World-Wide Web mirrors: likelihood of stale content

Mirroring is common practice for popular sites. Geographically distributed mirrors help to load-balance network traffic. Furthermore, content downloads are faster for users accessing a nearby mirror. Users, however, may value up-to-date content over performance and network optimality, so it is important to ensure that revisions are propagated to mirrors regularly. Triggered or frequently scheduled updates can place heavy loads on the network. Furthermore, content providers may wish to schedule mirror updates during off-peak times in order to take advantage of less than best effort services. The trade-off between update frequencies of mirror sites and the likelihood of stale content is explored