IAB Thoughts on Encodings for Internationalized Domain Names
RFC 6055
| Document | Type |
RFC - Informational
(February 2011; Errata)
Updates RFC 2130
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IAB | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | IAB state | (None) | |
| Consensus Boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
Internet Architecture Board (IAB) D. Thaler
Request for Comments: 6055 Microsoft
Updates: 2130 J. Klensin
Category: Informational
ISSN: 2070-1721 S. Cheshire
Apple
February 2011
IAB Thoughts on Encodings for Internationalized Domain Names
Abstract
This document explores issues with Internationalized Domain Names
(IDNs) that result from the use of various encoding schemes such as
UTF-8 and the ASCII-Compatible Encoding produced by the Punycode
algorithm. It focuses on the importance of agreeing on a single
encoding and how complicated the state of affairs ends up being as a
result of using different encodings today.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Architecture Board (IAB)
and represents information that the IAB has deemed valuable to
provide for permanent record. Documents approved for publication by
the IAB are not a candidate for any level of Internet Standard; see
Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6055.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
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RFC 6055 IDN Encodings February 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. APIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2. Use of Non-DNS Protocols . . . . . . . . . . . . . . . . . . . 9
3. Use of Non-ASCII in DNS . . . . . . . . . . . . . . . . . . . 10
3.1. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 18
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
7. IAB Members at the Time of Approval . . . . . . . . . . . . . 19
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
8.1. Normative References . . . . . . . . . . . . . . . . . . . 20
8.2. Informative References . . . . . . . . . . . . . . . . . . 20
1. Introduction
The goal of this document is to explore what can be learned from some
current difficulties in implementing Internationalized Domain Names
(IDNs).
A domain name consists of a sequence of labels, conventionally
written separated by dots. An IDN is a domain name that contains one
or more labels that, in turn, contain one or more non-ASCII
characters. Just as with plain ASCII domain names, each IDN label
must be encoded using some mechanism before it can be transmitted in
network packets, stored in memory, stored on disk, etc. These
encodings need to be reversible, but they need not store domain names
the same way humans conventionally write them on paper. For example,
when transmitted over the network in DNS packets, domain name labels
are *not* separated with dots.
Internationalized Domain Names for Applications (IDNA), discussed
later in this document, is the standard that defines the use and
coding of internationalized domain names for use on the public
Internet [RFC5890]. An earlier version of IDNA [RFC3490] is now
being phased out. Except where noted, the two versions are
approximately the same with regard to the issues discussed in this
document. However, some explanations appeared in the earlier
documents that were no longer considered useful when the later
revision was created; they are quoted here from the documents in
which they appear. In addition, the terminology of the two versions
differ somewhat; this document reflects the terminology of the
current version.
Unicode [Unicode] is a list of characters (including non-spacing
marks that are used to form some other characters), where each
character is assigned an integer value, called a code point. In
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