This is a project on the control of asynchronous transfer mode (ATM) networks and of optical networks. We focus on three sets of issues central to the operations of high speed networks: Traffic shaping for ATM networks Multiplexing for optical networks Feedback control with delayed information We will use the limit results for fast and large networks to analyze these three sets of issues. Specifically, we will use fluid and diffusion limits and large deviation bounds. For traffic shaping we will use a new strategy (periodic averaging of rate). We believe this strategy can reduce significantly the amount of queuing required inside the network, and that this strategy can simplify both the design and control of networks. the multiplexing approach that we will study for optical networks is statistical look-ahead multiplexing. This multiplexing approach is designed for star optical networks. It uses the connectivity properties of these networks but does not require tunable lasers or filters. The objectives in the study of feedback control with information delay are to identify the feedback control strategies that can improve the operations of high speed networks and quantify the gain achieved by these strategies.