The design of fault-tolerant asynchronous networks has been an unsolved problem. In this paper, necessary and sufficient conditions on state assignments for fault-tolerant asynchronous networks are given. Three design techniques, based on Liu's 2 so  - 1 assignment, Friedman et al.'s (2, 2) separating system, and (2s o  + 1) assignments, are given for fault-tolerant asynchronous networks. The earlier Liu's upper bound on state variables for USTI assignment for 2 so  rows is improved to 2 so  - 2 so  ?3 .
['Dhiraj K. Pradhan', 'Sudhakar M. Reddy']
Fault-Tolerant Asynchronous Networks