光互联网:重画网络蓝图

多业务网络模型的演进过程中,显然一直存在着两种对立的模型,即面向连接的技术（采用带外信令）和无连接的技术。无论哪一种模型都没有试图解决可靠性、可扩展性以及保证提供服务质量（QoS）的基本问题。我们面临的挑战是如何实现动态互动、平滑过渡和分布智能。解决方法和策略一直在变化,其中包括演进的QoS模型、创新的复用技术、综合分组/光的策略,以及不断增加的可扩展性产品,但是每种方法都有其优点和缺点。自从上一世纪90年代末以来,光技术已经大举进入运营商的网络。光学系统能否最终替换分组交换技术？答案似乎很清楚：这些…     

广义全保护的动态ASON规划研究

传送网络正由传统光网络向智能光网络演进,文章提出了"广义全保护的动态自动交换光网络(ASON)"的概念,该网络可满足无阻塞的动态业务提供和对于任何网络失效的完全可生存性.文章还讨论了满足如上要求的数学算法模型,阐述了该网络的容量规划问题.     

ASON演讲与移动光传输网的发展

1 ASON的基本概念和移动光传输网的要求 ASON(自动交换光网络)是指一种具有灵活性、高可扩展性的、能直接在光层上按需提供服务的光网络基础设施,是具有动态连接管理能力的光传送网络.     

互联网动态地址命名与解析服务

命名解析机制作为互联网的核心组件，其固化的静态设计以及可扩展性的缺失是导致体系结构陷入僵化的主要原因.针对网络核心层面的创新困境，提出了一种动态的命名与解析服务，允许按需设计、构建和部署多样的地址策略，灵活支撑顶层业务需求.基于xml的通用地址描述规范通过精心抽象的元素属性以及灵活的组合方式，提供了对异构命名模型的统一表达和解释能力；动态解析服务基于预先配置的对象绑定拓扑，支持新型命名空间、协议实体以及解析机制的透明引入.试验表明，通用命名与解析服务具备良好的可扩展性和时间性能，相比传统互联网地址系统，能够赋予网络核心层面的演进能力，从而为体系结构维度的创新提供良好支撑.     

光传送网演进过程中的OTN技术应用分析

随着数据流量在网络中激增,IP业务逐渐成为电信网络的主导业务,由于IP业务本身的不确定性和不可预见性,特别是IP业务的多样性、精细颗粒和大颗粒等特性对作为电信业务基础承载网络的光传送网提出了新的挑战。本文总结出在新业务驱动下光网络的近期演进方向为向统一传送网演进,对于光网络向统一传送网演进过程中重要的OTN（Optical Transport Network）技术进行了技术特征、设备形态及应用场景的分析,提出了相应应用建议及案例。     

多媒体干线网--iLYNX 基于下一代SDH的广电数字传送网

SDH是电信网长途传输的主流技术，随着数字视频和数据业务的增长，保证SDH从单纯满足语音传输为主、相对静态的网络过渡到支持多业务、动态可扩展性强的网络是SDH演进的重要课题。本文介绍了一种专门为广电设计的数字视频和多媒体基于下一代SDH的解决方案。     

多层网络测试加速通信网发展进程——访NetTest光网络测试业务部副总裁兼总经理Jim Nerschook

目前的电信网络正从承载单一业务的独立网络向承载多种业务的下一代网络演进。运营商需要改变现有网络设计。加快光网络建设速度，以适应迅速增长的话音和数据通令业务以及市场潜力巨大的增值业务。同时，也要求现有的通信网络需要具备可扩展性和快速部署新业务的能力。     

动态可重构的智能光载无线接入技术

文章认为动态可重构的智能光载无线网络可以融合光纤和无线接入系统,通过引入新的网络架构、媒体访问控制(MAC)协议、系统链路以及关键器件等系列新技术,满足通信网对高效、宽带以及灵活等特性的需求。基于动态可重构的智能光载无线技术,文章在网络层提出适合智能光载无线技术的网络架构;在MAC层提出使光载无线MAC层的性能得到提升、保障联合资源的动态可管控的专用设计;在系统层提出在光域对射频信号进行处理、传输与控制的相关技术。文章还在器件方面提出利用特殊结构改善滤波、天线等性能的新技术。     

EPON系统的动态带宽分配算法的研究

在未来几年里，光网络已经为主宰接入网领域做好了准备。首先简单介绍了以太网无源光网络以及目前已经提出的不同的动态带宽分配算法，然后针对每个算法不同的特点与适用范围进行了性能分析和比较，最后对动态带宽算法未来的发展进行了展望。     

软件定义光网络研究进展与创新应用探讨

以软件定义网络(SDN)控制平面技术为特征的软件定义光网络(SDON)代表着未来传送网演进趋势,是新型超大容量光网络实现高度智能化的重要发展方向。认为通过在光层引入基于软件定义组网的控制平面解决方案,利用软件编程的方式对光网络的结构和功能进行动态定制,完成光网络设备配置、传输参数调整和带宽灵活分配,能够更好地适应新型光网络智能化发展的要求。认为开发软件定义光网络创新应用成为SDON领域新的研究热点。     

Architectures and technologies for high-speed optical data networks

Current optical networks are migrating to wavelength division multiplexing (WDM)-based fiber transport between traditional electronic multiplexers/demultiplexers, routers, and switches. Passive optical add-drop WDM networks have emerged but an optical data network that makes full use of the technologies of dynamic optical routing and switching exists only in experimental test-beds. This paper discusses architecture and technology issues for the design of high performance optical data networks with two classes of technologies, WDM and time division multiplexing (TDM). The WDM network architecture presented stresses WDM aware Internet protocol (IP), taking full advantage of optical reconfiguration, optical protection and restoration, traffic grooming to minimize electronics costs, and optical flow-switching for large transactions. Special attention is paid to the access network where innovative approaches to architecture may have a significant cost benefit. In the more distant future, ultrahigh-speed optical TDM networks, operating at single stream data rates of 100 Gb/s, may offer unique advantages over WDM networks. These advantages may include the ability to provide integrated services to high-end users, multiple quality-of-service (QoS) levels, and truly flexible bandwidth-on-demand. The paper gives an overview of an ultrahigh-speed TDM network architecture and describes recent key technology developments such as high-speed sources, switches, buffers, and rate converters     

Analysis of a dynamically wavelength-routed optical burst switchednetwork architecture

The concept of optical burst switching (OBS) aims to allow access to optical bandwidth in dense wavelength division multiplexed (DWDM) networks at fractions of the optical line rate to improve bandwidth utilization efficiency. This paper studies an alternative network architecture combining OBS with dynamic wavelength allocation under fast circuit switching to provide a scalable optical architecture with a guaranteed QoS in the presence of dynamic and bursty traffic loads. In the proposed architecture, all processing and buffering are concentrated at the network edge and bursts are routed over an optical transport core using dynamic wavelength assignment. It is assumed that there are no buffers or wavelength conversion in core nodes and that fast tuneable laser sources are used in the edge routers. This eliminates the forwarding bottleneck of electronic routers in DWDM networks for terabit-per-second throughput and guarantees forwarding with predefined delay at the edge and latency due only to propagation time in the core. The edge burst aggregation mechanisms are evaluated for a range of traffic statistics to identify their impact on the allowable burst lengths, required buffer size and achievable edge delays. Bandwidth utilization and wavelength reuse are introduced as new parameters characterizing the network performance in the case of dynamic wavelength allocation. Based on an analytical model, upper bounds for these parameters are derived to quantify the advantages of wavelength channel reuse, including the influence of the signaling round-trip time required for lightpath reservation. The results allow to quantify the operational gain achievable with fast wavelength switching compared to quasistatic wavelength-routed optical networks and can be applied to the design of future optical network architectures     

Applying PTF/VTF routing policies in multilayer IP/MPLS-based ASON/GMPLS multi-domain networks

The IP/MPLS-based ASON/GMPLS hybrid network architecture enables the interaction between the IP layer and the optical dense wavelength division multiplexing (DWDM) layer. This architecture makes it possible to transfer huge amounts of traffic data on DWDM networks, while supporting Internet Protocol (IP)-based service applications. Additionally, this architecture provides a unified routing scenario, which allows the dynamic routing in both the IP layer and/or optical layer. Cross- layer routing has been addressed in single domain networks scenarios, where the routing policies Physical Topology First (PTF) and Virtual Topology First (VTP) have been proposed and applied. However, applying cross-layer routing using both routing topology policies PTF and VTF has not been investigated in a multi-domain networks scenario yet. In this study, we address this issue and propose a routing scheme to establish traffic connections in the optical WDM layer and the IP layer, which makes the applicability of PTF and VTF in multilayer multi-domain network feasible.     

自由空间二维榕树网实现方法

鉴于榕树网在自由空间光子交换网络中具有重要的应用价值,分析了榕树网的特点和4×4二维榕树网的空间拓扑结构,通过偏振光分光棱镜、微闪耀光栅阵列、平面反射镜、半反半透镜和液晶空间光调制器的集成,构建二维的榕树交换网实验模块,利用微闪耀光栅的衍射特性,控制每块微闪耀光栅的周期,以实现入射光信号不同方向的闪耀输出,最终完成二维榕树网自由空间水平和竖直方向上的交叉互连,直通则由平面镜反射实现。对二维榕树网实验模块的功能分析表明,该实验模块理论上可以完成4×4二维面阵内光信号(或数据)的排序、交换、组播、广播、矩阵变换等操作,具有交换透明、速度快、空间带宽高等特点,在全光交换和光通信中具有一定的应用。     

Network architecture for optical path transport networks

This paper proposes a new layered transport network architecture on which the WDM optical path network can be effectively created. The optical path network will play a key role in the development of the transport network that will realize the bandwidth-abundant B-ISDN. This paper extends the layered transport network architecture described in ITU-T Recommendation G.803 which is applied in existing SDH networks. First, we elucidate an application example of WDM optical path networks. Next, we propose a new layered architecture for WDM-based transport networks that retains maximum commonality with the layered architectures developed for existing B-ISDN networks. The proposed architecture is composed of circuit layer networks, electrical path layer networks, optical layer networks, and physical media (fiber) networks. The optical layer is divided into an optical path layer and an optical section layer. The optical path layer accommodates electrical paths. Optical section layer networks are divided into optical multiplex section (OMS) layer networks and optical repeater section (ORS) layer networks. The OMS layer network is concerned with the end-to-end transfer of information between locations transferring or terminating optical paths, whereas the ORS layer is concerned with the transfer of information between individual optical repeaters. Finally, a detailed functional block model of WDM optical path networks, the function allocation of each layer, and an optical transport module (OTM) are developed     

Strategies Towords Next Generation IP Over Optical Networks

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A dynamic impairment-aware networking solution for transparent mesh optical networks - [Topics in optical communications]

Core networks of the future will have a translucent and eventually transparent optical structure. Ultra-high-speed end-to-end connectivity with high quality of service and high reliability will be realized through the exploitation of optimized protocols and lightpath routing algorithms. These algorithms will complement a flexible control and management plane integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment-aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that will consider dynamic traffic characteristics, a reconfigurable optical layer, and varying physical impairment and component characteristics. The network planning tool along with extended control planes will make it possible to realize the vision of optical transparency. This article presents a novel framework that addresses dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.     

Routing and wavelength assignment with multigranularity traffic in optical networks

We propose a novel switching architecture of multigranularity optical cross-connects (MG-OXCs) for dealing with multigranularity traffic in the optical domain. MG-OXCs can cooperate with the generalized multiprotocol label switching (MPLS) control plane, which provides the advantages of cost reduction, better scalability in physical size, and unified traffic management. Detailed discussions are provided on the characteristics and implementation issues for the switching architecture. Based on the proposed MG-OXCs, two routing and wavelength assignment (RWA) with tunnel allocation algorithms are presented: dynamic tunnel allocation (DTA) and capacity-balanced static tunnel allocation (CB-STA). In the former, we use fixed alternate routing with k-shortest paths to inspect network resources along each alternate path for dynamically setting up lightpaths. For the latter, fiber and waveband tunnels are allocated into networks at the planning stage (or off-line) according to weighted network link-state (W-NLS). We will show that with the proposed algorithms, the RWA problem with tunnel allocation in the optical networks containing MG-OXCs can be solved effectively. Simulation is conducted on networks with different percentages of switching capacity and traffic load. The simulation results show that DTA is outperformed by CB-STA in the same network environment due to a well-disciplined approach for allocating tunnels with CB-STA.. We also find that the mix of the two approaches yields the best performance given the same network environment apparatus.     

自相似业务在WDM网络中的动态性能分析

通过在几种颇具代表性的网络拓扑结构上进行仿真,对自相似业务在波分复用（WDM）光网络中的动态路由波长分配（RWA）问题进行了研究,分析了自相似业务在不同波长路由分配策略下的动态性能,并与相同条件下的泊松业务作了对比。     

Time-sensitive software-defined networking (Ts-SDN) control architecture for flexi-grid optical networks with data center application

Data center interconnected by flexi-grid optical networks is a promising scenario to meet the high burstiness and high bandwidth requirement of data center application, because flexi-grid optical networks can allocate spectral resources for applications in a dynamic, tunable and efficient control manner. Meanwhile, as centralized control architecture, the software-defined networking (SDN) enabled by OpenFlow protocol can provide maximum flexibility for the networks and make a unified control over various resources for the joint optimization of data center and network resources. Time factor is firstly introduced into SDN-based control architecture for flexi-grid optical networks supporting data center application. A traffic model considering time factor is proposed, and a requirement parameter, i.e., bandwidth-period product is adopted for the service requirement measurement. Then, time-sensitive software-defined networking (Ts-SDN)-based control architecture is designed with OpenFlow protocol extension. A novel deadline-driven PCE algorithm is proposed for the deadline-driven service under Ts-SDN-based control architecture, which can complete data center selection, path computation and bandwidth resource allocation. Finally, simulation results shows that our proposed Ts-SDN control architecture and deadline-driven PCE algorithm can improve the application and network performance to a large extent in blocking probability.