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The DNS Zone Version (ZONEVERSION) Option
draft-ietf-dnsop-zoneversion-05

Document Type Active Internet-Draft (dnsop WG)
Authors Hugo Salgado , Mauricio Vergara Ereche , Duane Wessels
Last updated 2024-01-15
Replaces draft-ietf-dnsop-rrserial
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
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Stream WG state WG Document
Document shepherd Tim Wicinski
Shepherd write-up Show Last changed 2023-09-27
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Responsible AD Warren "Ace" Kumari
Send notices to tjw.ietf@gmail.com
draft-ietf-dnsop-zoneversion-05
Internet Engineering Task Force                               H. Salgado
Internet-Draft                                                 NIC Chile
Intended status: Informational                                M. Vergara
Expires: 18 July 2024                                       DigitalOcean
                                                              D. Wessels
                                                                Verisign
                                                         15 January 2024

               The DNS Zone Version (ZONEVERSION) Option
                    draft-ietf-dnsop-zoneversion-05

Abstract

   The DNS ZONEVERSION option is a way for DNS clients to request, and
   for authoritative DNS servers to provide, information regarding the
   version of the zone from which a response is generated.  The Serial
   field from the Start Of Authority (SOA) resource record is a good
   example of a zone's version, and the only one defined by this
   specification.  Additional version types may be defined by future
   specifications.

   Including zone version data in a response simplifies and improves the
   quality of debugging and and diagnostics since the version and the
   data are provided atomically.  This can be especially useful for
   zones and DNS providers that leverage IP anycast or multiple backend
   systems.  It functions similarly to the NSID option.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on 18 July 2024.

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Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  The ZONEVERSION Option  . . . . . . . . . . . . . . . . . . .   4
     2.1.  Wire Format . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Presentation Format . . . . . . . . . . . . . . . . . . .   5
   3.  ZONEVERSION Processing  . . . . . . . . . . . . . . . . . . .   5
     3.1.  Initiators  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Responders  . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  The SOA-SERIAL ZONEVERSION Type . . . . . . . . . . . . . . .   6
     4.1.  Type SOA-SERIAL Presentation Format . . . . . . . . . . .   7
   5.  Example usage . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  DNS EDNS0 Option Code Registration  . . . . . . . . . . .   9
     7.2.  ZONEVERSION Registry  . . . . . . . . . . . . . . . . . .   9
       7.2.1.  Expert Review Directives  . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  11
   10. Informative References  . . . . . . . . . . . . . . . . . . .  11
   Appendix A.  Implementation Considerations  . . . . . . . . . . .  12
   Appendix B.  Implementation References  . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The ZONEVERSION option allows DNS queriers to request, and
   authoritative DNS severs to provide, a token representing the version
   of the zone from which a DNS response was generated.  It is similar
   to the NSID option, which can be used to convey the identification of
   a name server that generates a response.

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   The Domain Name System allows data to be loosely coherent [RFC3254],
   because synchronization can never be instantaneous, and some uses of
   DNS do not require strong coherency anyway.  This means that a record
   obtained by one response could be out-of-sync with other
   authoritative sources of the same data at the same point in time.
   This can make it difficult to debug some problems when there is a
   need to couple the data with the version of the zone it came from.
   Furthermore, in today's Internet, it is common for high volume and
   important DNS zones to utilize IP anycast Section 4.9 of [RFC4786]
   and/or load-balanced backend servers.  In general, there is no way to
   ensure that two separate queries are delivered to the same server.
   The ZONEVERSION option both simplifies and improves the DNS
   monitoring and debugging by directly associating the data and the
   version together in a single response.

   The SOA Serial field (Section 4.3.5 of [RFC1034]) is one example of
   zone versioning.  Its purpose is to facilitate the distribution of
   zone data between primary and secondary name servers.  It is also
   often useful in DNS monitoring and debugging.  This document
   specifies the SOA Serial as one type of ZONEVERSION data.

   Some DNS zones may use other distrubtion and synchronization
   mechanisms not based on the SOA Serial number, such as relational
   databases or other proprietary methods.  In those cases the SOA
   Serial field may not be relevant with respect to the versioning of
   its content.  To accomodate these use cases, new ZONEVERSION types
   should be defined in future specifications.  Alternatively, zone
   operators may use one of the private use ZONEVERSION code points
   allocated by this specification.

   The ZONEVERSION option is OPTIONAL to implement by DNS clients and
   name servers.  It is designed for use only when a name server
   provides authoritative response data.  It is intended only for hop-
   to-hop communication and is not transitive.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2.  Terminology

   In this document "original QNAME" is used to mean what the DNS
   terminology document [RFC8499] calls "QNAME (original)":

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   |  The name actually sent in the Question section in the original
   |  query, which is always echoed in the (final) reply in the Question
   |  section when the QR bit is set to 1.

2.  The ZONEVERSION Option

   This document specifies a new EDNS(0) Section 6.1.2 of [RFC6891]
   option, ZONEVERSION, which can be used by DNS clients and servers to
   provide information regarding the version of the zone from which a
   response is generated.

2.1.  Wire Format

   The ZONEVERSION option is encoded as follows:

   OPTION-CODE for the ZONEVERSION option is <TBD>.

   [RFC Editor: change <TBD> to the proper code when assigned by IANA.]

   OPTION-LENGTH for the ZONEVERSION option MUST have a value of 0 for
   queries, and MUST have the value of the length (in octets) of the
   OPTION-DATA for responses.

   OPTION-DATA for the ZONEVERSION option is omitted in queries.  For
   responses it is composed of three fields:

   *  An unsigned 1 octet Label Count (LABELCOUNT) indicating the number
      of labels for the name of the zone that VERSION value refers to.

   *  An unsigned 1 octet type number (TYPE) that distinguishes the
      format and meaning of VERSION.

   *  An opaque octet string conveying the zone version data (VERSION).

                   +0 (MSB)                       +1 (LSB)
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |           LABELCOUNT          |            TYPE               |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                            VERSION                            |
      /                                                               /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

    Figure 1: Diagram with the OPTION-DATA format for ZONEVERSION option

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   The LABELCOUNT field indicates the name of the zone that the
   ZONEVERSION option refers to, by means of taking the last LABELCOUNT
   labels of the original QNAME.  For example, an answer with QNAME
   "a.b.c.example.com" and a ZONEVERSION option with a LABELCOUNT of
   value 2, indicates that the zone name that this ZONEVERSION refers is
   "example.com.".

   The LABELCOUNT number helps to differentiate in the case of a
   downward referral response, where the parent server is authoritative
   for some portion of the QNAME that differs from a child server that
   is below the zone cut.  Also, if the ANSWER section has more than one
   RR set with different zones (like a CNAME and a target name in
   another zone) the number of labels in the QNAME disambiguates such a
   situation.

   The value of the LABELCOUNT field MUST NOT count the null (root)
   label that terminates the original QNAME.  The value of the
   LABELCOUNT field MUST be less than or equal to the number of labels
   in the original QNAME.  The Root zone (".") has a LABELCOUNT field
   value of 0.

2.2.  Presentation Format

   The presentation format of the ZONEVERSION option is as follows:

   The OPTION-CODE field MUST be represented as the mnemonic value
   ZONEVERSION.

   The OPTION-LENGTH field MAY be omitted, but if present it MUST be
   represented as an unsigned decimal integer.

   The LABELCOUNT value of OPTION-DATA field MAY be omitted, but if
   present it MUST be represented as an unsigned decimal integer.  The
   corresponding zone name SHOULD be displayed (i.e., LABELCOUNT labels
   of the original QNAME) for easier human consumption.

   The TYPE and VERSION fields of the option SHOULD be represented
   according to each specific TYPE.

3.  ZONEVERSION Processing

3.1.  Initiators

   A DNS client MAY signal its support and desire for zone version
   information by including an empty ZONEVERSION option in the EDNS(0)
   OPT pseudo-RR of a query to an authoritative name server.  An empty
   ZONEVERSION option has OPTION-LENGTH set to zero.

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   A DNS client SHOULD NOT send the ZONEVERSION option to non-
   authoritative name servers.

   A DNS client MUST NOT include more than one ZONEVERSION option in the
   OPT RR of a DNS query.

3.2.  Responders

   A name server that (a) understands the ZONEVERSION option, (b) is
   authoritative for the original QNAME, and (c) chooses to honor a
   particular ZONEVERSION request responds by including a TYPE and
   corresponding VERSION value in a ZONEVERSION option in an EDNS(0) OPT
   pseudo-RR in the response message.

   Otherwise, a server MUST NOT include a ZONEVERSION option in the
   response.

   A name server MUST ignore any non-empty ZONEVERSION payload data that
   might be present in the query message.

   A name server MAY include more than one ZONEVERSION option in the
   response if it supports multiple TYPEs.  A name server MUST NOT
   include more than one ZONEVERSION option for a given TYPE.

   A name server SHOULD include zone version information for downward
   referral responses (see "Referrals" in Section 4 of [RFC8499]).  Even
   though the response's Authoritative Answer bit is not set, the name
   server is authoritative for the zone from which the referral was
   generated.  In this case, the ZONEVERSION data MUST correspond do
   version of the referring zone.

   A name server SHOULD include zone version information in a server
   failure (SERVFAIL) response when it is authoritative for the original
   QNAME.

   A name server SHOULD include zone version information in a NODATA
   response (Section 3 of [RFC8499]).  Even though the NODATA response
   does not include an Answer section RRs, RCODE is NOERROR and the name
   server is still authoritative for the zone.

4.  The SOA-SERIAL ZONEVERSION Type

   The first and only ZONEVERSION option TYPE defined in this document
   is a zone's serial number as found in the Start of Authority (SOA)
   RR.

   The value for this type is: 0

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   The mnemonic of this type is: SOA-SERIAL.

   The OPTION-LENGTH for this type MUST be set to 6 in responses.

   The VERSION value for the SOA-SERIAL type MUST be a copy of the
   unsigned 32-bit SERIAL field of the SOA RR, as defined in
   Section 3.3.13 of [RFC1035].

4.1.  Type SOA-SERIAL Presentation Format

   The presentation format of this type content is as follows:

   The TYPE field MUST be represented as the mnemonic value "SOA-
   SERIAL".

   The VERSION field MUST be represented as an unsigned decimal integer.

5.  Example usage

   A name server which (a) implements this specification, (b) receives a
   query with the ZONEVERSION option, (c) is authoritative for the
   original QNAME, and (d) utilizes the SOA serial field for versioning
   of said zone should include a ZONEVERSION option in its response.  In
   the response's ZONEVERSION option the OPTION-LENGTH would be set to 6
   and the OPTION-DATA would consist of the 1-octet LABELCOUNT, the
   1-octet TYPE with value 0, and 4-octet SOA SERIAL value.

   The example below demonstrates expected output of a diagnostic tool
   that implements the ZONEVERSION option, displaying a response from a
   compliant authoritative DNS server:

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  $ dig @ns.example.com www.example.com aaaa +zoneversion

  ; <<>> DiG 9.17.14-patched <<>> @ns.example.com www.example.com aaaa +zoneversion
  ; (1 server found)
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7077
  ;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 2

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 1232
  ; ZONEVERSION: 02 00 78 95 a4 e9 ("SOA-SERIAL: 2023073001 (example.com.)")
  ;; QUESTION SECTION:
  ;www.example.com.    IN  AAAA

  ;; ANSWER SECTION:
  www.example.com.  43200  IN  AAAA  2001:db8::80

  ;; AUTHORITY SECTION:
  example.com.    43200  IN  NS  ns.example.com.

  ;; ADDITIONAL SECTION:
  ns.example.com.    43200  IN  AAAA  2001:db8::53

  ;; Query time: 15 msec
  ;; SERVER: 2001:db8::53#53(2001:db8::53) (UDP)
  ;; WHEN: dom jul 30 19:51:04 -04 2023
  ;; MSG SIZE  rcvd: 129

                Figure 2: Example usage and dig output

6.  Acknowledgements

   The authors thanks all the comments and support made in the DNSOP
   mailing list, chats and discussions.  In special for the suggestions
   to generalize the option using a registry of types from Petr Špaček
   and Florian Obser, suggestions for implementation from Stéphane
   Bortzmeyer, security clarifications from George Michaelson, zone name
   disambiguation from Joe Abley and Brian Dickson, and reviews from Tim
   Wicinski and Peter Thomassen.

7.  IANA Considerations

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7.1.  DNS EDNS0 Option Code Registration

   This document defines a new EDNS0 option, entitled ZONEVERSION (see
   Section 2), and assigns a value of <TBD> from the DNS EDNS0 Option
   Codes (OPT) Option space:

           +=======+=============+==========+=================+
           | Value | Name        | Status   | Reference       |
           +=======+=============+==========+=================+
           | <TBD> | ZONEVERSION | Standard | [this document] |
           +=======+=============+==========+=================+

                      Table 1: DNS EDNS0 Option code

   [RFC Editor: change <TBD> to the proper code when assigned by IANA.]

   [RFC Editor: change "this document" with the proper RFC number for
   this document when assigned by IANA.]

7.2.  ZONEVERSION Registry

   The ZONEVERSION option also defines a 8-bit TYPE field, for which
   IANA is requested to create and maintain a new registry entitled
   "ZONEVERSION TYPE Values" (abbreviation ZONEVERSION) used by the
   ZONEVERSION option, inside the "Domain Name System (DNS) Parameters"
   group.  Initial values for the ZONEVERSION TYPE values registry are
   given below; future assignments in the 1-245 values are to be made
   through Specification Required Review [BCP26].  Assignments consist
   of a TYPE value as an unsigned 8-bit integer recorded in decimal, a
   Mnemonic name as an uppercase ASCII string with maximum length of 15
   characters, and the required document reference.

       +==================+=====================+=================+
       | ZONEVERSION TYPE | Mnemonic            | Reference       |
       +==================+=====================+=================+
       | 0                | SOA-SERIAL          | [this document] |
       +==================+=====================+=================+
       | 1-245            | Unassigned          |                 |
       +==================+=====================+=================+
       | 246-254          | Reserved for Local/ | [this document] |
       |                  | Experimental Use    |                 |
       +==================+=====================+=================+
       | 255              | Reserved for future | [this document] |
       |                  | expansion           |                 |
       +==================+=====================+=================+

                      Table 2: ZONEVERSION Registry

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   [RFC Editor: change "this document" with the proper RFC number for
   this document when assigned by IANA.]

   The change control for this registry should be by means of an
   Standard action.

7.2.1.  Expert Review Directives

   Allocation procedures for new code points in the ZONEVERSION TYPE
   registry require Specification Required review, and so it requires
   Expert Reviews as stated in [BCP26].

   The expert should consider the following points:

   *  Duplication of code point allocations should be avoided.

   *  A Presentation Format section should be provided, with a clear
      code point mnemonic.

   *  The referenced document and stated use of the new code point
      should be appropriate for the intended use of a ZONEVERSION TYPE
      assignment.  In particular the reference should state clear
      instructions for implementers about the syntax and semantic of the
      data.  Also the Length of the Data must have proper limits.

   The expert reviewing the request MUST approve or disapprove the
   request within 10 business days from when she or he received the
   expert review request.

8.  Security Considerations

   The EDNS extension data it's not covered by RRSIG records, so there's
   no way to verify its authenticity nor integrity using DNSSEC and
   could theoretically be tampered by a person-in-the-middle if the
   transport is made by insecure means.  Caution should be taken to use
   the EDNS ZONEVERSION data for any means besides troubleshooting and
   debugging.

   If there's a need to certify the ZONEVERSION trustworthiness, it will
   be necessary to use an encrypted and authenticated DNS transport.

   If there's a need to authenticate data origin for the ZONEVERSION
   value, an answer with the SOA-SERIAL type as defined above could be
   compared to a separate regular SOA query with DO flag, whose answer
   shall be DNSSEC signed, with the cautions about Anycast and others as
   already stated in Introduction.

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   With the SOA-SERIAL type defined above, there's no risk on disclosure
   of private information, as the SERIAL of the SOA record is already
   publicly available.

   Please note that the ZONEVERSION option can not be used for checking
   the correctness of an entire zone in a server.  For such cases, the
   ZONEMD record [RFC8976] might be better suited at such a task.
   ZONEVERSION can help identify and correlate a certain specific answer
   with a version of a zone, but it has no special integrity or
   verification function besides a normal field value inside a zone, as
   stated above.

9.  Normative References

   [BCP26]    Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891,
              DOI 10.17487/RFC6891, April 2013,
              <https://www.rfc-editor.org/info/rfc6891>.

10.  Informative References

   [ImplRef]  Salgado, H., "Zoneversion Implementations", 2024,
              <https://github.com/huguei/rrserial>.

   [RFC3254]  Alvestrand, H., "Definitions for talking about
              directories", RFC 3254, DOI 10.17487/RFC3254, April 2002,
              <https://www.rfc-editor.org/info/rfc3254>.

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   [RFC4786]  Abley, J. and K. Lindqvist, "Operation of Anycast
              Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
              December 2006, <https://www.rfc-editor.org/info/rfc4786>.

   [RFC8499]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/info/rfc8499>.

   [RFC8976]  Wessels, D., Barber, P., Weinberg, M., Kumari, W., and W.
              Hardaker, "Message Digest for DNS Zones", RFC 8976,
              DOI 10.17487/RFC8976, February 2021,
              <https://www.rfc-editor.org/info/rfc8976>.

Appendix A.  Implementation Considerations

   With very few exceptions, EDNS options which elicit an EDNS option in
   the response are independent of the queried name.  This is not the
   case of ZONEVERSION, so its implementation may be more or less
   difficult depending on how EDNS options are handled in the name
   server.

Appendix B.  Implementation References

   There's a patched NSD server version 4.7.0 with support for
   ZONEVERSION with an experimental opcode, with live test servers
   installed for compliance tests.  Also there is a client command "dig"
   with added zoneversion support, along with test libraries in Perl,
   Python and Go.  More information in the working document [ImplRef].

Authors' Addresses

   Hugo Salgado
   NIC Chile
   Miraflores 222, piso 14
   CP 8320198 Santiago
   Chile
   Phone: +56 2 29407700
   Email: hsalgado@nic.cl

   Mauricio Vergara Ereche
   DigitalOcean
   101 6th Ave
   New York,  NY 10013
   United States of America
   Email: mvergara@digitalocean.com

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   Duane Wessels
   Verisign
   12061 Bluemont Way
   Reston, VA 20190
   United States of America
   Phone: +1 703 948-3200
   Email: dwessels@verisign.com
   URI:   https://verisign.com

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