A-Label: Difference between revisions
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An A-Label is the ASCII-compatible encoding (ACE) form of an [[IDN|Internationalized Domain Name]]. Each A-Label consists of two parts, beginning with the Internationalized Domain Name for Applications (IDNA) ACE prefix '''("xn--")''', which is followed by a string that is valid output from the [[Punycode]] algorithm. The maximum string length of the Punycode algorithm is 59 [[ASCII]] characters in length. The prefix and the string must conform to all the requirements of for the DNS protocol, including the naming rules for [[LDH]] labels.<ref>[https://tools.ietf.org/html/rfc5890#section-2.3.2.1 RFC 5890]. IETF.org. Retrieved 4 February 2019.</ref> | An '''A-Label''' is the ASCII-compatible encoding (ACE) form of an [[IDN|Internationalized Domain Name]]. Each A-Label consists of two parts, beginning with the Internationalized Domain Name for Applications (IDNA) ACE prefix '''("xn--")''', which is followed by a string that is valid output from the [[Punycode]] algorithm. The maximum string length of the Punycode algorithm is 59 [[ASCII]] characters in length. The prefix and the string must conform to all the requirements of for the DNS protocol, including the naming rules for [[LDH]] labels.<ref>[https://tools.ietf.org/html/rfc5890#section-2.3.2.1 RFC 5890]. IETF.org. Retrieved 4 February 2019.</ref> | ||
An A-Label only exists in the context of IDNs, which also require a [[U-Label]]. Therefore, a string must be able to be converted into a U-Label in order to be an A-Label. | An A-Label only exists in the context of IDNs, which also require a [[U-Label]]. Therefore, a string must be able to be converted into a U-Label in order to be an 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> The ACE prefix is represented by "xn--" and the output from the Punycode algorithm is "90ae." | |||
==Related Pages== | ==Related Pages== | ||
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*[[IDN]] | *[[IDN]] | ||
*[[Punycode]] | *[[Punycode]] | ||
==References== | |||
Latest revision as of 22:54, 5 February 2019
An A-Label is the ASCII-compatible encoding (ACE) form of an Internationalized Domain Name. Each A-Label consists of two parts, beginning with the Internationalized Domain Name for Applications (IDNA) ACE prefix ("xn--"), which is followed by a string that is valid output from the Punycode algorithm. The maximum string length of the Punycode algorithm is 59 ASCII characters in length. The prefix and the string must conform to all the requirements of for the DNS protocol, including the naming rules for LDH labels.[1]
An A-Label only exists in the context of IDNs, which also require a U-Label. Therefore, a string must be able to be converted into a U-Label in order to be an A-Label.
Example[edit | edit source]
The A-label for .бг is ".xn--90ae".[2] The ACE prefix is represented by "xn--" and the output from the Punycode algorithm is "90ae."