Configure Network Services - MCSA Windows Server 2012 R2: Installation and Configuration Study Guide - page 85

Table 2.2 lists the attributes stored in the SOA record.

Table 2.2 The SOA record structure

Field Meaning

Current zone The current zone for the SOA. This can be represented by an @ symbol

to indicate the current zone or by naming the zone itself. In the exam-
ple, the current zone is example.com . The trailing dot ( .com. ) indicates
the zone's place relative to the root of the DNS.

Class This will almost always be the letters IN for the Internet class.

Type of record The type of record follows. In this case, it's SOA.

Primary master The primary master for the zone on which this file is maintained.

Contact email The Internet email address for the person responsible for this domain's

database file. There is no @ symbol in this contact email address because
@ is a special character in zone files. The contact email address is sepa-
rated by a single dot ( . ). So the email address of [e-mail]
would be represented by root.example.com in a zone file.

Serial number This is the “version number” of this database file. It increases each

time the database file is changed.

Refresh time The amount of time (in seconds) that a secondary server will wait

between checks to its master server to see if the database file has
changed and a zone transfer should be requested.

Retry time The amount of time (in seconds) that a secondary server will wait

before retrying a failed zone transfer.

Expiration time The amount of time (in seconds) that a secondary server will spend

trying to download a zone. Once this time limit expires, the old zone
information will be discarded.

Time to live The amount of time (in seconds) that another DNS server is allowed to

cache any resource records from this database file. This is the value
that is sent out with all query responses from this zone file when the
individual resource record doesn't contain an overriding value.

Name Server Records

Name server (NS) records list the name servers for a domain. This record allows other
name servers to look up names in your domain. A zone file may contain more than one
name server record. The format of these records is simple:

example.com. IN NS Hostname.example.com