Network Working Group                                        M. Mealling
Internet-Draft                                   Network Solutions, Inc.
Category: Informational                                    February 1999
Expires: August 02, 1999 1, 2000                                      R.D. Daniel
                                                          Metacode, Inc.
                                                           February 2000

           Assignment Procedures for URI Resolution using DNS

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 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."

   To view the entire

     The list of current Internet-Drafts can be accessed at

     The list of Internet-Draft Shadow Directories, see Directories can be accessed at

   This Internet-Draft will expire on August 02, 1999. 1, 2000.

Copyright Notice

   Copyright (C) The Internet Society (2000). All Rights Reserved.



   RFCXXXX defines a how DNS resource record and an algorithm for using DNS is used as a registry for retrieving Resolver Discovery System
   database that contains 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 "" 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.

Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.    URI Resolution vs URN Resolution . . . . . . . . . . . . . . .  3
   3.  URI    Registration Procedure Policies  . . . . . . . . . . . . . . . . . . .  3
   4.  URN
   3.1   URI.NET Registration Procedure . . . . . . . . . . . . . . . . . . . .  3
   5.  Requirements on rules
   3.1.1 Only Schemes in the IETF Tree Allowed  . . . . . . . . . . .  3
   3.1.2 Scheme Registration Takes Precedence . . . . . . . . . . . .  3
   6.  Submission Procedure
   3.1.3 NAPTR Registration May Accompany Scheme Registration . . . .  4
   3.1.4 Registration or Changes after Scheme Registration  . . . . .  4
   3.2   URN.NET Registration . . . . . . . . . . . . . . . . . . . .  4
   3.2.1 NID Registration Template 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
   7.1 Key
   5.    Submission Procedure . . . . . . . . . . . . . . . . . . . .  6
   6.    Registration Template  . . . . . . . . .  5
   7.2 Authority . . . . . . . . . .  6
   6.1   Key  . . . . . . . . . . . . . . . .  5
   7.3 Records . . . . . . . . . . . .  6
   6.2   Authority  . . . . . . . . . . . . . . .  5
   8. . . . . . . . . . .  6
   6.3   Records  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   7.    Example Template . . . . . . . . . . . . . . . . . . . . . . .  5
   9.  7
   8.    The URN Registration in the URI.NET zone . . . . . . . . . . .  5
   10.  7
   9.    IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6  7
         References . . . . . . . . . . . . . . . . . . . . . . . . .  7
         Authors' Addresses . .  6
       Author's Address . . . . . . . . . . . . . . . . . . .  8
         Full Copyright Statement . . . .  7 . . . . . . . . . . . . . .  9

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 when DNS is used as the delegation rule (or hint) database.
   Specifically it says that all the initial instructions ('hints') for
   DNS-based resolution of URIs rules are registered stored as resource records in
   ''. the
   'URI.NET' DNS zone.

   Since a URN is a URI it follows the same rules. Thus one kind of URI, a hint for resolution of the rules in the '' zone is URI
   prefix 'urn:' will also be stored in the one for a URN. 'URI.NET' zone. This rule
   states that the namespace id [4] id[3] is extracted, '' 'URN.NET' is appended
   to the end of the namespace id, and the next NAPTR  record[2] result is
   retrieved. used as the key
   for retrieval of a subsequent NAPTR record[2].

3. URI Registration Procedure

   At this time there is no set procedure Policies

   The creation of a given URI scheme or URN namespace id (NID) follows
   the appropriate registration documents for registering new those spaces. URI schemes other than a published RFC. Due
   follow "Registration Procedures for URL Scheme Names"  (RFC
   2717)[7]. URN namespace ids follow "URN Namespace Definition
   Mechanisms" (RFC 2611)[6].

3.1 URI.NET Registration

3.1.1 Only Schemes in the IETF Tree Allowed

   In order to be inserted into the URI.NET zone, the subsequent URI
   scheme MUST be registered under the IETF URI tree. The requirements
   for this lack tree are specified in [7].

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 the
   existence publication of non-published schemes such as "about" a stable
   specification in accordance with [7]. The IESG or its designated
   expert will review the request for
   1.  correctness and "res", there
   is an IETF working group discussing how to deal technical soundness
   2.  consistency with this problem.
   Thus, at this time the only requirements published URI specification, and
   3.  to ensure that the NAPTR record for requesting an entry in a DNS-based URI does not
       delegate resolution of the zone URI to a party other than the holder
       of the DNS name.  This last rule is to insure that the 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.NET registration MAY accompany a request for a
   URI scheme (in accordance with [7]), in which case both requests
   will be published reviewed simultaneously by IESG or in use
   somewhere and that it not conflict with 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 scheme.

   When prefix has been
   registered.   If the IETF does standardize a set of procedures specification for vetting and
   registering new the URI schemes, prefix is controlled
   by some other party than IETF, IESG will require approval from the
   owner/maintainer of that specification before the '' registration procedures
   MUST adhere will
   be accepted. This is in addition to those procedures for determining if any technical review of the URI scheme
   NAPTR registration done by IESG or its designated experts.

3.2 URN.NET 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
   question accordance with [6]. This is valid.

4. URN to prevent the
   registration of a NAPTR record in URN.NET from circumventing the NID
   registration process.

3.2.2 NAPTR Registration Procedure

   RFCXXXX[6] defines May Accompany NID Registration

   A request for a URN.NET registration MAY accompany a request for a
   NID (in accordance with [6]), in which case both requests will be
   reviewed at the procedures same time.

3.2.3 Registration or Changes after Scheme Registration

   A request for assignment of new URN
   namespace-ids.  Since a NAPTR record (or an request to change an existing
   NAPTR record) MAY be submitted after the NID has been registered.
   If the '' registration procedures only
   deal with specification for the namespace-id portion of NID is controlled by some other party
   than IETF, IESG will require approval from the URN space, owner/maintainer of
   that document
   is specification before the sole determining document for what can registration will be entered into accepted. This is
   in addition to any technical review of the zone NAPTR registration done
   by IESG or its designated experts.

   Note that this applies to all NAPTR records for a URN.

5. particular NID,
   even though a NAPTR record might affect only part of the URN space
   assigned to an NID

4. Requirements on rules hints

   Delegation of a namespace can happen in two ways. In the case of
   most URIs where URIs, the entity key being delegated to is hard-coded into the
   identifier itself, the itself (i.e. a hostname in an HTTP URL). The syntax of
   where this new key is located is set. In predetermined by the case where syntax of the entity being delegated to is set in
   scheme. In other cases, the rule,
   that entity new key can change as be part of the rule changes.

   One hint itself.
   This is the functional equivalent of saying, "if this rule matches
   then this is always the optimizations that key."

   In order to minimize the both query load on the URI URI.NET and URN registries
   attempts to make URN.NET
   zones, it is anticipated that any entry the resource records in that zone should those zones
   will have an extremely long time "times to live. 'Extremely long' should be live" (TTLs), perhaps measured in
   years if possible.

   Thus, for any rule that can change must be delegated
   out of URI prefix or URN namespace for which the zone by a replacement resolution
   hints are likely to change, the actual rule should be stored in the some
   other (less stable) DNS zone, and within URI.NET or URN.NET a stable
   NAPTR record. record should be used to delegate queries to that less stable

   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  ""  "" ""

   Thus, when the client starts out in the resolution process, the
   first step will be to query foo.URN.NET to find the above record,
   the second step is to begin asking '' for the
   NAPTR records that contain the resolution rules. The TTL at the root
   is very long. The TTL at the '' 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 use the
   host contained domain-name found
   in the URL itself.

6. 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[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
   o  Registrations for the '' 'URN.NET' zone are sent to

   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
   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.


6.2 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.


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 RFCXXXX[2].


7. Example Template

      To: register@URN.NET

      Key: foo
      Authority: Foo Technology, Inc as specified in RFCFOO
      Record: foo	IN NAPTR 100 100 "" "" ""


8. 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
   registration template for the URN URI rule to be specified here:

      To: register@URI.NET
      From: The IETF URN Working Group

      Key: urn
      Authority: RFC2141
      Record: urn	IN NAPTR 0 0 "" "" "/urn:([^:]+)/\\2/i" .


9. 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 create and 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@URN.NET" as the forum for discussions of submissions;
   o  to act as the party that determines if all objections have been
      noted and accommodated.


   [1]  Mealling, M., M. and R. Daniel, R., "Resolution of Uniform Resource
        Identifiers using the Domain  Name System", November 1998.

   [2]  Mealling, M., M. and R. Daniel, R., "The Naming Authority Pointer
        (NAPTR) DNS Resource Record", November 1998.

   [3]  Moats, R., "URN Syntax", RFC 2141, May 1997. November 1998.

   [4]  Berners-Lee, T., Fielding, R., R. and L. Masinter, L., "Uniform
        Resource Identifiers (URI): Generic Syntax", RFC 2396, August

   [5]  Freed, N., Klensin, J., J. and J. Postel, J., "Multipurpose Internet
        Mail Extensions (MIME) Part Four: Registration Procedures", RFC
        2048, November 1996.

   [6]  Faltstrom, P., Iannella, R., Daigle, L., L. and D. van Gulik, D., "URN
        Namespace Definition Mechanisms", RFC 2611, October 1998.

   [7]  Petke, R., R. and I. King, I., "Registration Procedures for URL Scheme
        Names", RFC 2717, January 1999.

Author's Address

Authors' Addresses

   Michael Mealling
   Network Solutions, Inc.
   505 Huntmar Park Drive
   Herndon, VA  22070

   Phone: +1 770 935 5492 (703) 742-0400

   Metacode, Inc.
   139 Townsend Street, Ste. 100
   San Francisco, CA  94107

   Phone: +1 415 222 0100

Full Copyright Statement

   Copyright (C) The Internet Society (1999). (2000). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implmentation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an


   Funding for the RFC editor function is currently provided by the
   Internet Society.