Does a Fully Qualified Domain Name need a period?

Question

I'm confused about FQDN (Fully Qualified Domain Name). Is it necessary to end FQDN with a period? Like sun or sun.tuc.noao.edu. or sun.tuc.noao.edu. What's the difference?

Answer 1

How IT Works: Domain Name System

All DNS records actually end with the period character (.) which represents the root of the DNS hierarchy, but it's rarely printed and is usually just assumed. A domain name that includes the trailing period character is said to be a Fully Qualified Domain Name (FQDN). However, domain names where the period character is implicit are also commonly referred to as FQDNs.

^{Source: TechNet Magazine}

See also:

• Trailing Dots in Domain Names
• No, that dot in the domain name of the URL is not a mistake.

Answer 2

Usually you don't the (dot) . at the end of a FQDN except if it is in a DNS. If you are adding this FQDN for an internal machine/server at most of cases we don't add the (dot) at the end.

take a look at [2] DNS specification, RFC 1034, way back in 1987:

When a user needs to type a domain name, the length of each label is omitted and the labels are separated by dots ("."). Since a complete domain name ends with the root label, this leads to a printed form which ends in a dot. We use this property to distinguish between:

• a character string which represents a complete domain name (often called "absolute"). For example, "poneria.ISI.EDU."

• a character string that represents the starting labels of a domain name which is incomplete, and should be completed by local software using knowledge of the local domain (often called "relative"). For example, "poneria" used in the ISI.EDU domain.

References:

[1] http://www.dns-sd.org/trailingdotsindomainnames.html

[2] http://www.ietf.org/rfc/rfc1034.txt