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Network Working Group                                             X. LeeRequest for Comments: 4713                                        W. MaoCategory: Informational                                            CNNIC                                                                 E. Chen                                                                  N. Hsu                                                                   TWNIC                                                              J. Klensin                                                            October 2006Registration and Administration Recommendations for Chinese Domain NamesStatus of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2006).IESG Note   This RFC is not a candidate for any level of Internet Standard.  The   IETF disclaims any knowledge of the fitness of this RFC for any   purpose and in particular notes that the decision to publish is not   based on IETF review for such things as security, congestion control,   or inappropriate interaction with deployed protocols.  The RFC Editor   has chosen to publish this document at its discretion.  Readers of   this document should exercise caution in evaluating its value for   implementation and deployment.  SeeRFC 3932 for more information.Abstract   Many Chinese characters in common use have variants, which makes most   of the Chinese Domain Names (CDNs) have at least two different forms.   The equivalence between Simplified Chinese (SC) and Traditional   Chinese (TC) characters is very important for CDN registration.  This   memo builds on the basic concepts, general guidelines, and framework   ofRFC 3743 to specify proposed registration and administration   procedures for Chinese domain names.  The document provides the   information needed for understanding and using the tables defined in   the IANA table registrations for Simplified and Traditional Chinese.Lee, et al.                  Informational                      [Page 1]

RFC 4713        Recommendations for Chinese Domain Names    October 2006Table of Contents1. Introduction ....................................................22. Terminology .....................................................32.1. Chinese Characters .........................................32.2. Chinese Domain Name Label (CDNL) ...........................32.3. Simplified Chinese Variant Table (SCVT) ....................42.4. Traditional Chinese Variant Table (TCVT) ...................42.5. Original Chinese Domain Name Label (OCDNL) .................43. Procedure for Registration of Chinese Domain Name Labels ........43.1. Terminology and Context ....................................43.2. Procedure in Terms of theRFC 3743 Model ...................43.3.RFC 3743 Optional Registry Processing ......................54. Security Considerations .........................................55. Acknowledgements ................................................66. References ......................................................66.1. Normative References .......................................66.2. Informative References .....................................71.  Introduction   With the standardization of Internationalized Domain Names for   Application (IDNA, described in [RFC3490], [RFC3491], and [RFC3492]),   internationalized domain names (IDNs), i.e., those that contain non-   ASCII characters, are included in the DNS, and users can access the   Internet with their native languages, most of which are not English.   However, many languages have special requirements, which are not   addressed in the IDNA RFCs.  One way to deal with some of the   remaining issues involves grouping characters that could be confused   together as "variants".  The variant approach is discussed inRFC4290 [RFC4290] and specifically for documents written in Chinese,   Japanese, or Korean (CJK documents), in the so-called "JET   Guidelines"RFC 3743 [RFC3743].  Readers of this document are assumed   to be familiar with the concepts and terminology of the latter.  The   guidelines specified in this document provide a set of specific   tables and methods required to apply the JET Guidelines to Chinese   characters.  For example, changes were made in the forms of a large   number of Chinese characters during the last century to simplify   writing and reading.  These "Simplified" characters have been adopted   in some Chinese-speaking communities, while others continue to use   the "Traditional" forms.  On the global Internet, if IDNA were used   alone, there would be considerable potential for confusion if the two   forms were not considered together.  Consequently, effective use of   Chinese Domain Names (CDNs) requires variant equivalence, as   described inRFC 3743, to handle character differences between   Simplified and Traditional Chinese forms.Lee, et al.                  Informational                      [Page 2]

RFC 4713        Recommendations for Chinese Domain Names    October 2006   Chinese variant equivalence itself is very complicated in principle   (please read [C2C] for further information).  When it comes to the   usage of Chinese domain names, the basic requirement is to match the   user perception of Chinese characters between Simplified Chinese (SC)   and Traditional Chinese (TC) forms.  When users register SC or TC   domain names, they will wish to obtain the other forms (Traditional   or Simplified, respectively) as well, and expect others to be able to   access the website or other resources in both forms.   This document specifies a solution for Chinese domain name   registration and administration that has been adopted and deployed by   CNNIC (the top-level domain registry for "CN") and TWNIC (the top-   level domain registry for "TW") to manage Simplified Chinese and   Traditional Chinese domain name equivalence.  In the terminology ofRFC 3743, this solution is based on Internationalized Domain Labels   (IDLs).2.  Terminology   This document adopts the terminologies that are defined inRFC 3743.   It is not possible to understand this document without first   understanding the concepts and terminology orRFC 3743, including   terminology introduced in its examples.  Additional terminology is   defined later in this document.2.1.  Chinese Characters   This document suggests permitting only a subset of Chinese characters   in Chinese Domain Names (CDNs) and hence in the DNS.  When this   document discusses Chinese characters, it only refers to the subset   of the characters in the first column of the current IANA   registration tables for Chinese as discussed inSection 2.3 andSection 2.4.  These are defined, in detail, in [LVT-SC] and [LVT-TC].   Of course, characters excluded from these tables are still valid   Chinese characters.  However, this document strongly suggests that   registries do not permit any registration of Chinese characters that   are not listed in the tables.  The tables themselves will be updated   in the future if necessary.2.2.  Chinese Domain Name Label (CDNL)   If an IDN label includes at least one Chinese character, it is called   a Chinese Domain Name (CDN) Label.  CDN labels may contain characters   from the traditional letter-digit-hyphen (LDH) set as well as Chinese   characters.Lee, et al.                  Informational                      [Page 3]

RFC 4713        Recommendations for Chinese Domain Names    October 20062.3.  Simplified Chinese Variant Table (SCVT)   Based onRFC 3743 [RFC3743], a language table for Simplified Chinese   has been defined [LVT-SC].  It can be used for the registration of   Simplified Chinese domain names.  The key feature of this table is   that the preferred variant is the SC character, which is used by   Chinese mainland users or defined in Chinese-related standards.2.4.  Traditional Chinese Variant Table (TCVT)   Similarly, a language table has been defined for Traditional Chinese   [LVT-TC].  It is also based on the rules ofRFC 3743.  It can be used   for registration of Traditional Chinese domain names.  The preferred   variant is the TC character, which is used by Taiwan users or defined   in related standards.2.5.  Original Chinese Domain Name Label (OCDNL)   The Chinese Domain Name Label that users submit for registration.3.  Procedure for Registration of Chinese Domain Name Labels3.1.  Terminology and Context   This document adopts the same procedure for Chinese Domain Name Label   (CDNL) registration as the one defined for more general IDN labels insection 3.2.3 of RFC 3743 [RFC3743].  The terminology and notation   used below, and the steps that are mentioned, derive from that   document.  In particular, "CV" is the character variant associated   with an input character ("IN") and a language table.  The language   tables used here are those for Chinese as spoken and written in the   Chinese mainland (ZH-CN) and on Taiwan (ZH-TW).  "PV" is the selected   Preferred Variant.3.2.  Procedure in Terms of theRFC 3743 Model   The first column of the Simplified Chinese Variant Table (SCVT) is   the same as the first column of the corresponding Traditional Chinese   Variant Table (TCVT) and so are the third columns of both tables.   Consequently, the CV(IN, ZH-CN) will be same as the CV(IN, ZH-TW)   after Step 3; the PV(IN, ZH-CN) is in SC form, and the PV(IN, ZH-TW)   is in TC form.  As a result, there will not be more than three   records (i.e., for the original label (OCDNL), the Simplified Chinese   (SC) form, and the Traditional Chinese (TC) form) to be added into   the zone file after applying this procedure.  In other words, the   procedure does not generate labels that contain a mixture of   Simplified and Traditional Chinese as variants.Lee, et al.                  Informational                      [Page 4]

RFC 4713        Recommendations for Chinese Domain Names    October 2006   The set of languages associated with the input (IN) is both ZH-CN and   ZH-TW by default. The procedure for CDNL registration uses the   optional registry-defined rules provided inRFC 3743 for optional   processing, with the understanding that the rules may vary for   different registries supporting CDNs.  The motivation for such rules   is described below.   The preferred variant(s) is/are TC in TCVT, and SC in SCVT.  There   may be more than one preferred variant for a given valid character.3.3.RFC 3743 Optional Registry Processing   In actuality, while IDNA, and henceRFC 3743, process characters one   at a time, the actual relationship between the valid code point and   the preferred variant is contextual: whether one character can be   substituted for another depends on the characters with which it is   associated in a label or, more generally, in a phrase.  In   particular, some of the preferred variants make no sense in   combination with other characters; therefore, those combinations   should not be added into the Zone file (described as "ZV" or zone   variants inRFC 3743).  If desired, it should be possible to define   and implement rules to reduce the preferred variant labels to only   plausible ones.  This could be done, for example, with some   artificial intelligence tools, or with feedback from the registrant,   or with selection based on frequency of occurrence in other texts.   To illustrate one possibility, the OCDNL could be required to be TC-   only or SC-only, and if there is more than one preferred variant, the   OCDNL will be used as the PV, instead of the PV produced by the   algorithm.   To reemphasize, the tables in [LVT-SC] and [LVT-TC] follow the table   format and terminologies defined in [RFC3743].  If one intends to   implement Chinese domain name registrations based on these two tables   or ones similar to them, a complete understanding ofRFC 3743 is   needed for the proper use of those tables.4.  Security Considerations   This document is subject to the same security considerations asRFC3743, which defines the table formats and operations.  As with that   base document, part of its intent is to reduce the security problems   that might be caused by confusion among characters with similar   appearances or meanings.  While it will not introduce any additional   security issues, additional registration restrictions such as those   outlined inSection 3 may further reduce potential problems.Lee, et al.                  Informational                      [Page 5]

RFC 4713        Recommendations for Chinese Domain Names    October 20065.  Acknowledgements   Thanks to these people for their suggestions and for their efforts to   bring this tough work to conclusion and to promote the results: WANG   YanFeng, Ai-Chin LU, Shian-Shyong TSENG, QIAN HuaLin, and Li-Ming   TSENG.   The authors especially thank Joe ZHANG and XiaoMing WANG for their   outstanding contributions on SCVT in [LVT-SC].  Also, thanks to Kenny   HUANG, Zheng-Wei LIN, Shi-Xiong TSENG, Lie-Neng WU, Cheng-Wu PAN,   Lin-Mei WEI, and Qi-Qing HSU for their efforts and contributions on   editing the TCVT in [LVT-TC].  These experts provided basic materials   or gave very crucial suggestions and principles to accomplish these   two variant tables.   The authors also gratefully acknowledge the contributions of those   who commented and made suggestions on this document, including James   SENG, and other JET members.6.  References6.1.  Normative References   [LVT-SC]   QIAN, H. and X. LEE, ".CN Chinese Character Table", IANA              IDN Languages Tables, March 2005.   [LVT-TC]   LU, A., ".TW Traditional Chinese Character Table", IANA              IDN Languages Tables, March 2005.   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,              "Internationalizing Domain Names in Applications (IDNA)",RFC 3490, March 2003.   [RFC3491]  Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep              Profile for Internationalized Domain Names (IDN)",RFC3491, March 2003.   [RFC3492]  Costello, A., "Punycode: A Bootstring encoding of Unicode              for Internationalized Domain Names in Applications              (IDNA)",RFC 3492, March 2003.   [RFC3743]  Konishi, K., Huang, K., Qian, H., and Y. Ko, "Joint              Engineering Team (JET) Guidelines for Internationalized              Domain Names (IDN) Registration and Administration for              Chinese, Japanese, and Korean",RFC 3743, April 2004.Lee, et al.                  Informational                      [Page 6]

RFC 4713        Recommendations for Chinese Domain Names    October 20066.2.  Informative References   [C2C]      Halpern, J. and J. Kerman, "Pitfalls and Complexities of              Chinese to Chinese Conversion", International Unicode              Conference (14th) in Boston, March 1999.   [RFC4290]  Klensin, J., "Suggested Practices for Registration of              Internationalized Domain Names (IDN)",RFC 4290, December              2005.Lee, et al.                  Informational                      [Page 7]

RFC 4713        Recommendations for Chinese Domain Names    October 2006Authors' Addresses   LEE Xiaodong   CNNIC, No.4 South 4th Street, Zhongguancun   Beijing  100080   Phone: +86 10 58813020   EMail: lee@cnnic.cn   URI:http://www.cnnic.cn   MAO Wei   CNNIC, No.4 South 4th Street, Zhongguancun   Beijing  100080   Phone: +86 10 58813055   EMail: mao@cnnic.cn   URI:http://www.cnnic.cn   Erin CHEN   TWNIC, 4F-2, No. 9, Sec. 2, Roosevelt Rd.   Taipei  100   Phone: +886 2 23411313   EMail: erin@twnic.net.tw   URI:http://www.twnic.net.tw   Nai-Wen HSU   TWNIC, 4F-2, No. 9, Sec. 2, Roosevelt Rd.   Taipei  100   Phone: +886 2 23411313   EMail: snw@twnic.net.tw   URI:http://www.twnic.net.tw   John C KLENSIN   1770 Massachusetts Ave, #322   Cambridge, MA  02140   USA   Phone: +1 617 491 5735   EMail: john+ietf@jck.comLee, et al.                  Informational                      [Page 8]

RFC 4713        Recommendations for Chinese Domain Names    October 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 78 and at www.rfc-editor.org/copyright.html, and   except as set forth therein, the authors retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).Lee, et al.                  Informational                      [Page 9]