The tremendous power and low price of today's computer systems have created the opportunity for exciting applications rich with graphics, audio and video. These new applications promise to support and even enhance the work we do in teams by allowing users to collaborate across both time and space. Yet building distributed collaborative multimedia applications is very difficult and accurately predicting their performance can be even more difficult. We have developed a flexible model and method that allows us to predict multimedia application performance from the user's perspective. Our model takes into account the components fundamental to multimedia applications: latency, jitter and data loss. In applying our method to three specific applications, we have identified some general traits: 1) processors are the bottleneck in performance for many multimedia applications; 2) networks with more bandwidth often do not increase the quality of multimedia applications; and 3) performance for many multimedia applications can be improved greatly by shifting capacity demand from computer system components that are heavily loaded to those that are more lightly loaded.

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