Resource Records

A resource record, commonly referred to as an RR, is the unit of information entry in DNS zone files; RRs are the basic building blocks of host-name and IP information and are used to resolve all DNS queries. Resource records exist as many types to provide extended name-resolution services.

Different types of RRs have different formats, as they contain different data. In general, however, many RRs share a common format, as the following address resource records example illustrates. The following fictional example explains the fields found in an A resource record:

microsoft.com. 600 IN A 150.150.150.1

• The first field (microsoft.com) denotes the owner.
• The second field (600) is the time-to-live (TTL) parameter, in seconds.
• The third field (IN) is the class field that represents the protocol family, which is almost always IN, for Internet class.
• The fourth field (A) is the type of resource the RR is representing.
• The fifth field (150.150.150.1) is the resource data, or RDATA. This field is a variable type that provides information appropriate for the type of resource; in this case, it's a 32-bit IP address.

The following resource record types are commonly used in DNS:

• Start of authority (SOA)
• Name server (NS)
• Pointer record (PTR)
• Address (A)
• IPv6 Address (AAAA)
• Mail exchange (MX)
• Canonical name (CNAME)
• Windows Internet Naming Service (WINS)
• WINS Reverse Look up (WINSR)

There are many other resource record types in DNS. For more information, see DNS WMI Provider Reference.