Presence Based Availability and P2P Systems
The availability of a P2P service is a function of the individual peers' availabilities, and it is often desirable to estimate how available a particular P2P service will be given the availability of its peers. Prior work in this area has widely used the fraction of time the average peer is available as the basis for this estimate. The authors show here that this approach has serious drawbacks. They develop a different measure, which people call presence-based availability, which takes into account the availability of the individual peers.