Minimal-delay decentralized maintenance of processor-group membership in TDMA-bus LAN systems

Decentralized approaches to processor-group maintenance (GMM) are aimed at facilitating every active node in a real-time LAN system to maintain timely and consistent knowledge about the health status of all cooperating nodes and to recognize newly joining nodes. A practical scheme for this decentralized GMM (DGMM) in TDMA (time division multiple access) bus based real-time LAN systems, called here the periodic reception history broadcast (PRHB) scheme, was initially formulated by H. Kopetz et al. (1989) for application environments where the fault frequency is relatively low such that no more than one node fails in any interval of two TDMA cycle duration. The authors develop a major extension of the scheme, PRHB with multiple fault detection (PRHB/MD), which is applicable to environments where the fault frequency is much higher-to be more specific, where up to a half of the nodes map experience faults within any interval of three TDMA cycle duration. The scheme does not impose any limit on the number of transient faults of links that any one node may experience. The scheme yields the minimal detection delay for all major fault types and the delay does not exceed two TDMA cycles for the worst fault type. This detection delay characteristic is a significant improvement over those of previously developed DGMM schemes.<>