Network Working Group                                        M. Mealling
Request for Comments: 3405                                      VeriSign
BCP: 65                                                     October 2002
Category: Best Current Practice


    Dynamic Delegation Discovery System (DDDS) Part Five: URI.ARPA
                        Assignment Procedures

Status of this Memo

  This document specifies an Internet Best Current Practices for the
  Internet Community, and requests discussion and suggestions for
  improvements.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

  This document is fifth in a series that is completely specified in
  "Dynamic Delegation Discovery System (DDDS) Part One: The
  Comprehensive DDDS" (RFC 3401).  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 . . . . . . . . . . . . . . . . . . . . . . . .  2
  2.    URI Resolution vs URN Resolution . . . . . . . . . . . . . .  2
  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 . . . .  3
  3.1.4 Registration or Changes after Scheme Registration  . . . . .  3
  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  . . . . . . . . . . . . . . . . . . .  4
  5.    Submission Procedure . . . . . . . . . . . . . . . . . . . .  5
  6.    Registration Template  . . . . . . . . . . . . . . . . . . .  6
  6.1   Key  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
  6.2   Authority  . . . . . . . . . . . . . . . . . . . . . . . . .  6
  6.3   Records  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
  7.    Example Template . . . . . . . . . . . . . . . . . . . . . .  6



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  8.    The URN Registration in the URI.ARPA zone  . . . . . . . . .  7
  9.    IANA Considerations  . . . . . . . . . . . . . . . . . . . .  7
  10.   Security Considerations  . . . . . . . . . . . . . . . . . .  7
  11.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  7
  12.   References . . . . . . . . . . . . . . . . . . . . . . . . .  8
  13.   Author's Address . . . . . . . . . . . . . . . . . . . . . .  9
  14.   Full Copyright Statement . . . . . . . . . . . . . . . . . . 10

1. Introduction

  This document defines the policies and procedures for inserting
  Naming Authority Pointer (NAPTR) records into the 'URI.ARPA' and
  'URN.ARPA' zones for the purpose of resolving Uniform Resource
  Identifiers (URIs) according to "Dynamic Delegation Discovery System
  (DDDS) Part Four:  The URI Resolution Application" (RFC 3402) [2],
  which is an Application that uses the Domain Name System (DNS) based
  DDDS Database.  All of these concepts are defined in RFC 3401 [1].
  It is very important to note that it is impossible to correctly
  understand this document without reading RFC 3401 and the documents
  it specifies.

  RFC 3403 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.

2. URI Resolution vs URN Resolution

  RFC 3402 [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].







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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

     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.



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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 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 URI).  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.







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  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' URI scheme adheres to a particular syntax that
  specifies that the host to ask is specified in the URI in question.
  Since this syntax does not change, that rule can be specified in the
  URI.ARPA zone.  The record would look like this:

     http    IN NAPTR 100 100 "" ""  "/http:\\/\\/([^\\/:]+)/\\2/i" .


  Thus, the second step of resolution is to use the domain-name found
  in the URI 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
          '[email protected]'.





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      o  Registrations for the 'URN.ARPA' zone are sent to
          '[email protected]'.

      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 URI 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 URI 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 URI 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 URI schemes.

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 URI
  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 RFC 3404 [4].

7. Example Template

  To: [email protected]
  From: [email protected]

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




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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: [email protected]
        From: The IETF URN Working Group

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

9. IANA Considerations

  The IANA has created 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 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.

  The IANA has also created two discussion lists, [email protected] and
  [email protected], for the purposes described in this document.  The
  IANA will 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.








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12. References

  [1]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        One: The Comprehensive DDDS", RFC 3401, October 2002.

  [2]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        Two: The Algorithm", RFC 3402, October 2002.

  [3]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        Three: The Domain Name System (DNS) Database", RFC 3403,
        October 2002.

  [4]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        Four: The Uniform Resource Identifiers (URI) Resolution
        Application", RFC 3404, October 2002.

  [5]   Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
        Five: URI.ARPA Assignment Procedures", RFC 3405, October 2002.

  [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
        1998.

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

  [9]   Faltstrom, P., Iannella, R., Daigle, L. and D. van Gulik, "URN
        Namespace Definition Mechanisms", BCP 33, RFC 2611, October
        1998.

  [10]  Petke, R. and I. King, "Registration Procedures for URL Scheme
        Names", BCP 35, RFC 2717, January 1999.
















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13. Author's Address

  Michael Mealling
  VeriSign
  21345 Ridgetop Circle
  Sterling, VA  20166
  US

  EMail: [email protected]
  URI:  http://www.verisignlabs.com









































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14. Full Copyright Statement

  Copyright (C) The Internet Society (2002).  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 implementation 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
  English.

  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
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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



















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