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.
こういうことが書いてあって、FQDNの末尾にはドットをつける形式となっているようだけれど、FQDNの定義は曖昧らしい。
テストコードをうっすら眺めていると、 Route53レコードを作成するときは末尾ドットつきFQDNでも作成できるが、 github.com
ACMのdata参照ではドメインはドット付きのFQDNでは参照に失敗する。 github.com
