The Broadcast Disks/DBIS Project

"Being pushy since 1993..."


The Broadcast Disks project is focused on the use of data broadcast to provide improved performance, scalability, and availability in an increasingly important class of networked environments, namely, those with asymmetric communication. Examples include wireless networks with mobile clients, cable and direct satellite broadcast networks, information dissemination and information retrieval applications.

Broadcast Disks exploits communication asymmetry by treating a broadcast stream of data that are repeatedly and cyclicly transmitted as a storage device. The broadcast disk technique has two main components. First, multiple broadcast programs (or ``disks'') with different latencies are superimposed on a single broadcast channel, in order to provide improved performance for non-uniform data access patterns and increased availability for critical data. Second, the technique integrates the use of client storage resources for caching and prefetching data that is delivered over the broadcast.

The challenges being addressed in this project include: broadcast program generation, caching and prefetching strategies, and adapting to volatile data, changing client needs, and communication errors. We have also developed some very efficient algorithms for scheduling large-scale, on-demand data broadcast. The techniques have been implemented in a prototype running on Windows NT using IP Multicast.

Our current direction is to develop a general architecture for Dissemination-Based Information Systems (DBIS) that incorporate multiple modes of data delivery such as request/response, periodic broadcast, and publish/subscribe.

To get an quick idea of our current directions for this project, you can check out the slides on "Push vs. Pull" from the panel on "Scalability Issues in the Web" at ICDCS in Baltimore, May 1997. For a longer treatment, grab our invited paper that appeared in OOPSLA 97.

This project is a collaboration between Brown University and the University of Maryland. Funding for the project has been provided by DARPA, NSF, Intel, IBM, and NEC. Additional equipment and software has been provided by Intel and Microsoft.


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