Peer-to-peer communication.

Using the server for the global communication phase makes it easy for worker applets to communicate with each other despite the Java applet security restrictions that limit an applet to communicating only with its source host. Unfortunately, it can also be a serious and unnecessary sequential bottleneck in cases where such restrictions can be removed, such as within a trusted intranet. For these situations, we can implement peer-to-peer communication by modifying the work engine to send and accept communication requests to and from other work engines directly. We can still distribute the resulting worker code as an applet by either signing it, or asking volunteers to manually turn off their browser's applet network restrictions (Microsoft Internet Explorer 4.0, Sun's Hot Java browser, and Sun's Java plug-in [22], which works with Netscape, allow this). Implementing peer-to-peer communications should greatly improve the performance of parallel algorithms that depend on parallelizing communications as well as computation.