This paper is principally concerned with resource allocation for connections tolerating statistical qualityof service #QoS# guarantees in a public wide-area ATM network. Our aim is to sketch a framework, based on e#ective bandwidths, for call admission schemes that are sensitivetoindividual QoS requirements and account for statistical multiplexing. We begin by describing recent results approximating the e#ective bandwidth required by heterogeneous streams sharing bu#ered links, including results for the packetized generalized processor sharing service discipline. Extensions to networks follow via the concept of decoupling bandwidths - motivated by a study of the input-output properties of queues. Based on these results we claim that networks with su#cient routing diversity will inherently satisfy nodal decoupling. We then discuss on-line methods for estimating the e#ective bandwidth of a connection. Using this type of tra#c monitoring we propose an approach to usage parameter ...

We consider large buffer asymptotics for feed-forward networks of discrete-time queues with deterministic service rate shared by multiple classes of streams subject to work conserving service policies. First we review the concept of effective bandwidths for traffic streams sharing a common buffer subject to subject to tail constraints on the workload distribution. Next, we obtain the effective bandwidth of the departure process from such a queue, proving that in fact the effective bandwidth of the output is at worst equal to that of the input, and depending on the service rate, strictly less than that of the input. We then define the notion of a decoupling bandwidth and the associated constraints, guaranteeing that asymptotics within the network are decoupled. These results provide a framework for call admission schemes which are sensitive to constraints on the tail distribution of the workload or approximate cell loss probabilities. Our results require relatively weak assumptions on both the traffic streams and service policies. We consider the problem of “optimal ” traffic shaping (via buffering) subject to a loss constraint. Finally, we discuss our results in the context of resource management for ATM networks. 1

AbstractÐWith effective packet-scheduling mechanisms, modern integrated networks can support the diverse quality-of-service requirements of emerging applications. However, arbitrating between a large number of small packets on a high-speed link requires an efficient hardware implementation of a priority queue. To highlight the challenges of building scalable priority queue architectures, this paper includes a detailed comparison of four existing approaches: a binary tree of comparators, priority encoder with multiple first-infirst-out lists, shift register, and systolic array. Based on these comparison results, we propose two new architectures that scale to the large number of packets (N) and large number of priority levels (P) necessary in modern switch designs. The first architecture combines the faster clock speed of a systolic array with the lower memory requirements of a shift register, resulting in a hybrid design; a tunable parameter allows switch designers to carefully balance the trade-off between bus loading and chip area. We then extend this architecture to serve multiple output ports in a shared-memory switch. This significantly decreases complexity over the traditional approach of dedicating a separate priority queue to each outgoing link. Using the Verilog hardware description language and the Epoch silicon compiler, we have designed and simulated these two new architectures, as well as the four existing approaches. The simulation experiments compare the designs across a range of priority queue sizes and performance metrics, including enqueue/dequeue speed, chip area, and number of transistors. Index TermsÐPriority queue, packet switch, link scheduling, VLSI, real-time communications. 1

Quality-of-service (QoS) routing can satisfy application performance requirements and opti- mize network resource usage by selecting paths based on connection traffic parameters and link load information. However, effective path-selection schemes require the distribution of link-state information, which can cause a significant burden on the bandwidth and processing resources in the network. Wc investigate the fundamental tension between network overheads and the quality of routing decisions in the context of source-directed QoS routing algorithms. In contrast to previous performance studies that compare different routing algorithms under specific network configurations, wc characterize how the performance and overheads of QoS routing relate to the link-state update policies, as a function of the underlying traffic load, network topology, and link-cost metrics. Wc explore the interplay between stale link-state information and random fluctuations in traffic load through a broad set of simulation experiments on a paramctcrizcd model of QoS routing. These results suggest ways to tune the frequency of link-state update messages and the link-cost functions to strike a careful balance between high accuracy and low complexity.

The purpose of call admission control in Integrated Services Networks is to offer a guarantee that Quality of Service (QoS) bounds are not violated due to the admission of new calls into the network. This is typically accomplished using the declared worst-case traffic descriptors for incoming calls, a solution which results in poor bandwidth utilization. A measurement-based admission scheme is an appealing alternative: not only does it offer adaptivity to changing traffic conditions, it also allows statistical multiplexing gains to be exploited. In this paper, we examine the problem of determining which traffic characterization a measurement-based admission control algorithm should require of sources requesting access. Building on the work of [1], we also propose an adaptive measurement-based admission control algorithm that simplifies the estimation process. We test the new algorithm under different traffic scenarios and show that it can achieve a high level of utilization without vio...

This paper presents quality of service (QoS) metrics for continuity and synchronization specifications in continuous media (CM). Proposed metrics specify continuity and synchronization, with tolerable limits on average and bursty defaults from perfect continuity, timing and synchronization constraints. These metrics can be used in a distributed environment for resource allocation. Continuity specification of a CM stream consists of its sequencing, display rate and drift profiles. The sequencing profile of a CM stream consists of tolerable aggregate and consecutive frame miss ratios. Rate profiles specify the average rendition rate and its variation. Given a rate profile, the ideal time unit for frame display is determined as an offset from the beginning of the stream. Drift profile specifies the average and bursty deviation of schedules for frames from such fixed points in time. Synchronization requirements of a collection of CM streams are specified by mixing, rate and synchronization...

Increases in processor speeds and the availability of audio and video devices for personal computers have encouraged the development of interactive multimedia applications for teleconferencing and digital audio/video presentation among others. These applications have stringent timing constraints, and traditional operating systems are not well suited to satisfying such constraints. On the other hand, hard real-time systems that can meet these constraints are typically static and inflexible. This dissertation

This paper deals with QoS management for multimedia applications by taking remote access to multimedia database as a case study. The example application is introduced and the entities involved in QoS provision are identified. QoS management activities are defined and a basic QoS management architecture for multimedia applications is presented. A general framework for QoS (re)negotiation is defined and an instantiation of this framework in the context of the example application is presented.

Recent network denial-of-service attacks have brought about awareness of the vulnerability of increasingly important network services. While denial of service is not a new problem, and some of the network aspects of denial of service have been addressed, there is currently no unifying definition of what constitutes network denial of service. The goal of this paper is to propose a definition of network denial of service, and to demonstrate a simple network model that can be used to construct a taxonomy of network denial-of-service attacks. This taxonomy provides a means of categorizing existing attacks and demonstrating how future attacks might be constructed, as well as providing a simple and precise way of describing attacks.

The purpose of call admission control in Integrated Services Networks is to offer a guarantee that Quality of Service (QoS) bounds are not violated due to the admission of new calls into the network. This is typically accomplished using the declared worst-case traffic descriptors for incoming calls, a solution which results in poor bandwidth utilization. A measurement-based admission scheme is an appealing alternative: not only does it offer adaptivity to changing traffic conditions, it also allows statistical multiplexing gains to be exploited. In this paper, we examine the problem of determining which traffic characterization a measurement-based admission control algorithm should require of sources requesting access. Building on the work of Jamin et al. (1995), we also propose an adaptive measurement-based admission control algorithm that simplifies the estimation process, and show that it can achieve a high level of utilization without violating its delay-based QoS guarantees.