On Staleness and the Delivery of Web Pages

A popular technique to improve the scalabil-ity of a web based system is caching at proxy servers. Caching has the drawback that a cached page becomes stale when the page is updated at the web server. In some cases, stal-eness may not be completely avoided because the server may not wish to expend the pro-cessing and communication resources required to transmit all the updates immediately. In general, if updates are transmitted less fre-quently, the staleness will tend to increase, but the amount of resources consumed will be reduced. The tradeoff between resource con-sumption and staleness is investigated. A mea-sure of staleness is defined and optimization problems are formulated. The solutions to these problems allow one to come up with an optimal page transmission strategy. Numeri-cal examples showing the resource consump-tion/staleness tradeoff are presented.