Daniel Andresen

SWEB: towards a scalable World Wide Web server on multicomputers

We investigate the issues involved in developing a scalable World Wide Web (WWW) server on a cluster of workstations and parallel machines. The objective is to strengthen the processing capabilities of such a server by utilizing the power of multicomputers to match huge demands in simultaneous access requests from the Internet. We have implemented a system called SWEB on a distributed memory machine, the Meiko CS-2, and networked workstations. The scheduling component of the system actively monitors the usages of CPU, I/O channels and the interconnection network to effectively distribute HTTP requests across processing units to exploit task and I/O parallelism. We present the experimental results on the performance of this system.

Wearable sensor system for wireless state-of-health determination in cattle

Wearable systems for human and animal state-of-health determination share many design requirements. This paper discusses the design of a remote health monitoring system for cattle that hosts a suite of sensors and communicates wirelessly with a base station via Bluetooth telemetry.

An open test bed for medical device integration and coordination

Medical devices historically have been monolithic units — developed, validated, and approved by regulatory authorities as stand-alone entities. Modern medical devices increasingly incorporate connectivity mechanisms that offer the potential to stream device data into electronic health records, integrate information from multiple devices into single customizable displays, and coordinate the actions of groups of cooperating devices to realize “closed loop” scenarios and automate clinical workflows. However, it is not clear what middleware and integration architectures may be best suited for these possibly numerous scenarios. More troubling, current verification and validation techniques used in the device industry are not targeted to assuring groups of integrated devices. In this paper, we propose a publish-subscribe architecture for medical device integration based on the Java Messaging Service, and we report on our experience with this architecture in multiple scenarios that we believe represent the types of deployments that will benefit from rapid device integration. This implementation and the experiments presented in this paper are offered as an open test bed for exploring development, quality assurance, and regulatory issues related to medical device coordination.

Scalability issues for high performance digital libraries on the World Wide Web

We investigate scalability issues involved in developing high performance digital library systems. Our observations and solutions are based on our experience with the Alexandria Digital Library (ADL) testbed under development at UCSB. The current ADL system provides online browsing and processing of digitized maps and other geospatially mapped data via the World Wide Web (WWW). A primary activity of the ADL system involves computation and disk I/O for accessing compressed multi resolution images with hierarchical data structures, as well as other duties such as supporting database queries and on the fly HTML page generation. Providing multi resolution image browsing services can reduce network traffic but impose some additional cost at the server. We discuss the necessity of having a multiprocessor DL server to match potentially huge demands in simultaneous access requests from the Internet. We have developed a distributed scheduling system for processing DL requests, which actively monitors the usages of CPU, I/O channels and the interconnection network to effectively distribute work across processing units to exploit task and I/O parallelism. We present an experimental study on the performance of our scheme in addressing the scalability issues arising in ADL wavelet processing and file retrieval. Our results indicate that the system delivers good performance on these types of tasks.

Toward a Scalable Distributed WWW Server on Workstation Clusters

In this paper, we investigate the issues involved in developing a scalable World Wide Web (WWW) server called SWEB on a cluster of workstations. The objective is to strengthen the processing capabilities of such a server in order to match huge demands in simultaneous access requests from the Internet, especially when these requests involve delivery of large digitized documents. The scheduling component of the system actively monitors the usages of CPU, disk I/O channels and the interconnection network to effectively distribute HTTP requests across processing units to exploit task and I/O parallelism. We analyze the maximum number of requests that can be handled by the system and present several experiments to examine the performance of this system.

Multiprocessor scheduling with client resources to improve the response time of WWW applications

WWW-based information service has grown enormously during the last few years, and major performance bottlenecks have been caused by WWW server and Internet bandwidth inadequacies. Augmenting a server with multiprocessor support and shifting computation to client-site machines can substantially improve system response times and for some applications, it may also reduce network bandwidth requirements. In this paper, we propose adaptive scheduling techniques that optimize the use of a multiprocessor server with client resources by predicting demands of requests on I/O, CPU and network capabilities. We also provide a performance analysis under simplified assumptions for understanding the impact of system loads and network bandwidth when using our scheduling strategy. Finally we report preliminary experimental results to examine the system performance and verify the usefulness of the analytic model.

LYE: a high-performance caching SOAP implementation

The Simple Object Access Protocol (SOAP) is a dominant enabling technology in the field of Web services. Web services demand high performance, security and extensibility. SOAP, being based on extensible markup language (XML), inherits not only the advantages of XML, but its relatively poor performance. This makes SOAP a poor choice for many high-performance Web services. We present a new approach to implementing the SOAP protocol using caching on the SOAP server. This approach has significant performance advantages over current approaches while maintaining complete protocol compliance. We demonstrate its practicality by implementing a demonstration system under Linux, giving speedups of over 250% in our sample applications.

A distributed infrastructure for veterinary telemedicine

The livestock industry can benefit tremendously from systems that continuously monitor cattle state-of-health, allowing the industry to maintain high meat quality, react to the presence of disease, and predict its spread. Requirements for these monitoring systems are similar to requirements that drive human ambulatory monitoring systems based on wearable sensors and wireless data communication. This paper presents early results from an effort to develop a veterinary telemedicine infrastructure based upon wearable monitoring technology originally developed for home health care. The functional layout of the infrastructure is described, and initial hardware and physiological measurements are presented.

Towards a hierarchical scheduling system for distributed WWW server clusters

We present a model for dynamically scheduling HTTP requests across clusters of servers, optimizing the use of client resources as well as the scattered server nodes. We also present a system, H-SWEB, implementing our techniques and showing experimental improvements of over 250%, which have been achieved through utilizing a global approach to scheduling requests. This is the first system to provide a hierarchical scheduling mechanism for distributed HTTP server clusters incorporating dynamic client-server task distribution and distributed data access. H-SWEB uses sophisticated scheduling techniques in monitoring and adapting to workload variation at the client and server clusters for supporting typical digital library tasks, such as fast WWW image browsing. We provide a discussion of our system architecture and implementation, and briefly summarize the experimental results that have been achieved.

Ambulatory instrumentation suitable for long-term monitoring of cattle health

The benefits of real-time health diagnoses of cattle are potentially tremendous. Early detection of transmissible disease, whether from natural or terrorist events, could help to avoid huge financial losses in the agriculture industry while also improving meat quality. This work discusses physiological and behavioral parameters relevant to cattle state-of-health assessment. These parameters, along with a potentially harsh monitoring environment, drive a set of design considerations that must be addressed when building systems to acquire long-term, real-time measurements in the field. A prototype system is presented that supports the measurement of suitable physiologic parameters and begins to address the design constraints for continuous state-of-health determination in free-roaming cattle.