Many designs for integrated service networks offer a bounded delay packet delivery service to support real-time applications. To provide bounded delay service, networks must use admission control to regulate their load. Previous work on admission control mainly focused on algorithms that compute the worst case theoretical queueing delay to guarantee an absolute delay bound for all packets. In this paper we describe a measurement-based admission control algorithm for predictive service, which allows occasional delay violations. We have tested our algorithm through simulations on a wide variety of network topologies and driven with various source models, including some that exhibit long-range dependence, both in themselves and in their aggregation. Our simulation results suggest that, at least for the scenarios studied here, the measurement-based approach combined with the relaxed service commitment of predictive service enables us to achieve a high

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

We describe how a packet network with a simple pricing mechanism and no connection acceptance control may be used to carry a telephony-like service with low packet loss and some call blocking. The packet network uses packet marking to indicate congestion and endsystems are charged a fixed small amount per mark received. The end-systems are thus provided with the information and the incentive to use the packet network efficiently. We demonstrate that algorithms embedded in the end-systems are able to synthesize a telephony-like service by blocking calls at times when the load in the packet network is high. 1.

In networks that support Quality of Service (QoS), an admission control algorithm determines whether or not a new traffic flow can be admitted to the network such that all users will receive their required performance. Such an algorithm is a key component of future multi-service networks as it determines the extent to which network resources are utilized and whether the promised QoS parameters are actually delivered. Our goals in this paper are threefold. First, we describe and classify a broad set of proposed admission control algorithms. Second, we evaluate the accuracy of these algorithms via experiments using both on-off sources and long traces of compressed video; we compare the admissible regions and QoS parameters predicted by our implementations of the algorithms with those obtained from trace-driven simulations. Finally, we identify the key aspects of an admission control algorithm necessary for achieving a high degree of accuracy and hence a high statistical multiplexing gain...

This paper describes a framework for admission control for a packet-based network where the decisions are taken by edge devices or end-systems, rather than resources within the network. The decisions are based on the results of probe packets that the end-systems send through the network, and require only that resources apply a mark to packets in a way that is load dependent. One application example is the Internet, where marking information is fed back via an ECN bit, and we show howthis approach allows a rich QoS framework for ows or streams. Our approach allows networks to be explicitly analysed, and consequently engineered.

Relaxed real-time services that do not provide guaranteed loss rates or delay bounds are of considerable interest in the Internet, since these services can achieve higher utilization than hard real-time services while still providing adequate service to adaptive real-time applications. Achieving this higher level of utilization depends on an admission control algorithm that does not rely on worst-case bounds to guide its admission decisions. Measurement-based admission control is one such approach, and several measurement-based admission control algorithms have been proposed in the literature. In this paper, we use simulation to compare the performance of several of these algorithms. We find that all of them achieve nearly the same utilization for a given packet loss rate, and that none of them are capable of accurately meeting loss targets. I. INTRODUCTION In an effort to better support applications with real-time constraints, several new per-flow packet delivery services have been ...

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.

... In this paper we continue the development of a modelling approach which attempts to integrate these several time-scales, and illustrate its application to the analysis of a family of simple and robust measurement-based admission controls. A subsidiary aim of the paper is to shed light on the relationship between the admission control proposed for ATM networks by Gibbens et al [9] and that proposed for controlled-load Internet services by Floyd [7]. We shall see that their common origin in Chernoff bounds allows the definition of a simple and general family of admission controls, capable of tailoring for several implementation scenarios.

This paper proposes a controlled-load service that provides a network state with bounded and well known worst-case behavior. The service is primarily developed for real-time applications. The full system for achieving quality of service to the application consists of an admission control combined with forward-error correction. The admission control is used to limit the packet-loss probability to a known value; the errorcontrol coding (i.e., FEC) is then used to raise the quality above the level enforced by the admission control. The basic idea for the admission control is that a host must probe the path to the receiver before sending actual data. It accepts the session if the probe is received with no or at most a moderate amount of loss. The performance evaluation shows clearly that the proposed scheme avoids network congestion and high packet losses even over short time scales.

The goal of admission control is to support the quality-of-service demands of real-time applications via resource reservation. In this paper, we introduce a new approach to measurement-based admission control for multiclass networks with link sharing. We employ adaptive and measurement-based maximal rate envelopes of the aggregate traffic flow to provide a general and accurate traffic characterization that captures its temporal correlation as well as the available statistical multiplexing gain. In estimating applications' future performance, we introduce the notion of a schedulability confidence level which describes the uncertainty of the measurement-based "prediction" and reflects temporal variations in the measured envelope. We then devise techniques to control loss probability for a buffered multiplexer servicing heterogeneous and bursty traffic flows, even in the regime of a moderate number of traffic flows, which is important in link-sharing environments. Finally, we have developed an implementation of the scheme on a prototype router and performed a testbed measurement study, which together with extensive trace-driven simulations illustrates the effectiveness of the approach in practical scenarios.