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Proceedings of the 1997 ACM SIGMETRICS international conference on Measurement and modeling of computer systems

作者： Hari Balakrishnan Mark Stemm Srinivasan Seshan Randy H. Katz Computer Science Division University of California at Berkeley Berkeley CA IBM T.J. Watson Research Center Yorktown Heights NY

ISBN: (纸本)9780897919098

The internet is a very large scale, complex, dynamical system that is hard to model and analyze. In this paper, we develop and analyze statistical models for the observed end-to-end network performance based on extensive packet-level traces (consisting of approximately 1.5 billion packets) collected from the primary Web site for the Atlanta Summer Olympic Games in 1996. We find that observed mean throughputs for these transfers measured over 60 million complete connections vary widely as a function of end-host location and time of day, confirming that the internet is characterized by a large degree of heterogeneity. Despite this heterogeneity, we find (using best-fit linear regression techniques) that we can express the throughput for Web transfers to most hosts as a random variable with a log-normal distribution. Then, using observed throughput as the control parameter, we attempt to quantify the spatial (statistical similarity across neighboring hosts) and temporal (persistence over time) stability of network performance. We find that internet hosts that are close to each other often have almost identically distributed probability distributions of throughput. We also find that throughputs to individual hosts often do not change appreciably for several minutes. Overall, these results indicate that there is promise in protocol mechanisms that cache and share network characteristics both within a single host and amongst nearby hosts.

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Design of a DAVIC residential network based on Ethernet

Design of a DAVIC residential network based on Ethernet

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IEEE International conference on Embedded and Real-Time Computing systems and Applications (RTCSA)

作者： Junghoon Lee Seungjun Park Department of Computer Science and Statistics Cheju-National University Chejudo South Korea Research & Development Center Daewoo Telecom Telecommunication Laboratory Kyunggi South Korea

ISBN: (纸本)0818680733

This paper designs and evaluates an Ethernet-based residential network where cable length is very short and most traffic passes through a specific device. The design aims at enhancing the deadline meet ratio for the real-time traffic, such as the video stream, by applying such functionalities as queue discrimination and packet discard. The design includes the description of hardware interfaces as well as software modules such as the scheduler, device driver and connection manager. The simulation results suggest that the proposed network can be used as a cost-effective residential network. We also show the permissible bandwidth for non-real-time traffic without degrading the performance of real-time traffic.

关键词： Ethernet networks Telecommunication traffic Traffic control Access protocols Research and development management Telecommunication network management Asynchronous transfer mode Web and internet services Communication switching Optical fiber devices

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NFS dynamics over flow-controlled wide area networks

NFS dynamics over flow-controlled wide area networks

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IEEE Annual Joint conference: INFOCOM, IEEE Computer and Communications Societies

作者： K. Chang R. Morris H.T. Kung Division of Engineering and Applied Sciences Harvard University Cambridge MA USA

The network file system protocol (NFS) has been the leading distributed file system for workstations since it was first introduced by Sun Microsystems in 1986. The geographical scale of NFS has been limited to the local area due to its relatively low performance on the wide area internet. However, with the advent of high bandwidth wide area networks such as ATM, NFS over WANs may become more promising. In this paper, the performance of NFS over various sizes of WAN is studied The effects of ATM flow-control and queueing strategies on NFS are discussed, as are the performance of TCP and UDP as NFS transport protocols. The primary conclusion is that standard NFS over UDP works well over ATM WANs as long as ATM-level flow control keeps the cell loss rate under one percent. In some cases, NFS over TCP works badly with small packets due to unfortunate interactions with TCP's congestion window.

关键词： Wide area networks Asynchronous transfer mode Sun Bandwidth Propagation delay File systems Protocols Error correction Workstations internet

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New method for analyzing feedback-based protocols with applications to engineering Web traffic over the internet

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performance Evaluation Review 1997年第1期25卷 24-38页

作者： Heyman, D.P. Lakshman, T.V. Neidhardt, Arnold L. AT&T Labs Holmdel United States

Most of the studies of feedback-based flow and congestion control consider only persistent sources which always have data to send. However, with the rapid growth of internet applications built on TCP/IP such as the World Wide Web and the standardization of traffic management schemes such as Available Bit Rate (ABR) in Asynchronous Transfer Mode (ATM) networks, it is essential to evaluate the performance of feedback-based protocols using traffic models which are specific to dominant applications. This paper presents a method for analyzing feedback-based protocols with a Web-user-like input traffic where the source alternates between `transfer' periods followed by `think' periods. Our key results, which are presented for the TCP protocol, are: (1) The goodputs and the fraction of time that the system has some given number of transferring sources are insensitive to the distributions of transfer (file or page) sizes and think times except through the ratio of their means. Thus, apart from network round-trip times, only the ratio of average transfer sizes and think times of users need be known to size the network for achieving a specific quality of service. (2) The Engset model can be adapted to accurately compute goodputs for TCP and TCP over ATM, with different buffer management schemes. Though only these adaptations are given in the paper, the method based on the Engset model can be applied to analyze other feedback systems, such as ATM ABR, by finding a protocol specific adaptation. Hence, the method we develop is useful not only for analyzing TCP using a source model significantly different from the commonly used persistent sources, but also can be useful for analyzing other feedback schemes. (3) Comparisons of simulated TCP traffic to measured Ethernet traffic shows qualitatively similar autocorrelation when think times follow a Pareto distribution with infinite variance. Also, the simulated and measured traffic have long range dependence. In this sense our traffic

关键词： network protocols

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A mission-based ATM network manager

A mission-based ATM network manager

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MILCOM, Military Communications conference

作者： T.A. Parsons M. Martone Booz Allen and Hamilton Inc. Eatontown NJ USA

As military communication networks begin to migrate to hybrid internet protocol (IP)/asynchronous transfer mode (ATM) technology a new set of requirements for network management is evolving. The collaborative promise of ATM networking cannot be fully realized with current management systems. Moreover, emerging multimedia C2I applications impose unique, variable, and mission-sensitive requirements on the network infrastructure. A need exists for a new model of network management. This paper describes an ATM network manager which is capable of managing the ATM network, workstation, and user applications. The manager dynamically optimizes network routing, link bandwidth allocation, ATM policing, and other QoS parameters. Host configuration and application parameters can be tuned for optimum performance, where possible. The paper also outlines how a military operational scenario, a user/application description, and a historical network performance database are used, along with real-time network measurement inputs, to dynamically control and optimize the managed elements of the system. Before an operational mission, inputs such as data and application types, user/data priorities, network deployment information, and event timelines are translated into a management ruleset. This ruleset, along with historical data on network performance and real-time measured performance data, are used by the network manager whenever a communication occurs to optimally set up the ATM connection parameters of the network host, and application. Finally, the paper discusses an implementation of the mission-based ATM network manager. Progress to date is described.

关键词： Asynchronous transfer mode Military communication IP networks Protocols Technology management Collaboration Workstations Routing Channel allocation Databases

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Design and implementation of a QoS capable switch-router

Design and implementation of a QoS capable switch-router

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International conference on Computer Communications and networks (ICCCN)

作者： E. Basturk A. Birman G. Delp R. Guerin R. Haas S. Kamar D. Kandlur P. Pan D. Pendarakis V. Peris R. Rajan D. Saha D. Williams IBM Thomas J. Watson Research Center Yorktown Heights NY USA IBM Thomas J Watson Research Center Yorktown Heights NY US

An important challenge for the future growth of the internet is to design routers that can forward the exponentially increasing volume of traffic, and at the same time provide the service differentiation needed by new applications. In this paper, we describe the architecture, implementation, and initial experiences with a system designed to meet this challenge. This system, which we call a QoS capable switch-router (QSR), combines the salient features of switching and routing technologies to provide high throughput and support the different classes of service being defined by the IETF. It consists of a core (ATM) switch fabric connecting intelligent adapters, each capable of both routing and switching pockets. A control engine is responsible for routing, RSVP signalling, and resource management. We have built a prototype network of 3 systems connected to several UNIX hosts, and have conducted preliminary performance measurements on this network.

关键词： Routing Switches Web and internet services Throughput Asynchronous transfer mode Fabrics Joining processes Search engines Resource management Prototypes

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Comparison of two middleware data dissemination services in a wide-area distributed system

Comparison of two middleware data dissemination services in ...

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International conference on Distributed Computing systems

作者： G.R. Malan F. Jahanian P. Knoop Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The paper provides an experimental comparison of two middleware data dissemination services: a distributed object based service, and a message based service. The paper compares these two services in the context of a common application: a wide area network collaboratory, namely the Upper Atmospheric Research Collaboratory (UARC). UARC is an example of an application that reliably streams data from a set of suppliers to a set of receivers. This comparison highlights the tradeoffs between ease of implementation and performance for a data streaming middleware service. By relying on a rigid language primitive, namely remote method invocation, the object based dissemination service gave up the control over its transport policies. In contrast, the lower level socket based service was specifically constructed to provide a flexible interface to its applications. This flexibility allowed the middleware to better support data delivery to a heterogeneous set of receivers. This is important in a wide area distributed system where hosts are connected together over a broad spectrum of network links. The paper provides a concrete example of the effects of high level design choices in the implementation of a wide area distributed system's communication middleware.

关键词： Middleware Collaborative work Collaboration internet Application software Instruments Context-aware services Concrete Biomedical imaging Focusing

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The effectiveness of cell-level FEC for packet delivery in ATM networks

The effectiveness of cell-level FEC for packet delivery in A...

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conference on Local Computer networks (LCN)

作者： A. Guha Tai-Sheng Chang Storage Technology Corporation Louisville CO USA Network Systems Group Storage Technology Corporation Minneapolis MN USA

The authors examine the issue of how packet delivery can be made more reliable over ATM networks. While forward error correction (FEC) techniques have been proposed in the past by many researchers to address the data loss issues in ATM networks, the focus of the paper is on analyzing the cost-performance aspects of cell-level FEC for packet traffic. Specifically, they examine the tradeoff between the cost of increased bandwidth consumed by the FEC code versus the gain in packet error rate both through simulation and simple analytical models. The paper presents new analyses and results in two broad areas: i) the conditions under which FEC is effective in improving packer error rates, in terms of correlated cell loss levels for different packet sizes over different network extents, and ii) the cost-performance evaluation of using FEC in absolute terms that account for end-to-end delay, and the corresponding determination of the minimum physical network diameter over which FEC would be effective.

关键词： Intelligent networks Forward error correction Asynchronous transfer mode Switches Feedback Delay effects Telecommunication traffic Traffic control Virtual colonoscopy Error analysis

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A new method for analysing feedback-based protocols with applications to engineering Web traffic over the internet 97

A new method for analysing feedback-based protocols with app...

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Proceedings of the 1997 ACM SIGMETRICS international conference on Measurement and modeling of computer systems

作者： D. P. Heyman T. V. Lakshman Arnold L. Neidhardt AT&T Labs 101 Crawfords Corner Road Holmdel NJ Bell Labs 101 Crawfords Corner Road Holmdel NJ Bellcore 331 Newmans Springs Road Red Bank 07701 NJ

ISBN: (纸本)9780897919098

Most of the studies of feedback-based flow and congestion control consider only persistent sources which always have data to send. However, with the rapid growth of internet applications built on TCP/IP such as the World Wide Web and the standardization of traffic management schemes such as Available Bit Rate (ABR) in Asynchronous Transfer Mode (ATM) networks, it is essential to evaluate the performance of feedback-based protocols using traffic models which are specific to dominant applications. This paper presents a method for analysing feedback-based protocols with a Web-user-like input traffic where the source alternates between "transfer" periods followed by "think" periods. Our key results, which are presented for the TCP protocol, are:(1) The goodputs and the fraction of time that the system has some given number of transferring sources are insensitive to the distributions of transfer (file or page) sizes and think times except through the ratio of their means. Thus, apart from network round-trip times, only the ratio of average transfer sizes and think times of users need be known to size the network for achieving a specific quality of service.(2) The Engset model can be adapted to accurately compute goodputs for TCP and TCP over ATM, with different buffer management schemes. Though only these adaptations are given in the paper, the method based on the Engset model can be applied to analyze other feedback systems, such as ATM ABR, by finding a protocol specific adaptation. Hence, the method we develop is useful not only for analysing TCP using a source model significantly different from the commonly used persistent sources, but also can be useful for analysing other feedback schemes.(3) Comparisons of simulated TCP traffic to measured Ethernet traffic shows qualitatively similar autocorrelation when think times follow a Pareto distribution with infinite variance. Also, the simulated and measured traffic have long range dependence. In this sense our traffic mo

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A digital signal processor yields enhanced data/FAX pump

A digital signal processor yields enhanced data/FAX pump

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IEEE conference on Aerospace

作者： A. Chame Motorola Inc. Sunnyvale CA USA

The recent introduction of powerful special purpose semiconductor digital signal processing (DSP) circuits allows the implementation of complex and high performance communications functions. Specifically, the integration of such DSP circuits provides high speed communications capabilities to workstations and personal computers (PCs) for communication across the public switching telephone network (PSTN). The Motorola DSP56000 and DSP56300 family members of DSP circuits, designed as V.34 Plus data/V.17 fax/voice data pump modems, efficiently implement such functions. A data pump is a self-contained function block implemented with a combination of DSP circuitry and internal memory, that requires an analog front end and an external processor for control, but no additional user software programming is required. The data pump is responsible for the signal modulation and demodulation, coding, low level training, line equalization, echo canceling and the many other layer one (and part of layer two) functions such as those required by the V.34 Plus data modem and V.17 fax standards. By the simple addition of a DSP data/fax/voice pump, workstations and PCs can communicate with data resources such as electronic mail systems, bulletin boards, public data bases, internet Service Providers (ISPs), corporate data bases, distant local area networks (LANs) and other PCs. Workstations and PCs now not only have the ability to be linked via a high speed V.34 Plus telephone modem but also provide many additional functions such as a telephone dialer, a telephone answering machine, a hands-free speakerphone, and a facsimile machine amongst others. Further, users can implement a direct digital modem (DDM) efficiently connecting an Integrated Services Digital networks Services (ISDN) terminal adapter (TA) either to a far-end ISDN TA, or an analog modem which normally requires significant and complex circuitry. Similarly, the implementation of a "modem pool" is now implemented in a cost effe

关键词： Digital signal processors Digital signal processing Circuits Modems Personal communication networks Workstations internet telephony ISDN Costs Microcomputers

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