Extensible Provisioning Protocol (EPP) Mapping for DNS Time-To-Live (TTL) values
draft-regext-brown-epp-ttl-00

Registration Protocols Extensions (regext)                      G. Brown
Internet-Draft                                      CentralNic Group plc
Intended status: Experimental                               26 July 2022
Expires: 27 January 2023

  Extensible Provisioning Protocol (EPP) Mapping for DNS Time-To-Live
                              (TTL) values
                     draft-regext-brown-epp-ttl-00

Abstract

   This document describes how the Time-To-Live (TTL) value used for
   domain name delegation records can be managed in EPP.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   2
   2.  Extension Elements  . . . . . . . . . . . . . . . . . . . . .   3
   3.  EPP Command Mapping . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  EPP Query Commands  . . . . . . . . . . . . . . . . . . .   3
       3.1.1.  EPP <info> Command  . . . . . . . . . . . . . . . . .   3
     3.2.  EPP Transform Commands  . . . . . . . . . . . . . . . . .   4
       3.2.1.  EPP <create> Command  . . . . . . . . . . . . . . . .   5
       3.2.2.  EPP <update> Command  . . . . . . . . . . . . . . . .   5
   4.  Server Processing of TTL Values . . . . . . . . . . . . . . .   6
   5.  Out-of-band changes to TTL values . . . . . . . . . . . . . .   6
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .   7
     6.1.  Operational impact of TTL values  . . . . . . . . . . . .   7
     6.2.  When the TTL should be changed  . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  XML Namespace . . . . . . . . . . . . . . . . . . . . . .   7
     8.2.  EPP Extension Registry  . . . . . . . . . . . . . . . . .   8
   9.  Formal Specification  . . . . . . . . . . . . . . . . . . . .   8
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The principal artefact of any domain name provisioning system is a
   DNS zone file, which contains the delegation record(s) for names
   registered within the zone.  These records include at minimum one ore
   more NS records, but my also include A and/or AAAA glue records, and
   DS records.

   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 registrar of a domain name to
   change the TTL used for a particular domain: for example, to reduce
   the amount of time required to complete a change of DNS servers, or a
   DNSSEC key rollover.

   This document describes an EPP extension to the domain name object
   mapping (described in [RFC5731]) which allows the sponsor of a domain
   name object to change the TTL associated with a given domain.

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].

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   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.

2.  Extension Elements

   This specification defines a single new element, <ttl:secs>, whose
   contents is a 32-bit unsigned integer indicating the Time-To-Live
   which will be applied to the delegation records for the associated
   domain name.

   Example:

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

3.  EPP Command Mapping

3.1.  EPP Query Commands

3.1.1.  EPP <info> Command

   This extension defines additional elements EPP <info> responses.

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

   Example <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>

3.2.  EPP Transform Commands

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3.2.1.  EPP <create> Command

   This extension defines additional elements EPP <create> commands.

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

   Example <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>

3.2.2.  EPP <update> Command

   This extension defines additional elements EPP <update> commands.

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

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   Example <update> command:

   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>

4.  Server Processing of TTL Values

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

   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.

5.  Out-of-band changes to TTL values

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

   Additionall, 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 by means of the
   EPP message queue and/or the EPP Change Poll Extension ([RFC8590]).

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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 the increased DNS query traffic that
   short TTLs can bring.  Historically, registry operators specified a
   global TTL value that applies to all delegations within their zones,
   which has made it relatively easy to tune this value to an optimum
   value.

   Domain registry operators SHOULD implement limits on the maximum and
   minimum TTL values (that are narrower than the values permitted in
   the Formal Specification, which were chosen to allow any TTL
   permitted in DNS records), 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:

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   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

      Registrant Contact: See the author of this document

      XML: See the "Formal Syntax" 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.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", DOI 10.17487/RFC2119, BCP 14,
              RFC 2119, 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>.

   [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>.

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   [RFC7451]  Hollenbeck, S., "Extension Registry for the Extensible
              Provisioning Protocol", DOI 10.17487/RFC7451, RFC 7451,
              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>.

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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