Internet Based Real-Time Multiuser Simulation: Ppong!

There is a growing demand for real-time collaborative applications through the World Wide Web. New techniques are required for real-time applications to perform well in the face of changing network conditions that often include long delays. We present some of the key issues for implementors of real-time web-based applications, including choices on centralized versus distributed control, two versus multiuser considerations, synchronous versus asynchronous message protocols, and simulation divergence. We present an implementation for a web-based version of the classic Pong game, called Ppong!. Ppong! was selected for implementation since it strips to its essentials many components of real-time collaborative simulation. A key feature of Ppong! is implementation of a heuristic for "retarding" a user's view of the simulation to accommodate network delays.