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.     

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。     

Multi-tiered service survivability in next-generation SONET/SDH networks

Rapid advances in next-generation SONET/ SDH and optical switching technologies along with dynamic generalized multi-protocol label switching control architectures have enabled many new service provisioning paradigms. In particular, a key addition is the new virtual concatenation feature that allows for inverse multiplexing of connection demands across SONET/SDH domains. This paper presents a novel tiered survivability scheme that leverages this feature to support multiple levels of service survivability and higher load carrying capability and service resiliency. Detailed simulation performance analysis results are also presented along with conclusions and directions for future work.     

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     

Carrier ethernet

This article sets out the opportunity and the role of Ethernet within large-scale carrier networks. Carrier Ethernet can greatly reduce the consequences of the complexity associated with the large scale and broad scope of carriers' networks by being a cost-effective replacement for SONET/SDH. However, in order to achieve this, carrier Ethernet needs to provide the equivalent level of transparency, simplicity, and reliability currently achieved by SONET/SDH, and the emerging IEEE Ethernet standards for PBB and PBB-TE are well suited to this role. These technologies are an ideal complement to IP/MPLS for which they can provide highly cost-effective managed and guaranteed bit pipes.     

Value-added services in next-generation SONET/SDH networks

Advances in next-generation SONET/SDH have introduced novel features for generic protocol framing/encapsulation, virtual concatenation, inverse multiplexing, dynamic circuit adjustment, and so on. In turn, these provisions have enabled much improved multi-tiered service provisioning and are viewed very favorably by carriers, particularly incumbents. This article looks at this evolved framework with a particular focus on value-added services creation. Results from a sample performance evaluation study also are presented to quantify some of the achievable gains.     

以太网光接入系统中帧校验码的实现

以太网光接入技术实现了以太网数据在同步光纤网络中传输,结合了以太网和SDH两者的优点。循环冗余校验是一种高效的差错控制方法,由于其误码检测能力强,抗干扰性能优异,在数字通信领域有广泛的应用。针对优化硬件资源的要求,根据EoS系统中数据帧封装的差控校验码算法特点,提出基于FPGA的改进实现方法,通过电路仿真与编译综合结果表明,该方法实现了对高速并行化数据传输的有效保护,在减少资源消耗、提高系统效率两方面都取得了较好效果。     

GMPLS controlled ethernet: an emerging packet-oriented transport technology

Most of the world?s traffic is now packetbased. While SONET/SDH transport technology continues to evolve, there are now major standardization efforts to develop a native packet-oriented transport technology. Ethernet, long dominant in the enterprise, is one of the fastest developing technologies for the transport layer. GMPLS, based on mature signaling and routing protocols, is gaining traction as a transport control plane, providing fast restoration and supporting automation of provisioning. We will briefly highlight recent Ethernet standardization and then introduce the concepts and standards work allowing GMPLS to control Ethernet.     

New transport services for next-generation SONET/SDH systems

SONET/SDH systems have been the preferred transport technology over fiber optics for almost two decades now. Carriers have developed extensive expertise in operating, managing, and developing business models for these systems. Manufacturers' technical expertise in such systems has increased to a deep understanding of what transport over fiber is about. In short, SONET/SDH can be called a mature transport technology. Out of this mature expertise, new techniques for bettering transport over fiber services have appeared. These techniques are likely to considerably reshape the next generation of SONET/SDH systems in many aspects: new transport techniques, new transport services, new management systems and business models. We describe several new transport techniques, and discuss their impact on the creation of new transport services for next-generation SONET/SDH systems     

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.     

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.     

On IP-over-WDM integration

Expanding Internet-based services are driving the need for evermore bandwidth in the network backbone. These needs will grow further as new real-time multimedia applications become more feasible and pervasive. Currently, there is no other technology on the horizon that can effectively meet such a demand for bandwidth in the transport infrastructure other than WDM technology. This technology enables incremental and quick provisioning up to and beyond two orders of magnitude of today's fiber bandwidth levels. This precludes the need to deploy additional cabling and having to contend with right-of-way issues, a key advantage. Hence, it is only natural that over time optical/WDM technology will migrate closer to the end users, from core to regional, metropolitan, and ultimately access networks. At present, WDM deployment is mostly point-to-point and uses SONET/SDH as the standard layer for interfacing to the higher layers of the protocol stack. However, large-scale efforts are underway to develop standards and products that will eliminate one or more of these intermediate layers (e.g., SONET/SDH, ATM) and run IP directly over the WDM layer. IP over WDM has been envisioned as the winning combination due to the ability of the IP to be the common revenue-generating convergence sublayer and WDM as a bandwidth-rich transport sublayer. Various important concerns still need to be addressed regarding IP-WDM integration. These include lightpath routing coupled with tighter interworkings with IP routing and resource management protocols, survivability provisioning, framing/monitoring solutions, and others     

Cross-virtual concatenation for Ethernet-over-SONET/SDH networks

Ethernet-over-SONET/SDH (EoS) is a popular approach for interconnecting geographically distant Ethernet segments using a SONET/SDH transport infrastructure. It typically uses virtual concatenation (VC) for dynamic bandwidth management. The aggregate SONET/SDH bandwidth for a given EoS connection is obtained by “concatenating” a number of equal-capacity virtual channels. Together, these virtual channels form a virtually concatenated group (VCG). In this article, we introduce a new concatenation technique, referred to as cross-virtual concatenation (CVC), which involves the concatenation of virtual channels of heterogeneous capacities. We show that CVC can be implemented through a simple upgrade at the end node, thus utilizing the existing legacy SDH infrastructure. By employing CVC for EoS systems, we show that the SDH bandwidth can be harvested more efficiently than in conventional VC. We consider two problems associated with routing CVC connections: the connection establishment problem and the connection upgrade problem. The goal of the first problem is to compute a set of paths between two EoS end systems such that a total bandwidth demand and a constraint on the differential delay between the paths are satisfied. Among all feasible sets, the one that consumes the least amount of network bandwidth is selected. For this problem, we develop an integer linear program (ILP) and an efficient algorithm based on the sliding-window approach. For the connection upgrade problem, the goal is to augment an existing set of paths so as to increase the aggregate bandwidth, while continue to meet the differential-delay constraint. We model this problem as a flow-maximization problem with a constraint on the delay of the virtual channels with positive flow. We then consider the problem of path selection under imprecise network state information. Simulations are conducted to demonstrate the advantages of employing CVC and to evaluate the performance of the proposed algorithms.

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.     

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。     

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.     

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     

RPR技术在测量船光传输网中的应用

根据航天远洋测量船多业务SDH光传输网络中以太网业务特性,对几种在测量船光传输网络中应用的以太网技术从传输形式、实现方式、传输效率和最佳适应性等方面进行了比较,验证了RPR技术在测量船光传输网络中应用的先进性和高效性。在此基础上,对测量船光传输网络中RPR技术的几种应用方式进行了分析和比较,探讨了RPR技术在MSTP系统中具体实现方法,对应用RPR技术改善测量船以太网业务进行了展望。