4.1.3. Resource record format

The answer, authority, and additional sections all share the same format: a variable number of resource records, where the number of records is specified in the corresponding count field in the header. Each resource record has the following format:

where:

NAME

A domain-name to which this resource record pertains.

TYPE

two octets containing one of the RR type codes. This field specifies the meaning of the data in the RDATA field.

CLASS

two octets which specify the class of the data in the RDATA field.

TTL

a 32 bit unsigned integer that specifies the time interval (in seconds) that the resource record may be cached before it should be discarded. Zero values are interpreted to mean that the RR can only be used for the transaction in progress, and should not be cached.

RDLENGTH

an unsigned 16 bit integer that specifies the length in octets of the RDATA field.

RDATA

a variable length string of octets that describes the resource. The format of this information varies according to the TYPE and CLASS of the resource record. For example, the if the TYPE is A and the CLASS is IN, the RDATA field is a 4 octet ARPA Internet address.