Squid external overview

Cache Digests (ctd)
Pros
Extremely light-weight, only requires a periodic transfer of a relatively small object, then all lookups are done locally on each requesting cache
Scales well over a high number of caches on varying latent links

Cons
Is not entirely accurate, so your hit rate isn't as high as it could be
Being periodic, it is not totally up to date, so your hit rate drops further
Currently the entire digest must be rebuilt periodically - work is continuing on digest "deltas"
Still reasonably experimental