路径 ;(2 )如果在已经存在的 IP层路由 ,计算最佳路径。 (3)如果要创建新的波长交换路径 ,就决定选用哪些中间路由器 ,并计算最佳路径。性能目标是在不需要任何网络资源的将来可得性先验知识的情况下容纳尽可能多的连接请求。仿真结果显示 ,本算法在给定的性能尺度 (如被拒绝的连接请求数量 )上和集成最小跳数算法比较效果明显。     

智能光网络的路由技术

路由技术是智能光网络的核心技术之一,如何把IP路由技术运用到智能光网络中,以及如何利用路由技术提高智能光网络的生存性已成为研究热点.文中综述了光网络中路由技术的特点,分析了当今国内外智能光网络的部分路由算法,深入研究对比了它们各自的优缺点,以及对智能光网络生存性产生的影响,预测了智能光网络路由技术的未来发展趋势.     

IP over WDM 网络集成动态路由算法研究

提出了一种IP over WDM网络中有带宽保证的集成动态路由算法，称之为最大开放容量路由算法，它充分考虑了IP层和光层的拓扑和资源利用信息，能保证路径的带宽，算法可以决定：（1）是否将一个到达的请求路由到已经存在的拓扑上，还是重新建一条波长路径；（2）如果在已经存在的IP层路由，计算最佳路径。（3）如果要创建新的波长交换路径，就决定选用哪些中间路由器，并计算最佳路径，性能目标是在不需要任何网络资源的将来可得性先验知识的情况下容纳尽可能多的连接请求，仿真结果显示，本算法在给定的性能尺度（如被拒绝的连接请求数量）上和集成最小跳数算法比较效果明显。     

多域光网络联合路由保护算法

研究了多域光网络中的路由保护问题。为了避免多域光网络通路保护二步算法可能导致的多域陷阱问题,提出了一种基于Suurballe算法扩展的多域联合路由保护算法。仿真表明,相比传统的多域通路保护二步算法,该算法资源利用率高,阻塞率低,平均每连接跨域数小。     

组播技术及其在光层的实现

带宽密集型的多媒体应用对现有网络提出了新的要求,组播技术有助于解决其在网络带宽和服务质量方面的问题,而在光层实现组播具有更简单、高效的特点.然而,光层组播由于光缓存、光分束和光波长变换等光器件的限制,呈现出和IP层组播不同的特点.对IP层和光层组播进行了讨论,分析了光层组播模型,并对稀疏光分束和稀疏波长变换的光网络组播路由提出了重路由到源和重路由到相关节点两种重路由方式.     

基于机器学习的光网络路由与频谱分配机制研究

对于光网络而言,路由与频谱分配是制约光层资源利用率和光网络容量的重要问题之一.机器学习迅速发展,为光网络管理与控制的智能化、自动化提供了新的发展方向.本文回顾了近年来基于机器学习的路由频谱分配相关研究,介绍了光网络控制中常见的机器学习算法,描述了基于神经网络和强化学习的路由频谱分配机制,最后分析了当前研究在泛化性和可靠...     

光因特网中动态综合考虑的资源分配算法

该文研究了光因特网络中的动态资源分配问题，提出了基于分层图模型的路由选择和波长分配算法。对于动态变化的业务到达请求，如果在已有的基于IP级的逻辑拓扑上不能有效建立，则需要为该请求按算法分配资源，即解决路由选择和波长分配问题。由于该文算法将IP层和光层综合进行考虑，所以能大大提高资源利用的有效性，取得较好的阻塞性能。仿真结果表明，该算法既能选择比较短的路由，又能使网络取得较低的阻塞率。     

A Bandwidth Guaranteed Integrated Routing Algorithm in IP over WDM Optical Networks

In this paper, we have developed an integrated online algorithm for dynamic routing of bandwidth guaranteed label switched paths (LSPs) in IP-over-WDM optical networks. Traditionally, routing at an upper layer (e.g., IP layer) is independent of wavelength routing at the optical layer. Wavelength routing at the optical layer sets up a quasi-static logical topology which is then used at the IP layer for IP routing. The coarse-grain wavelength channels and the pre-determined virtual topologies with respect to some a priori assumed traffic distribution are barriers to efficient resource use and inflexible to changing traffic. We take into account the combined knowledge of resource and topology information at both IP and optical layers. With this added knowledge, an integrated routing approach may extract better network efficiencies, be more robust to changing traffic patterns at the IP layer than schemes that either use dynamic routing information at the IP layer or use a static wavelength topology only. LSP set-up requests are represented in terms of a pair of ingress and egress routers as well as its bandwidth requirement, and arrive one-by-one. There is no a priori knowledge regarding the arrivals and characteristics of future LSP set-up requests. Our proposed algorithm considers not only the importance of critical links, but also their relative importance to routing potential future LSP set-up requests by characterizing their normalized bandwidth contribution to routing future LSP requests with bandwidth requirements. Moreover, link residual bandwidth information that captures the link's capability of routing future LSPs is also incorporated into route calculation. Extensive simulation was conducted to study the performance of our proposed algorithm and to compare it with some existing ones, such as the integrated minimum hop routing algorithm and the maximum open capacity routing algorithm. Simulation results show that our proposed algorithm performs better than both routing algorithms in terms of the number of LSP set-up requests rejected and the total available bandwidth between router pairs.     

An Enquiry-Based Dynamic Service Provisioning Approach for Overlay IP-over-Optical Networks

Network control for IP-over-optical networks can be classified as falling under the overlay, augmented, or peer models. In the first two models, the IP layer and the optical layer only have the resource information of their respective layers. In the peer model, all the resource information is known to both layers; hence, it can potentially achieve better resource utilization. Unfortunately, the peer model approach is generally not acceptable to the operators if the IP layer and optical layer belong to two different administrations. In addition, it is much more complex and generally seen as not feasible in the near future In this paper, we propose an enquiry-based provisioning scheme based on the overlay model which can, however, utilize resources in both layers as in the peer model approach. Two simple and novel algorithms for routing labeled-switched path (LSP) requests for this provisioning scheme are proposed. Simulation results show that our proposed algorithms perform significantly better than other routing algorithms for the overlay model and are nearly as good as the integrated routing algorithm for the peer model.     

Integrated routing in GMPLS-based IP/WDM networks

The Internet traffic evolution has forced network operators to migrate toward an integrated infrastructure which brings the IP and optical layers under a unified model. The integration between the two technologies has been facilitated by the development of the Generalized Multi Protocol Label Switching. In the integrated scenario, Multilayer Traffic Engineering can be reinforced with integrated routing techniques. Integrated IP/WDM routing facilitates the routing decision phase by allowing a node to have a complete knowledge of the IP and WDM domains when accommodating traffic. This study focuses on integrated IP/WDM routing. We analyze two basic policies widely discussed in literature: one policy prioritizes the traffic accommodation on the virtual topology, while the other prioritizes the traffic accommodation on the physical topology. We show that both the mechanisms do not lead to efficient resource utilization because they tend to congest one layer more than the other one. We propose an adaptive heuristic which combines the advantages of both the policies. When accommodating traffic, the proposed approach selects the appropriate layer depending on the resource utilization being experienced in the virtual and the physical topologies. We demonstrate via simulations that the cross-layer resource optimization executed by the proposed scheme achieves significant improvements in terms of blocking ratio.     

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.     

Protection approaches for dynamic traffic in IP/MPLS-over-WDM networks

Due to the explosive growth of data-related traffic driven by the Internet, network reliability becomes an important issue. We investigate various protection approaches to handle failures for dynamic traffic demands in IP/MPLS-over-WDM networks. An LSP can be protected at either the IP/MPLS layer or the optical layer. In IP/MPLS layer protection, an LSP is protected by providing a link-disjoint backup LSP between its end nodes. In optical layer protection, an LSP is protected by the backup lightpath of each lightpath traversed by the LSP. We present two integrated routing algorithms: hop-based integrated routing algorithm and bandwidth-based integrated routing algorithm (BIRA) to set up the restorable bandwidth-guaranteed paths efficiently. Then we present a multilayer protection scheme for multiclass traffic in such networks. This scheme takes into account the different QoS and recovery requirements of the traffic to provide protection capability either at the MPLS layer or at the optical layer in a cost-effective manner. We use the connection blocking probability and number of optical-electrical-optical conversions as performance metrics to compare various protection approaches.     

IP over WDM联合路由框架

研究了IPoverWDMdirectly所面临的三大基本问题 ,重点对IP和WDM的联合路由框架进行了研究 ,分析了三种模型以及其中所用到的协议以及协议扩展。并对联合路由的控制面问题进行了研究 ,着重分析了对MPLS TE进行适当的光扩展以实现统一的控制平面。     

Internetworking connectionless and connection oriented networks

The use of connection-oriented (CO) networks for the transport of IP traffic is seen to have value to both users and service providers. Given the expectation that most endpoint-generated traffic will be in the form of connectionless (CL) IP datagrams, we address the problem of how to internetwork a CL (IP) network with a CO network. CO networks can be packet-switched or circuit-switched. Examples of packet-switched CO networks include ATM and MPLS networks, in which resource reservations are made at the ATM or shim layer, and IP-switch-based networks, in which resource reservations are made at the IP layer. Examples of circuit-switched networks include SONET/SDH and WDM networks that consist of programmable optical crossconnects. We consider the internetworking problem for two modes of operation of CO networks: provisioned, in which connections are set up a priori, and switched, in which connections are set up on demand. The main focus of this article is on the more complex problem: the internetworking of CL IP networks with CO networks operated in a switched mode. Our solution consists of (i) interworking user plane protocols with protocol conversion in some cases instead of always using protocol encapsulation, (ii) interworking routing protocols by either simply having gateways know routing information of both networks or having all nodes know routing information of both networks, and (iii) interworking signaling protocols by using application- or transport-layer end-to-end handshakes to trigger connection setups through the CO network. We demonstrate throughput improvements with our integrated routing interworking scheme over the MPOA IP-ATM internetworking solution for two example networks     

三层动态网络联合优化选路算法

 IP/MPLS over WDM被认为是下一代互联网络的最理想解决方案,但是在目前以及以后的很长一段时间内,网络结构仍然是IP/MPLS over SDH over WDM这样三层网络共存的情况。为了能够有效降低三层动态网络中的业务阻塞率,本文提出了三层动态网络联合优化选路算法。该算法分为两种模式,在模式1中,上层网络中被阻塞的业务可以开放的利用下层网络的空闲资源;在模式2中,将三层网络整合成为一个网络,在这个综合网络中为每一个业务进行选路。为了能够实时的传输每一个到达的动态业务,在这两种模式中采用蚁群策略为动态业务进行选路,提出了一个新的前向蚂蚁路径选择概率模型以及路径质量评判参数,使得所选的路径能兼顾链路利用率和路径跳数。仿真实验表明,同其他算法相比,本文提出的算法可以有效地降低三层动态网络的阻塞率。