Asynchronous Transfer Mode Forum Research Articles

A Novel, User-Level, Security-On-Demand Paradigm for ATM Networks: Modeling, Simulation, and Performance Analysis

With networks increasingly moving into virtually every aspect of our daily life, security is gaining importance, not only from the traditional perspective of communication but the network's growing role in modern automation and control. The traditional, certification based approach attempts to guarantee the security of a network through certification. Certified networks are generally confined to a limited domain and, as a result, they are isolated, costly, and under-utilized. In contrast, this paper presents a new principle – user-level, security-on-demand system, wherein the network allocates, where possible, the security resources commensurate with the user's request for transporting message(s) through the network securely. This principle is successfully demonstrated for the current Asynchronous Transfer Mode (ATM) networks, and is the result of an integration of the fundamental framework for network security, recently proposed by the authors in the literature, with the unique characteristics of ATM networks. The framework encapsulates the fundamental knowledge and set of relationships in network security and permits scientific and systematic reasoning about network security. It also enables all user groups – military, government, industry, and academia, to define their security requirements in a uniform manner. The security-on-demand approach promises the development of a "mixed use" class of networks in the future that may be simultaneously shared by different groups of users, with the system sustaining the diverse security requirements of each user. A unique characteristic in ATM network design is the dynamic call setup process. Under it, a network first establishes a virtual path or route for a user's call, guided by the user's requirements, and then transports the messages when a route has been successfully determined. This unique ATM characteristic is integrated with the framework to yield a successful demonstration of the proposed, user-level, security-on-demand approach. Utilizing the security framework as the foundation, every element of the network – node and link, is characterized by a security matrix that reflects its security resources. Every user is permitted to specify the security requirement for the call through a matrix, which expresses the limits of the security resources that the traffic cells must encounter during their transport through the network. Thus, during the dynamic establishment of the virtual path, every node and link is examined to ensure that the user-specified security is met, in addition to bandwidth and other Quality of Service (QoS) requirements. Traffic is launched when the call setup succeeds, otherwise, the call fails. Like all networks, the ATM network inherently consists of geographically dispersed entities and, as a result, the resource allocation strategy is necessarily distributed. Furthermore, as the network operation progresses, the resource availability scene changes dynamically. This paper proposes a unique function that reduces the key network resource parameters at a node to a single value, termed Node Status Indicator (NSI). The NSI value is computed dynamically at every node and disseminated across the network to be utilized by a node to refine its determination of a virtual path for a user call. The aim of the NSI is to improve the resource utilization in the network. The proposed approach is modeled for a large-scale, representative, 40-node ATM network. Utilizing stochastic input traffic that is synthesized to reflect realistic operating conditions, the model is simulated extensively on a testbed of 35+ Pentium workstations, under Linux, configured as a loosely-coupled parallel processor, utilizing an accurate, asynchronous, distributed simulator. The simulator implements the key characteristics of the ATM Forum proposed P-NNI 1.0 and UNI 3.0 standards. While the simulation results reflect a successful realization of the proposed approach, analysis reveals minimal impact of incorporating security on ATM network performance, as measured through call success rates and call setup times. In contrast, the tradition has been to incorporate security into large-scale systems and networks as an afterthought, i.e. adding hardware and software devices after the design has been completed, resulting in performance degradation. Also, while the use of NSI is observed to yield slightly lower average call setup rates and slightly higher average call setup times, a careful analysis of the trace of the calls as they progress through the system, reveals that, in general, calls are dispersed throughout the network, seeking to utilize all available resources of the network more evenly.

A frame-level measurement apparatus for performance testing of ATM equipment

Performance testing of asynchronous transfer mode (ATM) equipment is dealt with here. The attention is principally paid to frame-level metrics, recently proposed by the ATM Forum because of their suitability to reflect user-perceived performance better than traditional cell-level metrics. Following the suggestions of the ATM Forum, more and more network engineers and production managers are interested today in these metrics, thus increasing the need of instruments and measurement solutions appropriate to their estimation. Trying to satisfy this exigency, a new VME extension for instrumentation (VXI) based measurement apparatus is proposed in the paper. The apparatus features a suitable software, developed by the authors, which allows the evaluation of the aforementioned metrics by simply making use of common ATM analyzers; only two VXI line interfaces, capable of managing the physical and ATM layers, are, in fact, adopted. Some details concerning ATM technology and its hierarchical structure, as well as the main differences between frames, specific to the ATM adaptation layer, and cells, characterizing the underlying ATM layer, are first given. Both the hardware and software solutions of the measurement apparatus are then described in detail, paying particular attention to the measurement procedures implemented. In the end, the performance of a new ATM device is assessed through the proposed apparatus.

Broadband fiber access: A fiber-to-the-customer access architecture

The proliferation of high-bandwidth applications such as high-speed Internet access and telecommuting has created among network providers a growing interest in upgrading their networks to deliver broadband services to homes and small businesses. This paper describes broadband fiber access (BFA), a fiber-to-the-customer access architecture based on Lucent Technologies' broadband AnyMedia™ interface platform (AIP). The BFA architecture provides asynchronous transfer mode (ATM) connection to customer premises equipment (CPE) and supports full quality-of-service (QoS) and traffic management functions defined by the ATM Forum. The BFA line card, or application pack (AP), is designed to support the concentration of traffic from CPE at the OC-3c/STM-1 rate (155.52 Mb/s). It supports the use of single-fiber drop to CPE using bidirectional coarse wavelength division multiplexing (CWDM). A hardware-based flow-control mechanism, which is applied to low-priority traffic originated from the CPE, allows for fast response to congestion at the feeder multiplexer. This fast response to congestion allows fair and efficient utilization of the feeder bandwidth.

Mobile information infrastructure

Recent developments attest to wide interest in wireless asynchronous transfer mode (ATM). The Federal Communications Commission (FCC), for example, recently announced that it will open up 350 MHz of bandwidth in the 5-GHz band for inexpensive Internet access at schools and libraries. Moreover, in June 1996, the Wireless ATM Working Group was formed within the ATM Forum. Bell Labs has been working on a wireless ATM prototype in its Mobile information infrastructure (MII) project, which is partially funded by the National Institute of Standards and Technology of the U.S. Government. This paper describes the MII project, outlines several key technical issues and their proposed solutions, and discusses standardization and prototyping efforts. It also describes the system architecture; the protocol stack; the physical, multiaccess, and data link layers; connection control, location management, the handoff algorithm, and distributed address resolution; prototyping; standards; and a migration strategy from today's wireless local area network (LAN) to the future wireless ATM LAN.

Voice over ATM

Voice over asynchronous transfer mode (ATM) is part of an ongoing convergence to a single network technology that supports multimedia services and offers guaranteed quality of service (QoS). This paper explains the economic advantages of such a solution for both carrier networks and enterprise networks compared to traditionally separate circuit-switched networks. We describe how ATM supports voice traffic, as well as the various options defined by the ATM Forum and other standards bodies for voice and telephony over ATM (VTOA). We examine applications of VTOA in both carrier and enterprise network environments, and we describe the various products that form Lucent Technologies' VTOA solutions for the near term and beyond.

Connection control in ATM networks

This paper describes a new connection management algorithm called parallel connection control (PCC) that allows for fast connection setup in scaleable reliable asynchronous transfer mode (ATM) networks. The two main concepts of PCC are execution of connection setup actions at multiple switches on the route of a connection in parallel, and the separation of the route computation function into servers distinct from switch processors. The associated benefits of these concepts are fast connection setup and increased per-switch call handling capacity relative to the conventional approach of setting up connections sequentially switch-by-switch with switches performing route computation. The PCC solution is designed to work in conjunction with the current ATM Forum signaling and routing standards solutions, offering a means to achieve improved call handling performance. This paper also introduces the concept of application-dependent routing for setting up logical connections, which consist of multiple network-layer connections routed through application-layer resources, such as bridges and converters. In this paper, we propose two models for handling complex communication configurations: an end-host-driven model and a network-value-added model using application-dependent route (ADR) servers.

Inverse optimization in high-speed networks

A general approach is presented for handling the following inverse optimization problem: given solutions to each member of a family of combinatorial optimization tasks on a common underlying set, find a positive linear objective function (weighting) on the common underlying set that simultaneously makes each solution optimal in its own optimization task. Our motivation stems from the inverse shortest path problem that is made practically important in high-speed telecommunication networks by the Asynchronous Transfer Mode Forum's Private Network–Network Interface architecture, in which route finding can be based on administrative weights. Different variants of the problem are investigated, including uniqueness requirements and reserve routes.

Comparative study of two flow control mechanisms in high speed networks

Considerable protocol development efforts in recent ATM (Asynchronous Transfer Mode) Forum activities have been focused on the traffic management of available bit rate (ABR) service. It has been shown that ABR service enables persistent, greedy data sources to efficiently utilize ATM network resources with the help of a rate-based flow control mechanism. ATM Forum Traffic Management Specification Version 4.0 document gives a complete description of the end system behavior of the flow control mechanism, but it leaves the details of the switch behavior to be vendor-implementation dependent. For the sake of compatibility and interoperation among flow control mechanisms implemented by vendors, two rate-based mechanisms EPRCA (Enhanced Proportional Rate Control Algorithm) and ERICA (Explicit Rate Indication for Congestion Avoidance) have been recommended in the specification. In this paper, the mechanisms are studied and their performance is analyzed and compared with a material network. Simulation shows that ERICA is significantly better than EPRCA in the performance of steady state and instantaneous state of source end system ACR (Allowed Cell Rate) and buffer queue of bottleneck switch.

Efficient simulation of QoS in ATM switches using connection traffic descriptors

High speed networks using asynchronous transfer mode (ATM) will be able to carry a broad range of traffic classes and will be required to provide QoS measures, such as the cell loss and cell delay probabilities, to many of these traffic classes. The design and testing of ATM networks and the algorithms that perform connection admission control is difficult due to the rare event nature associated with QoS measures, and the unwieldiness of matching statistical models of the broad range of traffic classes entering the network to the connection traffic descriptors used by the connection admission control algorithms. In this paper, as an alternative to using statistical traffic models, we describe the traffic entering the network by the connection traffic descriptors standardized by the ATM Forum and used by the connection admission control algorithms. We present a Monte Carlo simulation model for estimating the cell loss and cell delay probabilities using a multinomial formulation to remove the correlation associated with estimating bursty events. We develop importance sampling techniques to increase the efficiency of the simulation for ATM networks with heterogeneous input traffic classes, namely constant bit rate and variable bit rate traffic. For the experimental examples considered here, the improvement in simulation efficiency compared to conventional Monte Carlo simulation is inversely proportional to the probability estimate. The efficient simulation methods developed here are suitable for the design and testing of the switches and connection admission control algorithms planned for use in ATM networks.

Call performance studies on the ATM forum UNI signalling implementations

Asynchronous Transfer Mode (ATM) is widely accepted as the transfer mode for Broadband Integrated Services Digital Networks (B-ISDN). As ATM networks provide connection-oriented services, signalling is an essential component of these networks. The performance of the signalling system is crucial in determining the scalability of the network. Call performance measurements on two different ATM switches were carried out using a broadband network analyser. Calls are generated according to a deterministic/Poisson distribution and various components of the call set up delay are analysed. The probability distribution of the delays is obtained and the correlation between the set up delay and its different constituents is established. It is observed that the delays at the calling and the called user entities of the UNI form a major component of the call set up delay. The average call set up delay is found to be 21 and 27 ms, respectively, when a single switch is involved in call set up and 50 ms when two switches are involved in call set up. With simultaneous call arrivals, though with higher delays, both the switches are found to establish calls at the rate of 100 calls/s.

Providing rate guarantees for internet application traffic across ATM networks

The TCP/IP protocol suite is the standard requirement for all applications that need to communicate over the Internet. As TCP/IP applications are unable to specify the QoS parameters needed for most asynchronous transfer mode (ATM) services, they tend to use the unspecified bit rate (UBR) service category when running across ATM networks. The UBR service utilizes any bandwidth that is left unused by the rest of the ATM services. This has led the ATM forum's traffic management group to define a new service category called guaranteed frame rate (GFR). GFR is intended to provide minimum cell rate guarantees and fair access to excess bandwidth left over from higher-priority services. This article first presents a tutorial overview of GFR and then presents a survey of the research work that has been carried out toward the design and implementation of associated ATM switch mechanisms.

Use-it-or-lose-it policies for the available bit rate (ABR) service in ATM networks

The Available Bit Rate (ABR) service has been developed to support data applications over Asynchronous Transfer Mode (ATM). The ABR service uses a closed-loop rate-based traffic management framework where the network divides left-over bandwidth among contending sources. The ATM Forum traffic management group also incorporated open-loop control capabilities to make the ABR service robust to temporary network failures and source inactivity. An important problem addressed was whether rate allocations of sources should be taken away if sources do not use them. The proposed solutions, popularly known as the Use-It-or-Lose-It (UILI) policies, have had significant impact on the ABR service capabilities. In this paper we discuss the design, development, and the final shape of these policies and their impact on the ABR service. We compare the various alternatives through a performance evaluation.

Performance of TCP in IP/ATM internetworks

The Asynchronous Transfer Mode (ATM) level flow control schemes and their impact on Transmission Control Protocol (TCP) over ATM have been extensively studied (Fang et al., A simulation study of TCP performance in ATM networks, in: Proceedings of IEEE GLOBECOM'94, San Francisco, 28 November–2 December 1994, pp. 1217–1223; S. Kalyanaraman et al., Performance of TCP/IP over ABR, in: Proceedings of Globecom'96, London, November 1996; H. Li et al., A simulation study of TCP performance in ATM networks with ABR and UBR services, in: INFOCOM'96, March 1996). In this paper, we extend the work of Yin and Jagannath (End-to-end traffic management in IP/ATM internetworks, ATM Forum Contribution 96-1406, October 1996) on TCP over available bit rate (ABR) and unspecified bit rate (UBR) services in an IP/ATM internetworking environment, and provide a more comprehensive study on this important issue. We compare TCP performance in terms of goodput and fairness and discuss the performance tradeoff among different types of services. We also investigate the ATM edge congestion with different traffic scenarios in various networks configurations and system setups. In particular, a simple and effective scheme to prevent ATM edge buffer overflow is proposed in this paper. Simulation results are provided to show that our scheme can reduce the ATM edge congestion, and therefore provide significant improvement of TCP goodput.

Supporting IP on the ATM networks: an overview

In the past 10 years, asynchronous transfer mode (ATM) technology has emerged as a key component of next-generation networks. It can offer unprecedented scalability and performance/cost ratio, as well as the ability to reserve network resources for real-time traffic and support for multimedia and multipoint communications. Obviously, in the future information infrastructure, ATM will play an important role. However, today's information infrastructure, e.g. the vast installed base of local area networks (LANs) and wide area networks (WANs) is constructed by using internetwork layer protocols such as IP, IPX and AppleTalk to internetwork the subnets. Therefore, a key to ATM's success and the Internet's further success will be the ability to allow for interoperation between existing network technologies and ATM. The key to such connectivity is the use of the same network layer protocols, such as IP and IPX, on both existing networks and on ATM, since it is the function of the network layer to provide a uniform network view to higher-level protocols and applications [RFC1943, IP over ATM: A Framework Document; A. Alles, ATM Internetworking, Cisco Systems, Inc., May, 1995]. Until now, there have been various different ways of running IP across an ATM network, e.g. LAN Emulation and Multiprotocol over ATM standardized by ATM Forum, classical IP over ATM and Next Hop Resolution Protocol proposed by the Internet Engineering Task Force, IP Switching implemented by Ipsilon Networks Inc., Tag Switching presented by Cisco Systems Inc., etc. This paper gives an overview and an assessment on these proposed schemes.

Experience with PACS in an ATM/Ethernet switched network environment.

Legacy local area network (LAN) technologies based on shared media concepts are not adequate for the growth of a large-scale picture archiving and communication system (PACS) in a client-server architecture. First, an asymmetric network load, due to the requests of a large number of PACS clients for only a few main servers, should be compensated by communication links to the servers with a higher bandwidth compared to the clients. Secondly, as the number of PACS nodes increases, the network throughout should not measurably cut production. These requirements can easily be fulfilled using switching technologies. Here asynchronous transfer mode (ATM) is clearly one of the hottest topics in networking because the ATM architecture provides integrated support for a variety of communication services, and it supports virtual networking. On the other hand, most of the imaging modalities are not yet ready for integration into a native ATM network. For a lot of nodes already joining an Ethernet, a cost-effective and pragmatic way to benefit from the switching concept would be a combined ATM/Ethernet switching environment. This incorporates an incremental migration strategy with the immediate benefits of high-speed, high-capacity ATM (for servers and high-sophisticated display workstations), while preserving elements of the existing network technologies. In addition, Ethernet switching instead of shared media Ethernet improves the performance considerably. The LAN emulation (LANE) specification by the ATM forum defines mechanisms that allow ATM networks to coexist with legacy systems using any data networking protocol. This paper points out the suitability of this network architecture in accordance with an appropriate system design.

Traffic management for an ATM switch with per-VC queuing: concept and implementation

The services to be supported by an asynchronous transfer mode (ATM)-based multiservice network differ significantly in terms of their traffic characteristics and required quality of service. During the last few years it has been broadly accepted that efficient use of transmission capacity is not possible unless these differences are reflected in the way the related traffic streams are handled within the ATM layer. To address this need, the ATM Forum and ITU-T have specified different real-time and non-real-time ATM-layer service categories. This article first discusses the requirements for traffic management in a switch supporting all these service categories from the service providers' and users' points of view. The first generation of ATM switches, typically equipped with small cell buffers, only satisfies the requirements for the real-time service categories (CBR, rt-VBR). Statistical multiplexing, if supported at all, is limited to connections with low peak cell rates. Larger cell buffers and new traffic control functions are required to support non-real-time service categories (nrt-VBR, ABR, UBR). A switch architecture which is scalable from small to large system sizes is presented. It provides the required buffering and additional functions for the non-real-time service categories with the aid of a statistical multiplexing unit (SMU), a module which can also be used as an optional addition to a conventional ATM switch. The focus is on the functional description of two novel yet key components of the SMU, namely the buffer management and cell scheduling functions. The buffer management function provides per-VC queuing and achieves an optimal utilization of the large cell buffer shared by connections of different service categories. The two-stage cell scheduling function supports traffic shaping on the VC and VP levels, and weighted fair queuing within groups of connections. The overall concept supports high link utilization, fairness, and throughput guarantees, and enables a migration from today's ATM networks to a fully integrated multiservice network. Finally, implementation aspects are discussed to show the feasibility of the concept for very high bit rates.

ATM Forum signalling protocols and their interworking

The ATM Forum is a key body which has been developing specifications for asynchronous transfer mode (ATM) technology over the past six years. It has produced a number of signalling specifications covering the user network interface, the inter-carrier interface and private networking environments. While work continues on ‘fine-tuning‘ these agreements, there is still discussion about how they are used in large scale networks, and in particular on the interworking of public and private network environments. This paper reviews the current status of the relevant protocols and their scope. It then explores the issues related to their interworking and discusses the role of the proposed ATM internetwork interface (AINI) as an alternative internetwork or inter-carrier interface to its broadband intercarrier interface (B-ICI).

Effective control of traffic flow in ATM networks using fuzzy explicit rate marking (FERM)

We describe the fuzzy explicit fate marking (FERM) traffic flow control algorithm for a class of best effort service, known as available bit rate (ABR), proposed by the ATM Forum. FERM is an explicit rate marking scheme in which an explicit rate is calculated at the asynchronous transfer mode (ATM) switch and sent back to the ABR traffic sources encapsulated within resource management (RM) cells. The flow rate is calculated by the fuzzy congestion control (FCC) module by monitoring the average ABR queue length and its rate of change, then by using a set of linguistic rules. We use simulation to compare the steady-state and transient performance of FERM with EPRCA (a current favourite by the ATM Forum) in the presence of high priority variable bit rate (VBR) video and constant bit rate (CBR) in both a local-area network (LAN) and a wide-area network (WAN) environment. Our experiments show that FERM exhibits a robust behavior, even under extreme network loading conditions, and ensures fair share of the bandwidth for all virtual channels (VCs) regardless of the number of hops they traverse. Additionally, FERM controls congestion substantially better than EPRCA, offers faster transient response, leads to lower end-to-end delay and better network utilization.

Internetworking based on cell switch router-architecture and protocol 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.

Wireless communications in the twenty-first century: a perspective

Wireless communications are expected to be the dominant mode of access technology in the next century. Besides voice, a new range of services such as multimedia, high-speed data, etc. are being offered for delivery over wireless networks. Mobility will be seamless, realizing the concept of persons being in contact anywhere, at any time. Two developments are likely to have a substantial impact on the mobile communications systems deployed in the twenty-first century: the adoption of International Mobile Telecommunications-2000 and wireless asynchronous transfer mode (ATM). They are two different but cooperative approaches to providing high-speed wireless access. The limitations of the radio-frequency spectrum and radio channel propagation impose special constraints on the technologies of systems to be deployed. To make future mobile systems globally acceptable, standardization efforts are underway in the International Telecommunications Union and the ATM Forum. This paper reviews the international standardization efforts, the challenges to the technologies imposed by the radio spectrum limitations, radio channel propagation-induced distortions, and possible solutions. Evolution, migration, and architecture issues also are discussed.