FAULT-TOLERANT REAL-TIME COMMUNICATION IN DISTRIBUTED COMPUTING SYSTEMS

The delivery delay in a point-to-point packet switching network is dif ficult to control due to the contention among randomly-arriving packet s at each node and multihops a packet must travel between its source a nd destination. Despite this difficulty, there are an increasing numbe r of applications that require packets to be delivered reliably within prespecified delay bounds. This paper shows how this can be achieved by using real-time channels which make ''soft'' reservation of network resources to ensure the timely delivery of real-time packets. We firs t present theoretical results and detailed procedures for the establis hment of real-time channels and then show how the basic real-time chan nels can be enhanced to be fault-tolerant using the multiple disjoint paths between a pair of communicating nodes. The contribution of the f ormer is a tighter schedulability condition which makes more efficient use of network resources than any other existing approaches, and that of the latter is a significant improvement in fault tolerance over th e basic real-time channel, which is inherently susceptible to componen t failures.