Network Working Group M. Mealling
Internet-Draft Network Solutions, Inc.
Category: Informational February 1999
Expires: August 02, 1999
Assignment Procedures for URI Resolution using DNS
draft-ietf-urn-net-procedures-02.txt
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on August 02, 1999.
Abstract
RFC2168 defines a DNS resource record and an algorithm for using DNS
as a registry for retrieving URI delegation rules (sometimes called
resolution hints). That document specifies that the first step in
that algorithm is to append 'uri.net' to the URI scheme and retrieve
the NAPTR record for that domain-name. I.e., the first step in
resolving "http://foo.com/" would be to look up a NAPTR record for
the domain "http.uri.net". URN resolution also follows a similar
procedure but uses the 'urn.net' zone as its root. This document
describes the procedures for inserting a new rule into the 'uri.net'
and 'urn.net' zones.
Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. URI Resolution vs URN Resolution . . . . . . . . . . . . . . . 3
3. URI Registration Procedure . . . . . . . . . . . . . . . . . . 3
4. URN Registration Procedure . . . . . . . . . . . . . . . . . . 3
5. Requirements on rules . . . . . . . . . . . . . . . . . . . . 3
6. Submission Procedure . . . . . . . . . . . . . . . . . . . . . 4
7. Registration Template . . . . . . . . . . . . . . . . . . . . 5
7.1 Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.2 Authority . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.3 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Example Template . . . . . . . . . . . . . . . . . . . . . . . 5
9. The URN Registration in the uri.net zone . . . . . . . . . . . 5
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This document defines the policies and procedures for inserting
NAPTR records into the 'uri.net' and 'urn.net' zones for the purpose
of resolving URIs according to "Resolution of Uniform Resource
Identifiers using the Domain Name System", RFCXXXX[1], which is an
application of the NAPTR DNS Resource Record defined in RFCXXXX[2].
2. URI Resolution vs URN Resolution
RFCXXXX[1] defines how both URI resolution and URN[3] resolution
work. Specifically it says that all URIs rules are registered in
'uri.net'. Since a URN is a URI it follows the same rules. Thus one
of the rules in the 'uri.net' zone is the one for a URN. This rule
states that the namespace id [4] is extracted, 'urn.net' is appended
to the end of the namespace id, and the next NAPTR record[2] is
retrieved.
3. URI Registration Procedure
At this time there is no set procedure for registering new URI
schemes other than a published RFC. Due to this lack and the
existence of non-published schemes such as "about" and "res", there
is an IETF working group discussing how to deal with this problem.
Thus, at this time the only requirements for requesting an entry in
the uri.net zone is that the URI scheme be published or in use
somewhere and that it not conflict with an existing URI scheme.
When the IETF does standardize a set of procedures for vetting and
registering new URI schemes, the 'uri.net' registration procedures
MUST adhere to those procedures for determining if the URI scheme in
question is valid.
4. URN Registration Procedure
RFCXXXX[6] defines the procedures for assignment of new URN
namespace-ids. Since the 'urn.net' registration procedures only
deal with the namespace-id portion of the URN space, that document
is the sole determining document for what can be entered into the
urn.net zone for a URN.
5. Requirements on rules
Delegation of a namespace can happen in two ways. In the case of
most URIs where the entity being delegated to is hard-coded into the
identifier itself, the syntax of where this is located is set. In
the case where the entity being delegated to is set in the rule,
that entity can change as the rule changes.
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One of the optimizations that the both the URI and URN registries
attempts to make is that any entry in that zone should have an
extremely long time to live. 'Extremely long' should be measured in
years if possible. Thus, any rule that can change must be delegated
out of the urn.net zone by a replacement rule in the NAPTR record.
For example, the 'foo' URN namespace has flexible rules for how
delegation takes place. Instead of putting those rules in the
urn.net zone, the entry instead punts those rules off to a
nameserver that has a shorter time to live. The record in urn.net
would look like this:
foo IN NAPTR 100 10 "" "" "" urn-resolver.foo.com.
Thus, when the client starts out in the resolution process, the
second step is to begin asking 'urn-resolver.foo.com' for the NAPTR
records that contain the resolution rules. The TTL at the root is
very long. The TTL at the 'urn-resolver.foo.com' is much shorter.
Conversely, the 'http' URL scheme adheres to a particular syntax
that specifies that the host to ask is specified in the URL in
question. Since this syntax does not change, that rule can be
specified in the uri.net zone. The record would look like this:
http IN NAPTR 100 100 "" "" "/http:\\/\\/([^\\/:]+)/\\2/i" .
Thus, the second step of resolution is to attempt to contact the
host contained in the URL itself.
6. Submission Procedure
Using the MIME Content-Type registration mechanism[5]as a model for
a successful registration mechanism, the 'uri.net' and 'urn.net'
procedures consist of a request template submitted to an open
mailing list made up of interested parties. If no objections are
made within a two week period, a representative of the registration
authority considers the submission to be accepted and enters that
submission into the nameserver.
o Registrations for the 'uri.net' zone are sent to
'register@uri.net'.
o Registrations for the 'urn.net' zone are sent to
'register@urn.net'.
At this time the registration authority is expected to be the IANA.
Objections are restricted to those that point out impacts on the
zone itself or to DNS in general. Objections to the URL scheme or to
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the URN namespace-id are not allowed, as these should be raised in
their respective forums. The logical conclusion of this is that ANY
sanctioned URL scheme or URN namespace MUST be allowed to be
registered if it meets the requirements specified in this document
as regards times to live and general impact to the DNS.
7. Registration Template
The template to be sent to the appropriate list MUST contain the
following values:
7.1 Key
This is the URN NID or URL scheme, which is used as the domain
portion of the DNS entry. It must be valid according to the
procedures specified in the URN namespace-id assignment document and
any future standards for registering new URL schemes.
7.2 Authority
This is the authority doing the registration of the record. It must
be an authority recognized as either the IESG or any authority
defined in the URN NID[6] or URL scheme registration[7] documents.
7.3 Records
The actual DNS records representing the rule set for the key. The
required values are Preference, Order, Flags, Services, Regex, and
Replacement as defined by RFCXXXX[2].
8. Example Template
To: register@urn.net
From: joe@foo.com
Key: foo
Authority: Foo Technology, Inc as specified in RFCFOO
Record: foo IN NAPTR 100 100 "" "" "" urn.foo.com.
9. The URN Registration in the uri.net zone
Since this document discusses the uri.net and urn.net zones and the
URN rule that exists in the uri.net zone, it makes sense for the
regisration template for the URN URI rule to be specified here:
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To: register@uri.net
From: The IETF URN Working Group
Key: urn
Authority: RFC2141
Record: urn IN NAPTR 0 0 "" "" "/urn:([^:]+)/\\2/i" .
10. IANA Considerations
This document describes a mechanism for registering representations
of protocol items that have already been registered with some IETF
sanctioned agency (probably the IANA as well). This means that the
IANA need not determine appropriateness of the underlying
namespaces, since that is determined by another process.
The only real impact on the IANA will be
o to maintain (or designate some other entity to maintain) a
primary nameserver for the uri.net and urn.net zones;
o to maintain the mailing lists "register@uri.net" and
"register@uri.net" as the forum for discussions of submissions;
and
o to act as the party that determines if all objections have been
noted and accommodated.
References
[1] Mealling, M., Daniel, R., "Resolution of Uniform Resource
Identifiers using the Domain Name System", November 1998.
[2] Mealling, M., Daniel, R., "The Naming Authority Pointer (NAPTR)
DNS Resource Record", November 1998.
[3] Moats, R., "URN Syntax", RFC 2141, May 1997.
[4] Berners-Lee, T., Fielding, R., Masinter, L., "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[5] Freed, N., Klensin, J., Postel, J., "Multipurpose Internet Mail
Extensions (MIME) Part Four: Registration Procedures", RFC
2048, November 1996.
[6] Faltstrom, P., Iannella, R., Daigle, L., van Gulik, D., "URN
Namespace Definition Mechanisms", October 1998.
[7] Petke, R., King, I., "Registration Procedures for URL Scheme
Names", January 1999.
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Author's Address
Michael Mealling
Network Solutions, Inc.
505 Huntmar Park Drive
Herndon, VA 22070
US
Phone: +1 770 935 5492
EMail: michaelm@netsol.com
URI: http://www.netsol.com
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