Steven Berson

Staggered striping in multimedia information systems

Multimedia information systems have emerged as an essential component of many application domains ranging from library information systems to entertainment technology. However, most implementations of these systems cannot support the continuous display of multimedia objects and suffer from frequent disruptions and delays termed hiccups. This is due to the low I/O bandwidth of the current disk technology, the high bandwidth requirement of multimedia objects, and the large size of these objects that almost always requires them to be disk resident. One approach to resolve this limitation is to decluster a multimedia object across multiple disk drives in order to employ the aggregate bandwidth of several disks to support the continuous retrieval (and display) of objects. This paper describes staggered striping as a novel technique to provide effective support for multiple users accessing the different objects in the database. Detailed simulations confirm the superiority of staggered striping.

Fault tolerant design of multimedia servers

Recent technological advances have made multimedia on-demand servers feasible. Two challenging tasks in such systems are: a) satisfying the real-time requirement for continuous delivery of objects at specified bandwidths and b) efficiently servicing multiple clients simultaneously. To accomplish these tasks and realize economies of scale associated with servicing a large user population, the multimedia server can require a large disk subsystem. Although a single disk is fairly reliable, a large disk farm can have an unacceptably high probability of disk failure. Further, due to the real-time constraint, the reliability and availability requirements of multimedia systems are very stringent. In this paper we investigate techniques for providing a high degree of reliability and availability, at low disk storage, bandwidth, and memory costs for on-demand multimedia servers.

Design of fault-tolerant large-scale VOD servers: With emphasis on high-performance and low-cost

Recent technological advances in digital signal processing, data compression techniques, and high-speed communication networks have made Video-on-Demand (VOD) servers feasible. A challenging task in such systems is servicing multiple clients simultaneously while satisfying real-time requirements of continuous delivery of objects at specified rates. To accomplish these tasks and realize economies of scale associated with servicing a large user population, a VOD server requires a large disk subsystem. Although a single disk is fairly reliable, a large disk farm can have an unacceptably high probability of disk failure. Furthermore, due to real-time constraints, the reliability requirements of VOD systems are even more stringent than those of traditional information systems. Traditional RAID solutions are inadequate due to poor resource usage. Thus, in this paper, we present alternative schemes which provide a high degree of reliability at low disk storage, bandwidth, and memory costs for on-demand multimedia servers. Moreover, we discuss some of the main issues and trade-offs associated with providing fault tolerance in multidisk VOD systems. We would like to impress upon the reader that one of the main points of this paper is the exposition of trade-offs and issues associated with designing fault-tolerant VOD servers. It is not the case that one fault tolerance scheme is absolutely better than another, but rather that one must understand the trade-offs as well as ones system constraints and then choose a fault tolerance scheme accordingly.

The ASP EE: an active network execution environment

This paper describes the ASP Execution Environment (EE), a prototype general-purpose active network execution environment that initiates and controls the execution of Java-based active applications. Features of the ASP EE include support for persistent active applications, fine-grained network I/O control, security, resource protection and timing services.

A programmable routing framework for autonomic sensor networks

This paper proposes a programmable routing framework that promotes the adaptivity in routing services for sensor networks. This framework includes a universal routing service and an automatic deployment service. The universal routing service allows the introduction of different services through its tunable parameters and programmable components. The deployment service completes the configuration of the universal routing service throughout a sensor network in an automatic and energy-efficient way. With this deployment service, a self-configuring ability is realized for sensor routing services. With the changeable parameters and programmable components of the universal routing service, the self-optimizing as well as other autonomic abilities can be explored in an experimental sensor network conforming to the proposed framework.

Evolution of an active networks testbed

This paper explores the requirements for a network testbed designed specifically to support research in active networking. It also describes the design of the wide-area active networks testbed named the ABone. The ABone provides a virtual and real network infrastructure for active network experiments, using a diverse set of OS platforms. Its design embodies a tradeoff among the testbed goals of scalability, availability, security, heterogeneity, and modularity.

Gathercast with active networks

Small packets constitute a large fraction of packets in the Internet. Gathercast is a network layer service that combines small packets going to the same destination into a single packet, reducing the number of packets in the network and saving computations at intermediate routers. We propose a new model for gathercast using active network techniques. With this model, gathercast is built throughout the network with low overhead, service parameters can be dynamically adjusted and end-user applications obtain benefits from gathercast without knowing its existence. We also present an implementation of the active gathercast.