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[idn] Internationalized PTR for IDN
- To: idn@ops.ietf.org
- Subject: [idn] Internationalized PTR for IDN
- From: jiang@i-dns.net
- Date: Mon, 18 Sep 2000 13:26:56 +0800
- Delivery-date: Sun, 17 Sep 2000 22:29:11 -0700
- Envelope-to: idn-data@psg.com
- Mail-Followup-To: idn@ops.ietf.org
Hi,
A simple draft concerning issues with PTR RR in
the context of IDN has been submited to the ID
editor.
While it is coming its way to the WG mailing list,
an unofficial version is here attached in this mail.
Your comments are most welcome.
Thanks and Have a nice day!
Yours, Mingliang & Hongbo.
INTERNET-DRAFT Hongbo Shi
draft-ietf-idn-iptr-00.txt Waseda University
Jiang Ming Liang
i-DNS.net
Sep 2000
Internationalized PTR Resource Record (IPTR)
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.
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
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 draft attempts to address the problem of how an IP address should
be properly mapped to a set of internationalized domain names(iDNs).
It is currently unspecified how a PTR record can be used for this
purpose. In addition, the syntax of the PTR resource record may be
too restrictive for such a mapping in a more culturally meaningful
context. This document suggests a new TYPE called IPTR using EDNS0
and a mechanism to combind language information with such a mapping.
1. Introduction
Reverse mapping is a very important and essential function in the DNS.
In today's Domain Name System, PTR RRs are used to support address-to-
domain mappings. However, a current PTR RR does not provide support
for proper address-to-iDN mappings, without certain modifications.
Shi, Jiang [Page 1]
INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
Modifying the PTR structure will also affect the current reverse
mapping architecture. This document describes a new RR TYPE named
IPTR to provide address-to-iDN mappings and it also specifies that on
receiving of a IPTR query a name server should respond with all the
corresponding IPTR RRs in one response. This document also specifies
that an IPTR RR SHOULD refer to one primary iDN per language only.
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 Background and Designs
When Internationalized Domain Names come into wide use, an Internet
host is likely to have domain names in different languages. In
today's Internet, because of the design of the PTR record and
implementation of most resolvers, IP address to domain names mapping
is limited to "one IP one domain name", the primary domain name of the
host. This is more restrictive in a world of iDNs, for choosing one
name in one particular language as the primary could have cultural
implications. The authors also believe that putting language
information into address-to-name mappings will be benifitial to future
applications.
The design purpose of the IPTR RR type is to provide a mechanism that
can map an IP address to all of the corresponding iDNs per language.
CNAME MUST continue to work for IPTR as it works now for PTR records.
An IPTR RR SHOULD be limited to one primary iDN per language.
The behavior of a resolver on the use of IPTR will be specified in a
seperate draft or a later version of this draft.
1.3 Functional Description
DNS query and responses involving IPTR type MUST have the following
properties:
- When the QTYPE is IPTR, the corresponding iDNs SHOULD be returned
in one response.
- The characters in the label MUST be encoded using UTF-8
[RFC2279].
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INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
- The entire label MUST be encoded EDNS [RFC2671].
2. IPTR definition
The structure of an IPTR RR is somewhat like the MX RR. :) In addtion
to the IP address in the IN-ADDR.ARPA domain and the domain name field
(similar to a PTR RR), a new field called LANGUAGE has been defined.
A domain name in an IPTR RR MUST be encoded in UTF8. Below is an
example of an IPTR RR:
1.2.3.4.IN-ADDR.ARPA. IPTR "language" "name-in-utf8"
[RFC1766] describes the ISO 639/ISO 3166 conventions. A language name
is always written in lower case, while country codes are written in
upper case. The "language" field in an IPTR RR MUST follow the con-
ventions defined in [RFC1766].
For Example:
4.3.2.1.IN-ADDR.ARPA. IPTR "zh-cn" "name-in-utf8"
4.3.2.1.IN-ADDR.ARPA. IPTR "zh-tw" "name-in-utf8"
4.3.2.1.IN-ADDR.ARPA. IPTR "ja-jp" "name-in-utf8"
4.3.2.1.IN-ADDR.ARPA. IPTR "ko-kr" "name-in-utf8"
The notion of canonical names and aliases described in 3.6.2 [RFC1034]
must be preserved for IPTR record types. An IPTR RR SHOULD be limited
to one primary iDN per language, similar to the a PTR RR.
3. IPTR on IPv6
Mapping IPv6 to iDNs can be similarly supported. This document recom-
mands to continue using the IP6.INT domain defined in [RFC1886] for
IPTR mappings. For example, the lookup corresponding to the address
4321:0:1:2:3:4:567:89ab would be:
b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.4.IP6.INT.
IPTR "language" "name-in-utf8"
4. Packet format for IPTR
EDNS0[RFC2671] is REQUIRED to implement IPTR.
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INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
0 1 2 3 4
bits 0 1 2 3 4 5 6 7 8 9 0 1...9 0...8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 ...
+-+-+-+-+-+-+-+-+-+-//-+-+-//-+-+-+-+-+-+-+-+-+-+-+-+-+-//-+-+-+
|0 1| ELT | LANGUAGE | Size | IDN label... |
+-+-+-+-+-+-+-+-+-+-//-+-+-//-+-+-+-+-+-+-+-+-+-+-+-+-+-//-+-+-+
LANGUAGE: An argument for IPTR to define the kind of languages
used in the following IDN label. The size is 2 octets.
ELT: To be defined.
5. IPTR query/response
When the QTYPE is IPTR in a query, all of the corresponding IPTR RRs
SHOULD be returned in one response. DNS messages are limited to 512
octets or less in size when sent over UDP. Therefore, if all the RRs
cannot fit in one UDP packet, this draft describe two solutions. One
is for recent environment and the other is for the near future.
5.1 Transport
Today, DNS queries and responses are carried in UDP datagrams or over
TCP connections.[RFC1034] specifies, IPTR RRSet is RECOMMENDED to be
returned in one response. The size of a DNS message could exceed 512
octets, when multiple RRs are present. Therefore, this draft makes
the two following recommendations.
- "Use UDP first, if UDP is not large enough then change to TCP" is
RECOMMENDED.
The server MUST send back the response with the TC bit set. Then
the resolver SHOULD resend the query using TCP on server port
53(decimal). This behavior is consistent with the current DNS
specification[RFC1035].
- In future, EDNS0 is REQUIRED to send large packets.
Hence, the size of the UDP payload is no longer limited to 512
octets any more.
5.2 Standard sample
A resolver who wants to find the iDNs corresponding to an IP address
1.2.3.4 whould pursue a query of the form QTYPE=IPTR, QCLASS=IN,
QNAME=4.3.2.1.IN-ADDR.ARPA, and would receive:
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INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
+------------------------------------------------------+
Header | OPCODE=SQUERY, RESPONSE, AA |
+------------------------------------------------------+
Question | QNAME=4.3.2.1.IN-ADDR.ARPA.,QCLASS=IN,QTYPE=IPTR |
+------------------------------------------------------+
Answer | 4.3.2.1.IN-ADDR.ARPA. IPTR "zh-cn" "name1-in-utf8" |
| 4.3.2.1.IN-ADDR.ARPA. IPTR "zh-tw" "name2-in-utf8" |
| 4.3.2.1.IN-ADDR.ARPA. IPTR "ja-jp" "name3-in-utf8" |
| 4.3.2.1.IN-ADDR.ARPA. IPTR "ko-kr" "name4-in-utf8" |
+------------------------------------------------------+
Authority | ... |
+------------------------------------------------------+
Additional | ... |
+------------------------------------------------------+
6 Open Issues
1. API issues on the resolver side.
2. the granularity of the language info. (per domain name? per
label? within label?)
Practically, we believe it is enough for the iPTR info to be
expressed as |01|ELT|language|size|utf8|size|utf8|...|, mean-
ing the LANGUAGE TAG is used to define the language of the
Fully Quantified Domain Name. However, FQDNs could still
exist in the form of "English-in-utf8.Chinese-in-utf8.English-
in-utf8." And more than 1 language can exist in the same
label. Should such level of detailedness be supported? Or a
simple meta-type like "mixed-language" is enough?
3. If language info should somehow be relatable to an iDN
itself(nothing to do with PTR...) and how?
As a suggestion, if a new RR TYPE INAME is established to
relate iDN to current domain name, there will be two merit.
One is we don't to do anything with PTR. Second is if we cache
the INAME RRs to the DNS caches, then it can reduce the upper
layer name servers' jobs. Actually, the feature of the new RR
TYPE is quite similar to CNAME and DNAME, meaning name-to-
name.
FQIDN: Fully Qualified Internationalized Domain Name.
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INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
Then the INAME RR is expressed following:
iDN INAME traditional domain name
About the first merit, When the client looks up an IP address
to iDNs then the server will reponse not only corresponding
PTR RR but corresponding INAME RRs to the client. Further-
more, the problem in LANGUAGE TAG can be avoided.
For example:
4.3.2.1.IN-ADDR.ARPA PTR traditional-domain-name
iDN-1 INAME traditional-domain-name
iDN-2 INAME traditional-domain-name
About the second merit, INAME is not only can be used in
address-to-name mapping but name-to-address mapping.
For example:
traditional domain name IN A host address
iDN-1 INAME traditional-domain-name
iDN-2 INAME traditional-domain-name
When the client looks up an iDN or traditional domain name to
its corresponding IP address, if the server reponses not only
A RR but INAME RRs to the client. And the client cache these
RRs to its DNS cache. Then the next time, maybe some queries
can be resolved in DNS cache.
References
[IDNE] Mrc Blanchet & Paul Hoffman, "Internationalized domain names
using EDNS", draft-ietf-idn-idne.
[RFC1034] P. Mockapetris, "DOMAIN NAMES - CONCEPTS AND FACILITIES",
November 1987, RFC1034
[RFC1035] P. Mockapetris, "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICA-
TION", November 1987, RFC1035
[RFC1766] H. Alvestrand, "Tags for the Identification of Languages",
March 1999, RFC 1766
[RFC1886] S. Thomson, C. Huitema, "DNS Extensions to support IP version
6", December 1995, RFC1886
[RFC2279] Francois Yergeau, "UTF-8, a transformation format of ISO
10646", January 1998, RFC 2279.
Shi, Jiang [Page 6]
INTERNET-DRAFT Internationalized PTR Resource Record Sep 2000
[RFC2671] Paul Vixie, "Extension Mechanisms for DNS (EDNS0)", August
1999, RFC 2671.
[ISO 639] ISO 639:1988 (E/F) - Code for the representation of names of
languages - The International Organization for Standardization, 1st edi-
tion, 1988 17 pages Prepared by ISO/TC 37 - Terminology (principles and
coordination).
[ISO 3166] ISO 3166:1988 (E/F) - Codes for the representation of names
of countries - The International Organization for Standardization, 3rd
edition, 1988-08-15.
Acknowledgements
James Seng has given many comments in our e-mail discussions.
Authors' Information
Hongbo Shi
Waseda University
3-4-1 Okubo, Shinjyuku-ku
Tokyo, 169-8555 Japan
shi@goto.info.waseda.ac.jp
Jiang Ming Liang
i-DNS.net
8 Temasek Boulevard
#24-02 Suntec Tower Three
Singapore 038988
jiang@i-DNS.net
Shi, Jiang [Page 7]