Web Caching and Replication

10.1. Cache Validation

A key question for cache validation is when to send validation messages. The tradeoff is between the degree of consistency and the message and latency overhead. The more frequent the validation messages are, the lower the probability of delivering stale content from the cache, but the higher the message and latency overhead for validating unchanged objects. The extreme options are to validate on every access, which provides strong consistency at the expense of a large number of unnecessary validation messages, or never to validate, which has zero message overhead but a high probability of stale delivery. The following subsections discuss a number of intermediate solutions.

A further issue that arises with the validation ...