Negative caching

sulekha

this is what i have read about negative caching in the book , "practical guide to Ubuntu Linux by mark sobell"

Storing the knowledge that something does not exist. A cache normally stores information about something that exists. A negative cache stores the information that something, such as a record, does not exist.

can any one give an example(s) / practical situation(s) where and why this is used ?


iponeverything

Squid does negative caching, it saves a lot of time with not having to go out and look for something that you already know does not exist.


kenjackson

DNS requires that caching nameservers remember negative responses as well as positive ones. If an authoritative nameserver returns a negative response, indicating that a name does not exist, this is cached. The negative response may be perceived as a failure at the application level; however, to the nameserver caching it, it is not a failure.