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.

In this paper, we develop a general model, called Latency-Rate servers (LR-servers), for the analysis of traffic scheduling algorithms in broadband packet networks. The behavior of an LR scheduler is determined by two parameters --- the latency and the allocated rate. We show that several well-known scheduling algorithms, such as Weighted Fair Queueing, VirtualClock, Self-Clocked Fair Queueing, Weighted Round Robin, and Deficit Round Robin, belong to the class of LR-servers. We derive tight upper bounds on the end-to-end delay, internal burstiness, and buffer requirements of individual sessions in an arbitrary network of LR- servers in terms of the latencies of the individual schedulers in the network, when the session traffic is shaped by a leaky bucket. Thus, the theory of LR-servers enables computation of tight upper-bounds on end-to-end delay and buffer requirements in a heterogeneous network, where individual servers may support different scheduling architectures, and under diff...

The dramatically increased bandwidths and processing capabilities of future high-speed networks make possible many distributed real-time applications, such as sensor-based applications and multimedia services. Since these applications will have traffic characteristics and performance requirements that differ dramatically from those of current data-oriented applications, new communication network architectures and protocols will be required. In this paper we discuss the performance requirements and traffic characteristics of various real-time applications, survey recent developments in the areas of network architecture and protocols for supporting real-time services, and develop frameworks in which these, and future, research efforts can be considered.

We define a class of Guaranteed Rate (GR) scheduling algorithms. The GR class includes Virtual Clock, Packet-by-Packet Generalized Processor Sharing and Self Clocked Fair Queuing. For networks that employ scheduling algorithms belonging to GR, we present a method for determining an upper bound on end-to-end delay. The method facilitates determination of end-to-end delay bounds for a variety of sources. We illustrate the method by determining end-to-end delay bounds for sources conforming to Leaky Bucket and Exponentially Bounded Burstiness.

In this paper, we define a class of generalized Guaranteed Rate (GR) scheduling algorithms that includes algorithms which allocate variable rate to packets of a flow. We define work-conserving generalized Virtual Clock, Packet-by-Packet Generalized Processor Sharing, and Self-Clocked Fair Queuing scheduling algorithms that can allocate variable rate to the packets of a flow. We also define scheduling algorithms suitable for servers where packet fragmentation may occur. We demonstrate that if a class of rate controllers is employed for a flow in conjunction with any scheduling algorithm in GR, then the resulting non-work-conserving algorithm also belongs to GR. This leads to the definition of several non-work-conserving algorithms. We then present a method for deriving the delay guarantee of a network of servers when: 1) different rates are allocated to packets of a flow at different servers along the path and the bottleneck server for each packet may be different, and 2) packet fragmentation and/or reassembly may occur. This delay guarantee enables a network to provide various service guarantees to flows conforming to any specification. We illustrate this by utilizing delay guarantee to derive delay bounds for flows conforming to Leaky Bucket, Exponentially Bounded Burstiness, and Flow Specification. Our method for determining these bounds is valid in internetworks and leads to tighter results.

this paper we present a class of scheduling algorithms --- called Rate-Proportional Servers (RPS) --- with bounds on end-to-end delays, buffer requirements and internal traffic burstiness equal to those of Weighted Fair Queueing. This class of algorithms is based on the notion of the potential

Variable bit rate traffic that requires a boundeddelay network service is one of the most important types of traffic in future integrated services networks. In this paper, we introduce a new deterministic traffic model called Deterministic Bounding INterval-length Dependent (D-BIND) to capture the important multiplexing properties of bursty streams. With the D-BIND model, clients specify their traffic to the network via multiple rate-interval pairs, (Rk ; I k ), where a rate Rk is a bounding or worst-case rate over every interval of length I k . The model captures the intuitive property that over longer interval lengths, a source may be bounded by a rate lower than its peak rate and closer to its long-term average rate. We analyze the new model in the context of a deterministic service, and we quantify its performance benefits using a set of experiments with traces of MPEG-compressed video. We show that D-BIND's more accurate characterization of traffic streams leads to substantial im...

In this paper we introduce and analyze frame-based fair queueing, a novel traffic scheduling algorithm for packetswitched networks. The algorithm provides end-to-end delay bounds identical to those of PGPS (packet-level generalized processor sharing), without the complexity of simulating the fluid-model system in the background as required in PGPS. The algorithm is therefore ideally suited for implementation in packet switches supporting a large number of sessions. We present a simple implementation of the algorithm for a general packet switch. In addition, we prove that the algorithm is fair in the sense that sessions are not penalized for excess bandwidth they received while other sessions were idle. Frame-based fair queueing belongs to a general class of scheduling algorithms, which we call Rate-Proportional Servers. This class of algorithms provides the same end-toend delay and burstiness bounds as PGPS, but allows more flexibility in the design and implementation of the algorithm....

This paper addresses the integration of services in the Internet and the resulting impact on pricing policies. I first address why an integrated services Internet is desirable, and give an overview of the services it is likely to offer. I then argue that an integrated services Internet, in order to be efficient, must employ per-user, quality-ofservice sensitive, and usage-based pricing policies. 1 Introduction In the next five years, the Internet will undergo significant technical changes. These will probably include dramatic increases in bandwidth 1 on the backbone transmission links, better physical access from homes and businesses, and a more sophisticated network architecture. Internet policies are also likely to change; these policy changes will probably include allowing more public access, increasing privatization of service provision, reduced or at least modified government subsidies, and new pricing schemes. These policy and technical changes will reinforce each other: some...

It has been known for several years now that variable-bit-rate video sources are strongly auto-correlated. Recently, several studies have indicated that the resulting stochastic processes exhibit long-range dependence properties. This implies that large buffers at intermediate switching points may not provide adequate delay performance for such classes of traffic in Broadband packet-switched networks (such as ATM). In this paper, we study the effect of long-memory processes on queue length statistics of a single queue system through a controlled fractionally differenced ARIMA(1; d; 0) input process. This process has two parameters OE 1 (0 OE 1 1) and d (0 d ! 1=2) representing an auto-regressive component and a long-range dependent component, respectively. Results show that the queue length statistics studied (mean, variance and the 0:999 quantile) are proportional to e c1 OE 1 e c2 d ; where (c 1 ; c 2 ) are positive constants, and c 2 ? c 1 : The effect of the auto-correlation...