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.

We formulate and solve a problem of allocating resources among competing services differentiated by user traffic characteristics and maximum end-to-end delay. The solution leads to an alternative approach to service provisioning in an ATM network, in which the network offers directly for rent its bandwidth and buffers and users purchase freely resources to meet their desired quality. Users make their decisions based on their own traffic parameters and delay requirements and the network sets prices for those resources. The procedure is iterative in that the network periodically adjusts prices based on monitored user demand, and is decentralized in that only local information is needed for individual users to determine resource requests. We derive network's adjustment scheme and users' decision rule and establish their optimality. Since our approach does not require the network to know user traffic and delay parameters, it does not require traffic policing on the part of the network. 1 I...

It has been known for several years now that variable-bit-rate video sources are strongly auto-correlated. Recently, several studies have indicated that the resulting stochastic processes exhibit long-range dependence properties. This implies that large buffers at intermediate switching points may not provide adequate delay performance for such classes of traffic in Broadband packet-switched networks (such as ATM). In this paper, we study the effect of long-memory processes on queue length statistics of a single queue system through a controlled fractionally differenced ARIMA(1; d; 0) input process. This process has two parameters OE 1 (0 OE 1 1) and d (0 d ! 1=2) representing an auto-regressive component and a long-range dependent component, respectively. Results show that the queue length statistics studied (mean, variance and the 0:999 quantile) are proportional to e c1 OE 1 e c2 d ; where (c 1 ; c 2 ) are positive constants, and c 2 ? c 1 : The effect of the auto-correlation...

This paper presents the packet-pair rate-based feedback flow control scheme. This scheme is designed for networks where individual connections do not reserve bandwidth and for the available bitrate (best-effort) component of integrated networks. We assume a round-robin-like queue service discipline in the output queues of the network's switches, and propose a linear stochastic model for a single conversation in a network of such switches. These model motivates the Packet-Pair rate probing technique, which forms the basis for provably stable discrete and continuous time rate-based flow control schemes. We present a novel state estimation scheme based on fuzzy logic. We then address several practical concerns: dealing with system startup, retransmission and timeout strategy, and dynamic setpoint probing. We present a finite state machine as well as source code for a model implementation. The dynamics of a single source, the interactions of multiple sources, and the behavior of packet-pai...

We survey recent advances in theories and models for Internet Quality of Service (QoS). We start with the theory of network calculus, which lays the foundation for support of deterministic performance guarantees in networks, and illustrate its applications to integrated services, differentiated services, and streaming media playback delays. We also present mechanisms and architecture for scalable support of guaranteed services in the Internet, based on the concept of a stateless core. Methods for scalable control operations are also briefly discussed. We then turn our attention to statistical performance guarantees, and describe several new probabilistic results that can be used for a statistical dimensioning of differentiated services. Lastly, we review recent proposals and results in supporting performance guarantees in a best effort context. These include models for elastic throughput guarantees based on TCP performance modeling, techniques for some quality of service differentiation without access control, and methods that allow an application to control the performance it receives, in the absence of network support.

We propose a work-conserving scheduling mechanism for providing deterministic performance guarantees in ATM networks. The most attractive feature of the proposed mechanism, which we call Carry-Over Round Robin (CORR), is its simplicity. It is an extension of weighted round robin scheduling. We have derived closed form bounds for worst case end-to-end delay when CORR is used in conjunction with composite leaky bucket, moving window and jumping window regulators. We have also analyzed the fairness properties of CORR scheduling. Our results show that albeit its simplicity, CORR is very competitive with some of the more complex scheduling disciplines such as Packet-by-Packet Generalized Processor Sharing and Self Clocked Fair Queuing, both in terms of delay performance and fairness. Besides the scheduling mechanism and its analysis, one of the important contributions of this study is the characterization of traffic envelopes defined by composite shapers consisting of multiple lea...

This paper describes the design and analysis of the scheduling algorithm for EC-MAC (energy conserving medium access control) [1], a low-power medium access control (MAC) protocol for wireless and mobile ATM networks. Based on the structure of EC-MAC and the characteristics of wireless channel, we propose a new algorithm which can deal with the bursty errors and the location-dependent errors. Most scheduling algorithms proposed for either wired or wireless networks were analyzed with homogeneous traffic or multimedia services with simplified traffic models. We analyze our scheduling algorithm with more realistic multimedia traffic models. One of the key goals of the scheduling algorithm is simplicity and fast implementation. Unlike the time-stamp based algorithm, our algorithm does not need to sort the virtual time, thus reducing the complexity of the algorithm significantly.

This paper addresses the problem of finding the worst case end-toend delay and buffer occupancy bounds in networks of rate-controlled, non-work conserving servers. The calculations are based on a simple fluid model, but care is taken so that the computed delay and buffer occupancy values are upper bounds on actual values. A simple algorithm is presented to perform these calculations in linear time. Simulation results compare the computed worst case delays with the actual delays obtained on some simple network topologies. The algorithm is found to predict node delays well for bursty input traffic, but poorly for smooth input traffic. Buffer requirements are predicted well in both cases. ################## A. Banerjea was supported by the National Science Foundation and the Defense Advanced Research Projects Agency (DARPA) under Cooperative Agreement NCR-8919038 with the Corporation for National Research Initiatives, by AT&T Bell Laboratories, Hitachi, Ltd., Hitachi America, Ltd., the U...

This paper addresses the problem of finding the worst case end-to-end delay and buffer occupancy bounds in ATM networks with rate-controlled, non-work conserving servers. A theoretical framework is constructed to analyze such servers in isolation and in tandem. The analysis is based on a simple fluid model, but care is taken so that the computed delay and buffer occupancy values are upper bounds on actual values. A simple algorithm is presented to perform these calculations in linear time. Simulation results compare the computed worst case delays with the actual delays obtained on some simple network topologies. The algorithm is found to predict node delays well for bursty input traffic, but poorly for smooth input traffic. Buffer requirements are predicted well in both cases. 1. Introduction Recent work has shown that framed, non-workconserving servers can provide end-to-end delay bounds to users who need strict guarantees on network performance [15]. By framed we mean that the serv...

: Distributed multimedia (MM) applications are very sensitive to the quality of service (QoS) provided by their computing and communication environment. This paper surveys the QoS issues behind distributed MM applications. MM applications characteristics and requirements are identified; QoS notions are defined. The role of all system components, namely transport protocols, networks, operating systems, file servers, multimedia databases, and user interfaces, in the provisioning of QoS is described. The need for QoS management to support distributed MM applications is motivated. The different QoS management functions are defined and examples of realizations are presented. Finally some representative QoS architectures are presented, their limitations are identified, and the requirements of an "ideal QoS architecture" are presented. Keywords: distributed multimedia applications, quality of service, quality of service management, quality of service architectures 1 Introduction Currently ...