Modeling of user perceived webserver availability

We propose to use Markov regenerative process (MRGP) models to study the availability of Internet-based services perceived by a web user, which capture the interactions between the service facility and the user. The necessity of the sophisticated MRGP modeling is evidenced by the comparisons with the corresponding continuous time Markov chain (CTMC) models, which show that the popular convenient CTMC models tend to overestimate user-perceived service unavailabilities by 26% to 125%. We study two different online service scenarios: (1) single-user-single-host and (2) single-user-multiple-host. It is found that user-perceived service unavailability depends not only on the infrastructure's failure-recovery characteristics but also, more importantly, on the user's behavior. Also, for a service provider, to improve users' satisfaction, inventing a fast recovery mechanism is more effective than striving for a more reliable platform given the platform availability is the same.