On Tue, 21 May 2002, Smitty wrote:
> Anyone know which keyboard characters one cannot use in a domain name?
> Smitty
Historically, permissible are:
[a-z][a-z0-9\-]*.TLD
leading alpha, balance alpha, numeric, and hyphen
RFC 1035, section 2.3.1 shows this BNF:
The following syntax will result in fewer problems with many
applications that use domain names (e.g., mail, TELNET).
<domain> ::= <subdomain> | " "
<subdomain> ::= <label> | <subdomain> "." <label>
<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]
<ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>
<let-dig-hyp> ::= <let-dig> | "-"
<let-dig> ::= <letter> | <digit>
<letter> ::= any one of the 52 alphabetic characters A through
Z in upper case and a through z in lower case
<digit> ::= any one of the ten digits 0 through 9
Note that while upper and lower case letters are allowed in
domain
names, no significance is attached to the case.
-------------------quote ends--------------------
Prohibited (despite MS' netbios hopes to the contrary) are
'space; and 'underscore'
------------------------------------
The CJK extensions change this recently.
-- Russ Herrold
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