Supplementary services in the H.323 IP telephony network

Traditionally, different networks were developed to handle voice, data, and video. The circuit-switched telephone network carried voice and the packet network carried data. Due to different deployment of these networks, different services were developed, such as voice mail in the telephone network and electronic mail on the Internet. With the revolution of multimedia in the computer industry, voice, video, and data are now being carried on both networks. Supplementary services, such as transfer and forwarding (which were originally developed for private telephone networks and later migrated to public telephone networks) are now being developed for packet networks. The standards for packet networks are being defined in the H.323-based series of ITU-T recommendations. This article provides the H.323 architecture for supplementary services, the differences in deployment of these services between the circuit-switched and packet-switched networks, and interworking of these services across hybrid networks     

IP/MPLS-Over-WDM网络的生存性

Internet的发展和数据业务的爆炸性增长对当前网络提出了更高的要求。网络将演变为IP/MPLS-over-WDM。对于这种以光网络为基础的网络构架,网络生存性问题变得尤为重要。由于以数据业务为中心的光网络至少包含IP层和光层,笔者提出了几个在多层网络生存性面临的问题,并给出了几种方案。最后,讨论了IP/MPLS--Over-WDM特有的生存性思考。     

Media access control for high-speed local area and metropolitanarea communications networks

The features, architectures, and principles of key media access control (MAC) schemes for high-speed LAN and MAN systems are categorized and reviewed. These architectures are related to the hierarchical structure of a telecommunications network. An overview is given of the MAC protocol operation of key local- and metropolitan-area network systems, as defined by standards committees, covering current methods as well as approaches for future broadband integrated services digital networks. Modeling and analysis techniques are then reviewed for key classes of relevant MAC schemes, including fixed-assignment time-division-multiaccess (TDMA) schemes; demand-assignment reservation schemes, involving, in particular, pure packet-switched, pure circuit-switched and hybrid-switched integrated-services demand-assignment TDMA and time-division-multiplexing structures; demand-assigned polling procedures; and random-access policies     

Telecommunications management network (TMN) architecture andinterworking designs

The authors discuss data communications networks (DCNs) used by operating telephone companies to interconnect large numbers of telecommunications network elements with operations systems and workstations to support and manage telecommunications networks, referred to by the international telegraph and telephone consultative committee (CCITT) as a telecommunications management network (TMN). The TMNs can include different types of DCNs such as private lines, circuit-switched networks, packet-switched networks, and integrated services digital networks (ISDNs). These can be divided into two classes: connection-mode and connectionless-mode networks. The authors briefly consider TMN concepts and implementation architectures. They then focus on TMN internetworking design alternatives, issues, and protocol stacks, in order to provide data network designers and implementors with the necessary fundamentals in considering and choosing interworking solutions for TMN applications     

分组网络中同步标准的进展及分析

如何解决同步信号地面链路传递问题,是目前分组传送网络中研究的一个重要课题。传统同步体系中的标准仅适用基于电路交叉技术的网络,并不适用于指导分组传送网络中面临的问题。目前虽已有运营商应用1588v2,满足移动回传网络中的时间同步需求,但随着网络复杂性的逐步增强,以及对设备时间(时钟)能力要求的不断提高,亟待相关标准的出台及完善。文章对分组网络中的同步标准进行了讨论,并就当前包交换技术实现频率和时间同步的热点应用给出了建议。     

Polymorphic Architectures for Optical Networks and their Seamless Evolution towards Next Generation Networks

This paper proposes a novel polymorphic framework for optical networking and a seamless evolution path from optical circuit-switched towards optical packet-switched networks. We show that by simultaneously supporting several optical switching paradigms in a single physical topology, efficient and flexible optical networks can be built. The supported paradigms are associated with different Classes of Service (CoS) in order to provide service differentiation at the optical layer. Two polymorphic architectures are presented, one based on optical circuit switching paradigms with different grades of dynamism, and a second one based on optical labeled burst-switched networks with the added capability of dynamic lightpath provisioning. These architectures provide a seamless evolution path towards an efficient IP-over-WDM approach with service differentiation. Moreover, the proposed polymorphic architectures are fully compatible with the GMPLS unified control plane. We present in a detailed form the proposed polymorphic framework, including the selection of switching paradigms, its support for CoS, the network and control architecture, and a possible seamless evolution towards optical packet-switched networks. Possible implementation examples of optical network nodes that support the proposed polymorphic architectures are also presented.     

Cost optimization methods in the design of next generation networks

A key development of telecommunication systems during the past two decades has been the evolution from the circuit-switched network toward the packet-switched network paradigm. Many operators are now migrating their PSTNs from circuit switched networks. This new approach is often called the next-generation network NGN enables network operators to run all services (i.e., voice, data and video) on one network. In this article the migration of Iceland Telecom's circuit-switched PSTN towards NGN is described. A cost model of the telecommunications system has been developed to enable cost and benefits analysis of transforming the network to NGN. Methods of optimization and their application to determine the optimal number and position of nodes in the future network are described. The optimization produces a network structure with the lowest possible total cost of ownership, and the model can also indicate how deviations from the optimum affect cost. The feasibility of NGN is assessed by comparing the cost of NGN migration to that of maintaining the current circuit-switched network.     

Spawning networks

The deployment of new network architectures, services, and protocols is often manual, ad hoc, and time-consuming. We introduce “spawning networks,” a new class of programmable networks that automate the life cycle process for the creation, deployment, and management of network architectures. These networks are capable of spawning distinct “child” virtual networks with their own transport, “parent's” network resources and in isolation from other spawned networks. Spawned child networks represent programmable virtual networks and support the controlled access to communities at users with specific connectivity, security, and quality of service requirements. In this article we present a framework for the realization of spawning networks based on the notion of the Genesis Kernel, a virtual network operating system capable of creating distinct virtual network architectures on the fly. We discuss the motivation and principles that underpin spawning networks and focus on the design of the transport, programming and life cycle environments, which comprise the main architectural components of the Genesis Kernel     

Call control and traffic transport for connection-oriented highspeed wireless personal communications over metropolitan area networks

A distributed circuit-switched approach for supporting the deployment of high speed wireless personal communication services in urban areas through the interconnection of base stations via metropolitan area networks (MANs) is proposed. Broadband MANs minimize traffic congestion by dynamic sharing of link capacity and by serving as distributed switches for partitioning call control functions. While the DQDB protocol readily supports distributed packet-switching over the IEEE 802.6 MAN, isochronous traffic such as voice and video is best supported by circuit-switched connections. The authors present an enhanced bi-state pre-arbitrated (PA) transport mechanism, and associated call control and handoff management techniques, which enable distributed circuit-switching over the MAN. These capabilities are not currently addressed in the 802.6 standards. The bi-state PA transport mechanism facilitates statistical multiplexing of variable rate isochronous traffic sources. The network capacity is constrained by the call setup delay performance, and is analyzed by simulations. Alternative signaling architectures, involving different placements of call control network elements, are evaluated. The effects of erasure nodes, and close bus versus open bus architectures, are considered. The overlap inter-MAN call setup procedure is proposed to reduce delays. Different call handoff procedures are formulated according to the type of handoff and the resulting change in call connectivity. Most handoffs are intra-MAN, requiring simple procedures with short delays     

The evolution of a reliable transport network

This article shows how transport networks may evolve in the future, driven by new technologies and new customer requirements for cost, reliability, and traffic growth. It does not simply compare new technologies and architectures, but accepts that most operators are not starting with a green-field site. It therefore also addresses the operator's problems of introducing and integrating new technologies into existing transport networks and migrating services from one transport technology to another. This in turn drives different technologies to evolve to new levels of reliability over time. The article is written from the perspective of an established European network operator, and differences are brought out from the evolution of networks in North America     

Data-centric optical networks and their survivability

The explosive growth of data traffic-for example, due to the popularity of the Internet-poses important emerging network requirements on today's telecommunication networks. This paper describes how core networks will evolve to optical transport networks (OTNs), which are optimized for the transport of data traffic, resulting in an IP-directly-over-OTN paradigm. Special attention is paid to the survivability of such data-centric optical networks. This becomes increasingly crucial since more and more traffic is multiplexed onto a single fiber (e.g., 160×10 Gb/s), implying that a single cable cut can affect incredible large traffic volumes. In particular, this paper is tackling multilayer survivability problems, since a data-centric optical network consists of at least an IP and optical layer. In practice, this means that the questions "in which layer or layers should survivability be provided?" and "if multiple layers are chosen for this purpose, then how should this functionality in these layers be coordinated?" have to be answered. In addition to a theoretical study, some case studies are presented in order to illustrate the relevance of the described issues and to help in strategic planning decisions. Two case studies are studying the problem from a capacity viewpoint. Another case study presents simulations from a timing/throughput performance viewpoint     

Nodal Architectures for Shared Mesh Restoration of IP and Wavelength Services

Future networks are expected to support heterogeneous traffic, including both Internet Protocol (IP) and wavelength services. IP services are typically restored using IP-layer rerouting mechanisms, whereas wavelength services are restored in the optical layer. With architectures where IP services are mapped into Layer-2 or time-division-multiplexing (TDM) protocols at the network edge, a common restoration mechanism can be utilized for both IP and wavelength services. This letter examines various nodal architectures that can be utilized to support such a unified restoration paradigm.      

SONET ring applications for survivable fiber loop networks

Synchronous optical network (SONET) self-healing rings (SHR) are studied in the loop environment. SONET SHR architectures for loop feeder networks are discussed, focusing on three possible dual central office (CO) architectures for fiber loop networks, using SONET SHRs to reduce network costs and provide network service survivability. These architectures reflect an integrated planning concept for SONET networks that eliminates the boundary between the access network and the inter-office network. It is shown that the use of SONET SHRs makes it easy to evolve to a protected dual CO access architecture. Economic and survivability studies are discussed. The economic studies show that using the ring approach yields significant advantages over the traditional diverse protection approach in terms of cost and survivability, especially for the dual CO architectures     

以太网电路仿真技术及其应用

在无连接的分组交换网络中,仿真电路交换业务可以采用电路仿真技术。时分复用(TDM)业务对时延、抖动以及分组丢失等特性非常敏感,因此电路仿真要解决的根本问题就是确保仿真业务的服务质量特性要求。由于以太网具有廉价、简单、扩展性强和分布广泛等特点,通过以太网传送TDM业务的需求变得越来越明显。以太网电路仿真技术可以实现以太网透明地传输TDM业务(E1/T1和E3/T3等)。文中主要介绍了TDMoverEthernet技术的基本概念、技术要点及面临的主要技术挑战;通过与TDMoverIP、VoIP和ATM等相关技术的比较,指出了该技术的优势;最后,给出了TDMoverEthernet技术的一个应用实例。     

Deployment of the GMPLS control plane for grid applications in experimental high-performance networks

In this article we present a review of the latest activities in recent experimental high-performance optical networks such as ultrascience network (USN), dynamic resource allocation via GMPLS optical network (DRAGON), and circuit-switched high-speed end-to-end transport architecture (CHEETAH). We compare the control and management approaches adopted in each of these networks and analyze their capabilities vis-a-vis the functional requirements of grid computing applications. Grid computing is increasingly on the rise to meet the massive processing and storage demands of a new class of e-science physics applications that may generate and require the processing of data sets reaching terabytes per day. The requirements of these applications challenge the limitations of the networking technologies that are in place today. In particular, the area of network management and control is undergoing significant developments in order to meet the demands of these applications. It is the purpose of this article to share our experiences in the deployment of the GMPLS control plane in these experimental optical networks. It is our belief that these and similar efforts will result in significant progress toward enabling connection-oriented high-performance networking. This new paradigm will encompass grid computing applications as well as commercial, health, and entertainment services, thus making it useful to the public at large.     

Wireless Internet access for mobile subscribers based on theGPRS/UMTS network

With the advent of IP technologies and the tremendous growth in data traffic, the wireless industry is evolving its core networks toward IP technology. Enabling wireless Internet access is one of the upcoming challenges for mobile radio network operators. The General Packet Radio Service is the packet-switched extension of GSM and was developed to facilitate access to IP-based services better than existing circuit-switched services provided by GSM. We illustrate how a visited mobile subscriber on a GPRS/UMTS network can access his/her home network via the gateway GPRS support node (GGSN). We also propose some implementation ideas on wireless Internet access for a remote mobile subscriber based on a GPRS/UMTS network     

Integrity of public telecommunications networks

Provides an overview of the special issue of the IEEE Journal of Communications, Volume 12, Number 1 (January 1994) which addresses open questions in network integrity, reliability and survivability. Current progress in this area is discussed. The questions addressed include user survivability perspectives on standards, planning, and deployment; the analysis and quantification of network disasters; survivable and fault-tolerant network architectures and associated economic analyses; and techniques to handle network restoration as a result of physical damage or failures in software and control systems. Special interests are devoted to the survivability of broadband networks employing the new transport/switching techniques based on the synchronous optical network (SONET) and asynchronous transfer mode (ATM) standards due to their emerging role in future B-ISDN. Network integrity due to failures of common channel signaling (CCS) systems is also very critical. The present special issue includes 22 papers and is organized into the following sections: user perspectives and planning, software quality and reliability, network survivability characterization and standards, network restoration for SONET networks, network restoration for ATM networks, traffic effect and performance enhancement for computer networks, and survivable network design methods. Network restoration methods for SONET, ATM, and computer networks correspond to those for the physical layer (SONET), ATM layer, and the network layer, defined in the CCITT broadband ISDN layer structure     

The “packing” and the “scheduling packet”switch architectures for almost all-optical lossless networks

This paper proposes two almost all-optical packet switch architectures, called the “packing switch” and the “scheduling switch” architecture, which when combined with appropriate wait-for-reservation or tell-and-go connection and how control protocols provide lossless communication for traffic that satisfies certain smoothness properties. Both switch architectures preserve the order of packets that use a given input-output pair, and are consistent with virtual circuit switching, The scheduling switch requires 2klogT+k² two-state elementary switches (or 2klogT+2klogk elementary switches, if a different version is used) where k is the number of inputs and T is a parameter that measures the allowed burstiness of the traffic. The packing switch requires very little processing of the packet header, and uses k²logT+klogk two-state switches. We also examine the suitability of the proposed architectures for the design of circuit switched networks. We find that the scheduling switch combines low hardware cost with little processing requirements at the nodes, and is an attractive architecture for both packet-switched and circuit-switched high-speed networks     

Considerations for ISDN planning and implementation

THE INFORMATION AGE has created such a diversity between the Communications needs of the business user and the residential Community that one common-denominator public telephone network can no longer serve everyone. The time when evolutionary network enhancements can be justified and implemented will come too late to be acceptable to a large body of business users, because of this diversity of needs. The emerging proliferation of technological bypass of local telephone facilities in the United States is symptomatic of the need for one or more shared wideband/ broadband overlay networks to serve the business community. This environment requires accelerated introduction of digital technologies in the telephone network for provision of high-speed end-to-end digital services including data, facsimile, and video. This necessitates the use of Overlay facilities and networks to meet present business customer demands until the loop plant in the common-denominator network can evolve to optimally meet the varied demands of the whole community. This paper describes past progress and current plans for the introduction of digital technologies for switching, interexchange trunking, and the local loop for an end-to-end digital network. The paper also discusses the implementation of common-channel signaling, based on CCITT's SSN07 in the circuit-switched network, as well as the use of an overlay packet-switched network for provision of data commumcations and videotex services.