Working Group Edmon Chung & David Leung
Internet Draft Neteka Inc.
<draft-ietf-idn-dnsii-trace-00.txt> September 2000
DNSII Transitional Reflexive ASCII Compatible Encoding (TRACE)
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
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Abstract
ASCII Compatible Encoding (ACE) schemes should only be used as a
transitional strategy with a well-defined way forward to the eventual
enabling of a truly multilingual name space for the DNS.
The previous DNSII documents surrounding multilingual domain names
have focused on the ultimate form with the DNSII-MDNR suggesting
possible tunneling techniques where ACE may be used. This document
furthers the discussion on an ACE system, which not only provides a
pathway towards the ultimate DNSII scheme but also an interim
solution taking care of the immediate needs.
A reflexive CNAME process RENAME is introduced where non-ASCII
incoming queries will be automatically CNAMEd to its ASCII
counterpart without requiring an actual lookup. The resolver will
then be responsible for recursively looking up the corresponding
translated alphanumeric name.
This document does not attempt to create another ACE scheme, instead
it discusses the way an ACE scheme could be used as a transition
towards the ultimate goal of a true multilingual name on the wire.
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Table of Contents
1. Introduction....................................................2
1.1 Terminology....................................................2
2. TRACE - Introduced with Due Obsolescence........................3
2.1 Problems & Benefits of ACE.....................................3
2.2 TRACE Format...................................................3
2.3 TRACE Identifier...............................................3
2.4 TRACE Zone Handling............................................4
3. REflexive CNAME (RENAME)........................................4
3.1 Non-Recursive Name Servers with RENAME-ON......................5
3.1 Recursive Name Servers (Resolvers) with RENAME-ON..............6
3.2 Benefits of RENAME.............................................6
3.3 Problems with RENAME...........................................7
4. Use of RENAME with Respect to DNS Hierarchy.....................7
4.1 General Rules for using RENAME.................................8
4.2 Transitioning towards Identification Based DNSII...............8
5. Security Considerations.........................................9
6. Conclusion......................................................9
7. Intellectual Property Considerations...........................10
8. References.....................................................10
1. Introduction
ACE usage should be limited to machine read only and steps should be
taken to avoid the user being able to easily input the names through
an application onto the wire. This is a well-understood concept
because without this requirement, the creation of an ACE system
effectively creates an alternate universe model that is counter to
the spirit of the DNS. In essence, if an ACE scheme could easily be
typed in, people who are typing that sequence of characters may be
unexpectedly be brought to another site which happens to have the
same "code".
TRACE outlines a scheme that uses an ACE scheme but is identified in
a 7-bit format that could not easily be typed in by a user. Thereby
preventing an inconsistent expectation of a domain name. Beyond the
specification of an identifier a RENAME function for an ACE
resolution process is also introduced.
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].
A number of characters used in this document are in a Big-5 encoding,
you could select your view encoding type to traditional Chinese or
Big-5 for it to be displayed properly.
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2. TRACE - Introduced with Due Obsolescence
TRACE is designed to be a transitional scheme with due obsolescence
once a full-fledged DNSII mode is attained.
2.1 Problems & Benefits of ACE
One of the major problems with ACE is the evident result of creating
an extra layer on top of the DNS. DNS was designed to be the human
friendly machine identifier with its names human readable. With ACE,
it is certain that an added layer is required to decode a domain
name. This also effectively results in a quasi-alternate universe
mode whereby the actual characters represent a translation into the
existing domain name space.
However, ACE has its benefits as well and the most prominent one is
that host servers need not migrate to new name servers. Also it will
ensure that there is a lengthy enough migration period for other
applications to start adapting to the new DNS specifications.
2.2 TRACE Format
TRACE does not intend to introduce a new type of encoding. Rather,
it is concerned with using a 7-bit compatible identifier and a
reflexive mechanism for switching from regular DNS packets to TRACE.
2.3 TRACE Identifier
In other ACE proposals, identifiers are often created from
alphanumeric characters, which end users can easily type in. The
problem with this approach is easy to understand, for each
multilingual name, one alphanumeric name must be reserved simply for
the use of the multilingual conversion and will not be available for
normal usage.
For example from Paul Hoffman's draft [RACE-01], the sample
conversion for a value 0x3a27 would result in a string "bq--hitq".
The name "bq--hitq" which is a perfectly usable name on its own must
now be reserved for a multilingual name. Also, 4 character spaces
will be wasted just for the identifier.
Instead of using an alphanumeric identifier, a single 7-bit compliant
control character is used. The proposed character is the control
character with the value 0x7F. With this character, a multilingual
name part could be effectively identified while it would be very
difficult for the average user to enter the character into an
application, thereby avoiding the issue discussed above.
In any case, an ACE form name is not intended for an end user to type
in. The only reason for ACE is that the current name servers could
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easily handle them. TRACE provides a simple and effective way which
is 7-bit compliant and a string that is could not be easily imitated.
2.4 TRACE Zone Handling
A zone administrator could also easily enter the TRACE Identifier
into the zone file. To insert the TRACE Identifier in a BIND server,
the administrator could simply append the string "\127" before the
ACE label. Current BIND servers will understand that "\127" calls
for the character with the value 127 and therefore load it into
memory accordingly. The BIND should also be reconfigured to set the
options for "check-names" to "ignore".
In the following examples, the ACE format used is simply the hex
value of the corresponding character encoding. RACE or other ACE
formats or hex of other encoding schemes may be used.
To set up an NS record to ns1.trace.tld and an A record to 123.4.5.6
for the name "ρρρ…" <U+4e2d><U+6587> in a BIND server, using UTF-8
(E4B8AD E69687) the following lines are included into the zone file:
\127e4b8ade69687 IN NS ns1.trace.tld.
\127e4b8ade69687 IN A 123.4.5.6
Section 4.3 will discuss a method to prepare the zone file for the
transition into a fully DNSII compliant mode.
3. REflexive CNAME (RENAME)
To complement an ACE transition, a reflexive mechanism is introduced.
REflexive CNAME (RENAME) successfully creates a scheme whereby child
DNS nodes could keep using their BIND name servers while be capable
of hosting multilingual domain names.
RENAME is simply a mechanism that attaches an incoming multilingual
name to its ACE counterpart as it enters a RENAME-ON name server.
When to use RENAME is discussed in Section 4.
As an example, if an incoming query contains a the domain name "ρρ
ρ….tld" <U+4e2d><U+6587>.tld in UTF-8 encoding reaches a RENAME-ON
name server, the following automatic response will be created:
ρρρ….tld IN CNAME \127e4b8ade69687.tld
If the server is in non-recursive mode, the RENAMEd name will now be
used for a lookup within the zone and the corresponding response
returned to the inquirer, including the CNAME process. If the server
is in recursive mode, the RENAMEd name will be used for lookup within
cache and passed on through the DNS hierarchy when not found.
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3.1 Non-Recursive Name Servers with RENAME-ON
The two basic modes for a name server includes a non-recursive mode,
which are usually used by registries, root or authoritative host
servers; and a recursive mode, which are usually resolvers installed
in ISPs.
A non-recursive mode server with RENAME-ON would upon receiving a
multilingual name label, automatically CNAME the name to an ACE
format. If a complete match is found, the response will be passed
back to the inquirer including the CNAME record. If no direct match
is found, it will pass along either an authoritative NXDomain or the
nearest NS Record in ACE format so that the inquirer may continue its
recursive request.
The following diagram and descriptions details the resolution process
for the domain "www.ρρρ….ρρρ….tld" or <U+4e2d><U+6587>.<U+4e2d>
<U+6587>.tld, with a DNSII TRACE RENAME-ON server installed at the
Parent domain "ρρρ….tld" and a BIND server installed at the Child DNS
domain "ρρρ….ρρρ….tld":
(3)
+--------+ +------------+ +---------------+
| | (1) | | (2) | |
| Client |-------->| Resolver |-------->| Parent Domain | ρρρ….tld
| |<--------| |<--------| (RENAME-ON) |
| | (8) | | (4) | |
+--------+ +------------+ +---------------+
^ |
| | (6)
| | (5) +--------------+
| +-------->| |
+-----------| Child Domain | ρρρ….ρρρ….tld
(7) | (using BIND) |
| |
+--------------+
(1) A user enters a query for the A record of "www.ρρρ….ρρρ….tld" or
<U+4e2d><U+6587>.<U+4e2d><U+6587>.tld using an ISO10646 encoding
input.
(2) The DNS recursive resolver arrives at the parent domain "ρρ
ρ….tld" <U+4e2d><U+6587>.tld
(3) With RENAME-ON and detection that the incoming query is non-ASCII,
the server reflexively assigns the CNAME to the domain:
www.ρρρ….ρρρ….tld. IN CNAME www.\127e4b8ade69687.
\127e4b8ade69687.tld.
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(4) Since a direct match is not found in the Parent DNS, the closest
NS record is returned to the Resolver, with the CNAME part
included:
www.ρρρ….ρρρ….tld. IN CNAME www.\127e4b8ade69687.
\127e4b8ade69687.tld.
\127e4b8ade69687.\127e4b8ade69687.tld. IN NS
ns1.\127e4b8ade69687.\127e4b8ade69687.tld.
ns1.\127e4b8ade69687.\127e4b8ade69687.tld. IN A 123.5.6.7
(5) The recursive resolver passes on the request using the CNAME
record to the Child DNS as:
www.\127e4b8ade69687.\127e4b8ade69687.tld.
Asking for an A record for the corresponding domain.
(6) The Child DNS simply does a regular look up for the domain with
the corresponding response.
(7) Assuming that the correct IP address for www.ρρρ….ρρρ….tld is
123.6.7.8, the response would be:
www.\127e4b8ade69687.\127e4b8ade69687.tld. IN A 123.6.7.8
(8) The resolver will then respond to the client request accordingly,
including the CNAME record.
3.1 Recursive Name Servers (Resolvers) with RENAME-ON
If the recursive resolver is DNSII compatible and have switched the
RENAME-ON, then both the parent and child DNSs could still run BIND
and be able to serve multilingual names. As the request goes through
the resolver, it is automatically CNAMEd to the corresponding ACE
format name and passed along for further resolution.
When the corresponding response is obtained, the definite answer
including the CNAME record will both be passed to the client.
3.2 Benefits of RENAME
The immediate benefit for using RENAME is that once it is deployed at
a particular DNS level, all its child, or sub-level DNSs could
continue to run a BIND-based or current name server while still be
capable of serving multilingual domain names.
Most ACE implementations expect the client application to begin
migration first. This is unfortunately would take a long time
because we understand that client end migration may take years to
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complete. With RENAME however, the migration could be dynamic.
Section 4 explains further how and when RENAME should be used to
complement and facilitate the resolution of multilingual names even
when some of the components are not fully multilingual aware.
3.3 Problems with RENAME
RENAME effectively creates an ACE based name space which is
ultimately undesired. Also, wherever the RENAME function is located,
it will intensify the processing requirements for the machine to
handle the conversion of the incoming multilingual label into an ACE
format and package the CNAME record accordingly.
4. Use of RENAME with Respect to DNS Hierarchy
For the discussion within this document, the DNS hierarchy is
summarized into four nodes, beginning with the client end
application, through the resolver, to the root or NIC servers then
finally at the authoritative host for a second-level domain. This
more or less summarizes the DNS process from the initiation of a
request to the authoritative host.
All together, there are 16 combinations with the basic DNS
environments. The following chart outlines the different
combinations with the denotations as:
B = B-DNS = Current Bind-based DNS
D = DNSII = DNSII Compliant Name Servers
RENAME(X-X-X-X) = RENAME(Client/application-Resolver-Root/NIC-Host)
with X = ON = RENAME-ON
FF = RENAME-OFF
OP = Optional ON/OFF
NA = Not Applicable
Scenario | Client |Resolver|Root/NIC| Host | RENAME(ON/OFF)
---------+--------+--------+--------+--------+---------------------
1) BBBB | B-DNS | B-DNS | B-DNS | B-DNS | existing system
+--------+--------+--------+--------+
2) BBBD | B-DNS | B DNS | B-DNS | DNSII | RENAME(NA-NA-NA-FF)
+--------+--------+--------+--------+
3) BBDB | B-DNS | B DNS | DNSII | B-DNS | RENAME(NA-NA-ON-NA)
+--------+--------+--------+--------+
4) BDBB | B-DNS | DNSII | B DNS | B-DNS | RENAME(NA-ON-NA-NA)
+--------+--------+--------+--------+
5) DBBB | DNSII | B-DNS | B-DNS | B-DNS | RENAME(ON-NA-NA-NA)
+--------+--------+--------+--------+
6) BBDD | B-DNS | B-DNS | DNSII | DNSII | RENAME(NA-NA-FF-FF)
+--------+--------+--------+--------+
7) DNND | B-DNS | DNSII | DNSII | B-DNS | RENAME(NA-OP-ON-NA)
+--------+--------+--------+--------+
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Scenario | Client |Resolver|Root/NIC| Host | RENAME(ON/OFF)
---------+--------+--------+--------+--------+---------------------
8) DDBB | DNSII | DNSII | B-DNS | B-DNS | RENAME(OP-ON-NA-NA)
+--------+--------+--------+--------+
9) DBBD | DNSII | B-DNS | B-DNS | DNSII | RENAME(ON-NA-NA-FF)
+--------+--------+--------+--------+
10) BDBD | B-DNS | DNSII | B-DNS | DNSII | RENAME(NA-ON-NA-FF)
+--------+--------+--------+--------+
11) DBDB | DNSII | B-DNS | DNSII | B-DNS | RENAME(ON-NA-OP-NA)
+--------+--------+--------+--------+
12) BDDD | B-DNS | DNSII | DNSII | DNSII | RENAME(NA-FF-FF-FF)
+--------+--------+--------+--------+
13) DDDB | DNSII | DNSII | DNSII | B-DNS | RENAME(OP-OP-ON-NA)
+--------+--------+--------+--------+
14) DDBD | DNSII | DNSII | B-DNS | DNSII | RENAME(OP-ON-NA-FF)
+--------+--------+--------+--------+
15) DBDD | DNSII | B-DNS | DNSII | DNSII | RENAME(ON-NA-FF-FF)
+--------+--------+--------+--------+
16) DDDD | DNSII | DNSII | DNSII | DNSII | Full DNSII mode
+--------+--------+--------+--------+
4.1 General Rules for using RENAME
As a general rule, RENAME should be turned on whenever there is an
anticipation that further down the DNS hierarchy or resolution
process, a host has not been migrated and is still using existing
name server software. For example, Scenario(3),(4) or (5) and their
equivalents.
If it is known that the entire set of child hosts is DNSII compliant,
then RENAME is optional even if there exists child sub-sub-domain
host beneath the sub-domain level that uses existing name servers.
For example, Scenario(7) and the sample given in Section 3.
The end host without any more child sub-domains SHOULD never turn on
RENAME. This consideration is given to reduce the amount of
transition traffic created due to the reflexive answer where no
further resolution is required.
4.2 Transitioning towards Identification Based DNSII
Following the DNSII-MDNP recommendations, TRACE could smooth the
transition into a multilingual name space by starting at the registry
level and without requiring the host DNSs to migrate.
As the user-end applications or recursive ISP resolvers began the
migration, new multilingual TLDs could also be introduced even before
the root servers begin any migration.
Eventually, when the root servers migrate, they should be enabled
with both the full DNSII capability with the InPacket Identifier,
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ILET as well as TRACE as a fallback should there be any host DNS
still using existing servers.
From the general rules, we understand that if the entire child DNSs
are DNSII enabled, then the RENAME function of the parent DNS could
be turned off. This therefore makes way for a very sensible
migration strategy owing to the hierarchical structure of the DNS.
Since a parent DNS must know a glue record for its immediate
children, it is easy for the zone administrator to determine whether
it could turn off the RENAME function for its zone.
While it is understood that gradually, all name servers should
migrate to be DNSII capable and that multilingual names, TRACE
creates a very effective way of monitoring the migration by
encouraging child DNSs to begin transition first followed by upper
and more important levels, up to the root.
A fully DNSII aware server should also be prepared for DNSII queries.
That is, it should be able to process requests containing the DNSII
Identifier and ILET. As a working example, a Neteka Enhanced BIND
(for a demo copy please mailto:netekare@neteka.com) has been
developed as a demonstration. To enter a full DNSII label, in the
product, simply duplicate the TRACE identifier and insert a
corresponding ILET. As an example, for "ρρρ….tld" <U+4e2d>
<U+6587>.tld with ILET = 1000 = Unicode, an A record for the IP
address 123.4.5.6 could be added to the zone file as:
\127\12710004e2d6587.tld. IN A 123.4.5.6
In such an environment, DNSII aware queries will be answered
accordingly utilizing the "\127\127" record.
5. Security Considerations
The implementation of TRACE constitutes no further security burden on
the DNS. DNSSEC could be used in parallel with TRACE resolution and
records. RENAME records will be secured through transaction
authentication, while authoritative records will have their own SIG
RRs.
Moreover, the TRACE identifier actually increases the security for
multilingual names over other ACE implementations by using the 0x7F
character, which is difficult for an end user to key in, thereby
reducing the possible confusions.
6. Conclusion
With any implementation, the first step towards universal deployment
of a multilingual aware name space should be an 8-bit clean approach.
For current BIND servers it is a simple configuration matter, which
could be set as an option for checknames to be ignored.
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With TRACE, the migration from the current system could be dynamic.
While it is encouraged that the registries begin the migration first
because it is most sensible, client end or recursive resolvers could
also begin the migration.
The use of the control character 0x7F also solves two problems at
once: 1) a 7-bit identifier to avoid disruption of other applications
using DNS; and, 2) an identifier that is not easily input by a client
end user to prevent confusion between a multilingual name and an
English alphanumeric only name.
RENAME successfully creates an environment where host level DNSs
could hold on to their existing BIND based name servers while being
able to host multilingual domains, thereby relieving the migration
stress for hosting facilities and ISPs.
7. Intellectual Property Considerations
It is the intention of Neteka to submit the DNSII protocol and other
elements of the multilingual domain name server software to IETF for
review, comment or standardization.
Neteka Inc. has applied for one or more patents on the technology
related to multilingual domain name server software and multilingual
email server software suite. If a standard is adopted by IETF and
any patents are issued to Neteka with claims that are necessary for
practicing the standard, any party will be able to obtain the right
to implement, use and distribute the technology or works when
implementing, using or distributing technology based upon the
specific specifications under fair, reasonable and non-discriminatory
terms.
8. References
[DNSII-MDNP] E. Chung & D. Leung "DNSII Multilingual Domain Name
Protocol", August 2000
[RACE] P. Hoffman "RACE: Row-based ASCII Compatible Encoding for
IDN", August 31, 2000
[RFC1700] J. Reynolds, J. Postel, "ASSIGNED NUMBERS", RFC
1700, October 1994.
[ISO10646] ISO/IEC 10646-1:2000. International Standard --
Information technology -- Universal Multiple-Octet Coded
Character Set (UCS)
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels," RFC 2119, March 1997
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Authors:
Edmon Chung
Neteka Inc.
2462 Yonge St. Toronto,
Ontario, Canada M4P 2H5
edmon@neteka.com
David Leung
Neteka Inc.
2462 Yonge St. Toronto,
Ontario, Canada M4P 2H5
david@neteka.com
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