软件定义光网络的机遇与挑战

提出软件定义光网络(SDON)是一种将软件定义技术融入到光通信网络的新型网络,代表了未来的光网络发展方向,其关键技术涉及到软件定义光传输、交换和联网等,其主要特征包括控制面与传送面分离、硬件通用化、协议标准化、光网行为软件可控、光网应用灵活快捷等。SDON在支撑新一代光网络向智能高效、灵活调度、虚拟重构等方向发展进程中将发挥重要作用,应用前景广阔,但目前尚处在发展初级阶段,仍面临很多挑战和问题。     

Transparent IP radio access for next-generation mobile networks

Advances in network architecture, enhancements in signaling protocols, provisioning of end-to-end QoS, worldwide seamless mobility, and flexible service provision are among the major research challenges toward next-generation wireless networks. The integration and interoperability of all these technologies, along with new truly broadband wireless innovations and intelligent user-oriented services will lead toward the so-called 4G wireless networks. In this article we identify the key issues of an innovative transparent IP radio access system that targets 4G networks.     

A management and visualization framework for reconfigurable WDM optical networks

As the phenomenal advance in optical WDM networking technologies continues, optical WDM network equipment has been deployed not only in backbone networks, but also in regional, metropolitan, and access networks. It is widely believed that a major component of the next-generation Internet will be an IP-based optical network employing WDM. WDM wavelength routing and signaling have become an active research field, and dynamic and adaptive wavelength routing and assignment algorithms have been proposed. However, there is less work on reporting network control and management system implementation efforts over testbed WDM networks. This article presents a network management and visualization framework aimed at guiding the development of management applications for reconfigurable WDM optical networks. A layered framework architecture including element and network management and visualization is provided, and an object-based information model representing the WDM network is introduced. Functional components on reconfiguration, software agent, and network visualization services are presented, and important issues related to optical lightpath generation are discussed. A network visualization service also provides WDM control and management APIs to applications and access networks such as an IP network management system. To illustrate the usage of the framework, we share our experience in implementing the MONET network control and management system, and present network visualization views obtained from the MONET WDM network to highlight the framework features.     

软件定义光接入网

提出一种基于软件定义的光接入网架构,可提升网络资源利用率,实现业务灵活接入与高效智能调度。该架构通过采用软件定义的光接入设备,可使接入网具备控制集中化、资源虚拟化、业务服务化等特点,进而降低网络运维成本,提升用户终端体验,为构建下一代简单、弹性、智能光接入网提供技术手段。     

Research activities on next-generation mobile communications and services in Korea

In this article we present a perspective on next-generation mobile communications and services. As a preliminary research work on next-generation mobile communications, we exploit what next-generation mobile services will be (S. Ryu et al., May 2003). We define next-generation mobile services as a hierarchy of services consisting of three different service levels: the service areas, the service functionalities, and the service technologies. We derive these service levels by means of scenario-based analysis. Next we propose conceptual reference network architecture, focusing on the realization of the service technologies. We divide the network into four different parts: a user equipments and access part, a network service provisioning layer part, a network control layer part, and non-mobile network operator service pan, according to characteristics of information and service flows within a network. In this reference network architecture, service elements such as servers, processors, and gateways are placed in each network part to support the derived next-generation mobile services. Finally, we give a brief introduction of research and development activities for next-generation mobile communication systems and services in Korea.     

Optical services in future broadband networks

Optical transmission technology is progressing to the point where it can deliver data at rates that can strain conventional electronic broadband networks. We discuss how optical networks may play a role in relieving this strain. Different optical network architectures are discussed according to the services they provide, the technologies used to implement those services, and the geographical size of the network. We first discuss broadband network architectures and where optics might play a role in the protocol stack. We then discuss in detail the services optical networks can provide, the technologies used to implement those services, and some of the major technological limitations. Finally, we use this knowledge base to analyze the potential role of optics in WANs, MANs, and then local area networks (LANs)     

The future of the intelligent network

This article examines the role the intelligent network (IN) can play as carriers move to next-generation networks. It discusses possible transition scenarios and examines how the IN could interwork with the Internet and packet-based networks to produce new hybrid services. The article presents a view of a fully converged network, and concludes that IN will continue have a vital role in voice and data services     

Amplifiers for the masses: EDFA, EDWA, and SOA amplets for metro and access applications

Small erbium-doped amplets and semiconductor optical amplifiers will be used in current and future metro and enterprise networks in various configurations. Many new system architectures will be enabled as these low-cost technologies are used to compensate for transmission and impairment-compensating component losses. This paper discusses the definition, use, and technologies associated with these new classes of optical amplifiers which, though little, will impact next-generation networks a great deal.     

Optical transport networks

The key technologies required for the development of optical transport networks, namely, optical fiber transmission and digital transport, which includes transmission signal multiplexing, transport nodes, and network operation functions, are highlighted. The trends in transport technology, the impact of synchronous digital hierarchy (SDH) and asynchronous transfer mode (ATM), the role of telecommunications management networks, and network integrity enhancement techniques are elucidated. It is demonstrated that these technologies have brought about a great change in transport network design and performance. Further innovations are required to fully realize a high-performance computer communication network, a cost-effective nationwide B-ISDN, and local networks for video distribution. These include the realization of an optical access transport network and the extension of trunk network capabilities which will be possible with optical path layer technologies     

A view of telecommunications network evolution

While deployment of new network technologies has not been steady over the years, it is useful to take a long-term view of how major new telecommunications infrastructures evolve. Since the beginning of this decade, we have witnessed the emergence of new generations of three major communication networks. This article addresses the market conditions, technology innovations, and services driving the need for intelligent all-optical, 3G wireless, and QoS-based packet networks. Market forces such as traffic and subscriber growth, equipment cost reduction, and new technology penetration have a deep impact on network buildouts. Technology innovations abound, especially in the optical domain. For example, Raman amplification, pure optical switches, and tunable lasers have had a major impact on the architecture of optical networks. Many key services, such as streaming audio and high-quality image transfer, were not possible using wireless access because of its limited bandwidth and performance. With 3G wireless technology, a true mobile Internet will become a reality. Businesses have shied away from the use of the public Internet because of service quality. Thanks to advances in MPLS and service intelligence, this is expected to change. For each type of network, we survey the key factors shaping its evolution and implications on network architectures.     

An integrated network management approach for managing hybrid IP and WDM networks

Pacing toward converged voice and data networks, the IP over WDM/OTN network architecture supported by MPLS satisfies the advanced next-generation network requirements to provide fast, reliable and flexible connectivity services. Acknowledging the advantages of networks that utilize the above technologies, operators evolve their networks in that direction, while continuously working to provide new services to attract customers. In their effort to facilitate such services in a flexible and cost-effective way, an integrated network management system for IP and WDM technologies is a prerequisite. This article proposes a management architecture that provides for this integration. Different approaches to integrating multilayer networks are briefly described covering both the control and management planes. The adopted solution is based mainly on the management plane utilizing the control plane wherever possible. Additionally, preliminary results from the evaluation of the configuration management functionality of the proposed system in a testbed environment are presented, concluding with future extensions that also cover fault and performance management.     

Surviving a disaster [optical communications]

The next-generation optical communications network, not surprisingly at all, will be as optical as it can be. Only optical dense wavelength-division multiplexing can provide the bandwidth elasticity that new emerging communications services demand. This is well understood, and despite an apparent slowdown in the world economy, multibillion-dollar commitments have been made to upgrade existing networks to next-generation DWDM. The next optical network is expected to be massive, yet flexible and ubiquitous. Current DWDM technology supports 160 wavelengths (in the C+L bands) per fiber; at 10 Gb/s this amounts to an astonishing 1.6 Tb/s aggregate bandwidth per fiber. Research has also demonstrated that ultra dense WDM (UDWDM) is possible, and it is a matter of time until 320 wavelengths (and a little later 640) will be multiplexed in a single fiber. As a consequence, we examine what the next optical network should be like, and proactively identify some areas that require special attention. One of the critical areas is service and network survivability not only when a node and/or link fails, but also when a cluster of nodes and/or links fail; that is, avoiding a disaster. Disaster avoidance has also become more important for both natural disasters and geo-political unrest     

Architecting the services optical network

In this new millennium, the most valuable commodity will be information, as seen by the surge in demand for faster access technologies such as cable modems, xDSL, and wireless data. The tremendous growth in data traffic, particularly that associated with the Internet, is changing the way it is carried over public and private networks. Together with the rapid advances in optical networking technology and the spawning of a new category of wavelength services stimulated by new high-speed data requirements, this is dramatically changing network architectures and the relationship between network service providers and their customers. Incumbent carrier globalization and new carrier entry require support for a broader set of business models and range of service interfaces. The growth and expansion of networks imply a greater need for more scalable solutions and more automation for network maintenance. An intelligent optical core optimized for service optical networking, the services optical network, needs to take the best aspects of both the transport and data networking domains to meet the above needs. This article focuses on architecting the services optical network to meet the challenges of optical data networking, and includes a snapshot of supporting standardization activities     

Layer 1 Virtual Private Networks in Multidomain Next-Generation Networks

High-capacity e-science and consumer applications require transport networks that are dynamically provisioned. Rapid advances in next-generation SONET/SPH and optical switching along with GMPLS control have enabled many new services' provisioning capabilities. In particular, a key paradigm is the new layer 1 virtual private network framework, which allows clients to directly provision their own services without deploying expensive infrastructures. This article presents an overview of L1-VPN and describes a resource management scheme that will enable transport network virtualization across a multidomain network infrastructure. The scheme is implemented in both centralized and distributed control frameworks, and allows for dynamic sharing of transport resources. A case study of performance analysis results is presented showing a distributed control plane in a multidomain network architecture achieving higher VPN carrying capacity than a centralized control plane     

ASON组播技术及其应用研究

业务的多样性和不断出现的新业务正在驱动网络的发展，以IPTV为代表的基于流媒体的业务对光网络提出了新的挑战，光网络需要引入组播功能，支持组播业务。组播功能的引入使得光网络的带宽利用率得到有效提高。组播是未来光网络必不可少的技术。层叠网络的进一步演进，将进一步融合IP组播和光网络组播。未来，可以通过降低光网络组播树的粒度来降低光组播的使用门槛，这将有利于促进组播技术的更广泛使用。     

新一代MSTP的关键技术和发展方向

目前,基于同步数字体系(SDH)的多业务传送平台(MSTP)在国内已成为城域汇聚层和接入层的主流技术。为了进一步增强数据处理能力,更好地与数据网络结合,新技术和新功能层出不穷。随着通用成帧规程(GFP)、虚级联(VCat)、链路容量调整(LCAS)、弹性分组环(RPR)、多协议标签交换(MPLS)、自动交换光网络(ASON)等技术国际标准的相继推出,新一代MSTP设备将逐步采用这些核心技术,面对新时期城域网IP业务大量兴起,MSTP逐步从简单透传、汇聚、共享发展到带宽管理,具备面向数据优化的传送能力。文中对新一代MSTP的关键技术进行讨论,着重分析这些新技术在MSTP中的功能和应用,并探讨新一代MSTP的发展方向。     

无源光网络与无线回传的融合技术

文章认为新一代无线回传承载网将需要提供更高的传输带宽、更多的用户数量以及更好的服务质量才能满足3G技术的需求,无源光网络具有带宽大、部署灵活、多业务承载能力强等特点,适合建设新一代无线回传承载网。文章给出了一种基于无源光网络(PON)的无线回传网络结构。在该网络中,光线路终端(OLT)放置在中心局,与无线核心网络连接;光网络单元(ONU)放置在移动基站处。无源光分路器和光缆构成OLT和ONU之间的无源光纤传输网络。     

Implementation of IPv6 services over a GMPLS-based IP/optical network

In recent days, there has been considerable interest in deploying IPv6-based services. Trial and commercial IPv6 services offering has already begun, especially in Japan, Korea, China, and other parts of the world. At the same time, many service providers have embraced MPLS as the enabler for the required multiservice capabilities of their next-generation packet networks. Also, the widespread deployment of DWDM-based optical transport systems in the core network to satisfy the tremendous need and increase in capacity demand has led network planners to reconsider traditional approaches to provisioning and network restoration, and plan integration of the optical layer into the MPLS infrastructure according to the emerging GMPLS technology. The purpose of this article is to discuss next-generation network architecture evolution and present a detailed architecture for transport of emerging IPv6 services and applications over next-generation GMPLS multiservice backbone networks. This article also presents an implementation and demonstration of this technique for IPv6 transport over a GMPLS backbone network as well as interoperability verification of IPv6 and GMPLS using a GMPLS network testbed.     

EPON中一种动态带宽分配算法

以太无源光网络(EPON)被认为是下一代宽带接入的最有效的解决方案。文章提出了一种新的基于EOPN提供多种服务的动态带宽分配算法。为了能够应用这种算法还给出了协助带宽分配多点控制协议(MPCP)的控制消息的格式。     

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