Fail-softness evaluation in multiple-bus local computer networks

A fail-softness evaluation methodology is presented which is suitable for quantifying the graceful degradation characteristics of local computer networks (LCN) using multiple buses. The approach quantifies degradation of performance due to failure over any given application lifetime and also yields a single figure of merit that can be used for comparison of alternative multiple-bus LCN architectures with specific reliability/cost constraints. The analysis technique models both network service failures and configuration-related delay characteristics. Existing notions of performability analysis and bandwidth availability are used in the modeling process to derive a combined performance/reliability measure. The fail-softness analysis is used to compare several alternative multiple-bus architectures, which use different demand-assignment multiple-access (DAMA) methods. A class of integrated access methodologies that use a single shared token to arbitrate access to all buses is shown to exhibit generally superior performance/reliability characteristics as compared to other alternatives, such as those which use an independent DAMA protocol for each bus.<>