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Versions: 00 01                                                         
IDN                                           Edmon Chung & David Leung
Internet Draft                                              Neteka Inc.
<draft-ietf-idn-dnsii-trace-01.txt>
Intended Category: Informational                              July 2002


           Transitional Reflexive ACE û IDN Transition (IDNX)


STATUS OF THIS MEMO

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026 except that the right to
   produce derivative works is not granted.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.  Internet-Drafts are draft documents valid for a maximum of
   six months and may be updated, replaced, or obsoleted by other
   documents at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than as "work in progress."

   The reader is cautioned not to depend on the values that appear in
   examples to be current or complete, since their purpose is primarily
   educational.  Distribution of this memo is unlimited.

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   This document, while sharing a similar concept, is an overhaul of
   TRACE-00 and describes a strategy for domain name server operators to
   prepare and transition their services for multilingual domain names
   (IDN û Internationalized Domain Names).

   The TRACE-01 or IDNX (IDN Transition) approach accepts that users
   with non-IDN aware applications will be attempting to access
   multilingual domain names.  Hence it is the registry or domain
   operator's responsibility to provide an IDN solution that resolves
   these issues to make it a seamless transition experience for
   technically unsophisticated users.

   In essence, the IDNX approach embraces a complementary server-side
   implementation to smooth the transition.  IDNX ready domain servers
   should be backward compatible, and successfully resolve IDN requests
   sent via non-IDN aware applications, whether they are formatted in
   local encoding, UTF-8 or an identifiable variant; as well as forward
   compatible, and be able to resolve ACE requests.



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   The IDNX approach also utilizes a dynamic CNAME mechanism (similar to
   TRACE-00) to provision for the sub-delegation of multilingual domain
   names to hosts running non-IDN aware DNS servers.

Table of Contents

   Abstract...........................................................1
   1. Introduction....................................................2
   1.1 Terminology....................................................3
   1.2 Assumptions....................................................3
   2. Common Misconceptions...........................................3
   3. The reality of a Purebred IDNA Approach.........................3
   3.1 Lengthy Transition & User Confusion............................4
   3.2 Registry Responsibilities......................................5
   4. Complementary Server-end Brute Force Resolution.................5
   4.1 The IDNX Premise...............................................5
   4.2 Resolving Domain Names.........................................6
   4.3 Extent of Resolution...........................................6
   4.4 Ambiguity Resolution...........................................7
   4.5 Complementing IDNA (OPTIONAL)..................................7
   5. Delegating Multilingual Domain Names............................8
   5.1 Dynamic CNAME..................................................8
   5.2 Setting up a Multilingual Domain Name at the Registry..........9
   5.2.1 Character Equivalence Policies (OPTIONAL)...................10
   5.3 Setting up a Multilingual Domain Zone at the Host.............11
   5.4 Complementing IDNA............................................11
   6. Using Multilingual Domains on other Applications...............11
   6.1 IDN in Email Addresses........................................11
   6.2 Hosting Websites based on IDN.................................12
   6.3 Other Known Issues about using IDN............................12
   7. Security Considerations........................................13
   References........................................................13
   Acknowledgements..................................................14

1. Introduction

   During the lengthy discussion at the IETF IDN workgroup, the question
   about time-to-deployment is often being raised and considered a
   critical concern.  However little word was said on any actual
   transition path towards IDN.  This document provides a comprehensive
   guide to the issues surrounding the deployment as well as information
   on resolving them during the transition period.

   This document is intended to be an informational paper offering
   suggestions to implementers of IDN and registries wishing to provide
   IDN registration to make it a more seamless transition for end users.
   IDNX is a transitory approach and is complementary and compatible to
   the eventual standard protocol for IDN.

   In fact, some or all of the aspects and suggestions discussed in this
   paper has been implemented at various domain registries already.  The
   extent of coverage differs from the different implementations.  One


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   key observation however is that all are compatible and cause no
   damage to the Internet at large.

1.1 Terminology

   The key words "MUST", "SHALL", "REQUIRED", "SHOULD", "RECOMMENDED",
   and "MAY" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

1.2 Assumptions

   This document assumes that the reader has basic knowledge of the DNS
   and IDN.  For more information on the IDN discussions and background
   knowledge checkout: http://neteka.com/en/pages/products/position.html

2. Common Misconceptions

   There is a common misconception among domain registries and
   registrars that once a proposed IETF standard (in the form of an RFC:
   Request for Comments) for multilingual and Internationalized domain
   names (IDNÆs) is published; Registries will immediately be able to
   accept registrations and deliver working multilingual domain names to
   end-users.  In fact, the publishing of RFCs for IDN is but the
   beginning of a long transition towards a common and universal
   multilingual namespace.

   Another common misconception is that a server-end approach would
   cause a lengthier transition.  That however is only based on a server
   protocol overhaul for IDN and not the use of a server-end transitory
   solution.  This document specifically describes a solution for the
   transition and utilizes a complementary server-end approach to smooth
   the move with the end user in mind.

3. The reality of a Purebred IDNA Approach

   Simply put, ACE is a process whereby multilingual domain names are
   converted into an alphanumeric string containing only A-Z, 0-9 and
   hyphens "-" (e.g. bq--ad9ebbvfnqerv.example).  IDNA mandates that
   this transformation take place before an application, for example the
   browser, sends a DNS request over the Internet (over-the-wire) to a
   registry name server.

   Success of this "Client" only approach therefore has two inherent
   pre-conditions;

   1. Firstly, in order for IDNA to function universally, all software
      programs that interact with a domain name MUST be upgraded with
      the ACE standard (browsers, email applications, html editors,
      audio/video streaming applications, word processors, operating
      system tools, ftp agents, etc.).  Or the user will have to type
      in the ACE string to reach multilingual domains; and



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   2. The success of IDNÆs will depend on the successful propagation of
      those client software, which will be highly dependant on a) the
      successful dustribution of client plug-in in the short-term and
      b) the incorporation of the standard in next generations of
      application software (e.g. MSIE and MS Outlook)

3.1 Lengthy Transition & User Confusion

   A key concern with respect to a purebred client approach to IDN is
   that there are simply no efficient or effective means to distribute
   the client plug-ins.

   Even if we assume that a dominant software provider, such as
   Microsoft, with their penetration into the browser and email client
   market, was to introduce a new version of its Internet Explorer and
   Outlook line of products with the IDNA client built in, it will still
   take a considerable amount of time before these new versions reach
   the majority of desktops around the Internet.

   Using Microsoft IE 6.0 as a yardstick for new browser adoption rates,
   which yielded an eye-popping 34% penetration within 7 months of its
   release, the industry is still effectively looking at a minimum of
   24-36 months or more before a critical mass of Internet users will
   have adopted an IDN standard-ready-browser.  That is not taking into
   consideration the lead-time for Microsoft to release the next version
   of their software, let alone whether IDN will make the cut for its
   next version, and that the IDNA components are stable.  This will
   realistically add another 12 months to the process.

   Adoption rate from different regions however may be different and
   correlated to the urgency of having a complete IDN system in place.
   For example, regions where non-Latin based character sets may have
   more adoption faster.  However early set backs by domain providers
   who have not addressed the transitional issues for the user may cause
   loss of confidence by users of multilingual domain names.

   Finally, the client side approach to internationalized domains is
   especially susceptible to client plug-in software conflicts as
   providers scramble to push out these plug-in software applications.
   Client plug-in providers may purposefully or inadvertently interfere
   with how the browsers handle multilingual characters causing greater
   confusion.

   To summarize, the purebred IDNA approach requires no changes to the
   DNS infrastructure but does require fast and efficient distribution
   of client software that supports the standard, which is difficult to
   achieve.  Registries that cannot provide reasonable access to IDNs
   from the start will likely experience support headaches and many
   dissatisfied users who are confused and frustrated because their
   multilingual domain names do not work.  Further, without general
   accessibility, the value of multilingual domains will be compromised,
   ultimately causing the move towards IDN to be even slower.


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3.2 Registry Responsibilities

   Because the average Internet user is not expected to be technically
   sophisticated and know that they have to upgrade their existing
   applications (such as the browser) before using multilingual domain
   names, it is the opinion of the authors that it becomes the
   registryÆs responsibility to provide a multilingual domain deployment
   that is transparent to its users.

   In other words, the registry should be prepared to accept and resolve
   multilingual domain requests from users with existing software when
   they deploy and offer multilingual domain registrations to
   registrants.

   Of course, individual policies for each registry may differ.  This
   document intends to offer some suggested solutions to domain registry
   operators in dealing with real life issues about the deployment of
   multilingual domain names.

4. Complementary Server-end Brute Force Resolution

   We understand that it will be a lengthy transition to IDNA given that
   it requires upgrade of millions of clients and applications that are
   already out there.  IDNX complements it with a solution that can be
   deployed at one single node (the registry) and make it possible for
   the millions of existing users and hosts to immediately be able to
   access and use multilingual domains.

4.1 The IDNX Premise

   The premises of IDNX are:

   1. To support and complement the adoption of the open IDN standard;
   2. To present an option for a working solution that provides a
      seamless transition to the IDN standard;
   3. Be fully compliant with the IDN standard by preparing the
      registry for multilingual domain requests sent via existing
      applications as well as upgraded IDN aware applications;
   4. Accepting and addressing the fact that multilingual domain
      requests will be successfully sent to the registry from existing
      software and will resolve those requests instead of avoid them;
   5. To provide a transitory solution that will make multilingual
      domain names functional immediately;
   6. To allow the host for a multilingual domain name to use an
      existing (BIND, etc.) DNS software by using only an ACE record
      (only registry Servers need be updated or supplemented);

   In short, the authors believe that a complementary server side
   approach to IDN is a crucial component for the successful deployment
   of IDNs at a registry.  This document outlines possible approaches to
   the resolving of an IDN and how IDNX can both accelerate adoption and
   reduce the risk of deployment of the IDN standard for registries.


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4.2 Resolving Domain Names

   In general, there are three types of IDN requests that a registry
   server may receive: 1. Domain in the form of UTF8 encoding; 2. Domain
   in the form of its local encoding (GB, Big-5, JIS, KSC, ISO8859-1..13
   etc.); 3. Domain is in an ACE (ASCII Compatible Encoding) format.
   Each of these types includes both the possibility that the received
   request is in its pure form or that it is a variant of the type.
   Because the application (browser or the operating system) was not
   designed for multilingual domain names, even though it does send out
   the domain request, it often tampers with the characters before
   sending, causing the advent of a variant being generated.

4.3 Extent of Resolution

   Type 1 requests, where a domain is sent in the form of UTF8 encoded
   characters, are generally received from more recent versions of
   browsers and operating platforms.  These include Microsoft Internet
   Explorer 5 and above, Netscape 6 and above and applications based on
   the Windows 2000 or XP platform.  These applications were designed to
   deal with multilingual characters using Unicode, however, because it
   was not specifically programmed for IDNs, it sometimes malfunction
   when presented with such.  The result is that a variant of the
   original UTF8 character is formed and sent to the DNS.

   Type 2 requests, where a domain is sent in the form of local encoded
   characters (GB, Big-5, JIS, KSC, ISO8859-1..13, etc.), are generally
   received from earlier versions of browsers and operating platforms.
   These include Microsoft Internet Explorer 4, Netscape 4 most other
   applications based on the Windows 98 or earlier platform.  These
   applications were not designed to deal with multilingual characters
   using Unicode at all and therefore will be sending out the IDN in its
   local encoding.  Mostly, the domain is also not tampered with before
   sending; therefore a pure local encoding may be received.  However
   under some platforms and circumstances, it will also try to
   reinterpret a multilingual domain name.  The result is that a variant
   of the original local encoding is formed and sent to the DNS.

   Type 3 requests, where a domain is sent in the form of ACE encoded
   characters (RACE, DUDE, UTF5, AMC-Z, etc.), means that the
   application has been upgraded with an IDN client.  Because of the
   evolving standard, depending on the version or provider of the
   client, the type of ACE string may be different.  Additionally, these
   client plug-ins are susceptible to buggy code, as they are being
   created as beta products by providers experimenting with the evolving
   IDN standard.  Misbehaviors caused by browsers and operating systems,
   which are not taken into consideration by the client software also
   gives way to the creation of variants in ACE formats.

   Even though variants are created as a derivation form the pure form,
   these variations are consistent and predictable, and therefore can be
   resolved definitively and uniquely.  There is no guessing involved.
   An IDNX server could be designed to handle both requests sent in its

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   pure form as well as its variants from the three types of
   multilingual domain name requests.  The extent of the coverage is
   only dependent on the extent of research an implementer has put on
   the subject and their understanding of the IDN issues.

4.4 Ambiguity Resolution

   Another concern is for character encoding conflicts between the
   various 8-bit encoding schemes (including UTF8 and local encoding
   schemes).  IDNX suggests the handling of these issues at the point of
   registration.  On the registration side, the domain name is
   definitively registered using Unicode, regardless of whether Unicode
   or local encoding was used as input.  The desired domain name is
   confirmed with the user at the interface, ensuring that the name
   registered is accurate.

   During the availability search, encoding conflict is checked to
   ensure no existing domain name caused an encoding conflict with the
   requested domain.  In essence, it SHOULD maintain uniqueness of a
   codepoint string (in its raw hex values) regardless of its original
   encoding scheme.  The system SHOULD reject domain names on a first
   come first serve basis for domains that will cause conflict with any
   local encoding or UTF8 string (or variants if applicable).

   By taking care of both the domain registration and the resolution
   side at a domain registry, IDNX can ensure a complete solution and
   extensive coverage for multilingual domain resolution right from the
   start.  Not only will users with IDN aware plug-ins be able to access
   the multilingual domain names offered by registries or domain
   operators with IDNX, users with existing software, existing browsers
   will also be able to successfully access these names, making it a
   truly seamless and transparent transition.

4.5 Complementing IDNA (OPTIONAL)

   Note that this is an optional feature that can be deployed
   independently with other parts of the IDNX suggestions, this
   particular functionality could be omitted without losing the other
   benefits of deploying the IDNX solution.

   To complement the propagation of IDNA clients, IDNX servers could
   also improve the download experience by dynamically prompting the
   user for download when users first try to access a multilingual
   domain name.  Because the IDNX solution includes a server-end
   deployment, the server could be configured to act as a channel for
   the IDN client at the point of access to multilingual domain names.

   In essence, with an IDNX capable server, the registry would be able
   to successfully intercept multilingual domain requests and offer the
   user the option to download an IDN client plug-in.  If the user
   chooses to download the plug-in, then the domain would be resolved
   using the ACE format.  If the user declines the option to download,


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   IDNX, preserving the seamless resolution experience for the end-user,
   would still resolve the domain.

   The implementer should pay special attention in deploying this mode
   of operation for an IDNX server.  For example, the implementation
   should avoid prompting the user too many times for the download.
   There are three precautions that may be helpful:

   1. Before prompting for download, ensure that the user do not
      already have the client plug-in;
   2. Cache the user and refrain from prompting again for a given
      period of time; and
   3. Since the download will likely make use of the http server,
      setting up cookies may provide a solution for achieving 2.

   More specifically, the implementer should take into consideration the
   end-user and try not to annoy and inundate them with download
   options.

   Finally, note again that this is an optional feature that can be
   independently deployed.

5. Delegating Multilingual Domain Names

   Besides being backward compatible with existing client side
   applications, the IDNX solution also intends to make it backward
   compatible for name servers hosting delegated IDNs, as well as for
   resolvers in the path of resolution.

   The biggest challenge, aside from resolving the IDNs, for a registry
   in rolling out multilingual domain names is how domain registrants
   could host it.  IDNX suggests a Dynamic CNAME mechanism, which when
   deployed at the registry level, the delegated domain hosts could
   simply use their existing name server (BIND, etc.) to load in the
   long term ACE as the domain.  It is also possible to further delegate
   sub-domains to other hosts, just like with the current English only
   domain names.

5.1 Dynamic CNAME

   The ability to sub-delegate multilingual domain names to ACE only
   hosts is achieved by using a dynamic CNAME mechanism (similar in
   concept but different in practice to TRACE-00) to glue the
   multilingual domain name to the long term ACE equivalent at the
   registry DNS server.

   The existing STD13 DNS servers do NOT support this feature.  A
   registry operator or zone administrator MUST upgrade their name
   servers to an IDNX ready system if they wish to use Dynamic CNAME for
   multilingual domain transition.  The main reason for not using DNAME
   or another form of resource record is that existing resolvers readily
   support CNAME and not the others, thereby ensuring backward
   compatibility.  Furthermore, the use of a wildcard CNAME record also

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   allows Dynamic CNAME to be DNSSEC compatible (This will be further
   discussed in Section 7).

   The following is a brief explanation on how the dynamic CNAME should
   work:
   - Application sends www.<ML>.example to resolver
   - .example Registry responds with:
        www.<ML>.example   CNAME   www.xx--ACE.example
   - Resolver then uses www.xx--ACE.example to query the host
   - Therefore the host will only have to setup the xx--ACE.example zone

   With Dynamic CNAME, the registrant for a multilingual domain name
   will be able to host their domain with their existing DNS server
   software and be able to create English sub-domains from it (e.g.
   ldh.<ML>.example).

   If multilingual sub-domains are desired (e.g. <ML>.<ML>.example),
   then the registrant could opt to also make their system IDNX capable.

   This transitional strategy could also be deployed at the root level
   so that multilingual TLDs could be issued and be backward compatibly
   functional.  Therefore, full multilingual addresses could be used
   (i.e. <ML>.<ML>.<ML>).

5.2 Setting up a Multilingual Domain Name at the Registry

   The concept of Dynamic CNAME is relatively simple, imagine the
   multilingual domain name being setup at the registry as:

   *.<ML>.example   IN CNAME    *.xx--ACE.example
   xx--ACE.example  IN NS       ns1.xx--ACE.example

   Note again that you must upgrade to an IDNX ready DNS server in order
   for this setup to work.  Existing STD13 name servers (BIND, etc.) do
   not readily support setting up of wildcard CNAME records as such.

   An IDNX compatible DNS will therefore successfully provide a
   requestor the corresponding ACE record of a multilingual domain
   request via a CNAME response.  Because STD13 DNS resolvers support a
   CNAME RR, the resolution path would be seamless.  Note that the
   response from the registry server (as indicated in Section 5.1)
   should be "CNAME www.xx--ACE.example" and NOT "CNAME *.xx--
   ACE.example".

   In essence, no matter what the sub-domains may be for the
   <ML>.example domain, it will be successfully sub-delegated to the
   host server using its ACE name.

   Conceptually, we could also setup the different types of possible
   multilingual domain requests and variants as follows:

   *.<ML-Type1>.example           IN CNAME    *.xx--ACE.example
   *.<ML-Type1Æ>.example   IN CNAME    *.xx--ACE.example

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   *.<ML-Type2>.example           IN CNAME    *.xx--ACE.example

   The actual implementation of an IDNX compatible server however may
   cause the setup to be different.

   For example, the implementation could make the forking of the
   variants transparent to the zone administrator, so the administrator
   only needs to provide one definitive record, for example, simply:

   xx--ACE.example                IN NS       ns1.xx--ACE.example

   Upon loading the zone file, the IDNX server would identify the xx--
   ACE.example domain as a multilingual domain and fork the variants out
   automatically for resolution purposes.

   Note that your current DNS server (BIND, etc.) MAY NOT be capable of
   handling such a setup.  IDNX capability MUST be patched or otherwise
   upgraded and installed into the existing server if this feature is
   desired.

5.2.1 Character Equivalence Policies (OPTIONAL)

   This is an optional possible feature that can be implemented based on
   the policy of the zone operator / domain registry.

   By using the same concept, a registry may also choose to deploy
   character equivalency policies for multilingual domain names. For
   example to deal with identical Latin characters such as the capital
   letter Alpha "A" and the English capital letter "A".  Similarly, it
   could also be applied to the mapping of Simplified and Traditional
   Chinese characters.

   Essentially, the zone operator may setup a Traditional Chinese domain
   and dynamically CNAME it to the Simplified version in ACE format (or
   vice versa).  The operator again would ultimately determine the
   extent of coverage.  The more equivalency records are added, the more
   variations would be taken care of, and the more complete the coverage
   will be, but the fewer names would be available for registration.

   For example:
   *.<ML>.example    IN CNAME    *.xx--ACE.example
   *.<MLÆ>.example   IN CNAME    *.xx--ACE.example

   <MLÆ> denotes a multilingual domain name in an equivalent form.  To
   prevent conflicts, this should be considered like that discussed in
   Section 4.4 for ambiguity resolution.  That is, it should be taken
   care of at the point of registration, when domain availability is
   checked.

   Take note again that this is just a possible transitory strategy.  A
   more permanent strategy for character equivalency issues may be
   further discussed in a different context.


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5.3 Setting up a Multilingual Domain Zone at the Host

   At the host, the multilingual domain name will simply be setup as a
   regular English only domain name with the ACE record.  The host DNS
   server does NOT need to be upgraded to IDNX.

   For example:

   xx--ACE.example       IN SOA       ns1.xx--ACE.example dnsmaster.xx
                            NS        ns1.xx--ACE.example
                            MX 0      mail.xx--ACE.example
   ns1                      A         123.4.5.6
   www                      A         123.4.5.7
   mail                     A         123.4.5.8

   As you may see, it is exactly identical to what you would do for
   setting up an English only domain, and using English alphanumeric
   characters only.

5.4 Complementing IDNA

   Furthermore, because the IDNX architecture for registries allows for
   the delegation of IDNs in ACE format to non-IDN aware host servers,
   this again complements the evolving IDNA side standard whereby the
   hosts do not necessarily have to upgrade their system for
   multilingual domains.

6. Using Multilingual Domains on other Applications

   Because domain names are used in many applications, they must be
   taken into consideration for the transitional strategy as well.  The
   two more prominent applications are: email and website hosting.

6.1 IDN in Email Addresses

   The IDNX approach will support the use of IDNs in email addresses
   immediately.  With a similar concept deployed at the email servers,
   users will also be able to use multilingual user names along with
   IDNs for their email address (i.e. <ML>@<ML>.example).

   From Section 5.3, note that the MX RR (Mail Exchange Resource Record)
   could be easily set in any existing DNS server (BIND, etc.) by simply
   using the ACE equivalent of the multilingual domain name.   It is
   actually also possible to setup your existing mail server software
   for email addresses with English user names (i.e. ldh@<ML>.example)
   by using a domain independent IP setup.

   In order to offer multilingualized user names for email addresses, an
   email server with the IDNX concept incorporated for the management of
   user names could be used.  Similar to the domain situation, because
   the email applications were not designed to handle multilingual email
   addresses, some issues may arise.  Also, similarly, we should take
   that into consideration in the design and deployment of an IDNX ready

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   email server, to make the user experience seamless as multilingual
   names are deployed.

   The same three types of scenarios exist for multilingual email
   addresses: 1. Address arrives in the form of UTF8 encoding; 2.
   Address arrives in local encoding format; 3. Address has already been
   converted to ACE before it arrives.  For type 1 & 2, variants may
   also be generated and are possibly caused by the multilingual email
   address being converted into MIME format.  As for type 3, the same
   causes for domain names apply.  That is, caused by experimental
   software, versioning, as well as lack of consideration for
   interaction with other applications.  Unlike domain names, variants
   of email addresses are less likely caused by malfunctioning of the
   software agent during transport but rather as an effect by design.

   Therefore, to successfully provide comprehensive coverage for
   immediately usable multilingual email addresses before massive
   distribution of client side plug-ins is achieved, we should
   incorporate in the design, consideration for all these variants,
   sharing a similar strategy as IDNX.

   Furthermore, IDNs within the email headers could be inscribed in ACE
   format.  This inscription could take place at the SMTP server to
   allow the user to send the email using their existing MUA.  Again,
   this strategy would further promote and complement the IDNA approach.

6.2 Hosting Websites based on IDN

   Besides hosting the domain name (as discussed in Section 5.3), under
   an IDNX registry, registrants can also use their existing web servers
   to host websites for multilingual domain names.

   To host the multilingual domain name site using an existing web
   server, the user should configure their web server for IP hosting.
   In order to offer virtual name hosting however, because it involves
   the configuration of multilingual domain names, users should elect to
   use a multilingual enhanced web server based on an IDNX type concept.

   That is, having the web server capable of accepting the three types
   of possible requests: 1. Http requests in the form of UTF8 encoding;
   2. Http requests in the form of local encoding; 3. Http requests in
   the form of ACE.  For 1 & 2, there are possibility that the domain
   name request comes in an http escaped form (i.e. %XX%XX) as well as a
   variant of the pure form.  The same variances for 3 applies.

6.3 Other Known Issues about using IDN

   No matter how multilingual names are deployed, a set of problematic
   glitches would arise as the transition takes place and as users learn
   to understand more about these issues.  The three main reasons being
   that: 1. The average user is unaware of these problems; 2. System
   administrators may arbitrarily block multilingual requests by setting


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   up their system that mistake IDNs to be malicious requests; and 3.
   Existing software was not originally designed for IDNs.

   For example, some browsers simply block all entry of multilingual
   domain names, others try to implement some form of transformation
   causing loss of character information, which is may be irrecoverable.
   The DNS resolvers residing at the ISP level are very important
   "messengers" in the DNS.  Since the original DNS protocol itself is
   arguably 8-bit capable, this middleman usually just pass requests
   along the DNS path, however proxy and caching issues could complicate
   matters.  Proxy servers and cache servers will contribute to the
   blocking of multilingual names, by misinterpreting them as malicious
   requests or other undesired traffic.  Consequently creating a barrier
   for multilingual names to be successfully transported.

   Multilingual email addresses also have its share of issues.  There
   are three main areas where issues may arise: during the sending of
   emails through the SMTP servers; the retrieval of emails from the POP
   servers; and client side blocks.  For example, some existing MTAs
   equipped with ASCII-check statements may simply deny receipt of
   messages from a multilingual address, while others equipped with
   virus scanning features, may reject non-ASCII characters in an e-mail
   address misinterpreting them as potential malicious attacks.  The
   interfaces of some email user agents as well as mail portals are
   equipped with ASCII-check statements, blocking all attempts to send
   messages to multilingual email addresses.  The major email clients
   however will be able to manage multilingual email addresses when
   setup correctly.

   While the authors admits that there will be some stubborn known
   issues surrounding the deployment and usage of multilingual domain
   names, the IDNX strategy suggests a comprehensive solution for a
   registry in the deployment of multilingual domain names to
   substantially reduce complications brought by technical issues as
   well as for customer support issues.

7. Security Considerations

   Because DNSSEC provides coverage for wildcard records, the Dynamic
   CNAME feature should not cause any additional security concerns.

   Besides the above, this document does not talk about DNS security
   issues, and it is believed that the proposal does not introduce
   additional security problems not already existent and/or anticipated
   by adding multilingual characters to the DNS.

References

   [IDNA]      Internationalizing Domain Names in Applications,
               draft-ietf-idn-idna, Feb 2002, Patrik Faltstrom,
               Paul Hoffman, Adam M. Costella

   [PUNYCODE]  Punycode: An encoding of Unicode for use with IDNA,

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               draft-ietf-idn-punycode, Feb 2002, Adam M. Costella


   [STRINGPREP]Preparation of Internationalized Strings,
               draft-hoffman-stringprep, Feb 2002, Paul Hoffman,
               Marc Blanchet

   [NAMEPREP]  Nameprep: A Stringprep Profile for Internationalized
               Domain Names, draft-ietf-idn-nameprep, Feb 2002,
               Paul Hoffman, Marc Blanchet

Acknowledgements

   The authors would like to take this opportunity to thank all those
   who have provided precious comments and feedback during the
   preparation of this paper.

   Special thanks to the following persons whose comments have been
   invaluable to this document:

   Mark Davis
   Eric Hall
   Tedd Stirling
   Maynard Kang
   Deng Xiang
   Prof. L. M. Tseng
   Liana Ye
   Martin Duerst
   Dan Oscarsson





   Authors:

   Edmon Chung
   Neteka Inc.
   Suite 100, 243 College St. Toronto,
   Ontario, Canada M5T 1R5
   edmon@neteka.com

   David Leung
   Neteka Inc.
   Suite 100, 243 College St. Toronto,
   Ontario, Canada M5T 1R5
   david@neteka.com







Chung & Leung                                                 [Page 14]