standardization of internationalized domain name at ietf 24 jan 2002 yoshiro yoneya jpnic
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Standardization of Internationalized Domain Name
at IETF
24 Jan 2002
Yoshiro YONEYA <[email protected]>
JPNIC
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What is IDN?
• Internationalized Domain Name.– Current domain name is represented with
ASCII alpha-numeric and hyphen characters.– IDN is a technical challenge to represent
domain name with not only ASCII but also NON-ASCII characters.
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What is Internationalization?
• Framework to extend character repertoire for domain names.
• Need to be a Global Standard not to lose global communication.
• IETF IDN (Internationalized Domain Name) WG is doing the work.
• Some confusion by using the word ‘Multilingualization’.– Character is just one of a component of languages.– Multilingual domain name is a service level’s aspect.
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Internationalized Domain Names
华人 .公司 .cn 華人 .商業 .tw
高島屋 . 会社 .jp
삼성 . 회사 .kr 三星 . 회사 .krم. االهرام
viagénie.qc.caקום.ישראל
ที�เอชนิ�ค.พาณิ�ชย์ .ไทีย์
現代 .com ヤフー .comhttp://www.jdna.jp/activities/event/jdn-tutorial/IDNSDK.pdf
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Why IDN?
• Increases of the Internet users who are not familiar with English.– Easy to memorize, type in, etc.
• Drastic changes of usage of domain name.– Domain name is now used as not only host
name but also signboard.
• Creates new business opportunities.– Many ventures began services.
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Drawback of IDN
• Loses global acceptability at end-user interface.– Hard to type in or display NON-ASCII characte
rs without appropriate I/O devices and / or softwares.
• Cause impact to the operation.– Requires software update and / or additional pr
ocessing.– Deployment issue.
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History of IDN WG
• Established on Jan 2000.– Mainly discussion is done on mailing list.
• Had 1st meeting at 47th IETF at Adelaide.– From then, having meeting every IETF.
• Decided WG’s solution at last (52nd) IETF.– IDNA, NAMEPREP and Punycode (formerly k
nown as AMC-ACE-Z).– Waiting for WG last call.
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Scope and priority of IDN WG
• Provide standard.– Not to divide the global connectivity and communication
of the Internet.
• Backward compatibility.– Compatibility with current DNS and application protocols
to work with current Internet infrastructure.
• No localization.– Independent from certain regions, countries and / or
languages– Refer to existing universal standards– Common framework essential to internationalization
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IDNA(Internationalizing Domain Names In Applications)
draft-ietf-idn-idna-06.txt
• An architecture denotes how to process IDN.– Use Unicode which is upper compatible with ASCII as
a character codeset.– Normalize internal representation of characters which h
as multiple code points such as upper/lower, full-width/half-width and composing characters, into a single representation not to fail matching.
– Represent NON-ASCII characters which inputted or displayed at user interface as an ASCII Compatible Encoding (ACE) string on the Network.
– Those processes be performed in application software.
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Important point of IDNA
• Representation at the user interface layer and the network layer is different.– Though the same for ASCII domain names.
• Application solution.– Least impact to the Internet infrastructure.
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Image of the IDNA
User
InternalRepresentation
UI
API
Application servers
End system
Application
Local
Int’l
Resolver
DNS servers
NAMEPREPTo/From Unicode
To/From ACE
NAMEPREP
To/From ACE
To/From Unicode
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NAMEPREP(Stringprep Profile for Internationalized Host Name
s) draft-ietf-idn-nameprep-07.txt
• Profile for STRINGPREP (Preparation of Internationalized Strings)– draft-hoffman-stringprep-00.txt
• Some scripts such as alphabet have multiple representation for a character.– Domain name is case insensitive.
• Normalization process to unify representation of strings that is the same in meaning or displaying into a single representation.– Case (upper / lower)– Compatible character (full / half width)– Composing character
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Important point of NAMEPREP
• Normalize representation of Internationalized domain name string to match correctly.– ‘a’ vs ‘A’– ‘u’+‘¨’ vs ‘ü’– ‘ ア’ vs ‘ ’ア
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Processes in NAMEPREP
1. map• Case folding of upper/lower characters
(UTR#21)
2. normalize• Normalize representation of string (UAX#15
NFKC)
3. prohibit• Check out inappropriate character as domain
name.
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ACE(ASCII Compatible Encoding)
• Represent NON-ASCII characters by ASCII characters.– Easy to apply current DNS.– Least impact to current applications.
• Decreases maximum characters in each label.– Penalty of using only 5bit to represent 8bit data.– Requires some sort of compression algorithm.
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ACE Identifier
• Requires explicit ACE-identifier.– For reverse conversion.– Choice of ACE-ID is political issue.
• ACE-ID itself is ASCII string, so that if any proposal for ACE-ID is raised, it will be registered as ASCII domain name.
• Actually happened at gTLD.
• IANA will assign the ACE-ID.
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Criteria of ACE selection
• Simple algorithm.– For ease implementation.– Interoperability.
• Effective compression results for practical IDNs.– To accommodate characters as much as possible.
• bilateral corresponding between encoding and decoding.– To avoid existence of alternative encoded representatio
n for one IDN.– Security consideration.
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Comparison of ACE proposals
RACE BQ--3BS6KZZMRKPDBSJQ4EYKIMHTKQGYUZU2CM.JP
Punycode ZQ--ECKWD4C7C777U7MWO4BOV4JIOAU09J.JP
Encoding sample of ‘ 日本語ドメイン名試験 .JP’
Evaluation resultfrom existingJapanese JPdomain names
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Punycode draft-ietf-idn-punycode-00.txt
• Selected ACE of IDN WG.• Compression algorithm.
– Extract characters by ascending order of codepoint.– Encode difference of codepoint from previously proces
sed character’s and the position into an integer.– Extract Letters, Digits and Hyphen as bootstring.
• ASCII conversion algorithm.– Introduced new concept named ‘Generalized variable-l
ength integers’.– BASE36 (A-Z, 0-9).
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Compression process of Punycode(simplified for understanding)
• “ 文字列例”• Compression.
1. 1:U+6587 2:U+5B57 3:U+5217 4:U+4F8B
2. 4:0x4F8B 3:0x28C 2:0x440 1:0xA30
3. 0x13E30 0xA33 0x1102 0x28C1
sort, diff
To integer(diff*chars+position)
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Generalized variable-length integers of Punycode
• 12345 in decimal is represented as 1*10^4+2*10^3+3*10^2+4*10^1+5*10^0
• Digits in all place are 0-9, so components in sequential 12345 cannot distinguish 123 and 45 or 1234 and 5.
• Furthermore, 012345 and 12345 are the same value with different representation.
• GVLI (Generalized variable-length integers) is an idea to solve this problem.
• Defines threshold for each place, and recognize a number below the threshold is delimiter.
• Threshold is an appropriate number smaller than base number.
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Encoding process of Punycode (simplified for understanding)
• Assign A-Z0-9 to GVLI.– Assume 36 for base, 10, 18, 25, 25 for thresholds.1. 0x13E30 0xA33 0x1102 0x28C1
2. OIUD3. BS44. CN85. XML
• “ 文字列例” =>“OUIDBS4CN8XML” .– Real Punycode generates “FSQW5D78MBSK”.
24*1+18*26(=1*(36-10))+30*468(=26*(36-18))+13*5148(=468*(36-25))
11*1+28*26+4*46812*1+23*26+8*468
33*1+22*26+21*468
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Standardization of IDN is just the start point of utilization
• End users uses IDN with application softwares.– Web, Mail, etc.
• IDNA requires application’s correspondence.• Must define how to deal IDNs in application proto
cols.
Standardization of IDN does not mean ready to use. Just a start point for applications incorporating
new features.
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HTTP Request(DNS resolve only)
Web
User
http:// ジェーピーニック .JP/
ZQ--HCKQZ9BZB1CYRB.JP
Web server’s
IP adress
GET http:// ジェーピーニック .JP/ HTTP/1.1Host: ジェーピーニック .JPReferer: http:// ジェーピーニック .JP/
Error!
DNS
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HTTP Request(ACE in HTTP header)
Web
User
http:// ジェーピーニック .JP/
ZQ--HCKQZ9BZB1CYRB.JP
Web server’s IP address
GET http://ZQ--HCKQZ9BZB1CYRB.JP/ HTTP/1.1Host: ZQ--HCKQZ9BZB1CYRB.JPReferer: http://ZQ--HCKQZ9BZB1CYRB.JP/
Contents
DNS
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References
• IETF IDN WG Web page– http://www.i-d-n.net/
• Unicode Consortium– http://www.unicode.org/
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Acknowledgement
• Telecommunications Advancement Organization of Japan (TAO).– JPNIC’s research activity of security investigati
on of IDN is a part of TAO’s research.– http://www.shiba.tao.go.jp/
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IDN Compliant clients & implementations
• Mozillahttp://playground.i-dns.net/mozilla/index.html– Plug-in to Mozilla, resolution using RACE
• Operahttp://www.opera.com/– Native, Resolution using RACE
• Internet Explorer 5 or higherhttp://www.microsoft.com/windows/ie/default.asp– Uses keyword search engine as RACE converter
• mDNkithttp://www.nic.ad.jp/jp/research/idn/mdnkit/download/– Opensource toolkit for developing IDN compliant softwares