Managing ATM-based broadband networks

Some of the asynchronous transfer mode (ATM) virtual path connection (VPC) and virtual channel connection (VCC) performance, fault, and traffic management functions that are currently being addressed in CCITT and T1 standards committees as well as in the ATM forum are presented. The functions include ATM VP/VC connection management, ATM layer operation flows, VP/VC connection performance monitoring, VP/VC connection failure reporting, VP/VC continuity checking, and VP/VC connection operations and maintenance (OAM) cell loopback testing     

ATM-layer OAM: principles and open issues [B-ISDN]

The principles of operation and maintenance (OAM) for broadband ISDN access, as well as some general OAM rules for an asynchronous transfer mode (ATM) network, are discussed. Standardization of the OAM functions and mechanisms for the ATM layer, which is based primarily on CCITT Recommendations, is considered. Issues regarding OAM flow at the ATM layer are examined. It is seen that although references can be made both to basic and primary rate ISDN, new solutions are necessary for the OAM of B-ISDN. Issues requiring further study are identified     

Terminal-to-network communication in an ATM-based ISDN

This paper addresses the topic of signalling and connectionless data transfer virtual channels in ATM at the UNI. It recapitulates on the access signalling support in narrowband ISDN, as a representative of an STM network and the predecessor of the coming broadband ISDN. Also, the influence of the customer premises network architecture is taken into account. From there, it is investigated in which ways these principles can be extended, into a general access infrastructure and access configuration management for signalling and connectionless services in the ATM-based broadband ISDN. Some possible implications for the internal architecture of the CPN and the network are discussed. This brings some insight into the restrictions which standardization of these principles at the UNI may bring along for the architecture.     

Broadband ISDN ATM layer management: operations, administration,and maintenance considerations

An overview and characteristics of the broadband integrated services digital network (ISDN) that is based on asynchronous transfer mode (ATM) is presented. ATM layer management across the user network interface (UNI) is discussed. The UNI is described, as are the ATM cell structure and its role in management protocols. There are two management protocol models which are explained; however, the focus is on the ATM layer management protocol. An overview of network management functions is provided. Some examples of ATM layer management functions based on the generic functions are provided     

OAM mechanisms in MPLS layer 2 transport networks

This article describes OAM in MPLS layer 2 transport networks. MPLS networks used to transport layer 2 traffic are referred to as MPLS layer 2 transport networks. They may be used to connect legacy layer 2 networks and/or provide layer 2 service to a user over a MPLS network. As legacy layer 2 networks migrate to use MPLS for transport, the role of MPLS OAM mechanisms is becoming increasingly important. This is because the converged network must offer the same OAM functionality as existing layer 2 networks. This article emphasizes the importance of end-to-end OAM, while emulating existing layer 2 services using MPLS transport. End-to-end fault detection is described in the context of various layer 2 over MPLS transport network models. The article focuses on state-of-the-art MPLS label switched path and pseudo wire OAM mechanisms being developed by the IETF. This includes fault detection and isolation mechanisms such as LSP-Ping, bidirectional forwarding detection, and virtual circuit connectivity verification. The applicability of each of these mechanisms is given. In some cases it may be possible to carry layer 2 OAM cells end-to-end, while in other cases this may not be possible. The relationship between segment-based OAM mechanisms and end-to-end OAM is described for each of these cases.     

ATM-layer OAM implementation issues [B-ISDN]

Some implementation issues pertaining to the asynchronous transfer mode (ATM) layer operations and maintenance (OAM) functionality are addressed. A brief summary is given of the current understanding in CCITT on ATM-layer OAM implementation. This is followed by discussions of fault management and performance management function implementations for the ATM virtual path connection and virtual channel connection. Some selected points for study are identified     

Internetworking based on cell switch router-architecture andprotocol overview

This paper describes an internetworking architecture and related protocol overview based on routers that have asynchronous transfer mode (ATM) cell switching capability in addition to conventional Internet protocol (IP) packet forwarding. The proposed architecture can provide high-throughput and low-latency switched paths for individual application flows or a group of application flows while retaining current router-based internetworking architecture. The proposed router is able to establish the switched path based on the characteristics of flows, e.g., arrival of a data packet with specific upper layer protocols or arrival of more than a certain amount of data packets in a predetermined period, as well as by the reception of an IP-layer resource reservation request, such as resource reservation protocol (RSVP). One important feature that is provided by the proposed router is interoperability with the emerging ATM network platform specified by the ATM Forum and the telecommunications sector of the International Telecommunications Union (ITU-T). The proposed routers can be interconnected with each other over the point-to-point synchronous optical network link as well as over the ATM network platform, which provides permanent virtual channel, virtual path, or switched virtual channel (SVC) services. That enables network carriers to provide Internet/intranet services as well as others, such as telephony, ATM/time division multiplexing leased line, or native ATM SVC services     

Ethernet-based public communication services: challenge and opportunity

Enterprises and residential customers increasingly take advantage of more sophisticated applications and evolve their business models. At the same time service providers face declining revenues from existing connectivity services. SPs respond to these trends and start to offer highly customized, high-bandwidth network services that complement and interwork with their existing leased line, ATM, or frame relay offerings. Ethernet is quickly becoming the customer UNI of choice. Ethernet, being a packet-based technology, complements IP-based services such as content, voice, data, video, and additional value-added services over a high-speed access connection. Ethernet also provides a flexible high-speed connection to the SP network and eliminates access bottlenecks. Using Ethernet as the common access interface, providers can employ flexible transport services that enable additional value-added services at layer 3 and above. At the same time the rollout of Ethernet services also challenges the installed base, given that bandwidth per customer is usually much higher and additional attributes for tight SLAs apply. This calls for an updated approach to network deployment and rollout: networks need to be planned and built in a service-centric fashion. Starting with a brief look at the driving forces for Ethernet-based public communication services, this article identifies five generic services for Ethernet MANs/WANs and discusses related deployment issues of the different service options, such as the degree of customization, geographic reach and bandwidth profile of the service, as well as evolution aspects of the installed base.     

Performance Benefits of Virtual Path Tunneling for Control and Management Flows in the Broadband ATM Networks

In this paper, we analyze the performance benefits of broadband ATM networks when the call control and management flows are separated from user data flows. The virtual path tunneling concept for control and management flows are applied to the same physical ATM networks. The behaviors of channel throughput and transfer delay are analyzed. It results that the proposed virtual short-cut paths can maintain the network being stable with acceptable bandwidth. They are very useful to provide the stable control and management capabilities for Internet and mobile applications in the broadband ATM networks. In our numerical results, the effective throughputs of the proposed virtual short-cut channel are about three times than those of end-to-end user data channels with hop distances of 10, and about two times than those with hop distance of 5 when the link blocking probability increases to 0.1. It concludes that the effective channel bandwidth are greatly reduced down while physical links are not stable and user traffic flows are occasionally overflowed.     

Introduction strategy and technologies for ATM VP-based broadbandnetworks

A credible introduction strategy for B-ISDN is described. The first step is the introduction of asynchronous transfer mode (ATM) techniques into the path layer. The strategy is shown to be effective, since it enables not only the realization of a cost-effective and flexible network infrastructure, but also the provision of high-speed multimedia leased line services. The service advantages possible with virtual paths are also demonstrated. The authors' technical advances, including ATM network resource management techniques and network utilization enhancement techniques, are highlighted     

Packet reassembly during cell loss

Asynchronous transfer mode (ATM) is a packet switched data transport system based on short, fixed length cells. Each cell carries a virtual channel indicator (VCI) and virtual path indicator (VPI) in its header. Essential to the services offered by the ATM networks is the ATM adaptation layer (AAL), an ITU-TSS defined layer that adapts the cell-based ATM physical layer to packet, datagram, or bit-stream-oriented higher layers. Failure modes causing cell loss along a virtual connection are examined, and the ways AALs cope are analyzed. The sources of cell loss and their effects on AAL3/4 or AAL5 type of service are described. The usefulness of the ability of AAL3/4 to pass fragments of corrupted data up to higher layer protocols is discussed, and the implementation of selective cell discarding within switching nodes is considered, and the limitations imposed by each AAL are examined     

Service convergence using MPLS multiservice networks

Enterprises are increasingly using virtual private networks to interconnect remote sites. Traditionally, service providers have used ATM core networks to deliver layer 2 services such as frame relay, ATM, or TDM private lines, which enterprise customers have then used to build their corporate network infrastructure. Such services account for the majority of data service revenues today. However, pressure has increased on service providers to combine increased flexibility with reduced costs in the context of a highly dynamic telecommunications market. Service providers also need to generate new revenues from their IP network infrastructure, through new opportunities such as IP VPNs and virtual private LAN services, while simultaneously achieving operational efficiencies through the convergence of all of their services on a common MPLS backbone. New access and metro network technologies, such as Ethernet, are also emerging that can be used to deliver these new services to enterprise customers alongside ATM and frame relay access. This must be achieved while also supporting existing technologies such as ATM, which continue to deliver highly profitable services. This article discusses the technical challenges in meeting the often conflicting requirements of delivering both traditional layer 2 services and new layer 3 services on a converged MPLS network. We show how both network and service interworking are required, and how these must operate at the user, control, and management planes to enable profitable services to be delivered over the new converged network. The different solutions being defined in the standards bodies are described, and the distinct scenarios they address are explained.     

Cost-effective network evolution

The synchronous optical network (SONET) asynchronous transfer mode (ATM) ring architecture called SONET/ATM ring using point-to-point virtual paths (SARPVPs) is discussed. A cost-effective three-phase network evolution path for supporting both the switched and nonswitched DS1 and DS3 services and a possible operations system (OS) evolution path under the proposed three-phase network evolution scenario are described     

An evolvable ATM-based video network design supporting multipleaccess network technologies

This article describes an overall video network architecture with primary focus on the ATM subnetwork. The ATM subnetwork provides efficient switching capability for providing constant bit rate and variable bit rate video communication services. The ATM subnetwork can support multiple access networks like hybrid fiber coax (HFC), asymmetric digital subscriber line (ADSL), and fiber to the curb (FTTC). A broadband network controller is presented as the external controller for the ATM subnetwork which performs the functions of the session/network manager and the ATM-based connection management. The initial deployment of video is likely to be permanent virtual connection (PVC)-based, so a dynamic PVC-based scenario is described. The ATM switch architecture presented here has been optimized to support video applications. An evolution to the switched virtual connection environment and support of multiple services over the ATM subnetwork is also addressed. Traffic management schemes are discussed which provide the negotiated quality of service to the connections     

Performance evaluation of broadband connections and services undervarying traffic loads

The authors present ongoing work in the RACE R1056 project which is related to the integration and verification part of the RACE programme. The project goal is to establish a basic business integrated broadband communications demonstrator in an evolutionary hybrid network environment. The demonstrator configuration consists of a switching node, a customer access network and a customer premises network; its physical implementation is described. Some key business services which are to be demonstrated together with the supporting user terminals are presented. Test objectives cover verification of the hardware performance, interface compatibility and verification of a new transfer mode technique: ATM (asynchronous transfer mode). Verification activity covers the network performance (verification of end-to-end connections and measurements of key parameters). Evaluation activities cover network performance and its relationship to the quality of service perceived by a user     

Technology interoperation in ATM networks: the REFORM system

This article addresses the applicability and interoperation of standards and emerging technologies for the operation and management of ATM networks. The issue is tackled from a practical perspective based on experiences gained through the design, realization, and experimentation of a system developed by the ACTS AC208 REFORM project. Assuming an ATM-based network infrastructure offering a range of services with distinct QoS guarantees, the REFORM system encompasses the required functions for ensuring cost-effective network survivability and availability; fast-responding reliable fault detection and self-healing mechanisms, distributed dynamic routing functions with inherent load balancing capabilities, efficient VP layer design, and dynamic network reconfiguration functions. A number of standards and emerging technologies were used for designing and realizing the wide spectrum of functionality incorporated within the REFORM system, including ITU-T OAM 1.610 and Q.2931, ATM Forum UNI 3.0 and PNNI v. 1, OMG CORBA and Component Model, TINA NRA and ISO/OSI, and ITU-T TMN. Based on the experience gained, the article discusses and draws conclusions on the applicability, coexistence, and interoperation of the adopted technologies. It is shown that these technologies can coexist, through careful design, to the benefit of network design and operation     

Restoration message transfer mechanism and restorationcharacteristics of double-search self-healing ATM network

The self-healing network is particularly interesting with regard to ATM networks, because the restoration time can be shortened by using the advantages of the ATM network. This paper studies a self-healing ATM network based on virtual path (VP) protection switching. First, a novel self-healing algorithm-the double-search self-healing algorithm-is proposed. It is shown that this algorithm can restore failed bidirectional VPs faster and find alternate VPs more effectively than existing self-healing algorithms. Second, it is shown that the restoration information for self-healing control (SHC) messages must be transferred by specific cells carrying the control and OAM information (Ic&o). Message parameters and a cell format are proposed. Third, evaluation of the restoration characteristics using the proposed self-healing algorithm by computer simulation indicates that good performance against a transmission link failure is obtained even in a large-scale network model with 110 nodes. The results also indicate that the VP group (VPG) method can improve the restoration time without reducing the restoration ratio     

The ATM layer chip: an ASIC for B-ISDN applications

The authors describe the architecture of an experimental research prototype application specific integrated circuit (ASIC) designed to serve as a generic building block of the future broadband integrated services digital network (B-ISDN). The chip performs common asynchronous transfer mode (ATM) layer functions such as cell assembly and cell disassembly. A new media access control (MAC) protocol developed for a broadband customer premises network is also integrated in the chip. The chip interfaces to the B-ISDN through a synchronous optical network (SONET) synchronous transmission signal-3c (STS-3c) framer chip. The ATM layer chip has been designed using 1.2 μm CMOS technology with a die area of 5.4×5.4 mm² and approximately 27000 transistors. Experimental results are described. At the user network interface, the chip can be used to implement broadband terminal adaptors and the network termination. At the broadband local exchange, the chip can be used in the implementation of ATM statistical multiplexers, ATM switch port controllers, etc     

A layered broadband switching architecture with physical or virtualpath configurations

The authors describe a multilayer connection control architecture for broadband communications. A graph framework is introduced to describe network layers of network design, path configurations, dynamic call routing, burst switching, and asynchronous transfer mode (ATM) cell switching. These hierarchical layers of switching are performed at decreasing time scales, respectively. Switching at the higher layer is performed to reduce blocking at the next smaller time scale. A layered notion of equivalent bandwidth for satisfying layered grade-of-service parameters is introduced for making connections at these time scales. The authors then focus on the path configuration layer. Two path setup methods, namely, physical and virtual path setup, are described. Mathematical programs minimizing path bandwidth usage subject to meeting grade-of-service requirements are formulated for both methods. The relative merits of these methods are compared. In one example, physical path setup is shown to require roughly 50% more bandwidth than virtual path setup