Registration Protocols Extensions (regext)                      G. Brown
Internet-Draft                                      CentralNic Group plc
Intended status: Experimental                          27 September 2022
Expires: 31 March 2023


  Extensible Provisioning Protocol (EPP) mapping for DNS Time-To-Live
                              (TTL) values
                     draft-regext-brown-epp-ttl-02

Abstract

   This document describes an extension to the Extensible Provisioning
   Protocol (EPP) that allows EPP clients to manage the Time-To-Live
   (TTL) value for domain name delegation records.

Status of This Memo

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

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   This Internet-Draft will expire on 31 March 2023.

Copyright Notice

   Copyright (c) 2022 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
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions used in this document . . . . . . . . . . . .   3
   2.  Extension elements  . . . . . . . . . . . . . . . . . . . . .   3
   3.  EPP command mapping . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  EPP query commands  . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  EPP <info> command  . . . . . . . . . . . . . . . . .   4
     3.2.  EPP transform commands  . . . . . . . . . . . . . . . . .   6
       3.2.1.  EPP <create> command  . . . . . . . . . . . . . . . .   6
       3.2.2.  EPP <update> command  . . . . . . . . . . . . . . . .   8
   4.  Server processing of TTL values . . . . . . . . . . . . . . .  10
     4.1.  Use of TTL values in delegation records . . . . . . . . .  10
     4.2.  Relationship between host object and domain object TTL
           values  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  Use of TTL values for IDN variants  . . . . . . . . . . .  11
   5.  Out-of-band changes to TTL values . . . . . . . . . . . . . .  11
   6.  Operational considerations  . . . . . . . . . . . . . . . . .  11
     6.1.  Operational impact of TTL values  . . . . . . . . . . . .  11
     6.2.  When the TTL should be changed  . . . . . . . . . . . . .  12
   7.  Security considerations . . . . . . . . . . . . . . . . . . .  12
   8.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  XML namespace . . . . . . . . . . . . . . . . . . . . . .  12
     8.2.  EPP extension registry  . . . . . . . . . . . . . . . . .  13
   9.  Formal specification  . . . . . . . . . . . . . . . . . . . .  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     10.1.  Normative references . . . . . . . . . . . . . . . . . .  14
     10.2.  Informative references . . . . . . . . . . . . . . . . .  15
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The principal output of any domain name provisioning system is a DNS
   zone file, which contains the delegation record(s) for names
   registered within a zone (such as a top-level domain).  These records
   include, at minimum, one or more NS records, but may also include A
   and/or AAAA glue records, DS records, and DNAME records for IDN
   variants.

   Typically, the Time-To-Live (TTL) of these records is determined by
   the registry operator.  However, in some circumstances it may be
   desirable to allow the sponsoring client of a domain name to change
   the TTL used for a that domain: for example, to reduce the amount of
   time required to complete a change of DNS servers, or a DNSSEC key
   rollover.






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   This document describes an EPP extension to the domain name and host
   object mappings (described in [RFC5731] and [RFC5732], respectively)
   which allows the sponsor of a domain name or host object to change
   the TTL associated with that object.

1.1.  Conventions used in this document

   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].

   In examples, "C:" represents lines sent by a protocol client and "S:"
   represents lines returned by a protocol server.  Indentation and
   white space in examples are provided only to illustrate element
   relationships and are not REQUIRED features of this protocol.

   A protocol client that is authorized to manage an existing object is
   described as a "sponsoring" client throughout this document.

   XML is case sensitive.  Unless stated otherwise, XML specifications
   and examples provided in this document MUST be interpreted in the
   character case presented in order to develop a conforming
   implementation.

   EPP uses XML namespaces to provide an extensible object management
   framework and to identify schemas required for XML instance parsing
   and validation.  These namespaces and schema definitions are used to
   identify both the base protocol schema and the schemas for managed
   objects.  The XML namespace prefixes used in examples (such as the
   string ttl in xmlns:ttl) are solely for illustrative purposes.  A
   conforming implementation MUST NOT require the use of these or any
   other specific namespace prefixes.

2.  Extension elements

   This specification defines a single new element, <ttl:secs>, which
   contains a 32-bit unsigned integer indicating the TTL (expressed in
   seconds) which will be applied to the delegation records for the
   associated domain name or host object.

   Example:

   <ttl xmlns="urn:ietf:params:xml:ns:ttl-1.0">3600</ttl>

3.  EPP command mapping

3.1.  EPP query commands




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3.1.1.  EPP <info> command

   This extension defines additional elements for EPP <info> responses
   for domain and host objects.

   The <info> response MAY contain an <extension> element, which MAY
   contain a <ttl:infData> element.  This element contains a single
   <ttl:secs> element.

   Example domain <info> response:









































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   S: <?xml version="1.0" encoding="utf-8" standalone="no"?>
   S: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:   <response>
   S:     <result code="1000">
   S:       <msg>Command completed successfully</msg>
   S:     </result>
   S:     <resData>
   S:       <domain:infData
   S:         xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
   S:         <domain:name>example.com</domain:name>
   S:         <domain:roid>EXAMPLE1-REP</domain:roid>
   S:         <domain:status s="ok" />
   S:         <domain:registrant>jd1234</domain:registrant>
   S:         <domain:contact type="admin">sh8013</domain:contact>
   S:         <domain:contact type="tech">sh8013</domain:contact>
   S:         <domain:ns>
   S:           <domain:hostObj>ns1.example.com</domain:hostObj>
   S:           <domain:hostObj>ns1.example.net</domain:hostObj>
   S:         </domain:ns>
   S:         <domain:clID>ClientX</domain:clID>
   S:         <domain:crID>ClientY</domain:crID>
   S:         <domain:crDate>1999-04-03T22:00:00.0Z</domain:crDate>
   S:         <domain:upID>ClientX</domain:upID>
   S:         <domain:upDate>1999-12-03T09:00:00.0Z</domain:upDate>
   S:         <domain:exDate>2005-04-03T22:00:00.0Z</domain:exDate>
   S:         <domain:trDate>2000-04-08T09:00:00.0Z</domain:trDate>
   S:         <domain:authInfo>
   S:           <domain:pw>2fooBAR</domain:pw>
   S:         </domain:authInfo>
   S:       </domain:infData>
   S:     </resData>
   S:     <extension>
   S:       <ttl:infData
   S:         xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   S:         <ttl:secs>3600</ttl:secs>
   S:       </ttl:infData>
   S:     </extension>
   S:     <trID>
   S:       <clTRID>ABC-12345</clTRID>
   S:       <svTRID>54322-XYZ</svTRID>
   S:     </trID>
   S:   </response>
   S: </epp>

   Example host <info> response:






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   S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   S: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   S:   <response>
   S:     <result code="1000">
   S:       <msg>Command completed successfully</msg>
   S:     </result>
   S:     <resData>
   S:       <host:infData
   S:        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
   S:         <host:name>ns1.example.com</host:name>
   S:         <host:roid>NS1_EXAMPLE1-REP</host:roid>
   S:         <host:status s="linked"/>
   S:         <host:status s="clientUpdateProhibited"/>
   S:         <host:addr ip="v4">192.0.2.2</host:addr>
   S:         <host:addr ip="v4">192.0.2.29</host:addr>
   S:         <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
   S:         <host:clID>ClientY</host:clID>
   S:         <host:crID>ClientX</host:crID>
   S:         <host:crDate>1999-04-03T22:00:00.0Z</host:crDate>
   S:         <host:upID>ClientX</host:upID>
   S:         <host:upDate>1999-12-03T09:00:00.0Z</host:upDate>
   S:         <host:trDate>2000-04-08T09:00:00.0Z</host:trDate>
   S:       </host:infData>
   S:     </resData>
   S:      <extension>
   S:        <ttl:infData
   S:          xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   S:          <ttl:secs>3600</ttl:secs>
   S:        </ttl:infData>
   S:      </extension>
   S:     <trID>
   S:       <clTRID>ABC-12345</clTRID>
   S:       <svTRID>54322-XYZ</svTRID>
   S:     </trID>
   S:   </response>
   S: </epp>

3.2.  EPP transform commands

3.2.1.  EPP <create> command

   This extension defines additional elements for EPP <create> commands
   for domain and host objects.

   The <create> command MAY contain an <extension> element which MAY
   contain a <ttl:create> element.  This element contains a single
   <ttl:secs> element.




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   Example domain <create> command:

   C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   C:   <command>
   C:     <create>
   C:       <domain:create
   C:        xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
   C:         <domain:name>example.com</domain:name>
   C:         <domain:period unit="y">2</domain:period>
   C:         <domain:ns>
   C:           <domain:hostObj>ns1.example.net</domain:hostObj>
   C:           <domain:hostObj>ns2.example.net</domain:hostObj>
   C:         </domain:ns>
   C:         <domain:registrant>jd1234</domain:registrant>
   C:         <domain:contact type="admin">sh8013</domain:contact>
   C:         <domain:contact type="tech">sh8013</domain:contact>
   C:         <domain:authInfo>
   C:           <domain:pw>2fooBAR</domain:pw>
   C:         </domain:authInfo>
   C:       </domain:create>
   C:     </create>
   C:     <extension>
   C:       <ttl:create
   C:         xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   C:         <ttl:secs>3600</ttl:secs>
   C:       </ttl:create>
   C:     </extension>
   C:     <clTRID>ABC-12345</clTRID>
   C:   </command>
   C: </epp>

   Example host <create> command:


















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   C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   C:   <command>
   C:     <create>
   C:       <host:create
   C:        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
   C:         <host:name>ns1.example.com</host:name>
   C:         <host:addr ip="v4">192.0.2.2</host:addr>
   C:         <host:addr ip="v4">192.0.2.29</host:addr>
   C:         <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
   C:       </host:create>
   C:     </create>
   C:     <extension>
   C:       <ttl:create
   C:         xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   C:         <ttl:secs>3600</ttl:secs>
   C:       </ttl:create>
   C:     </extension>
   C:     <clTRID>ABC-12345</clTRID>
   C:   </command>
   C: </epp>

3.2.2.  EPP <update> command

   This extension defines additional elements for EPP <update> commands
   for domain and host objects.

   The <update> command MAY contain an <extension> element which MAY
   contain a <ttl:update> element.  This element contains a single
   <ttl:secs> element.

   Example domain <update> command:



















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   C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0"
   C:      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   C:   <command>
   C:     <update>
   C:       <domain:update
   C:        xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
   C:         <domain:name>example.com</domain:name>
   C:       </domain:update>
   C:     </update>
   C:     <extension>
   C:        <ttl:update>
   C:          xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   C:          <ttl:secs>3600</ttl:secs>
   C:        </ttl:update>
   C:      </extension>
   C:     <clTRID>ABC-12345</clTRID>
   C:   </command>
   C: </epp>

   Example host <update> command:






























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   C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
   C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
   C:   <command>
   C:     <update>
   C:       <host:update
   C:        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
   C:         <host:name>ns1.example.com</host:name>
   C:         <host:add>
   C:           <host:addr ip="v4">192.0.2.22</host:addr>
   C:           <host:status s="clientUpdateProhibited"/>
   C:         </host:add>
   C:         <host:rem>
   C:           <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
   C:         </host:rem>
   C:         <host:chg>
   C:           <host:name>ns2.example.com</host:name>
   C:         </host:chg>
   C:       </host:update>
   C:     </update>
   C:     <extension>
   C:        <ttl:update>
   C:          xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
   C:          <ttl:secs>3600</ttl:secs>
   C:        </ttl:update>
   C:      </extension>
   C:     <clTRID>ABC-12345</clTRID>
   C:   </command>
   C: </epp>

4.  Server processing of TTL values

   If an EPP server receives a command containing a TTL that is outside
   the server's permitted range (see Operational considerations and
   Security considerations below), it MUST reject the command with a
   2004 "Parameter value range error" response.

4.1.  Use of TTL values in delegation records

   EPP servers which implement this extension SHOULD use the values
   provided by EPP clients for the TTL values of NS, A, AAAA and DS
   records published in the DNS for the corresponding delegation.










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4.2.  Relationship between host object and domain object TTL values

   The extension in this document allows TTL values to be configured for
   both domain and host objects.  In domain name registries, these
   object types have a hierarchical relationship, in that a host object
   may be subordinate to a domain object: for example, the host object
   ns1.example.com is subordinate to the domain object example.com.

   When publishing A and AAAA for host objects, TTL values for host
   objects SHOULD take precedence over the TTL of the superordinate
   domain object.  However, if no TTL value is configured for a
   subordinate host object, but a TTL value is configured for the
   superordinate domain object, then the domain object's TTL value
   SHOULD be used for the host object instead of the default TTL value.

4.3.  Use of TTL values for IDN variants

   If a domain name has variants ([RFC6927]) that are linked to that
   domain, then any NS or DNAME records published for those variants
   MUST use the same TTL as that used for the primary domain.

5.  Out-of-band changes to TTL values

   EPP server operators MAY, in order to address operational or security
   issues, make changes to TTL values out-of-band (that is, not in
   response to an <update> command received from the sponsoring client).

   Additionally, server operators may implement an automatic reset of
   TTL values, so that they may be changed for a finite period before
   and after a planned change, and then revert to a standard value.

   In the event of changes to TTL values taking place out-of-band, EPP
   server operators SHOULD notify the sponsoring client using the EPP
   Change Poll extension ([RFC8590]).

6.  Operational considerations

6.1.  Operational impact of TTL values

   Domain registry operators must strike a balance between, on the one
   hand, the desire of registrants for changes to their domains to be
   visible in the DNS quickly, and on the other, the increased DNS query
   traffic that short TTLs can bring.  Historically, registry operators
   have used a global TTL value which was applied to all delegations
   within their zones, which could then be tuned to an optimum value.






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   Domain registry operators SHOULD implement limits on the maximum and
   minimum accepted TTL values that are narrower than the values
   permitted in the XML schema in the Formal specification (which were
   chosen to allow any TTL permitted in DNS records), in order to
   prevent scenarios where an excessively high or low TTL causes
   operational issues on either side of the zone cut.

6.2.  When the TTL should be changed

   A common operational mistake is changing of DNS record TTLs during or
   after the planned change to the records themselves.  This arises due
   to a misunderstanding about how TTLs work.

   Client implementations of this specification SHOULD ensure that the
   user understands that changes to a TTL are only effective in
   shortening transition periods if implemented a period of time -- at
   least equal to the current TTL -- _before_ the planned change.

7.  Security considerations

   Many malicious actors use a technique called "fast flux DNS" to
   rapidly change the DNS configuration for a zone in order to evade
   takedown and law enforcement activity.

   Registry operators SHOULD take this into consideration when setting
   the lower limit on TTL values, since a short TTL on delegations has
   the potential to enhance the effectiveness of fast flux techniques on
   evasion.

8.  IANA considerations

8.1.  XML namespace

   This document uses URNs to describe XML namespaces and XML schemas
   conforming to a registry mechanism described in [RFC3688].  The
   following URI assignment has been made by IANA:

   Registration for the TTL namespace:

      *URI:* urn:ietf:params:xml:ns:ttl-1.0

      *Registrant Contact:* See the author of this document

      *XML:* None.  Namespace URIs do not represent an XML specification

   Registration for the TTL XML schema:

      *URI:* urn:ietf:params:xml:ns:ttl-1.0



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      *Registrant Contact:* See the author of this document

      *XML:* See the "Formal specification" section of this document

8.2.  EPP extension registry

   The EPP extension described in this document has been registered by
   the IANA in the Extensions for the "Extensible Provisioning Protocol
   (EPP)" registry described in [RFC7451].  The details of the
   registration are as follows:

      *Name of Extension:* Extensible Provisioning Protocol (EPP)
      Mapping for DNS Time-To-Live (TTL) values

      *Document Status:* Experimental

      *Reference:* URL of this document

      *Registrant Name and Email Address:* See the author of this
      document

      *TLDs:* Any

      *IPR Disclosure:* None

      *Status:* Active

      *Notes:* None

9.  Formal specification





















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   <?xml version="1.0" encoding="UTF-8"?>
   <schema xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0">
     <annotation>
       <documentation>
         Extensible Provisioning Protocol v1.0 domain name
         extension schema for Time-To-Live (TTL) modification
         in all DNS responses for a domain name including
         delegation (NS) records and any address (A) records.
       </documentation>
     </annotation>

     <!-- Child elements found in EPP commands -->
     <element name="create" type="ttl:secs"/>
     <element name="update" type="ttl:secs"/>

     <!-- Child elements found in EPP responses -->
     <element name="infData" type="ttl:secs"/>

     <complexType name="secs">
       <sequence>
         <element name="secs" type="ttl:nonNegativeInteger"/>
       </sequence>
     </complexType>

     <simpleType name="nonNegativeInteger">
       <restriction base="nonNegativeInteger">
         <minInclusive value="1"/>
         <maxInclusive value="4294967295"/>
       </restriction>
     </simpleType>
   </schema>

10.  References

10.1.  Normative references

   [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>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.







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   [RFC5731]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
              Domain Name Mapping", STD 69, RFC 5731,
              DOI 10.17487/RFC5731, August 2009,
              <https://www.rfc-editor.org/info/rfc5731>.

   [RFC5732]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
              Host Mapping", STD 69, RFC 5732, DOI 10.17487/RFC5732,
              August 2009, <https://www.rfc-editor.org/info/rfc5732>.

   [RFC7451]  Hollenbeck, S., "Extension Registry for the Extensible
              Provisioning Protocol", RFC 7451, DOI 10.17487/RFC7451,
              February 2015, <https://www.rfc-editor.org/info/rfc7451>.

   [RFC8590]  Gould, J. and K. Feher, "Change Poll Extension for the
              Extensible Provisioning Protocol (EPP)", RFC 8590,
              DOI 10.17487/RFC8590, May 2019,
              <https://www.rfc-editor.org/info/rfc8590>.

10.2.  Informative references

   [RFC6927]  Levine, J. and P. Hoffman, "Variants in Second-Level Names
              Registered in Top-Level Domains", RFC 6927,
              DOI 10.17487/RFC6927, May 2013,
              <https://www.rfc-editor.org/info/rfc6927>.

Author's Address

   Gavin Brown
   CentralNic Group plc
   44 Gutter Lane
   London
   EC2V 6BR
   United Kingdom
   Phone: +44 20 33 88 0600
   Email: gavin.brown@centralnic.com
   URI:   https://www.centralnic.com















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