maximum packet size
maximum domain name
maximum compressed domain name
maximum length of domain label
bytes of fixed data in header
bytes of fixed data in query
bytes of fixed data in r record
bytes of data in a u_int32_t
bytes of data in a u_int16_t
IPv4 T_A
IPv6 T_AAAA
Flag bits indicating name compression.
For both TCP and UDP.
Standard query.
Inverse query (deprecated or unsupported).
Name server status query (unsupported).
Zone change notification.
No error occurred.
Format error.
Server failure
Name error.
Unimplemented
Operation refused.