Next-generation distributed systems will support corLtLzLzLous medLa (digztal audio and video) in the same framework as other data. Many applications that use continuous media need guaran-teed end-to-end performance (bounds on throughput and delay). To reliably support these requirements, system components such as CPU schedulers, networks, and file systems must offer performance guarantees. A rnetasclzedtder coordinates these components, negotiating end-to-end guarantees on behalf of clients. The CM-resource model, described in this paper, provides a basis for such a metascheduler. It defines a workload parameterizatlon, an abstract interface to resources, and an algorithm for reserving multiple resources. The model uses an economic approach to dividing end-to-end delay, and it allows system components to “work ahead,” improving the performance of nonreal-time workload.

This paper presents a personal view of work to date on effective bandwidths, emphasising the unifying role of the concept: as a summary of the statistical characteristics of sources over different time and space scales; in bounds, limits and approximations for various models of multiplexing under quality of service constraints; and as the basis for simple and robust tariffing and connection acceptance control mechanisms for poorly characterized traffic. The framework assumes only stationarity of sources, and illustrative examples include periodic streams, fractional Brownian input, policed and shaped sources, and deterministic multiplexing.

We consider packet routing when packets are injected continuously into a network. We develop an adversarial theory of queuing aimed at addressing some of the restrictions inherent in probabilistic analysis and queuing theory based on time-invariant stochastic generation. We examine the stability of queuing networks and policies when the arrival process is adversarial, and provide some preliminary results in this direction. Our approach sheds light on various queuing policies in simple networks, and paves the way for a systematic study of queuing with few or no probabilistic assumptions.

This paper describes methods of computing usage charges from simple measurements and relating these to bounds on the effective bandwidth. Thus we show that charging for usage on the basis of effective bandwidths can be well-approximated by charges based on simple measurements. Charging and pricing are essential requirements in the operation of a communication network. They are needed not only to recover costs and make a profit. Even if a generous operator is willing to offer a network for free, there are still compelling reasons to charges for services in order to exercise control. The congestion that has plagued the Internet because it lacks any mechanism for charging and pricing highlights the fact that without charges it is difficult to control congestion or divide network resources amongst users in a workable and stable way. Subject classifications: Communications: measurement-based charging. Of course there are many considerations that influence the prices at which an operator will choose to sell network services. Marketing and regulation are certainly important, but these considerations are not unique to the operation of a communications network. Special considerations do, however, arise from the fact that a broadband communications network is intended simultaneously to carry a wide variety of traffic types. Our conception of a broadband network is that of a collection of resources (links, buffers, switches, etc.) which can be used to provide a wide variety of communications services. These services are distinguished by traffic contracts, which specify parameters to which the traffic must adhere (a maximum peak rate, for example), and the quality of service which the network undertakes to guarantee (typically, cell loss or delay). These concepts are accepted as ...

In this paper, we propose and analyze a methodology for providing absolute differentiated services for real-time applications in networks that use static-priority schedulers. We extend previous work on worst-case delay analysis and develop a method that can be used to derive delay bounds without specific information on flow population. With this new method, we are able to successfully employ a utilization-based admission control approach for flow admission. This approach does not require explicit delay computation at admission time and hence is scalable to large systems. We assume the underlying network to use static-priority schedulers. We design and analyze several priority assignment algorithms, and investigate their ability to achieve higher utilization bounds. Traditionally, schedulers in differentiated services networks assign priorities on a classby -class basis, with the same priority for each class on each router. In this paper, we show that relaxing this requirement, that is, allowing different routers to assign different priorities to classes, achieves significantly higher utilization bounds.

Abstract—This paper presents the general approach, design, implementation, and evaluation of NetCamo, which is a system to prevent traffic analysis in systems with real-time requirements. Integrated support for both security and real-time is becoming necessary for computer networks that support mission critical applications. This study focuses on how to integrate both the prevention of traffic analysis and guarantees for worst-case delays in an internetwork. We propose and analyze techniques that efficiently camouflage network traffic and correctly plan and schedule the transmission of payload traffic so that both security and real-time requirements are met. The performance evaluation shows that our Net-Camo system is effective and efficient. By using the error between target camouflaged traffic and the observed (camouflaged) traffic as metric to measure the quality of the camouflaging, we show that NetCamo achieves very high levels of camouflaging without compromising real-time requirements. Index Terms—Anonymous communication, network security, QoS, traffic padding, traffic rerouting. I.

We present an analytical method to evaluate embedded network packet processor architectures, and to explore their design space. Our approach is in contrast to those based on simulation, which tend to be infeasible when the design space is very large. We illustrate the feasibility of our method using a detailed case study.

Our work is motivated by the desire to design packet switches with large aggregate capacity and fast line rates. In this paper, we consider building a packet switch from multiple lower speed packet switches operating independently and in parallel. In particular, we consider a (perhaps obvious) parallel packet switch (PPS) architecture in which arriving traffic is demultiplexed over identical lower speed packet switches, switched to the correct output port, then recombined (multiplexed) before departing from the system. Essentially, the packet switch performs packet-by-packet load balancing, or inverse multiplexing, over multiple independent packet switches. Each lower speed packet switch operates at a fraction of the line rate . For example, each packet switch can operate at rate . It is a goal of our work that all memory buffers in the PPS run slower than the line rate. Ideally, a PPS would share the benefits of an output-queued switch, i.e., the delay of individual packets could be precisely controlled, allowing the provision of guaranteed qualities of service. In this

We describe an approach to explore the design space of architectures of packet processing devices on the system level. Our method is specific to the application domain of network packet processors and is based on (1) models for packet processing tasks, a specification of the workload generated by traffic flows, and a description of the feasible space of architectures involving computation and communication resources, (2) a measure to characterize the performance of network processors under different usage scenarios, (3) a new method to estimate end-to-end packet delays and queuing memory, taking task scheduling policies and bus arbitration schemes into account, and (4) an evolutionary algorithm for multi-objective design space exploration. Our method is analytical and is based on a high level of abstraction, where the goal is to quickly identify interesting architectures, which may then be subjected to a more detailed evaluation, e.g. using simulation. The feasibility of our approach is shown by a detailed case study, where the final output is three candidate architectures, representing different cost versus performance tradeoffs.

In this paper a practically efficient QoS routing method is presented, which provides a solution to the delay constrained least cost routing problem. The algorithm uses the concept of aggregated costs and provides an efficient method to find the optimal multiplier based on Lagrange relaxation. This method is proven to be polynomial and it is also efficient in practice. The benefit of this method is that it also gives a lower bound on the theoretical optimal solution along with the result. The difference between the lower bound and the cost of the found path is very small proving the good quality of the result. Moreover, by further relaxing the optimality of paths, an easy way is provided to control the trade-off between the running time of the algorithm and the quality of the found paths. We present a comprehensive numerical evaluation of the algorithm, by comparing it to a wide range of QoS routing algorithms proposed in the literature. It is shown that the performance of the proposed polynomial time algorithm is close to the optimal solution computed by an exponential algorithm. Keywords---QoS routing, delay, optimization, Lagrange relaxation I.