一种IP网络友好的Overlay路由机制*

现有IP网络存在不支持QoS,故障恢复速度慢等问题。作为克服或屏蔽这些缺陷的一种有效手段,Overlay网络在当前Internet上被广泛部署和应用。目前存在很多的Overlay路由结构和方法。然而在现存的多层路由中,上层Overlay网络在路由决策时通常对底层的IP网络性能和状态缺乏有效的协调和感知,致使上层Overlay路由和底层IP路由常常处于非协同、非优化工作状态,产生大量路由抖动和次优路由。为解决这些问题,提出了一种底层IP网络友好的Overlay路由机制,其基本思路为：增加Overlay网络的层感知能力,减少路由抖动增加Overlay路由的稳定性。Overlay网络根据底层IP网络的节点跳数、链路带宽、丢包率等反映底层IP网络性能的信息做出路由决策。实际网络中,通过调整Overlay网络的链路代价有效控制Overlay网络的路由决策。最后仿真结果表明：与传统双重路由（Dual Routing）相比,此IP网络友好Overlay路由机制在减少Overlay网络路由抖动,降低Overlay网络路径代价膨胀,提高Overlay网络故障恢复成功率和满足Overlay业务需求等方面有优势。     

层叠IP/WDM网络中的区分服务

为层叠IP/WDM网络提出基于光通路物理跳距评估的区分服务机制。在使用层叠模型的IP/WDM网络体系中,如IP/MPLS层不了解光通路的物理跳距,现有文献中以此信息为基础的区分服务策略即不再适用。采用光通路区分策略评估光通路的物理跳距,映射为连接消耗的波长资源量,使用QoS接入控制机制拒绝占用大量资源的低优先级连接请求。仿真结果表明,该机制能够为不同等级业务提供良好的区分服务。     

IP/WDM网络的虚拓扑设计

为解决IP网络与光网络融合过程中虚拓扑设计的问题,提出基于短光路优先建立的IP/WDM网络动态虚拓扑配置方法。该方法通过引入光通道跳距限制,避免长光路对资源的浪费,达到缩短光通道长度和增强光层建路能力的目的。仿真结果表明,利用该机制配置的虚拓扑进行业务梳理,能够在较宽的负载范围内降低网络阻塞率,提高业务梳理效率。     

一种综合IP层和WDM层资源的光网络动态路由优化模型及其性能研究

在分层图模型的基础上,本文提出一种以最小化全网光路总代价为优化目标的IP over WDM光网络动态路由优化模型,设计了一种针对该模型的在线综合路由算法——MCTLP（Minimizing the Cost of Total Lightpaths）,MCTLP通过综合考虑IP逻辑层带宽资源分配和WDM光物理层波长链路资源的占用以优化网络资源。与两种有代表性的IP over WDM光网络路由算法的性能仿真时比表明：MCTLP能够在IP逻辑层和WDM光物理层都使用较少的链路以承载IP业务流,接纳更多的IP业务连接请求,有效地降低网络阻塞率．     

Ad hoc网络中的简单跨层流控机制

为了提高Ad hoc网络中传输层协议的性能,基于跨层思想设计了一种简单可行的跨层流控机制。该机制结合网络层路由反馈、传输层协议和应用层速率自适应调节,通过跨层信息交互,应用层可根据网络层反馈的路由信息来调节业务的发送速率,将网络负载维持在合理的水平以最大化网络吞吐量。计算机模拟评价表明该机制能改善基于UDP和TCP的业务性能,在网络负载较低的情况下效果尤为明显。     

一种无线Mesh网络跨层丢包通告机制

现有TCP机制无法有效区分网络丢包是拥塞丢包还是“失聪”丢包。针对该问题,提出一种在无线Mesh网络环境下跨层显示“失聪”丢包通告机制。该机制在系统使用定向天线条件下采用基于忙音的媒体接入控制机制区分数据丢包原因,通过IP和TCP跨层设计显示通告帧和定义的多跳转发规则向源端进行正确的通告。利用该机制对线性无线Mesh网络进行理论推导和分析,并通过数值实验证明其可行性和有效性。     

基于跨层议价博弈的认知无线电网络资源优化分配策略

如何合理分配有限的频谱资源是认知无线电网络的核心问题之一.通过对物理层功率控制和MAC层带宽分配需求的研究,建立以最大化系统吞吐量为目标的跨层优化模型.并在该模型的基础上设计一种基于跨层议价博弈的带宽与功率分配算法(Bandwidth and Power Allocation Algorithm-Cross Layer Bargaining Game,BPAA-CLBG).仿真结果表明该算法可以有效地提高认知无线电网络的频谱利用率,且在系统吞吐量方面较现有算法有明显的改善.     

网格业务:下一代电信业务资源管理的核心技术

建立在IP基础设施上的、结合了多种接入网络和传统业务网络能力的下一代网络，具有提供开放的下一代电信业务的能力，也产生了在多网络多业务环境下实现业务资源的同步管理问题。文章提出了基于开放网络业务体系结构的资源同步管理业务模型。通过对跨网络资源管理业务能力的抽象建立网格业务，从而在不影响现有各个网络和平台业务和信令的情况下，实现了下一代网络中组合业务资源的动态同步管理。     

无线Mesh网络入侵检测关键技术研究

本文研究了无线Mesh网络的结构和特点,以及入侵检测系统(IDS)在构建安全WMN中不可替代的作用。深入分析了AdHoc网络IDS、跨层和网络故障检测技术特点以及无线Mesh网络自身的安全需求。在此基础上,本文结合网络故障检测与跨层技术提出了一种基于代理的非对称分布式协作IDS结构,对代理模块设计原则进行了详细分析。最后以MAC自私行为攻击为例对该结构进行了模拟。结果显示,该结构能够很好地适应无线Mesh网络。     

复杂网络特性对大规模多智能体协同控制的影响

随着分布式多智能体系统应用领域和系统规模的不断扩大,网络特性已成为影响系统性能的一个重要因素.通过研究和分析复杂网络特性对大规模分布式多智能体系统协同控制的影响,对多智能体系统性能的影响做出系统性分析,同时为提出大规模多智能体组织结构的优化算法提供依据.主要针对随机网络、小世界网络、网格网络和无尺度网络这4种典型复杂网络特性,从理论和仿真两方面进行分析.在理论方面,通过基于马尔可夫链的信息传输过程在不同网络结构下的建模,对比分析了信息无偏随机游走模型和智能决策模型下的传输效率.在仿真建模中,主要从智能体间信息传输效率、不同应用领域中集成协同控制效率、对网络故障恢复的影响这3个典型的多智能体系统协同控制应用对比分析复杂网络特性对系统性能的影响.研究结果表明,复杂网络特性如小世界和无尺度特性可以在相同的控制策略下形成明显的性能差异,如果设计合理的控制算法,复杂网络结构将有助于多智能体系统性能的提升.     

Integrated Differentiated Survivability in IP over WDM Networks

The problem of differentiated Multi-Layer Integrated Survivability (MLIS) in IP over WDM networks is studied, which is decomposed into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCD), and dynamic survivable routing (DSR). A related work of network survivability in IP over WDM networks is firstly provided, and adaptive survivable strategies are also designed. A new Integrated Shared Pool (ISP) approach for SCD is then proposed, which is formulated by using integer-programming theory.Moreover, a novel survivable routing scheme called Differentiated Integrated Survivability Algorithm (DISA) for DSR is developed. Simulation results show that the proposed integrated survivability scheme performs much better than other solutions (e.g., “highest layer recovery” and “lowest layer recovery” schemes) in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio in IP over WDM networks.     

分级跨层设计的宽带无线接入网QoS架构

针对当前跨层设计导致信号流向混乱和处理时延长等问题,提出一种新的分级跨层设计的宽带无线接入网QoS架构。该架构具有链路独立层、链路独立-链路依赖的业务接口与链路依赖层,并给出各分级内及接口的QoS管理结构及模块功能。其中,物理层和无线链路层构成的链路依赖层可实现链路对信道的自适应,IP层及其上的各层构成的链路独立层在链路独立-链路依赖接口,通过业务QoS参数与无线资源的映射实现端到端的自适应,信号流向简单且处理时延减小。仿真结果表明,该架构的资源利用率明显优于分层结构。     

An enhanced cross-layer fast handover scheme for mobile IPv6 in the IEEE 802.16e networks

The IEEE 802.16e standard enhances the IEEE 802.16 for the mobility support. Mobile stations can move while receiving services, thus ongoing IP sessions may be maintained during a handover in the IEEE 802.16e. To reduce handover latency, the idea of cross-layer handover which incorporates layer 2 handover with IP layer has been devised. Various cross-layer handover schemes supporting fast handover in the IEEE 802.16e networks have been proposed. However, the problem of the conventional cross-layer fast handover schemes is that they are heavily influenced by the new address confirmation latency which is the most time-consuming procedure. In this paper, we propose an enhanced cross-layer fast handover scheme which is not susceptible to the new address confirmation latency. Detailed performance analysis is performed in terms of the signaling costs and the handover latencies to show the effectiveness of the proposed scheme compared with the conventional ones. The results of the performance evaluation confirm the effectiveness of the proposed scheme.     

Hierarchical Mobility Label Based Network: System model and performance analysis

Hierarchical Mobility Label Based Network (H-MLBN) is a new approach to the network layer mobility management problem that relies on MPLS-aware control plane and MPLS-based forwarding plane to provide IP mobility support for IPv4 and IPv6 mobile hosts and routers while being able to ensure optimal traffic delivery between the communicating devices. The hierarchical system is capable of both macro- and micro-mobility support without the use of Mobile IP and its derivatives thus eliminating the user and network facing performance penalties associated with triangular routing and bi-directional tunneling. This paper presents a system model and provides performance analysis for H-MLBN and compares its performance with the Mobile IP based schemes. The results indicate significant performance improvements in the forwarding plane traffic delivery as well as the control plane network update costs.     

基于UWB的无线传感器网络跨层优化模型研究

跨层设计是提高无线传感器网络整体性能的一种有效方法。在综合考虑MAC层调度、物理层功率控制、网络层路由三方面因素的基础上,结合超宽带技术大带宽、低信号功率的特点,以实现网络最大数据传输速率为目标,构建了基于超宽带技术的无线传感器网络跨层优化模型。仿真实验表明：模型最优解可有效提高网络数据传输速率;物理层功率控制对优化结果有着至关重要的影响。这证明以构建、求解优化模型的方式解决跨层设计问题是切实可行的,同时也为解决大规模超宽带传感器网络数据传输问题提供了一条新的解决思路。     

A Cross-Layer Optimization and Design approach under QoS constraints for green IP over WDM networks

Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demands. It is important and valuable to find a way to save power for such networking systems. In this paper, we propose a Cross-Layer Optimization and Design (CLOD) approach to improve the energy efficiency of Internet Protocol (IP) over Wavelength Division Multiplexing (WDM) backbone networks under QoS constraints. CLOD makes use of the skew spatial distribution (i.e. 80–20 law) of traffic demands to construct the virtual topology of IP layer with a consideration of the cross-layer resource constraints. Also, CLOD takes advantage of the constraint-based routing to satisfy the QoS constraints in terms of allowed maximum hop count and allowed maximum link utilization. Taking into account the connection between base network design and network operation, CLOD dimensions the base network by using pattern of network operation and optimizes network power consumption by reconfiguring network to adapt traffic variation and the available resources. Simulation results indicate that CLOD can save power significantly and achieve near energy-proportional networks. In addition, an analysis on trade-off performance between the hop count and power consumption is given.     

Architectural considerations in the design of WDM-based optical access networks

We describe a WDM-based optical access network architecture for providing broadband Internet services. The architecture uses a passive collection and distribution network and a configurable Feeder network. Unlike earlier papers that concentrate on the physical layer design of the network, we focus on higher layer architectural considerations. In particular we discuss the joint design of the electronic and optical layers including: WDM Medium Access Control protocols; the choice of electronic multiplexing and switching between the IP and WDM layers; joint optical and electronic protection mechanisms; network reconfiguration algorithms that alter the logical topology of the network in response to changes in traffic; and traffic grooming algorithms to minimize the cost of electronic multiplexing. Finally we also discuss the impact of the optical topology on higher layer protocols such as IP routing, TCP flow control and multi-layer switching.     

基于OpenFlow的自适应QoS流量控制方法设计与实现

随着新型业务类型如视频会议、网络游戏、交互应用等不断涌现,如何利用有限的网络资源进行有效的流量控制,以保障业务的服务质量(Quality of Service,QoS)已成为一个非常迫切的问题。而目前已有的QoS流量控制方法大多存在着对网络资源的利用率低、可靠性差、粒度粗、实现困难,可扩展性差等问题。软件定义网络(Software Defined Network,SDN)提出的控制层与数据层分离思想,为解决此类问题提供了崭新的思路。本文提出了一种基于OpenFlow技术的QoS流量控制方法,利用自适应多约束QoS路由技术,提高了QoS控制的灵活性与可靠性,实现了对网络资源的高效利用和业务流控制的细粒度。最后,我们在OpenvSwitch环境下验证了该方法的有效性。     

A novel admission control mechanism in GMPLS-based IP over optical networks

With the migration of real-time and high-priority traffic in IP networks, dynamic admission control mechanisms are very important in high-capacity networks where IP and optical technologies have converged with a GMPLS-based control-plane. In this paper proposes, we propose an integrated multilayer traffic engineering framework that considers both physical and logical (optical layer) topologies for dynamically admitting new label switched paths (LSPs) in GMPLS networks. The dynamic admission control mechanism is based on an optimal resolution of an integer linear programming model that takes into account both lightpaths availability, wavelength continuity and routing constraints. In order to minimize LSPs set up delays, this mechanism first considers the logical topology (set of lightpaths) that is already in place before setting up a new lightpath for the incoming LSP, resulting in an additional set up signaling delay. When tested by simulations, results confirm that the proposed formulation effectively improves the network performance by reducing the connection blocking rate, while guaranteeing strict delay and noise constraints.     

Forward-Looking WDM Network Reconfiguration with Per-Link Congestion Control

We study reconfigurations of wavelength-routed Wavelength Division Multiplexing (WDM) networks in response to lightpath demand changes, with the objective of servicing more lightpath demands without additional network resources from a long-term network operation point of view. For the reconfiguration problem under study, we assume WDM network operators are provided with lightpath demands in batches. With limited network resources, our problem has two unique challenges: balancing network resource allocations between current and future lightpath demands, and modeling future lightpath demands. The first challenge implies making tradeoffs between accepting as many current immediate lightpath demands as possible and reserving a certain amount of network resources for near future predicted lightpath demands. The second challenge implies modeling future predicted lightpath demands, which are not exactly known or certain as the current lightpath demands. Our proposed model allows a natural separation between the operation of the optical layer and the user traffic layer (predominantly the IP-layer), while supporting their interactions, for which we propose a new formulation for per-link congestion control, associated with a mathematical solution procedure. Our simulation results reveal that by properly controlling resource allocations in the current session using our proposed mechanism, rejections in future sessions are greatly reduced.