The demand for integrated services local area networks is increasing at a rapid pace with the advent of many new and exciting applications: office and factory automation, distributed computing, and multimedia communications. To support these new applications, it is imperative to integrate traffic with diverse statistical characteristics and differing delay requirements on the same network. An attractive approach for integrating traffic has been adopted in two token passing local area network standards, the IEEE 802.4 token bus standard and FDDI. The idea is to control the transmissions of each station based on a distributed timing algorithm, so as to achieve the following goals: (i) to limit the token cycles so that time-critical traffic can be accommodated, and (ii) to allocate pre-specified bandwidths to different stations when the network is overloaded. We have investigated the analysis and design of this protocol previously (see Pang and Tobagi, 1989). In this paper, we generalize the transmission control algorithm used with that protocol. The major advantages of the generalization over the original protocol are: (i) it provides a much expanded design space, (ii) it guarantees convergent behavior, and (iii) it gives meaningful insights into the dynamics of the basic control algorithm.>

The characteristics of digital video files and traffic differ substantially from those encountered with data applications: (i) video files are much larger than data files, and (ii) video traffic is continuous in nature while data traffic is bursty, with the data rate of a video stream much higher than the mean rate of a data traffic source.Accordingly, conventional file servers and associated storage systems are not well suited to support video services over local area networks; instead, new servers capable of handling the specific characteristics of video files and traffic are needed.In this paper, we describe a video applications server software called StarWorks ™ , focusing primarily on its underlying storage management system.The latter manages an array of Winchester disks, and uses a disk access algorithm particularly suitable for video streaming, and is thus referred to as "Streaming RAID".We also characterize the performance of the system by determining the number of streams that can be supported for a given memory size and a given start-up latency requirement.

A very large class of access control strategies is proposed and studied for token passing systems, generalized from the timer-based approach. The idea is to assign transmission quotas dependent on past service times to control the token cycles dynamically while utilizing the token channel efficiently. The dynamics inherent in the control scheme are identified as an important issue and, under heavy load and a few other assumptions, it is shown that the proposed strategies have stable dynamics. Furthermore, the ability of the proposed strategies to control the token cycles is demonstrated. Theoretical results are derived, followed by a thorough discussion on the crucial properties of the new strategies.>

An analysis is presented of the throughput performance of some recently proposed token-passing local area network (LAN) protocols under a heavy load assumption. The IEEE 802.4 token bus standard which uses a cycle-dependent timing mechanism to control station access to the channel, is studied. It is shown that the cycle-dependent timing mechanism limits the token circulation times properly. Moreover, priority among different access classes is being implemented. Analytic results for computations of throughputs and cycle lengths are derived. These results provide insights into the cycle-dependent timing mechanism and also guidelines for design. Using the results derived, examples concerning the throughput behavior under different heavy load configurations, the sensitivity to parameters, system optimization with delay and bandwidth constraints, and comparison with the other integrated access schemes are studied.>

To support real-time applications on a local area network, some recently proposed standards, such as the IEEE 802.4 token bus standard and FDDI, use timers to control station access of the channel in addition to a basic token-passing protocol. The major reason for incorporating the timing mechanism is to avoid excessively long cycles in token-passing that can disrupt real-time services for packetized voice and real-time control. Nevertheless, the timing mechanism is flexible enough to provide priority among non-real-time traffic as well. The authors present an analysis of the throughput performance of the timer-controlled token-passing protocol under heavy load and a few other assumptions. The analysis not only reveals the priority structure of the protocol but also some salient features that render the protocol more favorable than other cycle-limiting schemes (e.g., fixed-maximum channel access per cycle).>

Notwithstanding much effort, explicit analytical results for average message delays for asymmetric token rings are currently unavailable. We develop an excellent and relatively simple analytic approximation which readily demonstrates the effects of the many system parameters on delay-throughput performance. The approximation applies to any cyclically served network (including rings, polling networks, and unidirectional fiber optic broadcast networks) with independent time-slot arrivals and gated service. The approximation becomes exact for symmetric loading. An equation for the moment-generating function of the joint terminal service times is obtained via an imbedded Markov chain. Two matrix equations are then derived, one for the mean terminal service times of theNqueues and another for the joint second central moments. A two-dimensional difference equation for the second central moments is then obtained. This difference equation together with Kleinrock's conservation law is used to approximate the mean delay at each queue. The peak approximation error is typically a few percent for various loading distributions including heavy or highly asymmetric loading, even if the statistics for message arrivals, message lengths, or walk times vary among the queues. Actual delay-throughput results are presented for various terminal loadings. Also included is a procedure to upperbound the error of our approximation for any message and walk time statistics, given the terminal utilizations.