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.

One of the most interesting improvements of the Internet today is the provisioning of services for interactive audio--visual applications. Such applications have quality requirements which place limits on both transfer delays and information losses. Our goal is to support interactive video with only small modifications to network routers and control systems. The approach we favor is to ensure the quality for a session by forward--error correction. The code strength is dynamically tuned to meet a user's quality expectation, given the experienced loss process of the transfer. To make the tuning feasible, the network state must be predictable. We accomplish this by regulation of the load through sender--based admission control. It uses end--to--end probes of the network state and a self--imposed blocking if then sender determines that a sensible transfer cannot be made. The paper outlines this procedure along with a review of source coding considerations and a description of tunable error...

Abstract. A resource reservation scheme is an important mechanism of providing guaranteed QoS to applications. Today the only protocol that is standardized by IETF is the resource reservation protocol RSVP. Development of the next generation of signaling protocols is still open for research and development. We now propose SOS – a simple signaling protocol for guaranteed service connections. It overcomes poor scalability of RSVP and is simpler than existing proposals: Our protocol does not require per-flow soft states in core routers; it is robust and can handle losses of all types of signaling messages. Simple operations in the routers allow processing of 700 thousand messages per second. 1

Much effort today in the Internet research community is aimed at providing network services for applications that were not under consideration when the Internet was originally designed. Nowadays the network has to support real-time communication services that allow clients to transport information with expectations on network performance in terms of loss rate, maximum end-toend delay, and maximum delay jitter. Today there exist two quality of service (QoS) architecture for the Internet: The integrated services, which is usually referred to as intserv, and the differentiated services referred to as diffserv. Although the intserv clearly defines the quality levels for each of its three service classes, the limited scalability of this QoS architecture is a continuous topic for discussion among the researchers. The analysis of the tradeoffs of the two QoS architectures motivated us to design a new QoS architecture which will take the strength of the existing approaches and will combine them in a simpler, efficient and more scalable manner.

Abstract. The support of real-time traffic in class-based IP networks requires reservation of resources, accompanied by admission control in order to guarantee that newly admitted real-time traffic flows do not cause any violation to the Quality of Service (QoS) perceived by the already established ones. In this paper we highlight certain issues with respect to bandwidth allocation and admission control for supporting real-time traffic in class-based IP networks. We investigate the implications of topological placement of both bandwidth allocation and admission control schemes. We show that their performance depends highly on the location of the employed procedures with respect to the end-users and the various network boundaries. We conclude that the strategies for applying these schemes should be location-aware, because their performance at different points in a class-based IP network can be different and can deviate from the expected performance. Through simulations we also provide a quantitative view of these deviations. 1

Resource reservation and QoS negotiation is a common way to guarantee timely progress of programs in distributed multimedia systems. For this, determining the available resource capacity, resource budget, is important. The resource budget depends on resource characteristics (e.g., processor, memory, disk, and network bandwidth)and scheduling algorithms. This paper provides an improved processor budget for the fixed-priority scheduling algorithm, which is most common in commercial real-time operating systems. The improvement is possible by noting that, in multimedia systems, there is a prefixed set of task periods for the finite set of QoS options and parameters. Our approach explicitly takes these periods into account and calculates the tight bound of the processor budget using the linear programming technique. This bound significantly improves Liu and Layland bound [23] and also it is proved to be better than any other bounds in the literature. We also show how this bound is effectively used for resource reservation and QoS re-negotiation for adapting to dynamic workload.

The bandwidth reservation for multimedia traffic poses technical challenges due to bursty and delay sensitive nature of applications. The objectives of bandwidth reservation schemes are: optimize network utilization, minimize the packet losses and delays. The growth of multimedia services on Internet and the possible discovery of programmable networks has made us to investigate new techniques for resolving bandwidth issues in multimedia communication. Mobile agent technology seems to be the promising solution for network management and QoS control. In this paper, we consider joint problems of adaptive bandwidth reservation and link rearrangement (rerouting) for multimedia traffic under the event of congestion/failures of link, and propose a mobile agent based approach to achieve these objectives. The scheme is simulated using a multimedia traffic model. Simulation results show that the use of agents increase the network utilization, acceptance ratio of applications, flexibility and efficiency of bandwidth reservation. The flexibility in using agent technology is that the policies can be changed and implemented easily by encoding in the agents. 1

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