DNS on Windows Server 2003, 3rd Edition

Answer, Authority, and Additional Section Format

(From RFC 1035, pages 29-30)

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:

                                    1  1  1  1  1  1
      0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                                               |
    /                                               /
    /                      NAME                     /
    |                                               |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                      TYPE                     |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                     CLASS                     |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                      TTL                      |
    |                                               |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                   RDLENGTH                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
    /                     RDATA                     /
    /                                               /
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

where:

NAME

Is a domain name to which this resource record pertains.

TYPE

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

CLASS

Is two octets that specify the class of the data in the RDATA field.

TTL

Is a 32-bit unsigned integer that specifies the time interval (in seconds) that the resource record may be cached before it should be discarded. Values of 0 are interpreted to mean that the RR can only be used for the transaction in progress, and should not be cached.

RDLENGTH

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

RDATA

Is a variable-length string of octets that describes the resource. The format ...