考古学家在“南海一号”沉船发现年代最早的31粒胡椒

Network Working Group                  Internet Architecture Board (IAB)
Request for Comments: 2825                             L. Daigle, Editor
Category: Informational                                         May 2000

         A Tangled Web: Issues of I18N, Domain Names, and the
                        Other Internet protocols

Status 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.

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   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 standards

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   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.

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   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 to

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   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, RFC
             821, 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.

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   [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", RFC
             2826, 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 Schulzrinne

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9. 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.

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