Metrics for Quantifying Benefits and Cost of Session Switchovers

To persistently maintain client-server connections in mobile ad-hoc networks, we investigate the reliable server pooling (RSP), where servers that can provide equivalent functionality are pooled together. The RSP is meant to increase the availability and survivability of the battlefield infrastructure by allowing clients to access a pool of redundant information sources. As a result, some failed sessions are going to be prolonged through a series of transparent switchovers beyond the time of the first failure. However, both the prolonged sessions and the RSP infrastructure itself will put additional stress on the network and server resources. This paper introduces a classification of switchovers and sessions (sustained, lost, and inconclusive), and then defines several metrics that quantify the aggregate benefit and cost of RSP in a system: session sustainability throughput, gain, and cost, as well as switchover efficiency. A set of simulation experiments are run to better illustrate the meaning and practical application of the defined metrics.