> “testserver4.mycorp.example” (no trailing dot) is not fully-qualified and as such could refer to any number of things of differing identities, e.g. “testserver4.mycorp.example.atthomenetwork.com”.
Whether a domain is fully qualified depends on the application. There's no universal syntax. The trailing dot is merely an interface convention followed by some applications to allow the user to indicate that the domain name is complete. It's only useful for applications that don't always deal with fully qualified domains, and perhaps ones that deal with top level domains.
User interfaces MAY provide a method for users to enter
abbreviations for commonly-used names. [..]
If an abbreviation method is provided, then:
(a) There MUST be some convention for denoting that a name
is already complete, so that the abbreviation method(s)
are suppressed. A trailing dot is the usual method.
If you add trailing dots where the dns root would be implied anyway, this could be regarded as an "over-qualified" name. It is considered an error. For example in SMTP. RFC1123 5.2.18 Common Address Formatting Errors:
o Some systems over-qualify domain names by adding a
trailing dot to some or all domain names in addresses or
message-ids. This violates RFC-822 syntax.
RFC822 says "The root node is common to all addresses; consequently, it is not referenced."
Since SNI always uses fully qualified domain names, there is no purpose to having a trailing dot.
Whether a domain is fully qualified depends on the application. There's no universal syntax. The trailing dot is merely an interface convention followed by some applications to allow the user to indicate that the domain name is complete. It's only useful for applications that don't always deal with fully qualified domains, and perhaps ones that deal with top level domains.
RFC1123 6.1.4.3 Interface Abbreviation Facilities:
If you add trailing dots where the dns root would be implied anyway, this could be regarded as an "over-qualified" name. It is considered an error. For example in SMTP. RFC1123 5.2.18 Common Address Formatting Errors: RFC822 says "The root node is common to all addresses; consequently, it is not referenced."Since SNI always uses fully qualified domain names, there is no purpose to having a trailing dot.