Recoverable Mobile Environment: Design and Trade-o Analysis

The mobile wireless environment poses challenging problems in designing fault-tolerant systems because of the dynamics of mobility, and limited bandwidth available on wireless links. Traditional fault-tolerance schemes, therefore, cannot be directly applied to these systems. Mobile systems are often subject to environmental conditions which can cause loss of communications or data. Because of the consumer orientation of most mobile systems, run-time faults must be corrected with minimal (if any) intervention from the user. The fault-tolerance capability must, therefore, be transparent to the user. Presented here are schemes for recovery upon a failure of a mobile host. This paper portrays the limitations of the mobile wireless environment, and their impact on recovery protocols. Toward this, adaptation of well-known recovery schemes are presented which suit the mobile environment. The performance of these schemes has been analyzed to determine those environments where a particular recovery scheme is best-suited. The performance of the recovery schemes primarily depends on (i) the wireless bandwidth, (ii) the communication-mobility ratio of the user, and (iii) the failure rate of the mobile host.