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.
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.
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.
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.
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.
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.
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.
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.
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.
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].
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.
[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.
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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Copyright (C) The Internet Society (2000). All Rights Reserved.
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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