IETF IDN Working Group                  Editors Zita Wenzel, James Seng
Internet Draft                       draft-ietf-idn-requirements-02.txt
12th May 2000                                     Expires 12rd Oct 2000

             Requirements of Internationalized Domain Names

Status of this Memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

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 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 list of current Internet-Drafts can be accessed at

The list of Internet-Draft Shadow Directories can be accessed at


This document describes the requirement for encoding international
characters into DNS names and records. This document is guidance for
developing protocols for internationalized domain names.

1. Introduction

At present, the encoding of Internet domain names is restricted to a
subset of 7-bit ASCII (ISO/IEC 646). HTML, XML, IMAP, FTP, and many
other text based items on the Internet have already been at least
partially internationalized. It is important for domain names to be
similarly internationalized or for an equivalent solution to be found.
This document assumes that the most effective solution involves putting
non-ASCII names inside some parts of the overall DNS system.

This document is being discussed on the "idn" mailing list. To join the
list, send a message to <> with the words
"subscribe idn" in the body of the message. Archives of the mailing
list can also be found at*.

1.1 Definitions and Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
document are to be interpreted as described in [RFC2119].

Characters mentioned in this document are identified by their position

                     Expires 12th of October 2000       [Page  1]

Internet Draft            Requirements of IDN           12th May 2000

in the Unicode [UNICODE] character set. The notation U+12AB, for
example, indicates the character at position 12AB (hexadecimal) in the
Unicode character set. Note that the use of this notation is not an
indication of a requirement to use Unicode.

Examples quoted in this document should be considered as a method to
further explain the meanings and principles adopted by the document. It
is not a requirement for the protocol to satisfy the examples.

A character is a member of a set of elements used for organization,
control, or representation of data.

A coded character is a character with its coded representation.

A coded character set ("CCS") is a set of unambiguous rules that
establishes a character set and the relationship between the characters
of the set and their coded representation.

A graphic character or glyph is a character, other than a control
function, that has a visual representation normally handwritten,
printed, or displayed.

A character encoding scheme or "CES" is a mapping from one or more
coded character sets to a set of octets. Some CESs are associated with
a single CCS; for example, UTF-8 [RFC2279] applies only to ISO 10646.
Other CESs, such as ISO 2022, are associated with many CCSs.

A charset is a method of mapping a sequence of octets to a sequence of
abstract characters. A charset is, in effect, a combination of one or
more CCS with a CES. Charset names are registered by the IANA according
to procedures documented in RFC 2278.

A language is a way that humans interact. In written form, a language
is expressed in characters. The same set of characters can often be
used in many languages, and many languages can be expressed using
different scripts. A particular charset may have different glyphs
(shapes) depending on the language being used.

1.2 Description of the Domain Name System

The Domain Name System is defined by [RFC1034] and [RFC1035], with
clarifications, extensions and modifications given in [RFC1123],
[RFC1996], [RFC2181] and others. Of special importance here is the
security extensions described in [RFC2535] and companions.

Over the years, many different words have been used to describe the
components of resource naming on the Internet [URI], [URN], ...; to make
certain that the set of terms used in this document are well-defined and
non-ambiguous, the definitions are given here.

A master server for a zone holds the main copy of that zone. This copy
is sometimes stored in a zone file. A slave server for a zone holds a
complete copy of the records for that zone. Slave servers may be either
authorized by the zone owner (secondary servers) or unauthorized

                     Expires 12th of October 2000       [Page  2]

Internet Draft            Requirements of IDN           12th May 2000

(so-called "stealth secondaries"). Master and authorized slave servers
are listed in the NS records for the zone, and are termed
"authoritative" servers. In many contexts, outside this document the
term "primary" is used interchangeably with "master" and "secondary" is
used interchangeably with "slave".

A caching server holds temporary copies of DNS records; it uses records
to answer queries about domain names. Further explanation of these terms
can be found in [RFC1034] and [RFC1996].

DNS names can be represented in multiple forms, with different
properties for internationalization. The most important ones are:

- Domain name: The binary representation of a name used internally in
  the DNS protocol. This consists of a series of components of 1-63
  octets, with an overall length limited to 255 octets (including the
  length fields).
- Master file format domain name: This is a representation of the name
  as a sequence of characters in some character sets; the common
  convention (derived from [RFC1035] section 5.1) is to represent the
  octets of the name as ASCII characters where the octet is in the set
  corresponding to the ASCII values for [a-zA-Z0-9-], using an escape
  mechanism (\x or \NNN) where not, and separating the components of the
  name by the dot character (".").

The form specified for most protocols using the DNS is a limited form of
the master file format domain name. This limited form is defined in
[RFC1034] Section 3.5 and [RFC1123]. In most implementations of
applications today, domain names in the Internet have been limited to
the much more restricted forms used, e.g., in email.   Those names are
limited to the ASCII upper and lower-case characters (interpreted in a
case-independent fashion), the digits, and the hyphen, with the further
restrictions that a name may not consist entirely of digits and that a
hyphen cannot occur at the beginning or end of a component or following
another hyphen.

1.3 Definition of "hostname" and "Internationalized Domain Name"

In the DNS protocols, a name is referred to as a sequence of octets.
However, when discussing requirements for internationalized domain
names, what we are looking for is ways to represent characters,
something meaningful for humans.

In this document, this is referred to as a "hostname". While this term
has been used for many different purposes over the years, it is used
here in the sense of "sequence of characters (not octets) representing a
domain name conforming to the limited hostname syntax".

This document attempts to define the requirements for an
"Internationalized Domain Name" (IDN). This is defined as a sequence of
characters that can be used in the context of functions where a hostname
is used today, but contains one or more characters that are outside the
set of characters specified as legal characters for host names.

                     Expires 12th of October 2000       [Page  3]

Internet Draft            Requirements of IDN           12th May 2000

1.4 A multilayer model of the DNS function

The DNS can be seen as a multilayer function:

- The bottom layer is where the packets passed across the Net in a DNS
  query and a DNS response. At this level, what matters is the format
  and meaning of bits and octets in a DNS packet.
- Above that is the "DNS service", created by an infrastructure of DNS
  servers, NS records that point to those DNS servers, and is pointed to
  by the root servers (listed in the "root cache file" on each DNS
  server, often called "named.cache". It is at this level that the
  statement "the DNS has a single root" [UNIROOT] makes sense, but
  still, what are being transferred are octets, not characters.
- Interfacing to the user is a service layer, often called "the resolver
  library", and often embedded in the operating system or system
  libraries of the client machines. It is at the top of this layer that
  the API calls commonly known as "gethostbyname" and "gethostbyaddress"
  reside.  These calls are modified to support IPv6 [RFC2553]. A
  conceptually similar layer exists in authoritative DNS servers,
  comprising the parts that generate "meaningful" strings in DNS files.
  Due to the popularity of the "master file" format, this layer often
  exists only in the administrative routines of the service maintainers.
- The user of this layer (resolver library) is the application programs
  that use the DNS, such as mailers, mail servers, Web clients, Web
  servers, Web caches, IRC clients, FTP clients, distributed file
  systems, distributed databases, and almost all other applications on
  TCP/IP.  (preference not fact)

Graphically, one can illustrate it like this:

+---------------+                            +---------------------+
| Application   |                            | (Base data)         |
+---------------+                            +---------------------+
      |  Application service interface                 |
      |  For ex. GethostbyXXXX interface               | (no standard)
+---------------+                            +---------------------+
| Resolver      |                            | Auth DNS server     |
+---------------+                            +---------------------+
      |     <-----   DNS service interface   ----->    |
|  DNS service                                                     |
|  +-----------------------+         +--------------------+        |
|  | Forwarding DNS server |         | Caching DNS server |        |
|  +-----------------------+         +--------------------+        |
|                                                                  |
|                 +-------------------------+                      |
|                 | Parent-zone DNS servers |                      |
|                 +-------------------------+                      |
|                                                                  |
|                 +-------------------------+                      |
|                 | Root DNS servers        |                      |
|                 +-------------------------+                      |
|                                                                  |

                     Expires 12th of October 2000       [Page  4]

Internet Draft            Requirements of IDN           12th May 2000

1.5 Service model of the DNS
The Domain Name Service is used for multiple purposes, each of which is
characterized by what it puts into the system (the query) and what it
expects as a result (the reply).
The most used ones in the current DNS are:

- Hostname-to-address service (A, AAAA, A6): Enter a hostname, and get
  back an IPv4 or IPv6 address.
  Hostname-to-Mail server service (MX): As above, but the expected
  return value is a hostname and a priority, for smtp servers.
- Address-to-hostname service (PTR): Enter an IPv4 or IPv6 address (in or form respectively) and get back a hostname.
- Domain delegation service (NS). Enter a domain name and get back
  nameserver records (designated hosts who provides authoritive
  nameservice) for the domain.

New services are being defined, either as entirely new services (IPv6 to
hostname mapping using binary labels) or as embellishments to other
services (DNSSEC returning information about whether a given DNS service
is performed securely or not).

These services exist, conceptually, at the Application/Resolver
interface, NOT at the DNS-service interface. This document attempts to
set requirements for an equivalent of the "used services" given above,
where "hostname" is replaced by "Internationalized Domain Name". This
doesn't preclude the fact that IDN should work will any kind of DNS
queries.  IDN is a new service, since existing protocols like SMTP or
HTTP use the old service. it is a matter of great concern how the new
and old services work together, and how other protocols can take
advantage of the new service.
2. General Requirements
These requirements address two concerns: The service offered to the
users (the application service), and the protocol extensions, if needed,
added to support this service.

In the requirements, we attempt to use the term "service" whenever a
requirement concerns the service, and "protocol" whenever a requirement
is believed to constrain the possible implementation.

2.1 Compatibility and Interoperability

[1] The DNS is essential to the entire Internet. Therefore, the service
must not damage present DNS protocol interoperability. It must make the
minimum number of changes to existing protocols on all layers of the
stack. It must continue to allow any system anywhere to resolve any
internationalized domain name.

[2] The service must preserve the basic concept and facilities of domain
names as described in [RFC1034]. It must maintain a single, global,
universal and consistent hierarchical namespace.

[3] The same name resolution request must generate the same response,
regardless of the location or localization settings in the resolver, in

                     Expires 12th of October 2000       [Page  5]

Internet Draft            Requirements of IDN           12th May 2000

the master server, and in any slave servers involved in the resolution

[4] If the service allows more than one charset, the protocol should
also allow creation of caching servers that do not understand the
charset in which a request or response is encoded. Such caching servers
should work as well for IDNs as they do for current domain names. The
caching server performs correctly if it gives essentially the same
answer (without the authoritative bit) as the master server would have
if presented with the same request.

[5] A caching server must not return data in response to a query that
would not have been returned if the same query had been presented to an
authoritative server. This applies fully for the cases when:

- The caching server does not know about IDN
- The caching server implements the whole specification
- The caching server implements a valid subset of the specification

[6] The service should be able to be upgraded at any time with new
features and retain backwards compatibility with the current

[7] The service may modify the DNS protocol [RFC1035] and other related
work undertaken by the DNSEXT WG. However, these changes should be as
small as possible and any changes must be approved by the DNSEXT WG.

[8] The protocol supporting the service should be as simple as possible
from the user's perspective. Ideally, users should not realize that IDN
was added on to the existing DNS.

[9] A fall-back strategy or mechanism based upon ASCII may be needed
during a transition period during deployment and adoption of IDN.
Therefore, if an encoding is not mapped into ASCII, then there might be
an ASCII-only representation compatible with the current DNS and there
should be a way for a program to find the ASCII-only representation for
IDN. This is depending on how the protocol will handle exceptions.

[10] The best solution is one that maintains maximum feasible
compatibility with current DNS standards as long as it meets the other
requirements in this document.

2.2 Internationalization

[11] Internationalized characters must be allowed to be represented and
used in DNS names and records. The protocol must specify what charset is
used when resolving domain names and how characters are encoded in DNS

[12] This document does not recommend any charset for IDN. If more than
one charset is used, or might be used in future, in the protocol, then
the protocol must specify all the charsets being used and for what
purpose. It must also conform to [RFC1766] by tagging the charset. No
implicit rules should be allowed for multiple charsets. A CCS(s) chosen

                     Expires 12th of October 2000       [Page  6]

Internet Draft            Requirements of IDN           12th May 2000

must at least cover the range of characters as currently defined (and as
being added) by ISO 10646/Unicode.

[13] CES(s) chosen should not encode ASCII characters differently
depending on the other characters in the string. In other words, unless
IDN names are identified and coded differently from ASCII-only ones,
characters in the ASCII set should remain as specified in [US-ASCII].

[14] The protocol should not invent a new CCS for the purpose of IDN
only and should use existing CES. The charset(s) chosen should also be

[15] The protocol should not make any assumptions about the location in
a domain name where internationalization might appear. In other words,
it should not differentiate between any part of a domain name because
this may impose restrictions on future internationalization efforts.

[16] The protocol should also not make any localized restrictions in the
protocol. For example, an IDN implementation which only allows domain
names to use a single local script would immediately restrict
multinational organization.

[17] Because of the wide range of devices that use the DNS and the wide
range of characteristics of international scripts, the service might
need to allow more than one method of domain name input and display.
However, there must be a single way of encoding an internationalized
domain name within the core of the DNS.

2.3 Localization

[18] The service should be able to handle localized requirements of
different languages. For example, IDN must be able to handle
bi-directional writing for scripts such as Arabic.

[19] Historically, "." has been the separator of labels in the host
names. The service should not use different separators for different

[20] Most of the localization work could be handled by the user
interface. It should not matter how the domain names are input or
presented, such as in a reverse order or bi-directional, or with the
introduction of a new separator. However, the final wire format must be
in canonical order.

2.4 Canonicalization

[21] Matching rules are a complicated process for IDN. Canonicalization
of characters must follow precise and predictable rules to ensure
consistency. [CHARREQ] is a recommended as a guide on canonicalization.

[22] The DNS has to match a host name in a request with a host name held
in one or more zones. It also needs to sort names into order. It is
expected that some sort of canonicalization algorithm will be used as
the first step of this process. This section discusses some of the

                     Expires 12th of October 2000       [Page  7]

Internet Draft            Requirements of IDN           12th May 2000

properties which will be required of that algorithm.

[23] The canonicalization algorithm might specify operations for case,
ligature, and punctuation folding.

[24] In order to retain backwards compatibility with the current DNS,
the service must retain the case-insensitive comparison for US-ASCII as
specified in [RFC1035]. For example, Latin capital letter A (U+0041)
must match Latin small letter a (U+0061). [UTR-21] describes some of
the issues with case mapping. Case-insensitivity for non US-ASCII has to
be discussed in the protocol proposal.

[25] Case folding must  be locale independent. For example, Latin
capital letter I (U+0049) case folded to lower case in the Turkish
context will become Latin small letter dotless i (U+0131). But in the
English context, it will become Latin small letter i (U+0069).

[26] If other canonicalization is done, then it must be done before the
domain name is resolved. Further, the canonicalization must be easily
upgradable as new languages and writing systems are added.

[27] Any conversion (case, ligature folding, punctuation folding, ...)
from what the user enters into a client to what the client asks for
resolution must be done identically on any request from any client.

[28] If the protocol specifies a canonicalization algorithm, a caching
server should perform correctly regardless of how much (or how little)
of that algorithm it has implemented. [1 request to remove]

[29] If the protocol requires a canonicalization algorithm, all requests
sent to a caching server must already be in the canonical form.

[30] If the charset can be normalized, then it should be normalized
before it is used in IDN. (conflict)

[31] The protocol should avoid inventing a new normalization form
provided a technically sufficient one is available (such as in an ISO

2.5 Operational Issues

[32] Zone files should remain easily editable.

[33] An IDN-capable resolver or server shall not generate more traffic
than a non-IDN-capable resolver or server would when resolving an
ASCII-only domain name.  The amount of traffic generated when resolving
an IDN shall be similar to that generated when resolving an ASCII-only

[34] The service should not add  new centralized administration for the
DNS. A domain administrator should be able to create internationalized
names as easily as adding current domain names.

[35] Within a single zone, the zone manager must be able to define

                     Expires 12th of October 2000       [Page  8]

Internet Draft            Requirements of IDN           12th May 2000

equivalence rules that suit the purpose of the zone, such as, but not
limited to, and not necessarily, non-ASCII case folding, Unicode
normalizations (if Unicode is chosen), Cyrillic/Greek/Latin folding, or
traditional/simplified Chinese equivalence. Such defined equivalences
must not remove equivalences that are assumed by (old or
local-rule-ignorant) caches.

[36] The character set of a signed zone file should be the same as the
character set of the unsigned zone file. The protocol must allow offline
DNSSEC signing. It should be possible to look at the
signed file and see that it is the same as the unsigned one.

2.6 Others

[37] The service may provide the same DNS resources using
internationalized text as it currently provides using ASCII text.

[38] To get full semantics for IDN, an upgrade of the DNS and related
software may be needed.

[39] The protocol should consider new features of DNS such as DNSSEC and
DNAME. For example, DNAME might be useful to simplify canonicalization
for IDN.

[40] The protocol must work for IPv4 and IPv6.

3. Technical Analysis

There are many standard protocols and RFCs which depend on
domain names and have make various assumptions about the characters
in them always conforming to [RFC1034] and the other restriction
discussed above (see [IABIDN]). We expect that the protocols
listed below to be affected:

I RFC2813 Internet Relay Chat : Server Protocol
I RFC2805 Media Gateway Control Protocol Architecture and Requirements
S RFC2789 Mail Monitoring MIB
S RFC2782 A DNS RR for specifying the location of services (DNS SRV)
I RFC2775 Internet Transparency
I RFC2772 6Bone Backbone Routing Guidelines
I RFC2768 Network Policy and Services: A Report of a Workshop on
I RFC2767 Dual Stack Hosts using the "Bump-In-the-Stack" Technique (BIS)
S RFC2766 Network Address Translation - Protocol Translation (NAT-PT)
S RFC2765 Stateless IP/ICMP Translation Algorithm (SIIT)
I RFC2763 Dynamic Hostname Exchange Mechanism for IS-IS
E RFC2756 Hyper Text Caching Protocol (HTCP/0.0)
S RFC2748 The COPS (Common Open Policy Service) Protocol
S RFC2744 Generic Security Service API Version 2 : C-bindings
S RFC2743 Generic Security Service Application Program Interface
I RFC2705 Media Gateway Control Protocol (MGCP) Version 1.0
I RFC2694 DNS extensions to Network Address Translators (DNS_ALG)
E RFC2693 SPKI Certificate Theory
S RFC2673 Binary Labels in the Domain Name System

                     Expires 12th of October 2000       [Page  9]

Internet Draft            Requirements of IDN           12th May 2000

S RFC2672 Non-Terminal DNS Name Redirection
S RFC2671 Extension Mechanisms for DNS (EDNS0)
I RFC2663 IP Network Address Translator (NAT) Terminology and
S RFC2661 Layer Two Tunneling Protocol "L2TP"
E RFC2654 A Tagged Index Object for use in the Common Indexing Protocol
I RFC2637 Point-to-Point Tunneling Protocol (PPTP)
I RFC2636 Wireless Device Configuration (OTASP/OTAPA) via ACAP
S RFC2632 S/MIME Version 3 Certificate Handling
S RFC2622 Routing Policy Specification Language (RPSL)
S RFC1616 Hypertext Transfer Protocol -- HTTP/1.1
I RFC2614 An API for Service Location
S RFC2609 Service Templates and Service: Schemes
B RFC2606 Reserved Top Level DNS Names
I RFC2604 Wireless Device Configuration (OTASP/OTAPA) via ACAP
S RFC2600 Internet Official Protocol Standards
S RFC2595 Using TLS with IMAP, POP3 and ACAP
I RFC2553 Basic Socket Interface Extensions for IPv6
I RFC2546 6Bone Routing Practice
S RFC2543 SIP: Session Initiation Protocol
I RFC2541 DNS Security Operational Considerations
E RFC2540 Detached Domain Name System (DNS) Information
S RFC2539 Storage of Diffie-Hellman Keys in the Domain Name System (DNS)
S RFC2538 Storing Certificates in the Domain Name System (DNS)
S RFC2537 RSA/MD5 KEYs and SIGs in the Domain Name System (DNS)
S RFC2546 DSA KEYs and SIGs in the Domain Name System (DNS)
S RFC2535 Domain Name System Security Extensions
I RFC2517 Building Directories from DNS: Experiences from WWWSeeker
S RFC2511 Internet X.509 Certificate Request Message Format
B RFC2505 Anti-Spam Recommendations for SMTP MTAs
S RFC2500 Internet Official Protocol Standards
S RFC2486 The Network Access Identifier
S RFC2459 Internet X.509 Public Key Infrastructure Certificate and CRL
S RFC2421 Voice Profile for Internet Mail - version 2
I RFC2412 The OAKLEY Key Determination Protocol
S RFC2408 Internet Security Association and Key Management Protocol
S RFC2407 The Internet IP Security Domain of Interpretation for ISAKMP
S RFC2401 Security Architecture for the Internet Protocol
S RFC2396 Uniform Resource Identifiers (URI): Generic Syntax
I RFC2377 Naming Plan for Internet Directory-Enabled Applications
I RFC2367 "PF_KEY Key Management API, Version 2"
I RFC2353 APPN/HPR in IP Networks APPN Implementers' Workshop Closed
          Pages Document
E RFC2345 Domain Names and Company Name Retrieval
S RFC2326 Real Time Streaming Protocol (RTSP)
B RFC2317 Classless IN-ADDR.ARPA delegation
S RFC2308 Negative Caching of DNS Queries (DNS NCACHE)
S RFC2298 An Extensible Message Format for Message Disposition
S RFC2280 Routing Policy Specification Language (RPSL)

                     Expires 12th of October 2000       [Page 10]

Internet Draft            Requirements of IDN           12th May 2000

S RFC2249 Mail Monitoring MIB
S RFC2247 Using Domains in LDAP/X.500 Distinguished Names
I RFC2230 Key Exchange Delegation Record for the DNS
B RFC2219 Use of DNS Aliases for Network Services
I RFC2187 "Application of Internet Cache Protocol (ICP), version 2"
B RFC2182 Selection and Operation of Secondary DNS Servers
S RFC2181 Clarifications to the DNS Specification
E RFC2168 Resolution of Uniform Resource Identifiers using the Domain
          Name System
I RFC2167 Referral Whois (RWhois) Protocol V1.5
S RFC2163 Using the Internet DNS to Distribute MIXER Conformant Global
          Address Mapping (MCGAM)
S RFC2156 MIXER (Mime Internet X.400 Enhanced Relay): Mapping between
          X.400 and RFC 822/MIME
I RFC2151 A Primer On Internet and TCP/IP Tools and Utilities
I RFC2146 U.S. Government Internet Domain Names
S RFC2137 Secure Domain Name System Dynamic Update
S RFC2136 Dynamic Updates in the Domain Name System (DNS UPDATE)
I RFC2133 Basic Socket Interface Extensions for IPv6
S RFC2131 Dynamic Host Configuration Protocol
I RFC2130 The Report of the IAB Character Set Workshop
I RFC2101 IPv4 Address Behaviour Today
S RFC2078 "Generic Security Service Application Program Interface,
          Version 2"
S RFC2074 Remote Network Monitoring MIB Protocol Identifiers
I RFC2072 Router Renumbering Guide
S RFC2068 Hypertext Transfer Protocol -- HTTP/1.1
S RFC2065 Domain Name System Security Extensions
E RFC2052 A DNS RR for specifying the location of services (DNS SRV)
S RFC2034 SMTP Service Extension for Returning Enhanced Error Codes
I RFC2010 Operational Criteria for Root Name Servers
E RFC2009 GPS-Based Addressing and Routing
S RFC1996 A Mechanism for Prompt Notification of Zone Changes (DNS
S RFC1995 Incremental Zone Transfer in DNS
S RFC1985 SMTP Service Extension for Remote Message Queue Starting
I RFC1983 Internet Users' Glossary
S RFC1982 Serial Number Arithmetic
S RFC1964 The Kerberos Version 5 GSS-API Mechanism
I RFC1958 Architectural Principles of the Internet
I RFC1955 New Scheme for Internet Routing and Addressing (ENCAPS) for
S RFC1933 Transition Mechanisms for IPv6 Hosts and Routers
I RFC1919 Classical versus Transparent IP Proxies
I RFC1912 Common DNS Operational and Configuration Errors
I RFC1900 Renumbering Needs Work
S RFC1891 SMTP Service Extension for Delivery Status Notifications
I RFC1887 An Architecture for IPv6 Unicast Address Allocation
S RFC1886 DNS Extensions to support IP version 6

                     Expires 12th of October 2000       [Page 11]

Internet Draft            Requirements of IDN           12th May 2000

I RFC1877 PPP Internet Protocol Control Protocol Extensions for Name
          Server Addresses
E RFC1876 A Means for Expressing Location Information in the Domain Name
E RFC1845 SMTP Service Extension for Checkpoint/Restart
I RFC1816 U.S. Government Internet Domain Names
I RFC1794 DNS Support for Load Balancing
E RFC1788 ICMP Domain Name Messages
I RFC1739 A Primer On Internet and TCP/IP Tools
I RFC1713 Tools for DNS debugging
E RFC1712 DNS Encoding of Geographical Location
I RFC1711 Classifications in E-mail Routing
I RFC1709 K-12 Internetworking Guidelines
I RFC1707 CATNIP: Common Architecture for the Internet
I RFC1706 DNS NSAP Resource Records
I RFC1705 Six Virtual Inches to the Left: The Problem with IPng
I RFC1703 Principles of Operation for the TPC.INT Subdomain: Radio
          Paging -- Technical Procedures
I RFC1671 IPng White Paper on Transition and Other Considerations
E RFC1664 Using the Internet DNS to Distribute
  RFC1327 Mail Address Mapping Tables
E RFC1637 DNS NSAP Resource Records
I RFC1636 Report of IAB Workshop on Security in the Internet
          Architecture "February 8-10, 1994"
I RFC1630 Universal Resource Identifiers in WWW
I RFC1621 Pip Near-term Architecture
I RFC1616 X.400(1988) for the Academic and Research Community in Europe
S RFC1612 DNS Resolver MIB Extensions
S RFC1611 DNS Server MIB Extensions
E RFC1608 Representing IP Information in the X.500 Directory
I RFC1597 Address Allocation for Private Internets
I RFC1594 FYI on Questions and Answers "Answers to Commonly asked ""New
          Internet User"" Questions"
I RFC1591 Domain Name System Structure and Delegation
I RFC1569 Principles of Operation for the TPC.INT Subdomain: Radio
          Paging -- Technical Procedures
I RFC1546 Host Anycasting Service
I RFC1537 Common DNS Data File Configuration Errors
I RFC1536 Common DNS Implementation Errors and Suggested Fixes
I RFC1535 A Security Problem and Proposed Correction With Widely
          Deployed DNS Software
I RFC1530 Principles of Operation for the TPC.INT Subdomain: General
          Principles and Policy
E RFC1528 Principles of Operation for the TPC.INT Subdomain: Remote
          Printing -- Technical Procedures
S RFC1519 Classless Inter-Domain Routing (CIDR): an Address Assignment
          and Aggregation Strategy

                     Expires 12th of October 2000       [Page 12]

Internet Draft            Requirements of IDN           12th May 2000

- RFC1486 An Experiment in Remote Printing
- RFC1480 The US Domain
- RFC1470 FYI on a Network Management Tool Catalog: Tools for Monitoring
          and Debugging TCP/IP Internets and Interconnected Devices
- RFC1464 Using the Domain Name System To Store Arbitrary String
- RFC1459 Internet Relay Chat Protocol
- RFC1454 Comparison of Proposals for Next Version of IP
- RFC1430 A Strategic Plan for Deploying an Internet X.500 Directory
- RFC1415 FTP-FTAM Gateway Specification
- RFC1401 Correspondence between the IAB and DISA on the use of DNS
          throughout the Internet
- RFC1395 BOOTP Vendor Information Extensions
- RFC1392 Internet Users' Glossary
- RFC1386 The US Domain
- RFC1385 EIP: The Extended Internet Protocol A Framework for
          Maintaining Backward Compatibility
- RFC1383 An Experiment in DNS Based IP Routing
- RFC1347 "TCP and UDP with Bigger Addresses (TUBA)," A Simple Proposal
          for Internet Addressing and Routing
- RFC1335 A Two-Tier Address Structure for the Internet: A Solution to
          the Problem of Address Space Exhaustion
- RFC1325 FYI on Questions and Answers "Answers to Commonly asked ""New
          Internet User"" Questions"
- RFC1309 Technical Overview of Directory Services Using the X.500
- RFC1308 Executive Introduction to Directory Services Using the X.500
- RFC1291 Mid-Level Networks Potential Technical Services
- RFC1279 X.500 and Domains
- RFC1274 The COSINE and Internet X.500 Schema
- RFC1207 FYI on Questions and Answers "Answers to Commonly asked
          ""Experienced Internet User"" Questions"
- RFC1206 FYI on Questions and Answers "Answers to Commonly asked ""New
          Internet User"" Questions"
- RFC1183 New DNS RR Definitions
- RFC1177 FYI on Questions and Answers "Answers to Commonly asked ""New
          Internet User"" Questions"
- RFC1175 FYI on Where to Start - A Bibliography of Internetworking
- RFC1174 IAB Recommended Policy on Distributing Internet Identifier
          Assignment And "IAB Recommended Policy Change to Internet
          ""Connected"" Status"
- RFC1147 FYI on a Network Management Tool Catalog: Tools for Monitoring
          and Debugging TCP/IP Internets and Interconnected Devices

                     Expires 12th of October 2000       [Page 13]

Internet Draft            Requirements of IDN           12th May 2000

- RFC1123 Requirements for Internet Hosts -- Application and Support
- RFC1101 DNS Encoding of Network Names and Other Types
- RFC1085 ISO Presentation Services on top of TCP/IP-based internets
- RFC0830 A Distributed System for Internet Name Service

S - Standards Track        I - Informational
E - Experimental           B - Best Current Practice

All idn protocol proposal documents must fully detail the expected
effects of leaking of the specified encoding to protocols other than the
DNS resolution protocol.

4. Security Considerations

Any solution that meets the requirements in this document must not
be less secure than the current DNS. Specifically, the mapping of
internationalized host names to and from IP addresses must have the
same characteristics as the mapping of today's host names.

Specifying requirements for internationalized domain names does not
itself raise any new security issues. However, any change to the DNS may
affect the security of any protocol that relies on the DNS or on
DNS names. A thorough evaluation of those protocols for security
concerns will be needed when they are developed. In particular, IDNs
must be compatible with DNSSEC and, if multiple charsets or
representation forms are permitted, the implications of this name-spoof
must be throughly understood.

5. References

[CHARREQ]   "Requirements for string identity matching and String
            Indexing",, July 1998,
            World Wide Web Consortium.

[DNSEXT]    "IETF DNS Extensions Working Group",
  , Olafur Gudmundson, Randy Bush.

[RFC1034]   "Domain Names - Concepts and Facilities", rfc1034.txt,
            November 1987, P. Mockapetris.

[RFC1035]   "Domain Names - Implementation and Specification",
            rfc1035.txt, November 1987, P. Mockapetris.

[RFC1123]   "Requirements for Internet Hosts -- Application and
            Support", rfc1123.txt, October 1989, R. Braden.

[RFC1766]       Tags for the Identification of Languages, rfc1766.txt,
                    March 1995, H. Alvestrand.

[RFC1996]   "A Mechanism for Prompt Notification of Zone Changes

                     Expires 12th of October 2000       [Page 14]

Internet Draft            Requirements of IDN           12th May 2000

            (DNS NOTIFY)", rfc1996.txt, August 1996, P. Vixie.

[RFC2119]   "Key words for use in RFCs to Indicate Requirement
            Levels", rfc2119.txt, March 1997, S. Bradner.

[RFC2181]   "Clarifications to the DNS Specification", rfc2181.txt,
            July 1997, R. Elz, R. Bush.

[RFC2279]       F. Yergeau, "UTF-8, a transformation format of ISO 10646",
            RFC 2279, January 1998.

[RFC2535]   "Domain Name System Security Extensions", rfc2535.txt,
            March 1999, D. Eastlake.

[RFC2553]       "Basic Socket Interface Extensions for IPv6", rfc2553.txt,
                    March 1999, R. Gilligan and al.

[UNIROOT]   "IAB Technical Comment on the Unique DNS Root",

[IABIDN]    "A Tangled Web:issues of I18N domain names, and the
            other Internet protocols", rfc2825.txt

[UNICODE]   The Unicode Consortium, "The Unicode Standard -- Version
            3.0", ISBN 0-201-61633-5. Described at

[US-ASCII]  Coded Character Set -- 7-bit American Standard Code for
            Information Interchange, ANSI X3.4-1986.

[UTR15]     "Unicode Normalization Forms", Unicode Technical Report
            Nov 1999, M. Davis & M. Duerst, Unicode Consortium.

[UTR21]     "Case Mappings", Unicode Technical Report #21,
  , Dec 1999,
            M. Davis, Unicode Consortium.

6. Editors' Contact

Zita Wenzel
[ ... ]

James Seng
8 Temesek Boulevand
#24-02 Suntec Tower 3
Singapore 038988
Tel: +65 248-6208
Fax: +65 248-6198

                     Expires 12th of October 2000       [Page 15]

Internet Draft            Requirements of IDN           12th May 2000

7. Acknowledgements

The editor gratefully acknowledges the contributions of:

Harald Tveit Alvestrand <>
Martin Duerst <>
Patrik Faltstrom <>
Andrew Draper <>
Bill Manning <bmanning@ISI.EDU>
Paul Hoffman <>
James Seng <>
Randy Bush <>
Alan Barret <>
Olafur Gudmundsson <>
Karlsson Kent <>
Dan Oscarsson <>
J. William Semich <>
RJ Atkinson <request not to have email>
Simon Josefsson <>
Ned Freed <>
Dongman Lee <>
Mark Andrews <>
John Klensin <>
Tan Juay Kwang <>

                     Expires 12th of October 2000       [Page 16]