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Network Working Group                  Internet Architecture Board (IAB)Request for Comments: 2825                             L. Daigle, EditorCategory: Informational                                         May 2000A Tangled Web: Issues of I18N, Domain Names, and theOther Internet protocolsStatus 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 (2000).  All Rights Reserved.Abstract   The goals of the work to "internationalize" Internet protocols   include providing all users of the Internet with the capability of   using their own language and its standard character set to express   themselves, write names, and to navigate the network. This impacts   the domain names visible in e-mail addresses and so many of today's   URLs used to locate information on the World Wide Web, etc.  However,   domain names are used by Internet protocols that are used across   national boundaries. These services must interoperate worldwide, or   we risk isolating components of the network from each other along   locale boundaries.  This type of isolation could impede not only   communications among people, but opportunities of the areas involved   to participate effectively in e-commerce, distance learning, and   other activities at an international scale, thereby retarding   economic development.   There are several proposals for internationalizing domain names,   however it it is still to be determined whether any of them will   ensure this interoperability and global reach while addressing   visible-name representation.  Some of them obviously do not. This   document does not attempt to review any specific proposals, as that   is the work of the Internationalized Domain Name (IDN) Working Group   of the IETF, which is tasked with evaluating them in consideration of   the continued global network interoperation that is the deserved   expectation of all Internet users.IAB                          Informational                      [Page 1]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 2000   This document is a statement by the Internet Architecture Board. It   is not a protocol specification, but an attempt to clarify the range   of architectural issues that the internationalization of domain names   faces.1. A Definition of Success   The Internationalized Domain Names (IDN) Working Group is one   component of the IETF's continuing comprehensive effort to   internationalize language representation facilities in the protocols   that support the global functioning of the Internet.   In keeping with the principles of rough consensus, running code,   architectural integrity, and in the interest of ensuring the global   stability of the Internet, the IAB emphasizes that all solutions   proposed to the (IDN) Working Group will have to be evaluated not   only on their individual technical features, but also in terms of   impact on existing standards and operations of the Internet and the   total effect for end-users: solutions must not cause users to become   more isolated from their global neighbors even if they appear to   solve a local problem.  In some cases, existing protocols have   limitations on allowable characters, and in other cases   implementations of protocols used in the core of the Internet (beyond   individual organizations) have in practice not implemented all the   requisite options of the standards.2. Technical Challenges within the Domain Name System (DNS)   In many technical respects, the IDN work is not different from any   other effort to enable multiple character set representations in   textual elements that were traditionally restricted to English   language characters.   One aspect of the challenge is to decide how to represent the names   users want in the DNS in a way that is clear, technically feasible,   and ensures that a name always means the same thing.  Several   proposals have been suggested to address these issues.   These issues are being outlined in more detail in the IDN WG's   evolving draft requirements document; further discussion is deferred   to the WG and its documents.3. Integrating with Current Realities   Nevertheless, issues faced by the IDN working group are complex and   intricately intertwined with other operational components of the   Internet.  A key challenge in evaluating any proposed solution is the   analysis of the impact on existing critical operational standardsIAB                          Informational                      [Page 2]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 2000   which use fully-qualified domain names [RFC1034], or simply host   names [RFC1123].  Standards-changes can be effected, but the best   path forward is one that takes into account current realities and   (re)deployment latencies. In the Internet's global context, it is not   enough to update a few isolated systems, or even most of the systems   in a country or region.  Deployment must be nearly universal in order   to avoid the creation of "islands" of interoperation that provide   users with less access to and connection from the rest of the world.   These are not esoteric or ephemeral concerns.  Some specific issues   have already been identified as part of the IDN WG's efforts.  These   include (but are not limited to) the following examples.3.1 Domain Names and E-mail   As indicated in the IDN WG's draft requirements document, the issue   goes beyond standardization of DNS usage.  Electronic mail has long   been one of the most-used and most important applications of the   Internet.  Internet e-mail is also used as the bridge that permits   the users of a variety of local and proprietary mail systems to   communicate. The standard protocols that define its use (e.g., SMTP   [RFC821,RFC822] and MIME [RFC2045]) do not permit the full range of   characters allowed in the DNS specification. Certain characters are   not allowed in e-mail address domain portions of these   specifications.  Some mailers, built to adhere to these   specifications, are known to fail when on mail having non-ASCII   domain names in its address -- by discarding, misrouting or damaging   the mail.  Thus, it's not possible to simply switch to   internationalized domain names and expect global e-mail to continue   to work until most of the servers in the world are upgraded.3.2 Domain Names and Routing   At a lower level, the Routing Policy Specification Language (RPLS)   [RFC2622] makes use of "named objects" -- and inherits object naming   restrictions from older standards ([RFC822] for the same e-mail   address restrictions, [RFC1034] for hostnames).  This means that   until routing registries and their protocols are updated, it is not   possible to enter or retrieve network descriptions utilizing   internationalized domain names.3.3 Domain Names and Network Management   Also, the Simple Network Management Protocol (SNMP) uses the textual   representation defined in [RFC2579].  While that specification does   allow for UTF-8-based domain names, an informal survey of deployed   implementations of software libraries being used to build SNMP-   compliant software uncovered the fact that few (if any) implement it.IAB                          Informational                      [Page 3]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 2000   This may cause inability to enter or display correct data in network   management tools, if such names are internationalized domain names.3.4 Domain Names and Security   Critical components of Internet public key technologies (PKIX,   [RFC2459], IKE [RFC2409]) rely heavily on identification of servers   (hostnames, or fully qualified domain names) and users (e-mail   addresses).  Failure to respect the character restrictions in these   protocols will impact security tools built to use them -- Transport   Layer Security protocol (TLS, [RFC2246]), and IPsec [RFC2401] to name   two.   Failure may not be obvious.  For example, in TLS, it is common usage   for a server to display a certificate containing a domain name   purporting to be the domain name of the server, which the client can   then match with the server name he thought he used to reach the   service.   Unless comparison of domain names is properly defined, the client may   either fail to match the domain name of a legitimate server, or match   incorrectly the domain name of a server performing a man-in-the-   middle attack.  Either failure could enable attacks on systems that   are now impossible or at least far more difficult.4. Conclusion   It is therefore clear that, although there are many possible ways to   assign internationalized names that are compatible with today's DNS   (or a version that is easily-deployable in the near future), not all   of them are compatible with the full range of necessary networking   tools.  When designing a solution for internationalization of domain   names, the effects on the current Internet must be carefully   evaluated. Some types of solutions proposed would, if put into effect   immediately, cause Internet communications to fail in ways that would   be hard to detect by and pose problems for those who deploy the new   services, but also for those who do not; this would have the effect   of cutting those who deploy them off from effective use of the   Internet.   The IDN WG has been identified as the appropriate forum for   identifying and discussing solutions for such potential   interoperability issues.   Experience with deployment of other protocols has indicated that it   will take years before a new protocol or enhancement is used all over   the Internet.  So far, the IDN WG has benefited from proposed   solutions from all quarters, including organizations hoping toIAB                          Informational                      [Page 4]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 2000   provide services that address visible-name representation and   registration -- continuing this process with the aim of getting a   single, scalable and deployable solution to this problem is the only   way to ensure the continued global interoperation that is the   deserved expectation of all Internet users.5. Security Considerations   In general, assignment and use of names does not raise any special   security problems.  However, as noted above, some existing security   mechanisms are reliant on the current specification of domain names   and may not be expected to work, as is, with Internationalized domain   names.  Additionally, deployment of non-standard systems (e.g., in   response to current pressures to address national or regional   characterset representation) might result in name strings that are   not globally unique, thereby opening up the possibility of "spoofing"   hosts from one domain in another, as described in [RFC2826].6. Acknowledgements   This document is the outcome of the joint effort of the members of   the IAB.  Additionally, valuable remarks were provided by Randy Bush,   Patrik Faltstrom, Ted Hardie, Paul Hoffman, and Mark Kosters.7. References   [RFC821]  Postel, J., "Simple Mail Transfer Protocol", STD 10,RFC821, August 1982.   [RFC822]  Crocker, D., "Standard for the Format of ARPA Internet Text             Messages", STD 11,RFC 822, August 1982.   [RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities",             STD 13,RFC 1034, November 1987.   [RFC1123] Braden, R., "Requirements for Internet Hosts -- Application             and Support", STD 3,RFC 1123, November 1989.   [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the             Internet Protocol",RFC 2401, November 1998.   [RFC2409] Harkins, D and D. Carrel, "The Internet Key Exchange             (IKE)",RFC 2409, November 1998.   [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail             Extensions (MIME) Part One:  Format of Internet Message             Bodies",RFC 2045, November 1996.IAB                          Informational                      [Page 5]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 2000   [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",RFC 2246, January 1999.   [RFC2459] Housley, R., Ford, W., Polk, W. and D. Solo, "Internet             X.509 Public Key Infrastructure Certificate and CRL             Profile",RFC 2459, January 1999.   [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.             and M. Rose, "Textual Conventions for SMIv2",RFC 2579,             April 1999.   [RFC2622] Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D.,             Meyer, D., Bates, T., Karrenberg, D. and M. Terpstra,             "Routing Policy Specification Language (RPSL)",RFC 2622,             June 1999.   [RFC2826] IAB, "IAB Technical Comment on the Unique DNS Root",RFC2826, May 2000.8. Author's Address   Internet Architecture Board   EMail:  iab@iab.org   Membership at time this document was completed:      Harald Alvestrand      Ran Atkinson      Rob Austein      Brian Carpenter      Steve Bellovin      Jon Crowcroft      Leslie Daigle      Steve Deering      Tony Hain      Geoff Huston      John Klensin      Henning SchulzrinneIAB                          Informational                      [Page 6]

RFC 2825   Issues: I18N, Domain Names, and Internet Protocols   May 20009. Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS 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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.IAB                          Informational                      [Page 7]