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Created page with "'''LDH,''' or '''Letter, Digit, Hyphen''', refers to the Domain Name System's (DNS) hostname rule that restricts domain names to the use of letters (a-z), numbers (0-9), a..."
'''LDH,''' or '''Letter, Digit, Hyphen''', refers to the [[Domain Name System]]'s (DNS) hostname rule that restricts domain names to the use of letters (a-z), numbers (0-9), a hyphen (-) and a period (.) prior to internationalization of the DNS. The period is only allowed as a delimiter to separate different levels of a domain name.<ref>[https://tools.ietf.org/html/rfc952 RFC 952]. IETF.org. Retrieved 4 February 2019</ref>
==Introduction of IDNs==
With the Introduction of [[Internationalized Domain Name]]s in Application (IDNA) as the standard for IDNs, the LDH restriction no longer applies to domain names. IDNA makes this possible by using separate labels for display to end user and DNS processes.
===U-Labels===
IDNs are displayed to the end user using a Unicode encoding scheme. This is known as the '''U-Label.'''
'''Example:'''
The U-Label representation for [[.бг]], the [[ccTLD|country code top-level domain]] for Bulgaria, the Unicode codepoints are U+0431 (б) and U+0433 (г).
===A-Labels===
Wt the DNS level, IDNs are processed using an ASCII-compatible encoding scheme. This is known as the '''A-Label.'''
'''Example:'''
The A-label for [[.бг]] is xn--90ae.<ref>[https://www.iana.org/reports/2016/bg-report-20160610.html Report on the Delegation of the бг (“bg”) domain representing Bulgaria in Bulgarian language to Imena.BG AD]. IANA.org. Retrieved 4 February 2019</ref>
==References==
==Introduction of IDNs==
With the Introduction of [[Internationalized Domain Name]]s in Application (IDNA) as the standard for IDNs, the LDH restriction no longer applies to domain names. IDNA makes this possible by using separate labels for display to end user and DNS processes.
===U-Labels===
IDNs are displayed to the end user using a Unicode encoding scheme. This is known as the '''U-Label.'''
'''Example:'''
The U-Label representation for [[.бг]], the [[ccTLD|country code top-level domain]] for Bulgaria, the Unicode codepoints are U+0431 (б) and U+0433 (г).
===A-Labels===
Wt the DNS level, IDNs are processed using an ASCII-compatible encoding scheme. This is known as the '''A-Label.'''
'''Example:'''
The A-label for [[.бг]] is xn--90ae.<ref>[https://www.iana.org/reports/2016/bg-report-20160610.html Report on the Delegation of the бг (“bg”) domain representing Bulgaria in Bulgarian language to Imena.BG AD]. IANA.org. Retrieved 4 February 2019</ref>
==References==