Errors Tolerated
Suppose A and B share caches, A has a request for URL r that misses in A,
- false misses: r is cached at B, but A didn’t know
Effect: lower total cache hit ratio
- false hits: r is not cached at B, but A thought it is
Effect: wasted query messages
- stale hits: r is cached at B, but B’s copy is stale
Effect: wasted query messages