soa

Caching Negative Answers

Caching Negative Answers

Like normal answers negative answers have a time to live (TTL). As
there is no record in the answer section to which this TTL can be
applied, the TTL must be carried by another method. This is done by
including the SOA record from the zone in the authority section of
the reply. When the authoritative server creates this record its TTL
is taken from the minimum of the SOA.MINIMUM field and SOA's TTL.
This TTL decrements in a similar manner to a normal cached answer and