All-Optical Processing Based on a Logic xor Gate and a Flip-Flop Memory for Packet-Switched Networks

The routing functionality by all-optically interconnecting semiconductor-based all-optical logic gates and flip-flops is demonstrated in the frame of an all-optical label swapping (AOLS) network. We experimentally show that the output of the all-optical 2-bit correlator is capable of toggling the states of the integrated flip-flop every 2.5 ns via an adaptation stage. High extinction ratios are obtained at the output of the flip-flop, which can be used to feed a high-speed wavelength converter to complete the routing functionality of the AOLS node. The potential integration of these semiconductor optical amplifier integrated Mach-Zehnder interferometer-based devices make the proposed approach a very interesting solution for future packet switched optical networks.     

On an IP-centric optical control plane

This article presents an experimental study on adopting and integrating the existing IP protocols and mechanisms into an optical network control plane. Although there has been much research effort on the conceptual and functional requirements for the control of optical networks, this article focuses on the design and implementation of an optical control plane. The proposed control plane implements the key functions such as routing, signaling, protection/restoration, and quality of service     

ASON and GMPLS—Overview and Comparison

In automatic switched transport networks (ASTN), transport services of different granularity can be set up, modified and released on demand using the mechanisms in the control plane. Currently, this novel provisioning paradigm is being standardized under the umbrella of the automatic switched optical network (ASON) and generalized multiprotocol label switching (GMPLS) framework. This paper provides an overview of the ASON and GMPLS frameworks at the current stage of their development and aims in particular on comparing the concepts and pointing out some open issues. In this context, we first give a brief overview of ASON and GMPLS work, and then provide a concept and functionality mapping including network resource models, control plane architecture, discovery, call and control management, and resiliency. Finally we address some important provider requirements.     

A next-generation optical regional access network

We describe an optical regional access network which combines electronic IP routing with intelligent networking functionality of the optical WDM layer. The optical WDM layer provides such networking functions as network logical topology reconfiguration, optical flow switching to offload traffic and bypass IP routers, wavelength routing of signals, protection switching and restoration in the optical domain, and flexible network service provisioning by reconfigurable wavelength connectivity. We discuss key enabling technologies for the WDM layer and describe their limitations. The symbiosis of electronic and optical WDM networking functions also allows support for heterogeneous format traffic and will enable efficient gigabit-per-second user access in next-generation Internet networks     

基于GMPLS协议的ASON试验平台

文章介绍了清华大学自主研发的基于通用多协议标签交换(GMPLS)协议的自动交换光网络(ASON)试验平台.试验平台由3个层面构成,分别为传送层面、控制层面和管理层面.传送层面由4个光交叉连接(OXC)和1个光上下路复用器(OADM)构成的传送网络组成;控制平面由多个协议模块构成,包括链路管理、路由和信令模块,这些协议的实现都是基于互联网工程任务小组(IETF)的GMPLS协议开发和实现的;管理平面完成配置管理和故障管理,包括网元管理以及软永久连接的触发等.试验平台支持动态可配置的网络拓扑、自动邻居发现、受限路由以及光层快速的保护和恢复功能.     

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。     

All-optical wavelength conversion: technologies and applications inDWDM networks

Dense WDM technologies make effective use of the vast fiber bandwidth and offer an added dimension to all-optical networks. Wavelength conversion at key network nodes is emerging as a fundamental functionality that can allow transparent interoperability, contention resolution, wavelength routing, and, in general, better utilization of the network resources under dynamic traffic patterns. We offer an overview of the enabling technologies and extend the treatment to the network application of these converters. Attention is given to semiconductor optical amplifiers and their use in wavelength converters. Converters based on four-wave mixing as well as those based on nonlinear optical loop mirrors are evaluated, paying special attention to signal integrity and architectural as well as performance issues. The use of wavelength converters in wavelength routing networks is explored together with the application of these devices in contention resolution and in the routing wavelength assignment problem. Future directions are outlined at the system as well as network levels     

An InP-Based Monolithically Integrated Reconfigurable Optical Add–Drop Multiplexer

We demonstrate an InP-based monolithically integrated reconfigurable optical add-drop multiplexer consisting of an array waveguide grating, a semiconductor optical amplifier, four 2x2 Mach-Zehnder optical switches, and four PIN photodetectors using the asymmetric twin waveguide technology. The total chip size is 10 x 6 mm, and each of the components in the circuit exhibited performance similar to that achieved in a discrete form. The add-drop functionality of the chip is demonstrated via the routing of the signal from the add port to the drop/output port.     

基于GMPLS的OBS网络技术

GMPLS(通用多协议标签交换)是MPLS技术向光网络发展的产物。描述GMPLS和MPLS控制平台的区别,介绍引用GMPLS协议作为控制平面的OBS网络。提出的网络结构是在OBS的突发控制包中用通用标签代替源节点和目的节点地址,并使用GMPLS协议栈对路由协议、信令功能以及链路管理协议进行增强和扩展以便更好地支持OBS网络。     

GMPLS的动态路由机制研究

GMPLS由MPLS演进而来,它是MPLS向光层扩展的必然产物,路由技术是GMPLS的一项关键技术。这里简要回顾了MPLS技术,在此基础上对GMPLS中与路由相关的关键技术做了介绍,讨论GMPLS中现有的路由选择策略,论述基于GMPLS支持的对等网络模型对一种联合的网络结构及其控制平面的结构,最后提出基于GMPLS的网络中一种有QoS保证的动态路由机制。     

JumpStart deployments in ultra-high-performance optical networking testbeds

This article describes deployments of the JumpStart architecture and protocols in several ultra-high-performance optical networking testbeds. JumpStart interoperates with a variety of commercial optical switching gear, and supports operator-, user-, application-, and protocol-initiated ultra-fast lightpath provisioning. We briefly describe JumpStart's data and control plane architectures, and the functionality and performance of its edge and core components. We summarize results from JumpStart testbed demonstrations supporting ultra-fast lightpath provisioning for grids, high-performance file transfers, low-latency zero-jitter interactive visualization, and optical transport using optical burst switching.     

Using tunneling techniques to realize virtual routers

The evolution of the router architecture has gradually changed from a conventional architecture, which processes all functions on one operating system/processor, to a remote architecture, which can be split into a control plane and a data plane with their respective functions. The control plane is mainly responsible for the operations of the routing/signaling protocols and the data plane is responsible for forwarding the large amount of data packets. Furthermore, the remote architecture facilitates the realization of virtual routers. Virtual routers are created basically by logically splitting a routing processor in the control plane into many virtual routing units that have independent routing tables, use independent protocols, and connect to the external network through different interfaces. A virtual router with a remote architecture is more flexible and efficient than conventional routers; however, it requires an additional communication mechanism between the control plane and the data plane. We propose using existing tunneling techniques to provide a communication mechanism between the control plane and the data plane. Many design and implementation issues on the software architecture and protocol ramification are identified. We discuss solutions to these issues and successfully demonstrate a working virtual router with our proposed solutions.     

Distributed Optical Control Plane Architectures for Handling Transmission Impairments in Transparent Optical Networks

Transmission impairments in wavelength-division- multiplexing (WDM) transparent optical networks accumulate along an optical path and determine the feasibility of lightpaths; hence, the impairments need to be managed efficiently by the control plane. This paper presents impairment-aware distributed optical control plane (OCP) based on enhancements to resource reservation protocol–traffic engineering (RSVP–TE) signaling protocol (S-OCP). In particular, four architectural options [K-sequential (K-SEQ), K-parallel (K-PAR), hop-by-hop (HbH), and full flooding (FF)] within the S-OCP approach are defined and compared. Simulation results show that a combination of HbH routing and feasibility check can be considered as a good compromise both in terms of blocking probability and control plane overhead. The feasibility of a signaling-based approach for the control plane is further demonstrated by comparing simulation results with the results obtained from the implementation of the proposed architectural options in a commercial generalized multiprotocol label switching (GMPLS) protocol emulator. Furthermore, we argue that the real networks will rarely be homogeneous concerning transponder types, creating the need for a transponder selection policy at the end nodes. We introduce and compare two policies: best-first and worst-first. The results obtained from our experiments show that a worst-first policy for selecting transponders can save up to 50% enhanced transponders thereby reducing the overall cost.      

软件定义光网络中基于最小点覆盖的控制平面跨层生存性设计

为降低软件定义光网络对单控制器的依赖,并避免多控制器冲突,有效提升控制平面的生存性,该文提出基于最小点覆盖的控制平面生存性设计策略。该策略结合集中控制约束条件,以最小点覆盖理论为基础,建立可靠的分级管控模型,设定控制器的管控优先级:全局控制器具有最高管控优先级,对全网进行集中管控;本地控制器次之,只对本地业务进行集中管控;权威交换机的管控优先级最低,用于完成局部波长粒度的光层快速管控。在此基础上,基于跨层信息模型为控制信道路由和资源分配进行生存性冗余设计。仿真表明,该策略能够满足网络对控制时延的要求,使控制平面的故障概率降低了30%,有效提升了网络在恶劣环境下的生存性。     

智能光网络的体系架构和演进路线

本首先介绍智能光网络的基本概念和发展，然后介绍其标准化框架和进展，接下来全面介绍其控制面的功能要求，信令及相关接口，选路和信令网，控制面结构，网络性能要求等总体问题的规范和考虑，最后论述IP层与光传送层的融合及两种基本网络演进结构的特点。     

基于PNNI的ASON路由协议

通用多协议标签交换(GMPLS )是将多协议标签交换 /流量工程(MPLS-TE )进行光网络扩展,并被广泛接受作为自动交换光网络(ASON )控制面协议的理想选择,然而标准化组织正讨论研究将专用网网间接口( PNNI )协议用于 ASON 控制面的潜力。文中主要通过对 PNNI 的路由分层概念、 PNNI 的路由信息分发机制和 PNNI 的路径选择机制的介绍,给出 PNNI 路由的几个扩展,以适合 ASON 的路由需求。     

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).     

下一代光网络ASON中的控制组件

文章主要阐述了作为下一代光网络的自动交换光网络控制平面的基本功能,以及实现这些功能所需要的控制组件,并对几个主要控制组件的功能和接口作了描述,同时简单介绍了控制平面中信令、路由和链路管理所采用的相关协议。     

Balancing CapEx reduction and network stability with stable routing–virtual topology capacity adjustment (SR–VTCA)

This paper investigates the merits of the SR–VTCA (stable routing–virtual topology capacity adjustment) approach as a mechanism to find a beneficial trade-off between network stability and reduction in capital expenditures (CapEx). These are two main objectives for the entities that own the optical infrastructure, such as network operators (NOs), and those also acting as Internet service providers (ISPs). The SR–VTCA scheme is a novel approach to adapt transparent optical networks to time-varying traffic by adjusting the number of lightpaths between node pairs, while keeping the IP routing unchanged. Lightpath bundling (LB) and anycast (AS) switching are combined in SR–VTCA operation to advertise lightpath additions/removals to the IP layer as mere adjustments (increments or decrements) in the capacity, allowing to keep the IP routing stable, and thus, simplifying control plane operations. On the contrary, a fully-reconfigurable (FR) network design, where IP routing can be also modified, would increase the burden in the control plane, but at a higher CapEx reduction, since the optical infrastructure is used more efficiently. In this work, we investigate the CapEx overprovision introduced by SR–VTCA with respect to a FR scheme. In order to do this, SR–VTCA planning problem is first modeled as a MILP formulation. A heuristic procedure based on traffic domination is then proposed to solve large instances of the problem. Exhaustive experiments are conducted comparing the SR–VTCA solutions obtained by the aforementioned MILP and heuristic proposal with solutions found by other optimization methods presented in the literature to solve the FR planning problem. Finally, the results show that SR–VTCA can achieve similar results to the FR case in terms of CapEx reduction, while a huge number of IP reroutings are saved by maintaining IP stability. Thus, SR–VTCA provides an advantageous balance between CapEx overprovisioning and the control plane overhead associated with IP rerouting.     

All-optical tree-based greedy router using optical logic gates and optical flip-flops

Due to ever-increasing throughput demands, the lookup in conventional IP routers based on longest prefix matching is becoming a bottleneck. Additionally, the scalability of current routing protocols is limited by the size of the routing tables. Geometric greedy routing is an alternative to IP routing which replaces longest prefix matching with a simple calculation employing only local information for packet forwarding. For the first time, in this paper we propose a novel and truly all-optical geometric greedy router based on optical logic gates and optical flip-flops. The circuit of the router is constructed through the interconnection of SOAs and directional couplers. The successful functionality of the proposed router is verified through simulation. The circuit enables high data rate throughput.