Title: A Model for Analyzing the Interaction Between Bandwidth Demand and Supply The Internet has performed admirably well in coping with an exponential growth in traffic volume. Much credit for this robustness goes to TCP's congestion control mechanisms. However, TCP only controls the flow in a connection, whereas the number of connections is controlled by users. Borrowing terminology from economics, TCP controls bandwidth supply while the user controls bandwidth demand, and their equilibrium determines the network state. There is already a huge literature on modeling bandwidth supply, but very little has been done for bandwidth demand. This talk models separately this supply and demand, and use them to analyze the interaction between network and user behavior, and their complementary roles in Internet congestion. (This is work in progress, done in collaboration with Robert Morris.)