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Internationalized Domain Names (IDN) |
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Frequently Asked Questions (FAQ) |
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What is IDN?
The abbreviation IDN stands for Internationalized Domain Name, also called a
multilingual domain name. Both names are used interchangeably. An IDN is a
domain name that contains characters from the
Unicode character repertoire that other than letter/digit/hyphen (LDH)
characters, which are Latin letters (a-z case ignored so includes A-Z), digits
(0-9) and the hyphen (-). In other words, Internationalized Domain Names may
contain letters with diacritics, as required by many European languages, or
characters drawn from non-Latin scripts such as Arabic or Chinese.
What is IDNA?
IDNA (Internationalized Domain Names in Applications) is a mechanism devised to
handle Internet domain names containing characters other than
letter/digit/hyphen (LDH) characters, which are Latin letters (a-z case ignored
so includes A-Z), digits (0-9) and the hyphen (-). IDNA was worked out by the
IETF’s IDN Working Group. It
was announced by IETF as a proposed standard in March 2003. The full concept of
IDN is covered by: RFC 3490, RFC 3491, RFC 3492, RFC 3454.
Deployment of IDNA entails no changes to current Internet infrastructure and
preserves the robustness of the DNS. In general, the idea behind the IDNA
functioning is based on conversion of non-LDH characters of an IDN into suitable
LDH ones by a user application (e.g. web browsers). Such a solution is designed
for maximum backward compatibility with the existing DNS system, which supports
only domains using only LDH characters. The IDNA protocol implementation does
not introduce any change to the DNS infrastructure. It means that there is no
need to alter any of the existing Internet’s protocols, DNS servers and
resolvers on user’s computers in order to get the IDNs working. In other words,
lower-layer protocols do not need to be aware of IDNs. The IDNA is a protocol of
the top level layer of the OSI model, therefore the IDN introduction requires
only upgrades of software which interacts with domain names, such as web
browsers, e-mail and FTP clients, HTML editors, etc. In some cases, it is enough
to upgrade the underlying software infrastructure, for example runtime libraries
like libc, virtual machines, etc.
What is Punycode?
Punycode (RFC 3492) is an algorithm that uniquely and reversibly transforms Unicode strings into the limited character set supported by the Domain Name System. A
converted IDN contains only IRA (International Reference Alphabet) characters
and starts with the “xn--” prefix.
What is Unicode?
Unicode is a modern method of coding embracing characters used all over the
world (e.g. German diacritics, hieroglyphs, Cyrillic), musical, technical and
phonetic symbols and many more). Unicode assign the unique number - code point
(independent from an OS, application or language) - to each character. Essential
feature of Unicode is that the first 128 characters are equivalent to
International Reference Alphabet (IRA) character set for information interchange
international reference version. More information about Unicode is available at
www.unicode.org. The Unicode specification is maintained by the Unicode
Consortium and by ISO/IEC SC2. More on the relationship between both
organizations can be found here.
What is UTF-8?
UTF-8 (8-bit Unicode Transformation Format) is a variable-length character
encoding capable of representing any universal character in the Unicode
standard. UTF-8 is backwards compatible with the International Reference
Alphabet (IRA) character set for information interchange and uses from one to
four octets per character, depending on the Unicode symbol. Many ITU-T
Recommendations, ISO/IEC International Standards, IETF RFCs and ICT standards
from other SDOs use the UTF-8 transformation for carrying multilingual
information.
What is the International Reference Alphabet (IRA)?
The International Reference Alphabet No. 5 (formerly International Alphabet
No.5, or "IA5") is an international standard specified in ITU-T Recommendation
T.50 for information interchange among data processing systems and data
communications systems. Each IRA character is a 7-bit coded unique character.
The letters available in this character set are restricted to the Latin
uppercase A-Z and lowercase a-z letters. In addition to printing characters, IRA
also defines codes for control characters such as linefeed and non-printing
character such as space and delete, which are the same as ANSI X3.4-1986: ASCII
(American Standard Code for Information Interchange). The ASCII and ISO 646 are
equivalent to the International Reference Alphabet No. 5. The advantage of IRA
encoding is its (almost) universal acceptance and implementation.
Which browsers support IDN?
WINDOWS
- Firefox 0.6 and higher (http://www.mozilla.org/products/firefox/)
- Internet Explorer 5.0 and higher + i-NavTM plug-in (http://www.idnnow.com)
- Internet Explorer 7 Beta 2 (http://www.microsoft.com/windows/ie/downloads/)
- Mozilla 1.4 and higher (http://www.mozilla.org/products/mozilla1.x/)
- Netscape Navigator 7.1 and higher (http://www.netscape.com)
- Opera 7.11 and higher (http://www.opera.com)
Mac OS X
- Camino Version: 0.7 and higher (http://www.mozilla.org/products/camino/)
- Firefox 0.6 and higher (http://www.mozilla.org/products/firefox/)
- Mozilla 1.4 and higher (http://www.mozilla.org/products/mozilla1.x/)
- Netscape Navigator 7.1 and higher (http://www.netscape.com)
- Opera 7.11 and higher (http://www.opera.com)
- Safari 1.2 and higher (http://www.apple.com/safari/)
LINUX
- Epiphany 1.2.2 and higher (Gnome)(http://www.gnome.org/projects/epiphany/)
- 2. Firefox 0.6 and higher (http://www.mozilla.org/products/firefox/)
- 3. Galeon 1.3.14 and higher (Gnome) (http://galeon.sourceforge.net)
- 4. Konqueror 3.2 and higher (KDE) (http://www.konqueror.org/)
- 5. Mozilla 1.4 and higher (http://www.mozilla.org/products/mozilla1.x/)
- 6. Netscape Navigator 7.1 and higher (http://www.netscape.com)
- 7. Opera 7.11 and higher (http://www.opera.com)
Which e-mail clients support IDN?
WINDOWS
- Microsoft Outlook 2000, 2002 (XP), 2003; Outlook Express 5.0 and higher +
Verisign i-Nav PlugIn (http://www.idnnow.com)
LINUX
- Mutt 1.4.1 and higher (http://www.mutt.org)
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