Main interest is in the theory of probability and its applications, especially queueing theory (see Research Interests and Publications) and its applications in the analysis of computer systems and telecommunications networks.

Probabilistic models often reveal disagreement between the results of mathematical analysis and common-sense intuition; this observation informs and shapes his courses. The mathematical theory of queues provides examples of probabilistic models that are both intellectually interesting and widely useful in engineering.

A queue is a waiting line (like customers waiting at a supermarket checkout counter); queueing theory is the mathematical theory of waiting lines. More generally, queueing theory is concerned with the mathematical modeling and analysis of systems that provide service to random demands. In computer science, for example, queueing theory is used to describe the performance of the Internet.

A queueing model is an abstract description of such a system. Typically, a queueing model describes (1) the system's physical configuration, and (2) the stochastic (that is, probabilistic or statistical) nature of the demands, by specifying the variability in the arrival process and the service requirements. Mathematical analysis of simple queueing models often reveals surprising effects caused by this inherent randomness.