Network Working Group M. Mealling
Internet-Draft Verisign
Expires: April 28, 2002 October 28, 2001
Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA
Assignment Procedures
draft-ietf-urn-net-procedures-09.txt
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
RFCYYYY defines a how DNS is used as a DDDS database that contains
URI delegation rules (sometimes called resolution hints). That
document specifies that the first step in that algorithm is to append
'URI.ARPA' 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.ARPA".
URN resolution also follows a similar procedure but uses the
'URN.ARPA' zone as its root. This document describes the procedures
for inserting a new rule into the 'URI.ARPA' and 'URN.ARPA' zones.
This document is fifth in a series that is completely specified in
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"Dynamic Delegation Discovery System (DDDS) Part One: The
Comprehensive DDDS Standard" (RFC WWWW). It is very important to
note that it is impossible to read and understand any document in
this series without reading the others.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. URI Resolution vs URN Resolution . . . . . . . . . . . . . . 3
3. Registration Policies . . . . . . . . . . . . . . . . . . . 3
3.1 URI.ARPA Registration . . . . . . . . . . . . . . . . . . . 3
3.1.1 Only Schemes in the IETF Tree Allowed . . . . . . . . . . . 3
3.1.2 Scheme Registration Takes Precedence . . . . . . . . . . . . 3
3.1.3 NAPTR Registration May Accompany Scheme Registration . . . . 4
3.1.4 Registration or Changes after Scheme Registration . . . . . 4
3.2 URN.ARPA Registration . . . . . . . . . . . . . . . . . . . 4
3.2.1 NID Registration Takes Precedence . . . . . . . . . . . . . 4
3.2.2 NAPTR Registration May Accompany NID Registration . . . . . 4
3.2.3 Registration or Changes after Scheme Registration . . . . . 4
4. Requirements on hints . . . . . . . . . . . . . . . . . . . 5
5. Submission Procedure . . . . . . . . . . . . . . . . . . . . 6
6. Registration Template . . . . . . . . . . . . . . . . . . . 6
6.1 Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.2 Authority . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.3 Records . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Example Template . . . . . . . . . . . . . . . . . . . . . . 7
8. The URN Registration in the URI.ARPA zone . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 7
10. Security Considerations . . . . . . . . . . . . . . . . . . 8
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
References . . . . . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . 9
Full Copyright Statement . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document defines the policies and procedures for inserting NAPTR
records into the 'URI.ARPA' and 'URN.ARPA' zones for the purpose of
resolving URIs according to "Dynamic Delegation Discovery System
(DDDS) Part Four: The URI Resolution Application" (RFCXXXX) [2],
which is an Application that uses the DNS based DDDS Database. All
of these concepts are defined in RFC WWWW [1]. It is very important
to note that it is impossible to correctly understand this document
without reading RFC WWWW and the documents it specifies.
2. URI Resolution vs URN Resolution
RFCXXXX [2] defines how both URI [7] resolution and URN [6]
resolution work when DNS is used as the delegation rule (or hint)
database. Specifically it says that the initial instructions
('hints') for DNS-based resolution of URIs are stored as resource
records in the 'URI.ARPA' DNS zone.
Since a URN is a URI scheme, a hint for resolution of the URI prefix
'urn:' will also be stored in the 'URI.ARPA' zone. This rule states
that the namespace id [6] is extracted, 'URN.ARPA' is appended to the
end of the namespace id, and the result is used as the key for
retrieval of a subsequent NAPTR record [4].
3. Registration Policies
The creation of a given URI scheme or URN namespace id (NID) follows
the appropriate registration documents for those spaces. URI schemes
follow "Registration Procedures for URL Scheme Names" (RFC 2717)
[10]. URN namespace ids follow "URN Namespace Definition Mechanisms"
(RFC 2611) (or updates thereto) [9].
3.1 URI.ARPA Registration
3.1.1 Only Schemes in the IETF Tree Allowed
In order to be inserted into the URI.ARPA zone, the subsequent URI
scheme MUST be registered under the IETF URI tree. The requirements
for this tree are specified in [10].
3.1.2 Scheme Registration Takes Precedence
The registration of a NAPTR record for a URI scheme MUST NOT precede
proper registration of that scheme and publication of a stable
specification in accordance with [10]. The IESG or its designated
expert will review the request for
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1. correctness and technical soundness
2. consistency with the published URI specification, and
3. to ensure that the NAPTR record for a DNS-based URI does not
delegate resolution of the URI to a party other than the holder
of the DNS name. This last rule is to insure that a given URI's
resolution hint doesn't hijack (inadvertently or otherwise)
network traffic for a given domain.
3.1.3 NAPTR Registration May Accompany Scheme Registration
A request for a URI.ARPA registration MAY accompany a request for a
URI scheme (in accordance with [10]), in which case both requests
will be reviewed simultaneously by IESG or its designated experts.
3.1.4 Registration or Changes after Scheme Registration
A request for a NAPTR record (or an request to change an existing
NAPTR record) MAY be submitted after the URI prefix has been
registered. If the specification for the URI prefix is controlled
by some other party than IETF, IESG will require approval from the
owner/maintainer of that specification before the registration will
be accepted. This is in addition to any technical review of the
NAPTR registration done by IESG or its designated experts.
3.2 URN.ARPA Registration
3.2.1 NID Registration Takes Precedence
The registration of a NAPTR record for a URN NID MUST NOT precede
proper registration of that NID and publication of a stable
specification in accordance with [9]. This is to prevent the
registration of a NAPTR record in URN.ARPA from circumventing the NID
registration process.
3.2.2 NAPTR Registration May Accompany NID Registration
A request for a URN.ARPA registration MAY accompany a request for a
NID (in accordance with [9]), in which case both requests will be
reviewed at the same time.
3.2.3 Registration or Changes after Scheme Registration
A request for a NAPTR record (or an request to change an existing
NAPTR record) MAY be submitted after the NID has been registered.
If the specification for the NID is controlled by some other party
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than IETF, IESG will require approval from the owner/maintainer of
that specification before the registration will be accepted. This is
in addition to any technical review of the NAPTR registration done by
IESG or its designated experts.
Note that this applies to all NAPTR records for a particular NID,
even though a NAPTR record might affect only part of the URN space
assigned to an NID
4. Requirements on hints
Delegation of a namespace can happen in two ways. In the case of
most URIs, the key being delegated to is hard-coded into the
identifier itself (e.g. a hostname in an HTTP URL). The syntax of
where this new key is located is predetermined by the syntax of the
scheme. In other cases, the new key can be part of the hint itself.
This is the functional equivalent of saying, "if this rule matches
then this is always the key."
In order to minimize the query load on the URI.ARPA and URN.ARPA
zones, it is anticipated that the resource records in those zones
will have extremely long "times to live" (TTLs), perhaps measured in
years.
Thus, for any URI prefix or URN namespace for which the resolution
hints are likely to change, the actual rule should be stored in some
other (less stable) DNS zone, and within URI.ARPA or URN.ARPA a
stable NAPTR record should be used to delegate queries to that less
stable zone.
For example, the 'foo' URN namespace has flexible rules for how
delegation takes place. Instead of putting those rules in the
URN.ARPA zone, the entry instead punts those rules off to a
nameserver that has a shorter time to live. The record in URN.ARPA
would look like this:
foo IN NAPTR 100 10 "" "" "" urn-resolver.foo.com.
Thus, when the client starts out in the resolution process, the first
step will be to query foo.URN.ARPA to find the above record, 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.ARPA zone. The record would look like this:
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http IN NAPTR 100 100 "" "" "/http:\\/\\/([^\\/:]+)/\\2/i" .
Thus, the second step of resolution is to use the domain-name found
in the URL as the next key in the cycle. If, for example, that NAPTR
was terminal and contains some hostname in the replacement field,
then the client could contact that host in order to ask questions
about this particular URI.
5. Submission Procedure
Using the MIME Content-Type registration mechanism [8] as a model
for a successful registration mechanism, the 'URI.ARPA' and
'URN.ARPA' 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.ARPA' zone are sent to
'register@URI.ARPA'.
o Registrations for the 'URN.ARPA' zone are sent to
'register@URN.ARPA'.
The registration authority is the Internet Assigned Numbers Authority
(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 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.
6. Registration Template
The template to be sent to the appropriate list MUST contain the
following values:
6.1 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.
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6.2 Authority
This is the individual or organization (entity) which has authority
for registering the record. It must be an authority recognized as
either the IESG or any authority defined in the URN NID [9] or URL
scheme registration [10] documents.
6.3 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 RFCYYYY [4].
7. Example Template
To: register@URN.ARPA
From: joe@foo.com
Key: foo
Authority: Foo Technology, Inc as specified in RFCFOO
Record: foo IN NAPTR 100 100 "" "" "" urn.foo.com.
8. The URN Registration in the URI.ARPA zone
Since this document discusses the URI.ARPA and URN.ARPA zones and the
URN rule that exists in the URI.ARPA zone, it makes sense for the
registration template for the URN URI rule to be specified here:
To: register@URI.ARPA
From: The IETF URN Working Group
Key: urn
Authority: RFC2141
Record: urn IN NAPTR 0 0 "" "" "/urn:([^:]+)/\\2/i" .
9. IANA Considerations
This memo requests that the IANA create the zones URN.ARPA and
URI.ARPA. The hierarchical name structure, and the only names to be
assigned within these zones, are the "keys" as described in Section
6.1 of this document. The administrative and operational management
of these zones are recommended to be undertaken by the IANA. The DNS
records to be inserted in these zones are subject to the review
process described in this document.
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This memo also requires the creation of 2 discussion lists,
register@uri.arpa and register@urn.arpa, for the purposes described
in this document. It is recommended that IANA create and manage
these mailing lists."
10. Security Considerations
The 'uri.arpa' and 'urn.arpa' zones will be a common point of attack
both for Denial of Service and for spoofing entries in order to
redirect delegation paths. Any entity running nameservers that
contain these zones should take appropriate action for securing an
infrastructure level component of the Internet. When it becomes
possible for a nameserver to reliably sign the records in its zone it
should do so.
11. Acknowledgements
The author would like to thank Ron Daniel who was originally co-
author of these documents. Ron's original insite into the intricate
nature of delegation rules made these procedures and the DDDS itself
possible.
References
[1] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
One: The Comprehensive DDDS Standard", RFC WWWW, draft-ietf-
urn-ddds-toc-00.txt (work in progress), October 2001.
[2] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Two: The Algorithm", RFC XXXX, draft-ietf-urn-ddds-05.txt (work
in progress), May 2000.
[3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Three: The DNS Database", RFC ZZZZ, draft-ietf-urn-dns-ddds-
database-07.txt (work in progress), May 2000.
[4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Four: The URI Resolution Application", RFC YYYY, draft-ietf-
urn-uri-res-ddds-05.txt (work in progress), October 2000.
[5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Five: URI.ARPA Assignment Procedures", RFC VVVV, draft-ietf-
urn-net-procedures-09.txt (work in progress), October 2001.
[6] Moats, R., "URN Syntax", RFC 2141, November 1998.
[7] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August
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1998.
[8] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures", RFC
2048, November 1996.
[9] Faltstrom, P., Iannella, R., Daigle, L. and D. van Gulik, "URN
Namespace Definition Mechanisms", RFC 2611, October 1998.
[10] Petke, R. and I. King, "Registration Procedures for URL Scheme
Names", RFC 2717, January 1999.
Author's Address
Michael Mealling
Verisign
505 Huntmar Park Drive
Herndon, VA 22070
US
Phone: (770) 721-2251
EMail: michael@research.netsol.com
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