While today’s computer networks support only best-effort service, future packet-switching integrated-services networks will have to support real-time communication services that allow clients to transport information with performance guarantees expressed in terms of delay, delay jitter, throughput, and loss rate. An important issue in providing guaranteed performance service is the choice of the packet service discipline at switching nodes. In this paper, we survey several service disciplines that are proposed in the literature to provide per-connection end-to-end peqormance guarantees in packet-switching networks. We describe their mechanisms, their similarities and differences, and the performance guarantees they can provide. Various issues and tradeoffs in designing service disciplines for guaranteed performance service are discussed, and a general framework for studying and comparing these disciplines are presented. I.

To support the requirements for the transmission of continuous media, such as audio and video, multiservice packet switching networks must provide service guarantees to connections, including guarantees on throughput, network delays, and network delay variations. For the most demanding applications, the network must offer a service which can provide deterministic guarantees for the maximum delay ofpackets from all connections, referred to as bounded delay service. The admission control functions in a network with a bounded delay service must have available schedulability conditions that detect violations of delay guarantees in a network switch. In this study, exact schedulability conditions are presented for packet switches which transmit packets based on an Earliest-Deadline-First (EDF) or a Static-Priority (SP) algorithm. The schedulability conditions are given in terms of a general traffic model, making the conditions applicable to a large class of traffic specifications. A comparison of the new schedulability conditions with existing, less accurate, conditions show the e ciency gain obtained by using exact conditions. Examples are presented that show how the selection of a particular traffic specification and a schedulability condition impact the efficiency of a bounded delay service.

Variable bit-rate (VBR) compressed video traffic is expected to be a significant component of the traffic mix in integrated services networks. This traffic is hard to manage because it has strict delay and loss requirements while simultaneously exhibiting burstiness at multiple time scales. We show that burstiness over long time scales, in conjunction with resource reservation using one-shot traffic descriptors, can substantially degrade the loss rate, end-to-end delay, and statistical multiplexing gain of a connection. We use large-deviation theory to model the performance of multiple time-scale traffic and to motivate the design of renegotiated constant bit rate (RCBR) service. Sources using

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and tradeoffs in providing deterministic performance guarantees to video and use a set of 10 to 30 minute long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first conside...

Measurement-based admission control (MBAC) is an attractive mechanism to concurrently offer quality of service (QoS) to users, without requiring a priori traffic specification and on-line policing. However, several aspects of such a system need to be clearly understood in order to devise robust MBAC schemes, i.e., schemes that can match a given QoS target despite the inherent measurement uncertainty, and without the tuning of external system parameters. We study the impact of measurement uncertainty, flow arrival, departure dynamics, and of estimation memory on the performance of a generic MBAC system in a common analytical framework. We show that a certainty equivalence assumption, i.e., assuming that the measured parameters are the real ones, can grossly compromise the target performance of the system. We quantify the improvement in performance as a function of the length of the estimation window and an adjustment of the target QoS. We demonstrate the existence of a critical time scale over which the impact of admissin decisions persists. Our results yield new insights into the performance of MBAC schemes, and represent quantitative and qualitative guidelines for the design of robust schemes.

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and tradeoffs in providing deterministic performance guarantees to video and use a set of 10 to 90 minute long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first conside...

Current solutions to providing statistical performance guarantees to bursty traffic such as compressed video encounter several problems: 1) source traffic descriptors are often too simple to capture the burstiness and important time-correlations of VBR sources or too complex to be used for admission control algorithms; 2) stochastic descriptions of a source are inherently difficult for the network to enforce or police; 3) multiplexing inside the network's queues may change the stochastic properties of the source in an intractable way, precluding the provision of end-toend QoS guarantees to heterogeneous sources with different performance requirements. In this paper, we present a new approach to providing end-to-end statistical performance guarantees that overcomes these limitations. We term the approach Hybrid Bounding Interval Dependent (H-BIND) because it uses the Deterministic-BIND traffic model to capture the correlation structure and burstiness properties of a stream; but unlike a...

A non-work-conserving server is one that may be idle even when there are packets available to be sent. Since they do not provide the optimal average performance, non-work-conserving disciplines were seldom studied in the past. For the guaranteed performance service class in integrated services networks, the main performance index is the end-to-end delay bound, instead of the average delay. Providing end-to-end delay bounds in a networking environment is difficult. While bounding delay in any server requires a bound on the input traffic, complex interactions among traffic streams usually distort the traffic pattern so that traffic inside the network is different from the source traffic. Previous techniques of bounding end-to-end delay in a networking environment usually start from the source traffic characterizations and iteratively "push" the traffic characterizations through the network. This does not only require non trivial analysis, but also has several important limitations. In th...

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A key problem for modern network designers is to characterize /model the "bursty" traffic arising in broadband networks with a view on predicting and guaranteeing performance. In this paper we attempt to unify several approaches ranging from histogram/interval based methods to "frequency domain" approaches by further investigating the asymptotic behavior of a multiplexer carrying a large number of streams. This analysis reveals the salient traffic /performance relationships which should guide us in selecting successful methods for traffic management and network dimensioning. 1 Introduction Efficient methods for congestion control in high-speed communication networks will be based on reasonable characterizations for traffic flows and time scale decompositions of the network dynamics. With a view on resolving the question of admission control, including bandwidth allocation and routing, as well as other traffic management activities, researchers have developed several approaches to mod...