NAPTR – Name Authority Pointer

A Name Authority Pointer (NAPTR) is a type of resource record in the Domain Name System of the Internet.

NAPTR records are most commonly used for applications in Internet telephony, for example, in the mapping of servers and user addresses in the Session Initiation Protocol (SIP). The combination of NAPTR records with Service Records (SRV) allows the chaining of multiple records to form complex rewrite rules which produce new domain labels or uniform resource identifiers (URIs).

The DNS type code for the NAPTR record is 35

A common use for NAPTR records is in Session Initiation Protocol, where it is used to route telephony sessions over the IP networks. For example, the SIP URN for the US telephone number 1-800-555-1234 might be tel:+1-800-555-1234 and its domain name 4.3.2.1.5.5.5.0.0.8.1.e164.arpa. A SIP client querying that name might receive:

$ORIGIN 4.3.2.1.5.5.5.0.0.8.1.e164.arpa.
IN NAPTR 100 10 “U” “E2U+sip” “!^.*$!sip:customer-service@example.com!” .
IN NAPTR 102 10 “U” “E2U+email” “!^.*$!mailto:information@example.com!”