ATM Wide Area Networks Research Articles

A scheme for managing resource locations in broadband networks

The dynamic migration of data resources has become a strong tool for transaction processing in broadband networks such as ATM. As the data resources migrate from one node to the other, managing the locations of these resources becomes an important issue. This paper presents an information structure and the associated algorithm to locate and access these migratory data resources in an ATM wide area network. The proposed information structure includes multiple dynamic rooted tree structures (one for each data resource) logically connecting the nodes involved in the system and a behaviour attribute (transit or proxy) assigned to each node. The rooted tree structures are used to move the requests and the corresponding data resources. The performance of the proposed algorithm is evaluated and also compared with one of the existing algorithms for data resource location by a simulation study under different system parameters such as frequency of access to the data resources, frequency of data resource migrations and scale of network.

Grid-based switch fabrics: a new approach in designing fault-tolerant ATM switches

ATM is the switching and multiplexing technology chosen to be used in the implementation of B-ISDN, because of its superiority in fast packet switching. However, the use of ATM switches with large number of input and output ports have been proven to be a bottleneck in wide area ATM networks. In this paper, we propose a new space-division grid-based ATM architecture with fault tolerant characteristics and minimal number of switching elements (SE's).

Plan: a high performance shared-media ATM LAN protocol

This paper presents the architecture and performance of a new shared media ATM LAN protocol known as pipelined-access local ATM network (PLAN) which has high performance and operates in native ATM mode for efficient and simpler interworking with backbone ATM networks. PLAN is a reservation type bidirectional broadcast bus system protocol in which overhead due to bus propagation delay is limited to a total of twice the end-to-end propagation delay per transmission frame irrespective of the number of stations on the bus. It is designed to (i) support multimedia traffic, (ii) dynamically allocate bandwidth to various types of traffic and provide fair media access to stations, (iii) provide throughput close to 100%, (iv) operate at high bit rates and (v) use packets of ATM cell size and format for interoperability with wide-area ATM networks. In this paper we present the architecture, analysis and performance of the proposed PLAN protocol under various multimedia traffic conditions. The results show that its throughput approaches 100%, is independent of traffic composition and increases slowly with bit rate. It decreases only slightly as the bus length and/or number of stations increase. The proposed PLAN protocol is seen to be well suited for high-speed multimedia ATM LAN and MAN applications in the ATM networking environment. © 1998 John Wiley & Sons, Ltd.

First-order rate-based flow control with dynamic queue threshold for high-speed wide-area ATM networks

In this paper we present a new rate-based flow control scheme for ATM ABR services and analyze its performance. The proposed algorithm, which we refer to as first-order rate-based flow control (FRFC) is the most simple form of queue-length-based flow control. The asymptotic stability, the steady-state throughput, queue length and fairness, and the transient behavior are analyzed for the case of multiple connections with diverse round-trip delays. We also consider a novel approach to dynamically adjust a queue threshold in the FRFC according to the changes in the available bandwidth, and the arrival and departure of connections. Simulations show that the simple FRFC with dynamic queue threshold (DQT) effectively maintains high throughput, small loss and a desired fairness in these dynamic environments and is a promising solution for ABR flow control in ATM networks.

Performance benchmarking of signaling in ATM networks

The overhead associated with establishing switched virtual circuits (SVCs) in high-speed wide area ATM networks is an important performance factor in applications with client/server architectures, including the World Wide Web and low-latency applications such as command/control and modeling/simulation. This article quantifies this overhead by describing a benchmarking framework implemented in a reliable, portable, and easily expandable toolset designed to conduct measurements of well-defined parameters and performance metrics on equipment that is either isolated or connected to a live network. The usefulness of this toolset is then demonstrated in a test suite applied to assess call rates and connection establishment latency of point-to-point and point-to-multipoint ATM connections in the MAGIC, ATDnet, and AAI WANs, on the campus ATM LAN at NRL, and on individual switches in our laboratories.

ATM WAN performance tools, experiments, and results

Practical experiments in a wide-area ATM network environment are essential to gain a better understanding of the factors affecting ATM performance. This article summarizes the main lessons learned through the authors' practical experiences with ATM and how these can be applied to performance tuning. In order to achieve maximum performance from an ATM WAN, factors ranging from the transport protocol to the equipment used and the network conditions must be carefully taken into consideration. The authors also discuss some of the software-based throughput measurement tools available for the evaluation of high speed network performance, with particular emphasis on NetSpec.

Behaviour of XTPX in the European ATM pilot

AbstractWe present and discuss measurements performed with XTPX over the European ATM Pilot. The main characteristic of this wide area ATM network is that the traffic contract is enforced by a Usage Parameter Control (UPC) mechanism. When the ATM traffic is compliant with the traffic contract, XTPX achieves a good utilisation of the link. However, when the ATM traffic is not entirely compliant, the UPC discards cells and the link utilisation becomes very low.

Behaviour of TCP in the European ATM Pilot

We present and discuss detailed measurements of TCP in the European ATM Pilot. In this wide area ATM network, the traffic contract is enforced by a Usage Parameter Control (UPC) mechanism. We show that when the ATM level traffic was compliant, TCP achieved a good utilization of the link. However, when the ATM level traffic was only almost compliant, the TCP throughput almost collapsed.

MLAP: a MAC level access protocol for the HFC 802.14 network

Interactive residential broadband/multimedia services are expected to be the next main event in the cyberspace experience. The large excess bandwidth (well over 300 MHz) available in today's cable TV (CATV) hybrid fiber/coaxial (HFC) plants is an ideal candidate to provide the underlying communications infrastructure for interactive digital services to the home; cable operators that have not yet upgraded their all-coaxial plants to HFC are quickly moving in this direction. MLAP is a flexible ATM-friendly MAC protocol that is capable of supporting various types of traffic with diverse quality-of-service requirements. We introduce a very versatile MAC protocol for the HFC 802.14 network. MLAP can provide integrated broadband services to the home, internetwork easily with ATM wide area networks, support QoS constraints for various types of traffic, and operate over a variety of physical layer protocols. Our presentation is only an extended summary of our medium-sharing protocol proposal to the IEEE 802.14 WG. We consider only error-free system operation. MLAP provides for the use of timers for the recovery of error situations in the network. MLAP is also supported by a management suite of protocols for management of the overall system.

Taming Xunet III

An architecture for network management and control for emerging wide-area ATM networks is presented. The architecture was implemented on XUNET III, a nationwide ATM network deployed by AT&T. The Xunet network management system is based on the OSI standards and includes configuration, fault and performance management. An OSI agent resides at every switching node. Its capabilities include monitoring of cell level quality of service in real time and estimation of the schedulable region. The complexity and accuracy of real-time monitoring functionalities is investigated. To provide realistic traffic loads, distributed traffic generation systems both at the cell and call level have been implemented. In order to study the trade-off between the network transport and signalling system we have implemented a virtual path signalling capability. Our experiments show that the ability of a network to admit calls is limited by two distinct factors: the capacity of the network and the processing power of the signalling system. Depending on the bandwidth requirement of calls, the limit of one or the other will be first reached. This is a key observation, unique to broadband networks.

A wireless broadband ad-hoc ATM local-area network

We describe the theory, design and ongoing prototyping of a wireless ATM LAN/PBX capable of supporting mobile users with multi-Mb/s access rates and multi-Gb/s aggregate capacities. Our proposed LAN consists of network nodes called Portable Base Stations (PBS) providing microcell coverage. The PBSs are designed to be low-cost, compact and high-speed and can be relocated conveniently. We employ a concept of ad-hoc networking in the layout of the PBS-to-PBS interconnection. That is, the PBSs can be distributed in an arbitrary topology to form a backbone network and can be reconfigured with relative ease. The PBS-to-PBS backbone links are high-speed (Gb/s) for supporting high system capacity. Although they can either be wired or wireless, our emphasis is on wireless implementations. The user-to-PBS links, on the other hand, are primarily for mobile access (e.g., 2-20 Mb/s) and therefore are wireless. Wired connections from stationary users to PBSs are also possible. Typical mobile users are assumed to be laptops or notebook computers. Services supported include conventional data applications (e.g., over TCP/IP or SPX/IPX) as well as multimedia (video, voice and data) applications with QoS (Quality-of-Service) guarantees. A “wireless ATM” concept is proposed so as to provide seamless internetworking with other wired ATM local and wide-area networks. Algorithms and control in our network are highly distributed for simple implementations and ease of mobility management. A new wireless VP/VC concept and a Homing Algorithm are described to provide ATM cell routing and connections in the network. PBS hardware and software architectures are discussed. Call management, network management and signaling are designed for simplicity, high performance and modular implementations. A fast network restoration scheme is proposed to cope with the potential link or node failures in the ad-hoc network. Error control is addressed taking the unreliable wireless links into consideration. Finally, a prototyping project called BAHAMA (Broadband Ad Hoc ATM Anywhere) for demonstrating this network concept is briefly outlined.

Improvements to TCP performance in high-speed ATM networks

Performance of TCP connections in high-speed wide-area ATM networks is of great importance due to the widespread use of te TCP/IP protocol for data transfers and the increasing deployment of ATM networks. ATM technology promises substantial gains by allowing the available link bandwidth to be efficiently used by a mix of audio, video, and data traffic. However, certain features of ATM technology lead to a substantial degradation of TCP connection throughput under congestion conditions. The poor performance of TCP has been observed in a number of recent studies [7] and a number of remedies have been proposed [1, 8], but most of the additional mechanisms proposed to improve TCP performance in ATM networks require substantial complication of the ATM switches

Adaptive algorithms for feedback-based flow control in high-speed, wide-area ATM networks

This paper gives a class of flow control algorithms for the adaptive allocation of bandwidths to virtual connections (VC) in high-speed, wide-area ATM networks. The feedback rate to the source from the network is parsimonious, with each feedback bit indicating whether the buffer at a distant switch is above or below a threshold. The service discipline at the switch is first-come-first-served. The important goal of adaptability aims to make all of the network bandwidth available to the active VCs, even though the number of such VCs is variable over a given range. Each VC has two parameters, one giving its minimum guaranteed bandwidth and the other is the weight for determining its share of the uncommitted bandwidth. Judicious selection of these parameters defines distinctive services, such as best effort and best effort with minimum bandwidth. We derive design rules for selecting the parameters of the algorithms such that the appropriate guarantees and fairness properties are exhibited in the dynamical behavior. The systematic use of damping in right proportion with gain is shown to be a powerful device for stabilizing behavior and achieving fairness. Our analyses are based on a simple analytic fluid model composed of a system of first-order delay-differential equations, which reflect the propagation delay across the network. Extensive simulations examine the following: (1) fairness, especially to start-up VCs; (2) oscillations; (3) transient behavior, such as the rate of equalization from different initial conditions; (4) disparate bandwidth allocations; (5) multiple paths with diverse propagation delays; (6) adaptability and robustness with respect to parameters; and (7) interoperability of different algorithms. >

Resource management in wide-area ATM networks using effective bandwidths

This paper is principally concerned with resource allocation for connections tolerating statistical quality of service (QoS) guarantees in a public wide-area ATM network. Our aim is to sketch a framework, based on effective bandwidths, for call admission schemes that are sensitive to individual QoS requirements and account for statistical multiplexing. Results approximating the effective bandwidth required by heterogeneous streams sharing buffered links, including results for the packetized generalized processor sharing service discipline, are described. Extensions to networks follow via the concept of decoupling bandwidths, motivated by a study of the input-output properties of queues. Based on these results we claim that networks with sufficient routing diversity will inherently satisfy nodal decoupling. We then discuss on-line methods for estimating the effective bandwidth of connection. Using this type of traffic monitoring we propose an approach to usage parameter control (i.e., policing) for effective bandwidth descriptors. Finally, we suggest how on-line monitoring might be combined with admission control to exploit unknown statistical multiplexing gains and thus increase utilization. >

A feasible framework of traffic control on an ATM wide-area network

In this paper, we propose a framework of traffic control to accommodate multimedia connections on an ATM wide-area network. At the lower layer, an efficient bandwidth allocation method and a constant time cell scheduling algorithm are provided in each network node. These mechanisms have the capability of multiplexing traffics and satisfying diverse delay and loss performance requirements. At the higher layer, a three-phase connection establishment procedure is applied. It transforms the end-to-end performance requirement of a connection request into local requirements for each intermediate node of a routing path. If the requirements for each intermediate node can be satisfied, the connection is accepted; otherwise, another routing path will be examined. Without resort to any complicated rate control inside the network, in our system, time distances between successive cells while they are passing through the network are maintained by imposing an upper bound on the end-to-end queueing delay of each cell. Simulation results show that the connection establishment overhead of our system is almost independent of the traffic load of the network. Its value is very small so that the proposed framework is feasible in the future ATM networks. Besides, optimally transforming end-to-end performance requirement into those for each intermediate node to maximize the saturation load of the network has been proved to be an NP-Hard problem. Two heuristic algorithms are proposed. Experiments are performed to evaluate these algorithms.

Signaling and operating system support for native-mode ATM applications

Applications communicating over connectionless networks, such as IP, cannot obtain per-connection Quality of Service (QoS) guarantees. In contrast, the connection-oriented nature of the ATM layer and its per-virtual-circuit QoS guarantees are visible to a native-mode ATM application. We describe the design and implementation of operating system and signaling support for native-mode applications, independent of the semantics of the protocol layers or of the signaling protocol. The work was done in the context of a Unix-like operating system and the Xunet 2 wide-area high-speed ATM network. The IPC-based interface between an application and the signaling entity allows processes to request parameterized virtual circuits, and the signaling-kernel interface allows resources to be reclaimed from prematurely terminating processes. We also built a simple encapsulation layer over raw IP that allows any host with IP access to send AAL frames into the wide-area network with little performance degradation. Our design makes it simple to port existing TCP/IP socket applications to a native-mode ATM protocol stack and also enables interoperation of existing IP networks with our ATM network. Our experience has been positive - the design is robust, easily extendible and scales well with the number of open connections.

Supporting cooperative medicine: the Bermed Project

Bermed logically integrates distributed, multimedia patient data and gives authorized physicians transparent access to it through a single workstation. In conjunction with this integration, the project provides asynchronous remote access to the data and synchronous desktop conferencing between physicians connected by ATM and ISDN wide area networks. Although other projects around the world have similar aims and implementations, Bermed seems unique in its wide area logical integration of distributed patient records covering multiple specialties and in its large-scale field trials using advanced broadband communications. We summarize parts of the Bermed effort, concentrating on how it integrates patient data and supports physician cooperation through remote access to documents and multimedia desktop conferencing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>