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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  Name Systems and TCP/IP Name Registration and Name Resolution            9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)                 9  TCP/IP Domain Name System (DNS)                      9  DNS Name Servers and Name Resolution                           9  DNS Messaging and Message, Resource Record and Master File Formats

DNS Message Header and Question Section Format 1 2 3 4 5 DNS Name Notation and Message Compression Technique

RData Field Formats For Common Resource Records

The RData field consists of one or more subfields that carry the actual “payload” for the resource record. Below is a list of the most common resource record types. For each I have indicated the resource record text code, name, and Type value, provided a brief summary of the resource record’s use, and shown the structure of the RData field in a table:

This is the primary resource record type in DNS; it contains a 32-bit IP address associated with a domain name, as shown in Table 172.

In this record, the data field carries the domain Carries the domain name of a name server (Table 173).

The data field contains the real name of an a named object that has been referenced using an alias (Table 174).

Table 174: DNS Canonical Name Resource Record Data Format

Subfield Name	Size (bytes)	Description
CName	Variable	Canonical Name: The canonical (real) name of the named object. This name is then resolved using the standard DNS resolution procedure to get the address for the originally-specified name.

DNS Message Header and Question Section Format 1 2 3 4 5 DNS Name Notation and Message Compression Technique

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