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...

Broadband ISDN (B-ISDN) is expected to carry various types of traffic including besteffort as well as real-time traffic like video-on-demand, live multimedia conferences, and remote medical services for which stringent quality of service (QoS) requirements must be met. In particular, per-packet (per-cell) delay guarantees are an important QoS requirement for real-time applications. Although several methods have been proposed to provide delay guarantees in packet-switching networks, they are either too complex for ATM networks which allow only very simple operations to achieve high bandwidths (hence high-speed switching and routing), or too inefficient (in using network resources) to be cost-effective.

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

Future integrated services networks are expected to carry various types of traffic including real-time packet video for which stringent quality of service (QoS) requirements must be met. In this paper, we propose a cell multiplexing scheme for providing real-time communication services in point-to-point ATM networks. Our scheme is simple enough to be used in high-speed ATM networks, yet reasonably efficient in terms of accommodating channel requests. The scheme employs the leaky bucket model as the input traffic description model and regulates the input traffic at User Network Interface (UNI) to comply with the input traffic specification. Inside the network ATM switches provide bounded local delays to individual cells using a traffic controller and a non-preemptive rate-monotonic priority scheduler.

Many packet schedulers for QoS networks are equipped with a rate control mechanism. The function of a rate control mechanism (rate controller) is to buffer packets from flows which exceed their negotiated traffc profile. It has been established that rate controllers lead to reduced buffer requirements at packet switches, and do not increase the worst-case delays in a deterministic service. On the other hand, rate controllers make a scheduler non-workconserving, and, thus, may yield higher average end-to-end delays. In this study, we show that by properly modifying a rate controller, one can design a scheduler which balances buffer requirements against average delays. We present a scheduler, called Earliness-based Earliest Deadline First (EEDF), which achieves such a balancing using a tunable rate control mechanism. In simulation experiments, we compare EEDF with a rate-controlled EDF scheduler and a workconserving version of EDF.

This paper proposes a traffic control scheme for integrated services ATM networks. The control strategy comprises of two components: a shaping mechanism at the network entry point and a frame based service discipline at the switches. The shaper enforces a short trem peak rate, and a long term average rate. The multiplexing scheme at a switch allocates a guaranteed bandwidth to a connection. A connection may get more than the guaranteed amount, up to a connection specific maximum, if slack bandwidth is available. By imposing an upper bound on the allocated bandwidth, we secure a better handle on the delay jitter. Unlike most frame-based schemes, our scheme allows allocation of bandwidth at any arbitrary granularity. We suggest a simple admission control policy and derive deterministic bounds on end-to-end delay and jitter. An outline of a hardware realization of the scheme is also presented.

Packet switching data networks such as the Internet are migrating towards Integrated Services net-works. To provide end-to-end service guarantees across those networks requires supporting mecha-nisms on all links along the data path including Local Area Networks (LAN) which are typically deployed at the leaves of the Internet. There is however no standard mechanism for building advanced services in existing LANs because the medium access mechanisms of these technologies differ. This dissertation is about providing Integrated Services in IEEE 802.12 networks. 802.12 is the standard for a shared 100 Mbit/s LAN. Its Medium Access Control (MAC) protocol is called Demand Priority. In this work, we have proved that the Guaranteed and the Controlled Load service proposed for a future multi-services Internet, can be provided across shared and switched 802.12 LANs, even when the network is overloaded with best effort traffic. This is achieved using resource reservation with admission control and based on the Integrated Services Packet Network (ISPN) framework. The key design constraints of our reservation scheme were the variable data throughput in 802.12

A major challenge for the design of multiservice networks with quality of service guarantees is an efficient implementation of a bounded delay service, that is, a service that guarantees maximum end-to-end delays for every packet from a single traffic stream. A crucial component of a bounded delay service is the packet multiplexing technique employed at network switches that must keep the variable statistical multiplexing delays below a predetermined threshold. To achieve a high utilization of network resources, the multiplexing technique must be sufficiently sophisticated to support a variable set of delay bounds for a large number of traffic streams. On the other hand, since multiplexing of packets is to be performed at the data rate of the network links, the complexity of the multiplexer should be strictly limited. A novel packet multiplexing technique, called Rotating Priority Queues (RPQ), is presented which exploits the tradeoff between efficiency, i.e., the ability to support many connections with delay bounds, and low complexity. The operations required by the RPQ multiplexer are similar to those of the simple, but inefficient, Static Priority (SP) multiplexer. The overhead of RPQ, as compared to SP, consists of a periodic rearrangement (rotation) of the priority queues. It is shown that queue rotations can be implemented by updating a set of pointers. The efficiency of RPQ can be made arbitrarily close to the highly efficient, yet complex, Earliest Deadline First (EDF) multiplexer. Exact expressions for the worst case delays in an RPQ multiplexer are derived and compared to expressions for an EDF multiplexer.

Future integrated-services networks are expected to support applications with a wide range of service requirements. The most demanding applications require a bounded-delay service that provides deterministic (i.e., worst-case) bounds on network latencies for all packets. To provide such delay guarantees, a network must allocate network resources such as bandwidth and buffer space to individual connections. However, since resource availability is limited, the network must carefully manage its resources in order to ensure a high achievable network utilization.