A study on the inaccessibility characteristics of ISO 8802/4 token-bus LANs

Continuity of service and bounded and known message delivery latency are requirements of a number of applications, which are imperfectly fulfilled by standard LANs. Most previous studies have addressed this issue by computing worst-case access/transmission delays only for normal LAN operation. However, LANs are subject to failures, namely partitions. Since most applications can live with temporary glitches in LAN operation, an alternative approach is to quantify all these glitches or temporary partitions, called inaccessibilities, and to derive a worst-case figure, to be added to the worst-case transmission delay in the absence of faults. In these conditions, reliable real-time operation is possible on nonreplicated LANs. An exhaustive study of the inaccessibility characteristics of the ISO 8802/4 token-bus LAN is described