A description is given of the key characteristics of a local area network (LAN) architecture, Instanet, which retains these merits but provides the added features of rapid real-time response to allow direct coupling of sensor-based modules to the network. Instanet uses a distributed interrupt facility to provide high levels of service to time-critical traffic without imposing restrictions on flow control and/or packet length for non-time-critical traffic. The Instanet architecture and its implementation is based on the IEEE 802. 5 token ring standard. A detailed analytic model of Instanet's performance is presented. It is a generalization of the well-known walking server model (for token-passing networks) which takes into account provisions for priority handling. The analysis is backed up by simulation results which show performance of the network at various levels of real-time and non-real-time traffic.