Editing Domain Name System (section)

===Record caching===
A common approach to reduce the burden on DNS servers is to cache the results of name resolution locally or on intermediary resolver hosts. Each DNS query result comes with a time to live (TTL), which indicates how long the information remains valid before it needs to be discarded or refreshed. This TTL is determined by the administrator of the authoritative DNS server and can range from a few seconds to several days or even weeks.<ref>{{Cite web |title=What is DNS propagation? |url=https://www.ionos.com/digitalguide/server/know-how/dns-propagation/ |access-date=2022-04-22 |website=IONOS Digitalguide |language=en}}</ref>

As a result of this distributed caching architecture, changes to DNS records do not propagate throughout the network immediately, but require all caches to expire and to be refreshed after the TTL. RFC 1912 conveys basic rules for determining appropriate TTL values.

Some resolvers may override TTL values, as the protocol supports caching for up to sixty-eight years or no caching at all. [[Negative cache|Negative caching]], i.e. the caching of the fact of non-existence of a record, is determined by name servers authoritative for a zone which must include the [[SOA record|Start of Authority]] (SOA) record when reporting no data of the requested type exists. The value of the ''minimum'' field of the SOA record and the TTL of the SOA itself is used to establish the TTL for the negative answer.