Traffic engineering for ethernet over SONET/SDH: advances and frontiers

Continued growth in data services coupled with the entrenchment of existing carrier infrastructures have inevitably forced a convergence of SONET/SDH and Ethernet technologies. As a result, the very notion of Ethernet connectivity has expanded beyond traditional local area domains into broader metro/wide area settings. The key enabling advances have come in the form of improved SONET/SDH provisioning features as well as new carrier Ethernet services standards. These provisions have allowed carriers to build and deploy much improved multigrade point-to-point Ethernet line services and have also opened up new challenges for extended multipoint offerings. This article looks at this evolving area and summarizes recent advances in EoS traffic engineering. It also highlights some key future challenges and presents a novel scheme for multipoint services provisioning in EoS settings.     

The building blocks of a data-aware transport network: deploying viable Ethernet and virtual wire services via multiservice ADMs

SONET/SDH technologies constitute the core transport infrastructure of major telecom service providers worldwide. As the percentage of packet-oriented traffic in the overall traffic demand continues to rise, prompted by the widespread adoption of the Internet protocol suite, and recently by the fast adoption of Ethernet services, there is increasing pressure to improve the service provider's transport infrastructure in ways that make it data-aware and cost-effective for packet-oriented applications. Steps in this direction include the adoption of native physical interfaces, for Ethernet and storage area networks as service interfaces, or full integration of packet switching capabilities from Ethernet, resilient packet ring, and MPLS technologies. This article discusses the emerging building blocks for next-generation data-aware transport networks and next-generation transport network elements.     

EoS--实现电信级光以太网的新技术

从电信级光以太网的内涵出发 ,阐述了利用LAPS在SDH/SONET网上承载以太网 (EoS)的实现机制及其功能特性 ,介绍了EoS芯片、系统设备和相应的解决方案 ,重点指明了EoS对于以太网向电信级网络演进的意义。     

Initial implementations of point-to-point Ethernet over SONET/SDH transport

There is considerable interest in using Ethernet over SONET/SDH (EoS) for Ethernet transport in a wide area network. EoS leverages the existing SONET/SDH infrastructure to provide efficient Ethernet transport with excellent OAM capabilities. In our initial evaluations and deployments of EoS, we have encountered some issues, as is common with any new technology. These issues include non-transparent transport of Ethernet information, lack of carrier-class performance monitoring and fault propagation, and non-standardized implementation of basic concepts. Vendors, service providers, and standards bodies should work together to resolve these remaining issues and thus bring forth the full potential of EoS.     

Ethernet-over-SONET(EoS) over WDM in Optical Wide-Area Networks (WANs): Benefits and Challenges

Ethernet has been playing an increasingly important role in wide area networks (WANs), from both a service perspective and a transport-technology perspective. Unlike its dominant presence in local area networks (LANs), Ethernet in WANs has been increasing its popularity in three different directions, i.e., Ethernet-based layer-2 virtual private network (L2VPN) over layer-3 network, Ethernet over SONET (EoS), and Ethernet directly over WDM channels or optical fibers. In this paper, we investigate the benefits and challenges of using next-generation SONET/SDH techniques—namely SONET/SDH virtual concatenation (VCAT) and link-capacity adjustment scheme (LCAS)—to support Ethernet-based data services in intelligent optical WDM wide area networks. In particular, we evaluate the network performance improvement after employing VCAT. In order to fully utilize VCATs inverse-multiplexing capability, several simple and effective heuristic algorithms are proposed and evaluated.*Part of the work was accomplished while Keyao Zhu was a Ph.D. student in the Networks Research Lab. at University of California, Davis, under the supervision of Professor Biswanath Mukherjee. Summarized versions of this paper were presented at the IEEE/OSA Optical Fiber Communication Conferences OFC03 and OFC04 in Atlanta, GA, in March 2003 and in Los Angeles, CA, in March 2004, respectively.Corresponding author     

Operation, administration, and maintenance in MPLS networks

The boundaries between packet and circuit networks have long disappeared, with many traditional circuit-switched applications such as voice and video now being carried over packet-switched IP/MPLS or Ethernet networks. However, this transition has happened so fast that many OAM functions supported by circuit-switched networks such as SONET/SDH are still unmatched in packet networks. In order to match the quality sustained by circuit-switched networks, OAM functions must also be developed for such packet networks. A number of recent efforts have started to address OAM functions for IP/MPLS and Ethernet packet technologies. Service providers and carriers alike are the driving force behind the work, as there is general recognition that to generate sustained revenues, services must be efficiently managed. In this article we discuss issues in providing OAM features and capabilities for MPLS-based packet networks.     

同步以太网测试方法

得益于移动宽带业务的强劲增长,许多移动网络运营商已经或正在把移动回传网络从传统同步传输(如SONET/SDH和T1/E1)迁移到运营级以太网。传统TDM网络不仅提供数据传输,而且能实现频率同步。这样,原来由TDM网络提供的时钟同步也同样必须在以太网络中实现,并且同步的质量和网络性能不能受到影响。再者,3G/LTE无线网络不仅需要频率同步,还需要时间/相位的同步。所以,在部署前对以太网络各个部件作同步性能的验证就显得非常必要。本文介绍了实现以太网同步的各种方式和原理、同步精度测量面临的挑战。结合IXIA业界领先的同步测试工具Anue 3500,重点对PTP技术中的路径支持设备(如边界时钟和透明时钟)的测试方法进行了探讨。     

弹性分组环(RPR)技术分析

弹性分组环(Resilient Packet Ring)技术是主要结合了SONET／SDH和以太网的优点而形成的一种基于分组交换的城域网技术。本从讨论SONET／SDH和以太网技术的优缺点中引出弹性分组环的出现背景、分析了RPR的技术特点和实现方法。     

Interoperability update: dynamic ethernet services via intelligent optical networks

This article describes the 2005 Worldwide Interoperability Demonstration held by the Optical Internetworking Forum and showcased during SUPERCOMM 2005, The event highlighted Ethernet services transported over intelligent optical networks, using equipment from 13 of the industry's leading vendors located in seven carrier laboratory facilities around the world. The demonstration utilized a distributed optical control plane based on OIF Implementation Agreements to control a multilayer network providing Ethernet over SONET/SDH adaptation and transport. The article describes the global test network, services, architecture, and overall test approach. It also describes innovations made to the optical control plane to handle multilayer signaling and lists further refinements needed to make these services operational.     

Survivable virtual concatenation for data over SONET/SDH in optical transport networks

Next-generation SONET/SDH technologies-namely, generic framing procedure, virtual concatenation, and link-capacity-adjustment scheme-enable network operators to provide integrated data and voice services over their legacy SONET/SDH infrastructure to generate new revenue. An important open research problem on data over SONET/SDH (DoS) is survivability: SONET automatic protection switching is too resource inefficient for data services, and the protection mechanisms of data networks are too slow for mission-critical applications. We propose two approaches for provisioning survivable DoS connections. Our approaches exploit the tradeoff between resource overbuild and fault-recovery time while utilizing the inverse-multiplexing capability of virtual concatenation to increase backup sharing. Our results show that one approach achieves low resource overbuild and much faster fault recovery than that of data networks, and the other approach achieves fast fault recovery comparable to SONET 50-ms protection (for typical U.S. backbone networks) while still achieving modest backup sharing. We further investigate the tradeoff between network blocking performance and network control and management complexity resulting from the number of paths M a connection can be inversely multiplexed onto: larger M leads to more freedom in routing and better network performance but increases network control and management complexity. Our results indicate that the network blocking performance for small values of M (e.g., M=2 for some representative backbone network topologies) is almost as good as the case in which M is infinity.     

Comparison of SDH/SONET-WDM multi-layer networks with static and dynamic optical plane

SDH/SONET-WDM multi-layer networks are a very attractive solution to cope with the increasing dynamics and capacities in today’s core networks. In SDH/SONET multi-layer networks, client layer SDH/SONET connections are groomed to wavelength channels and transported using end-to-end lightpaths. Also, intermediate grooming can yield to a more efficient utilization of network resources.In this paper, two principal SDH/SONET-WDM multi-layer network architectures are investigated covering the dynamics either only in the electrical layer or in both layers, respectively. In order to show benefits and drawbacks for the introduction of dynamics in the optical plane of today’s backbone networks, we present a detailed performance evaluation based on simulation studies and compare both architectures for different total network capacities and grooming strategies. We also systematically analyze the traffic composition which until now has only rarely been investigated. We show that changes in the traffic pattern can be covered by a dynamic optical plane. Further, we figure out the timescale for switching operations in the optical layer which is at least two orders of magnitude below the connection’s interarrival rate.     

Optical networks—the electro-optic reality

A general overview of the current status and future trends in optical networking is given. Special attention is given to the coexistence of optical and electronic technologies in telecommunications networks. After reviewing the advantages of both technologies, their use in different network areas is discussed. A critical survey of current and new transport technologies in optical core and metropolitan networks is given, including SDH/SONET and its enhancements, OTN, RPR, and Ethernet. The current status and prospects for photonic switching are briefly presented. The paper is concluded with an overview of the control plane for optical transport networks.     

以太网知识讲座(3)--物理层器件

系统地介绍了以太网的基本概念，介质接入控制和物理层标准规范。以太网信号的帧结构、网络硬件设备、网络组成及主要性能，以及以太网信号在PDH、SDH/SONET中的传输等等。由于以太网中的各种设备必需通物理层接口器件才能与网络传输介质相连，因此本部分主要介绍物理层器件。     

以太网知识讲座⑴—以太网的基本概念

系统地介绍了以太网的基本概念、介质接入控制和物理层标准规范、以太网信号的帧结构、网络硬件设备、网络组成及主要的性能，以及以太网信号在PDH、SDH/SONET中的传输等等。     

On the resource efficiency of virtual concatenation in SDH/SONET mesh transport networks bearing protected scheduled connections

Virtual concatenation (VCAT) is a Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET) network functionality recently standardized by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T). VCAT provides the flexibility required to efficiently allocate network resources to Ethernet, Fiber Channel (FC), Enterprise System Connection (ESCON), and other important data traffic signals. In this article, we assess the resources' gain provided by VCAT with respect to contiguous concatenation (CCAT) in SDH/SONET mesh transport networks bearing protected scheduled connection demands (SCDs). As explained later, an SCD is a connection demand for which the set-up and tear-down dates are known in advance. We define mathematical models to quantify the add/drop and transmission resources required to instantiate a set of protected SCDs in VCAT- and CCAT-capable networks. Quantification of transmission resources requires a routing and slot assignment (RSA) problem to be solved. We formulate the RSA problem in VCAT- and CCAT-capable networks as two different combinatorial optimization problems: RSA in VCAT-capable networks (RSAv) and RSA in CCAT-capable networks (RSAc), respectively. Protection of the SCDs is considered in the formulations using a shared backup path protection (SBPP) technique. We propose a simulated annealing (SA)-based meta-heuristic algorithm to compute approximate solutions to these problems (i.e., solutions whose cost approximates the cost of the optimal ones). The gain in transmission resources and the cost structure of add/drop resources making VCAT-capable networks more economical are analyzed for different traffic scenarios.     

以太网知识讲座(4)--以太风名的中继器和网络节点

系统地介绍了以太网的基本概念、介质接入控制和物理层准规范、以太网信号帧结构、网络硬件设备、网络组成及主要性能，以及以太网信号在PDH、SDH／SONET中的传输等等。本部分主要介绍以太网中的中继器和网络节点。     

Framework for MPLS-based control of optical SDH/SONET networks

The suite of protocols that defines multiprotocol label switching is in the process of enhancement to generalize its applicability to the control of optical networks. One area of prime consideration is to use these generalized MPLS protocols in upgrading the control plane of optical transport networks. This article describes those extensions to MPLS directed toward controlling SDH/SONET networks. SDH/SONET networks are ideal candidates for this process since they possess a rich multiplex structure, and a variety of protection/restoration options are well defined and widely deployed. We discuss the extensions to MPLS routing protocols to disseminate information needed for transport path computation and network operations and the extensions to MPLS label distribution protocols needed for provisioning of transport circuits     

Multiservice Ethernet access

Ethernet is evolving from its origins in the local area network into a cost-effective and reliable wide area network technology. Market research shows that business customers are moving away from traditional leased lines and selecting Ethernet as the access network technology of choice due to its low cost, simplicity and flexibility. Developments in Ethernet technology are now offering service providers the opportunity to deliver cost-effective carrier class Ethernet services. In particular, a new generation of Ethernet network termination equipment (NTE) is emerging which provides remote management, flexible bandwidth and fault diagnosis while supporting access to multiple services delivered over a single physical connection. This paper describes the advantages and potential cost savings of using Ethernet in the access network. A case study for a city demonstrates significant capital expenditure cost savings and highlights the advantages of using new Ethernet NTEs, which can be up to ten times cheaper than SDH technology, delivering equivalent bandwidth. Remote management and fault diagnosis features can also reduce operational expenditure by avoiding unnecessary site visits. A network architecture is presented which supports delivery of Ethernet services over a combination of circuit-switched and packet-switched domains. New standards which are maturing in the IETF, IEEE and ITU to support Ethernet delivery of interoperable services with carrier class reliability are also discussed.     

以太网知识讲座(8)--以太网网络组织及其管理

系统地介绍了以太网的基本概念、介质接入控制和物理层准规范、以太网信号的帧结构、网络的硬件设备、网络的组成及主要性能，以及以太网信号在PDH、SDH／S0NET中的传输等等。本部分主要介绍以太网的网络组成及其性能和网络管理。     

以太网知识讲座(7)--以太网的传输介质

系统地介绍了以太网的基本概念，介质接入控制和物理层准规范，以太网信号的帧结构，网络的硬件设备，网络的组成及主要性能，以及以太网信号在PDH、SDH／SONET中的传输等等。本部分主要介绍以太网的传输介质。