This paper presents a control-theoretic approach to reactive flow control in networks that do not reserve bandwidth. We assume a round-robin-like queue service discipline in the output queues of the network’s switches, and propose deterministic and stochastic models for a single conversation in a network of such switches. These models motivate the Packet-Pair rate probing technique, and a provably stable rate-based flow control scheme. A Kalman state estimator is derived from discrete-time state space analysis, but there are difficulties in using the estimator in practice. These difficulties are overcome by a novel estimation scheme based on fuzzy logic. We then present a technique to extract and use additional information horn the system to develop a continuous-time system model. This is used to design a wuisnt of the control law that is also provably stable, and, in addition, takes control action as rapidly as possible. Finally, practical issues such as correcting parameter drift and cmmlination with window flow control are described.

Can end-to-end communication performance be guaranteed by a packet-switching internetwork? This paper addresses the question by examining the feasibility of extending to an internetwork the Tenet approach to real-time communication service design. The conditions to be satisfied by an internetwork so that the approach can be extended to it are investigated. These include conditions for the scheduling discipline to be used in the nodes of the internetwork. The original Tenet approach to real-time communication applies to a network consisting of hosts, homogeneous nodes (or switches), and physical links connecting nodes and hosts in an arbitrary topology. The nodes are store-and-forward, and are scheduled by a multi-class version of the Earliest Due Date deadline-based policy. The discussion presented in this paper results in extendibility conditions that are quite broad; hence, the Tenet approach may be used to establish and run real-time channels in a vast class of internetworks. A case...

This dissertation considers various problems associated with the scheduling and network I/O organisation found in conventional operating systems for effective support for multimedia applications which require Quality of Service. A solution for these problems is proposed in a micro-kernel structure. The pivotal features of the proposed design are that the processing of device interrupts is performed by user-space processes which are scheduled by the system like any other, that events are used for both inter- and intra- process synchronisation, and the use of a specially developed high performance I/O buffer management system. An evaluation of an experimental implementation is included. In addition to solving the scheduling and networking problems addressed, the prototype is shown to out-perform the Wanda system (a locally developed micro-kernel) on the same platform. This dissertation concludes that it is possible to construct an operating system where the kernel provides only the fu...

Integrated-services networks will provide the communication infrastructure in the future. Unlike traditional communication networks, which are designed to offer a single type of service, integrated-services networks will offer multiple services, including data, voice, video, and others. Supporting applications with diverse traffic characteristics and performance objectives requires the offered services to be both flexible and guaranteed. To be flexible, integrated-services networks will use packet-switching technology. To provide performance guarantees in terms of throughput, delay, delay jitter, and loss rate, a proactive network control approach is needed. One of the most important components in this architecture is the service discipline at the switching nodes...

this document are those of the author, and should not be interpreted as representing official policies, either expressed or implied, of the U.S. government or any of the sponsoring organizations. The author is grateful to the members of the Tenet Group for being intelligent and creative sounding boards in several discussions of these topics. He is particularly indebted to Amit Gupta, who provided many suggestions and substantially simplified the formulation of the delay bound computation (inequality (1)), and to Eberhard Mueller-Menrad, who discovered several bugs in an earlier version of Tables 5.1 and 5.2. He is also thankful to Ellen Boyle for her invaluable help with the preparation of the manuscript. References

An architecture for integrating the Virtual Path service into the network management system of future broadband networks is presented. Complete definitions and behavioral descriptions of Managed Object Classes are given. An experimental platform on top of the XUNET III ATM network provides the proof of concept. The Xunet manager is equipped with the necessary monitoring tools for evaluating the performance of the network and controls for changing the parameters of the VP connection services. Performance data from Xunet is presented to highlight the issues underlying the fundamentals of the operation of the VP management model such as the trade-off between throughput and call processing load.

The Real-time Message Transport Protocol (RMTP) and the RealTime Internetwork Protocol (RTIP) are the transport and network layer data delivery protocols in the Tenet Protocol Suite. We implemented the protocols in Ultrix on the DECstation 5000 workstations and in HP/UX on the HP 9000/7000 workstations. A preliminary measurement study has been conducted to evaluate the performance of the prototype implementation. Some of the results are: the throughput obtained by using RMTP/RTIP is comparable to that obtained by using raw IP; the rate control mechanism in RMTP/RTIP effectively enforces the traffic specification of communication clients; the scheduling mechanism in RTIP protects the real-time channel so that the performance of a real-time channel is not affected by the presence of IP traffic or other real-time channels in the network. 1 Introduction There is an increasing demand to support real-time applications such as video conferencing, scientific visualization and medical imaging ...

ATM networks will carry a wide variety of data over the same packet switching network. A majority of this traffic is expected to be real-time video generated by video on demand, video conferencing systems, etc. We study the characteristics of video data compressed using standard coding algorithms namely, JPEG, MPEG and also popular ones such as the video conferencing software NV. A wide range of video sources from movies to a class lecture were analyzed. Most of the traces were longer than an hour. The bit rate of the traces has been characterized using the leaky bucket model. We also show a method of choosing appropriate leaky bucket parameters. Burstiness function is used to characterize the burstiness of the video traffic at different time scales. Our studies indicate that JPEG compressed has very little short term burstiness. MPEG and NV traffic shows high burstiness over small time scales. JPEG and MPEG video exhibit burstiness over long time scales, whereas NV shows no burstiness...

Our prototype of a fully-functional Asynchronous Transfer Mode #ATM# switch validates the design of a 128 Gb#s optoelectronic ATM switch. Optoelectronics, rather than all optical componets, are used to simutaneously address all of the speci#c requirements mandated by the ATM protocol. In this paper, we present the Illinois Pulsar-based Optical Interconnect #iPOINT# testbed, and present our results obtained for the prototype switchinaworking environment consisting of an optical network of Sun SPARCStations and other local and wide-area ATM switches.

An important problem with cell-switched technologies such as Asynchronous Transfer Mode (ATM) is the provision of customized multiplexing behavior to applications. This customization takes the form of setting up processes in the network and end-points to meet application "Quality of Service" (QoS) requirements. The proposed thesis work examines the necessary components of a software architecture to provide QoS in the end-points of a cell-switched network. An architecture has been developed, and the thesis work will refine it using a "driving" application of the full-feedback teleoperation of a robotics system. Preliminary experimental results indicate that such teleoperation is possible using generalpurpose workstations and a lightly-loaded ATM link. An important result of the experimental portion of the thesis work will be a study of the domain of applicability for various resource management techniques. Contents 1 Introduction 4 1.1 Problem Description : : : : : : : : : : : : : :...