RFC 9803

RFC 9803: Extensible Provisioning Protocol (EPP) Mapping for DNS Time-to-Live (TTL) Values 🎀

Okay, the title block is the vibe check first 💅

This one comes from the Internet Engineering Task Force (IETF) 🌸 and it's RFC 9803 🦋. The author is G. Brown from ICANN 💜. It's a Standards Track document ✨, which means it's an Internet Standards Track document, the real deal. It's dated June 2025 📅 and the ISSN is 2070-1721 🌈. There's no Obsoletes or Updates line in the header, so this doc doesn't list any other RFCs it replaces or updates 🙈

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 is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9803.

Copyright Notice ©️

Copyright (c) 2025 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
     1.1.  Conventions Used in This Document
     1.2.  Extension Elements
       1.2.1.  The <ttl:ttl> Element
         1.2.1.1.  Element Content
         1.2.1.2.  Supported DNS Record Types
         1.2.1.3.  The <ttl:info> Element
       1.2.2.  Examples
         1.2.2.1.  Explicit TTL Value (<create> or <update> Command)
         1.2.2.2.  Explicit TTL Value (<info> Policy Mode)
         1.2.2.3.  Empty Value Indicating Default TTL (<create> or
                 <update> Command, <info> Default Mode)
         1.2.2.4.  Custom Record Type (<create> or <update> Command,
                 <info> Default Mode)
   2.  EPP Command Mapping
     2.1.  EPP Query Commands
       2.1.1.  EPP <info> Command
         2.1.1.1.  Default Mode
         2.1.1.2.  Policy Mode
     2.2.  EPP Transform Commands
       2.2.1.  EPP <create> Command
       2.2.2.  EPP <update> Command
   3.  Server Processing of TTL Values
     3.1.  Permitted Record Types
     3.2.  Use of TTL Values in Delegation Records
   4.  Out-of-Band Changes to TTL Values
   5.  Operational Considerations
     5.1.  Operational Impact of TTL Values
     5.2.  When TTL Values Should Be Changed
     5.3.  Changes to Server Policy
   6.  Security Considerations
     6.1.  Fast Flux DNS
     6.2.  Compromised User Accounts
   7.  IANA Considerations
     7.1.  XML Namespace
     7.2.  EPP Extension Registry
   8.  Formal Syntax
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Acknowledgments
   Author's Address

1. Introduction ✨

Okay so the big output of any domain name registry system is a DNS zone file 📜. It holds the delegation record(s) for names registered within a zone (like a top-level domain). These usually include one or more NS records, but they can also include DS records for domains secured with DNSSEC [RFC9364], and DNAME records for Internationalized Domain Name (IDN) variants [RFC6927]. A and/or AAAA records may also get published for nameservers where DNS resolvers require them to avoid an infinite loop 🔁.

Typically, the Time-to-Live (TTL) value (see Section 5 of [RFC9499]) of these records is set by the registry operator ⏰. But sometimes it's useful to let the sponsoring client of a domain name change the TTL values used for that domain's delegation 💅. For example, that could shorten the time it takes to finish a change of DNS servers, DNSSEC deployment or key rollover, or allow for a fast rollback of those changes 🏃‍♀️.

This document describes an EPP extension to the domain name and host object mappings (described in [RFC5731] and [RFC5732], respectively) that lets the sponsor of a domain name or host object change the TTL values of the resource record(s) associated with that object 🎀. It also describes how EPP servers should handle TTLs specified by EPP clients, and how both parties coordinate to manage TTL values when operational or security requirements change 🫶.

1.1. Conventions Used in This Document 📖

Okay, the BCP 14 key words are the bossy ones 💅 In this document, "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

In this document's examples, "C:" represents lines sent by a protocol client and "S:" represents lines returned by a protocol server. Indentation and white space in these 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, the 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 these examples (such as the string ttl in ttl:create) are solely for illustrative purposes. A conforming implementation MUST NOT require the use of these or any other specific namespace prefixes 🦋.

In accordance with Section 3.2.2.1 of XML Schema Part 2: Datatypes [XSD-DATATYPES], the allowable lexical representations for the xs:boolean datatype are the strings "0" and "false" for the concept 'false' and the strings "1" and "true" for the concept 'true'. Implementations MUST support both styles of lexical representation 🍓.

1.2. Extension Elements 🧩

This extension adds additional elements to the EPP domain and host mappings ✨.

1.2.1. The <ttl:ttl> Element 💖

The <ttl:ttl> element is used to define TTL values for the DNS resource records associated with domain and host objects 🎀.

<ttl:ttl> elements have the optional following attributes, depending on whether they appear in an EPP command or response:

• for: REQUIRED in both commands and responses, and specifies the DNS record type to which the TTL value pertains. This attribute MUST have one of the following values: "NS", "DS", "DNAME", "A", "AAAA" or "custom".
• custom: If the value of the "for" attribute is "custom", then the <ttl:ttl> element MUST also have a "custom" attribute containing a DNS record type conforming with the regular expression in Section 3.1 of [RFC6895]. Additionally, the record type MUST be registered with IANA in [IANA-RRTYPES].
• min: MUST NOT be present in EPP commands but MAY be present in EPP responses (see Section 2.1.1). It is used by the server to indicate the lowest value that may be set 📉.
• default: MUST NOT be present in EPP commands but MAY be present in EPP responses (see Section 2.1.1). It is used by the server to indicate the default value 🎯.
• max: MUST NOT be present in EPP commands but MAY be present in EPP responses (see Section 2.1.1). It is used by the server to indicate the highest value that may be set 📈.

When present, the value of the "min" attribute MUST be lower than the value of the "max" attribute. The "default" attribute MUST be between the "min" and "max" values, inclusively 💅.

1.2.1.1. Element Content 🍰

The XML schema found in Section 8 of this document restricts the content of <ttl:ttl> elements to be either:

1. a non-negative integer, indicating the value of the TTL in seconds, or
2. empty, in which case the server's default TTL for the given record type is to be applied.

1.2.1.2. Supported DNS Record Types 🌈

To facilitate forward compatibility with future changes to the DNS protocol, this document does not enumerate or restrict the DNS record types that can be included in the "custom" attribute of the <ttl:ttl> element 🔮.

The regular expression that is used to validate the values of the "custom" attribute is based on the expression found in Section 3.1 of [RFC6895], and it is intended to match both existing and future RRTYPE mnemonics. This means there's no need to update this document if new DNS records that exist above a zone cut (Section 7 of [RFC9499]) are specified 🙌.

Nevertheless, EPP servers that implement this extension MUST restrict the DNS record types that are accepted in <create> and <update> commands, and included in <info> responses, allowing only those types that are (a) registered in [IANA-RRTYPES] and (b) appropriate for use above a zone cut 🚧.

A server that receives a <create> or <update> command that attempts to set TTL values for inapplicable DNS record types MUST respond with a 2306 "Parameter value policy" error 🙅‍♀️.

As an illustrative example, a server MAY allow clients to specify TTL values for the following record types for domain objects:

1. NS;
2. DS (if the server also implements [RFC5910]);
3. DNAME (if the server implements IDN variants using DNAME records).

1.2.1.2.1. Glue Records 🔗

Glue records are described in Section 7 of [RFC9499].

Servers that implement host objects [RFC5732] MAY allow clients to specify TTL values for A and AAAA records for host objects 🏠.

A server supporting host objects that receives a command that attempts to set TTL values for A and AAAA records on a domain object MUST respond with a 2306 "Parameter value policy" error 🚫.

EPP servers that use the host attribute model (described in Section 1.1 of [RFC5731]) MAY allow clients to specify TTL values for A and AAAA records for domain objects 🌟.

1.2.1.3. The <ttl:info> Element 🔍

The <ttl:info> element is used by clients to request that the server include additional information in <info> responses for domain and host objects 💌.

It has a single OPTIONAL "policy" attribute, which takes a boolean value with a default value of "false" 🎀.

The semantics of this element are described in Section 2.1.1.

Below is an example of a <ttl:info> element with an explicit "policy" attribute:

<ttl:info policy="true"/>

1.2.2. Examples 🍓

1.2.2.1. Explicit TTL Value (<create> or <update> Command) 🧁

<ttl:ttl for="NS">3600</ttl:ttl>

1.2.2.2. Explicit TTL Value (<info> Policy Mode) 🌸

<ttl:ttl
  for="NS"
  min="60"
  default="86400"
  max="172800">3600</ttl:ttl>

1.2.2.3. Empty Value Indicating Default TTL (<create> or <update> Command, <info> Default Mode) 🫧

<ttl:ttl for="NS"/>

1.2.2.4. Custom Record Type (<create> or <update> Command, <info> Default Mode) 🦄

<ttl:ttl
  for="custom"
  custom="NEWRRTYPE">3600</ttl:ttl>

2. EPP Command Mapping 💫

Okay bestie, that's the end of part 1 💜 Part 2 picks up right here with the EPP command mapping, so stay tuned 🫶

2.1. EPP Query Commands 🔍✨

2.1.1. EPP <info> Command 💅

Okay so this extension slides one brand-new element into EPP <info> commands and their responses, for domain and host objects. 🎀

The EPP <info> command gets a glow-up and now has two modes:

1. Default Mode (Section 2.1.1.1): asks for every non-default TTL value to be included in the response. 🌸
2. Policy Mode (Section 2.1.1.2): asks for TTL information for every supported DNS record type, plus the minimum, default, and maximum values for those records. 👑

2.1.1.1. Default Mode 🌸

Default Mode is giving "just the spicy stuff" 💅. If a server gets an <info> command for a domain or host object that includes a <ttl:info> element whose "policy" attribute is "0" or "false", the EPP response MUST contain <ttl:ttl> records for all DNS record types that have non-default TTL values. These elements MUST NOT have the "min", "default", and "max" attributes. 🙈

Here's an example domain <info> command with a <ttl:info> element whose "policy" attribute is "false" 🦋:

C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C:   <command>
C:     <info>
C:       <domain:info
C:        xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
C:         <domain:name>example.com</domain:name>
C:       </domain:info>
C:     </info>
C:     <extension>
C:       <ttl:info
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
C:         policy="false"/>
C:     </extension>
C:   </command>
C: </epp>

And here's the domain <info> response to that command with a <ttl:info> element whose "policy" attribute is "false" 💖:

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: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>ClientX</domain:crID>
S:         <domain:crDate>2023-11-08T10:14:55.0Z</domain:crDate>
S:         <domain:exDate>2024-11-08T10:14:55.0Z</domain:exDate>
S:       </domain:infData>
S:     </resData>
S:     <extension>
S:       <ttl:infData
S:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S:         <ttl:ttl for="NS">172800</ttl:ttl>
S:         <ttl:ttl for="DS">300</ttl:ttl>
S:       </ttl:infData>
S:       <secDNS:infData
S:         xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1">
S:         <secDNS:dsData>
S:           <secDNS:keyTag>12345</secDNS:keyTag>
S:           <secDNS:alg>13</secDNS:alg>
S:           <secDNS:digestType>2</secDNS:digestType>
S:           <secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest>
S:         </secDNS:dsData>
S:       </secDNS:infData>
S:     </extension>
S:     <trID>
S:       <clTRID>ABC-12345</clTRID>
S:       <svTRID>54322-XYZ</svTRID>
S:     </trID>
S:   </response>
S: </epp>

Here's an example host <info> command with a <ttl:info> element whose "policy" attribute is "false" 🧚:

C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C:   <command>
C:     <info>
C:       <host:info
C:        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
C:         <host:name>ns1.example.com</host:name>
C:       </host:info>
C:     </info>
C:     <extension>
C:       <ttl:info
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
C:         policy="false"/>
C:     </extension>
C:   </command>
C: </epp>

And the host <info> response to a command with a <ttl:info> element whose "policy" attribute is "false" ⭐:

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="ok"/>
S:         <host:addr ip="v4">192.0.2.2</host:addr>
S:         <host:addr ip="v6">2001:db8::8:800:200c:417a</host:addr>
S:         <host:clID>ClientX</host:clID>
S:         <host:crID>ClientX</host:crID>
S:         <host:crDate>2023-11-08T10:14:55.0Z</host:crDate>
S:       </host:infData>
S:     </resData>
S:     <extension>
S:       <ttl:infData
S:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S:         <ttl:ttl for="A">172800</ttl:ttl>
S:         <ttl:ttl for="AAAA">86400</ttl:ttl>
S:       </ttl:infData>
S:     </extension>
S:     <trID>
S:       <clTRID>ABC-12345</clTRID>
S:       <svTRID>54322-XYZ</svTRID>
S:     </trID>
S:   </response>
S: </epp>

2.1.1.2. Policy Mode 👑

Policy Mode is the "show me everything" setting 🌈. If a server receives an <info> command for a domain or host object that includes a <ttl:info> element whose "policy" attribute is "1" or "true", the EPP response MUST contain <ttl:ttl> records for all supported DNS record types, no matter whether the object is actually using those record types. These elements MUST have the "min", "default", and "max" attributes. ✨

Here's an example domain <info> command asking for the server policies 🦋:

C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C:   <command>
C:     <info>
C:       <domain:info
C:        xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
C:         <domain:name>example.com</domain:name>
C:       </domain:info>
C:     </info>
C:     <extension>
C:       <ttl:info
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
C:         policy="true"/>
C:     </extension>
C:   </command>
C: </epp>

And here's the domain <info> response providing the server policies 💜:

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: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>ClientX</domain:crID>
S:         <domain:crDate>2023-11-08T10:14:55.0Z</domain:crDate>
S:         <domain:exDate>2024-11-08T10:14:55.0Z</domain:exDate>
S:       </domain:infData>
S:     </resData>
S:     <extension>
S:       <ttl:infData
S:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S:         <ttl:ttl for="NS"
S:           min="3600"
S:           default="86400"
S:           max="172800">172800</ttl:ttl>
S:         <ttl:ttl for="DS"
S:           min="60"
S:           default="86400"
S:           max="172800">300</ttl:ttl>
S:       </ttl:infData>
S:       <secDNS:infData
S:         xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1">
S:         <secDNS:dsData>
S:           <secDNS:keyTag>12345</secDNS:keyTag>
S:           <secDNS:alg>13</secDNS:alg>
S:           <secDNS:digestType>2</secDNS:digestType>
S:           <secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest>
S:         </secDNS:dsData>
S:       </secDNS:infData>
S:     </extension>
S:     <trID>
S:       <clTRID>ABC-12345</clTRID>
S:       <svTRID>54322-XYZ</svTRID>
S:     </trID>
S:   </response>
S: </epp>

Here's an example host <info> command asking for the server policies 🌸:

C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C:   <command>
C:     <info>
C:       <host:info
C:        xmlns:host="urn:ietf:params:xml:ns:host-1.0">
C:         <host:name>ns1.example.com</host:name>
C:       </host:info>
C:     </info>
C:     <extension>
C:       <ttl:info
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
C:         policy="true"/>
C:     </extension>
C:   </command>
C: </epp>

And the host <info> response providing the server policies 🫶:

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="ok"/>
S:         <host:addr ip="v4">192.0.2.2</host:addr>
S:         <host:addr ip="v6">2001:db8::8:800:200c:417a</host:addr>
S:         <host:clID>ClientX</host:clID>
S:         <host:crID>ClientX</host:crID>
S:         <host:crDate>2023-11-08T10:14:55.0Z</host:crDate>
S:       </host:infData>
S:     </resData>
S:     <extension>
S:       <ttl:infData
S:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S:         <ttl:ttl for="A"
S:           min="3600"
S:           default="86400"
S:           max="172800">172800</ttl:ttl>
S:         <ttl:ttl for="AAAA"
S:           min="3600"
S:           default="86400"
S:           max="172800">86400</ttl:ttl>
S:       </ttl:infData>
S:     </extension>
S:     <trID>
S:       <clTRID>ABC-12345</clTRID>
S:       <svTRID>54322-XYZ</svTRID>
S:     </trID>
S:   </response>
S: </epp>

2.2. EPP Transform Commands ⚡

2.2.1. EPP <create> Command

okay bestie, this extension adds one extra element to EPP <create> commands, and it works for both domain and host objects 🎀

The <command> element of a <create> command MAY contain an <extension> element, and that extension MAY contain a <ttl:create> element. If you include a <ttl:create>, it MUST contain one or more <ttl:ttl> records, which are explained in Section 1.2 💅

If an EPP server gets a <create> command with a TTL value outside its permitted range, it MUST reject the command with a 2004 "Parameter value range error" response. Not it 💀

Below is an 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">1</domain:period>
C:         <domain:ns>
C:           <domain:hostObj>ns1.example.com</domain:hostObj>
C:           <domain:hostObj>ns1.example.net</domain:hostObj>
C:         </domain:ns>
C:         <domain:authInfo>
C:           <domain:pw/>
C:         </domain:authInfo>
C:       </domain:create>
C:     </create>
C:     <extension>
C:       <ttl:create
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C:         <ttl:ttl for="NS">172800</ttl:ttl>
C:         <ttl:ttl for="DS">300</ttl:ttl>
C:       </ttl:create>
C:       <secDNS:create
C:         xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1">
C:         <secDNS:dsData>
C:           <secDNS:keyTag>12345</secDNS:keyTag>
C:           <secDNS:alg>13</secDNS:alg>
C:           <secDNS:digestType>2</secDNS:digestType>
C:           <secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest>
C:         </secDNS:dsData>
C:       </secDNS:create>
C:     </extension>
C:     <clTRID>ABC-12345</clTRID>
C:   </command>
C: </epp>

Below is an example host <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:       <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="v6">2001:db8::8:800:200c:417a</host:addr>
C:       </host:create>
C:     </create>
C:     <extension>
C:       <ttl:create
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C:         <ttl:ttl for="A"/>
C:         <ttl:ttl for="AAAA">86400</ttl:ttl>
C:       </ttl:create>
C:     </extension>
C:     <clTRID>ABC-12345</clTRID>
C:   </command>
C: </epp>

2.2.2. EPP <update> Command

same energy as the last one, but for <update> 🦋 This extension adds an element to EPP <update> commands for domain and host objects.

The <command> element of an <update> command MAY contain an <extension> element, and that extension MAY contain a <ttl:update> element. That <ttl:update> MUST contain one or more <ttl:ttl> records, as described in Section 1.2 🫶

If an EPP server receives an <update> command with a TTL value outside its permitted range, it MUST reject the command with a 2004 "Parameter value range error" response. Rude, but it's the rule 😭

Below is an example domain <update> 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:     <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:epp:ttl-1.0">
C:         <ttl:ttl for="NS"/>
C:         <ttl:ttl for="custom"
C:           custom="DELEG"/>
C:         <ttl:ttl for="DS">86400</ttl:ttl>
C:       </ttl:update>
C:     </extension>
C:     <clTRID>ABC-12345</clTRID>
C:   </command>
C: </epp>

Below is an example host <update> 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:     <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:update>
C:     </update>
C:     <extension>
C:       <ttl:update
C:         xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C:         <ttl:ttl for="A">86400</ttl:ttl>
C:         <ttl:ttl for="AAAA">3600</ttl:ttl>
C:       </ttl:update>
C:     </extension>
C:     <clTRID>ABC-12345</clTRID>
C:   </command>
C: </epp>

---

3. Server Processing of TTL Values

3.1. Permitted Record Types

EPP servers MAY restrict the supported DNS record types. For example, a server MAY allow clients to specify TTL values for DS records only 🔥

A server that receives a <create> or <update> command that includes a restricted record type MUST respond with a 2306 "Parameter value policy" error. Blocked, bestie 🙈

Clients can find out which DNS record types an EPP server lets them change TTLs for by running a Policy Mode <info> command, as laid out in Section 2.1.1.2 🌈

3.2. Use of TTL Values in Delegation Records

EPP servers that implement this extension SHOULD use the values provided by EPP clients for the TTL values of records published in the DNS for domain and (if supported) host objects. Server operators MAY disregard these values to address security and stability issues, as described in Section 5 and Section 6 🛡️

EPP servers that use the host attribute model SHOULD use any NS, A, and/or AAAA TTL values specified for the domain object when publishing NS, A, and/or AAAA records derived from host attributes ✨

---

4. Out-of-Band Changes to TTL Values

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

Server operators MAY also implement automatic reset of TTL values, so they revert to the default value a certain amount of time after an update has been made. Like a glow-up timer ⏰

If a TTL value is changed out-of-band, EPP server operators MAY notify the sponsoring client using the EPP Change Poll Extension [RFC8590]. That extension gives EPP servers a generalized way to tell clients about changes to objects under their sponsorship 📬

---

5. Operational Considerations

5.1. Operational Impact of TTL Values

Registry operators have to weigh registrants' wish to see domain changes show up in the DNS quickly against the extra DNS query traffic that short TTLs can bring 🚦

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 Section 8 (which were chosen to allow any TTL permitted in DNS records). This is so nobody ends up with an excessively high or low TTL causing operational issues on either side of the zone cut 🧱

Section 4 explains how server operators MAY unilaterally change TTL values to address operational or security issues, or only permit changes for limited time periods (after which TTLs revert to the default) ⏳

5.2. When TTL Values Should Be Changed

A super common mistake is changing the DNS record TTLs during or after the planned change to the records themselves. This happens because of a misunderstanding about how TTLs work 😩

It is RECOMMENDED that users get guidance so they know that a TTL change only shortens transition periods if it's implemented a period of time (at least equal to the current TTL) before the planned change. The delay between receiving the <update> command and the changes actually being published in the DNS should also be counted in that math 🧮

5.3. Changes to Server Policy

Registry operators can change their TTL policies from time to time, so previously configured TTL values might end up outside a newly applied policy. This document places no obligation on EPP server operators for these values, and as part of a policy change, server operators can change the TTL values clients specified for domain and host objects. Section 4 describes how those out-of-band changes should be carried out 🔄

---

6. Security Considerations

6.1. Fast Flux DNS

Some bad actors use a technique called "fast flux DNS" [SAC-025] to rapidly change the DNS configuration for a zone so they can dodge takedowns and law enforcement 🚨 Server operators ought to keep this in mind when setting the lower limit on TTL values, since a short TTL on delegations may make fast flux techniques work better for evasion. Dangerous, not cute 💀

Client implementations that give customers an interface for configuring TTL values for domain names ought to think about adding controls to deter and mitigate abusive behavior, like the ones in the "Current and Possible Mitigation Alternatives" section of [SAC-025] 🛑

6.2. Compromised User Accounts

Say an attacker gets into a customer account at a domain registrar that supports this extension. They could make unauthorized changes to the NS and/or glue records for a domain, then bump the associated TTLs so the changes stick around in caches for a long time after the attack is detected. Scary stuff 😱

Client implementations that give customers an interface for configuring TTL values for domain names ought to think about adding upper limits to reduce the impact of account compromise. This is on top of the usual best practices for credential management, multi-factor authentication, risk-based access control, and so on 🔐

---

7. IANA Considerations

7.1. XML Namespace

This document uses URNs to describe XML namespaces and XML schemas that follow a registry mechanism described in [RFC3688]. IANA has made the following URI assignments 📚

Registration for the TTL namespace:

URI:  urn:ietf:params:xml:ns:epp:ttl-1.0
Registrant Contact:  IESG
XML:  None.  Namespace URIs do not represent an XML specification.

Registration for the TTL XML schema:

URI:  urn:ietf:params:xml:schema:epp:ttl-1.0
Registrant Contact:  IESG
XML:  See Section 8 of this document.

7.2. EPP Extension Registry

IANA has registered the EPP extension in this document in the "Extensions for the Extensible Provisioning Protocol (EPP)" registry described in [RFC7451]. Here are the registration details 🎀

Name of Extension:  Extensible Provisioning Protocol (EPP) Mapping
   for DNS Time-to-Live (TTL) Values
Document Status:  Standards Track
Reference:  RFC 9803
Registrant:  IESG
TLDs:  Any
IPR Disclosure:  None
Status:  Active
Notes:  None

8. Formal Syntax ✨

okay bestie, this section is the schema zone 🤓💅 The formal syntax is a complete schema version of the extension, so tools can automatically validate EPP XML instances. no more guessing if your XML is valid 🫶

<?xml version="1.0" encoding="UTF-8"?>
<schema
  xmlns="http://www.w3.org/2001/XMLSchema"
  targetNamespace="urn:ietf:params:xml:ns:epp:ttl-1.0"
  xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
  elementFormDefault="qualified">
  <annotation>
    <documentation>
      Extensible Provisioning Protocol v1.0 extension
      schema for Time-to-Live (TTL) Values for domain
      and host objects.
    </documentation>
  </annotation>

  <element name="info">
    <complexType>
      <attribute name="policy" type="boolean" default="false"/>
    </complexType>
  </element>

  <!--
    <ttl> elements can appear in <create> and
    <update> commands, and <info> responses
  -->

  <element name="create" type="ttl:commandContainer">
    <unique name="uniqueRRTypeForCreate">
      <selector xpath="ttl:ttl"/>
      <field xpath="@for"/>
    </unique>
  </element>

  <element name="update" type="ttl:commandContainer">
    <unique name="uniqueRRTypeForUpdate">
      <selector xpath="ttl:ttl"/>
      <field xpath="@for"/>
    </unique>
  </element>

  <element name="infData" type="ttl:responseContainer">
    <unique name="uniqueRRTypeForInfo">
      <selector xpath="ttl:ttl"/>
      <field xpath="@for"/>
    </unique>
  </element>

  <complexType name="commandContainer">
    <sequence>
      <element
        name="ttl"
        type="ttl:commandTTLType"
        minOccurs="1"
        maxOccurs="unbounded"/>
    </sequence>
  </complexType>

  <complexType name="responseContainer">
    <sequence>
      <element
        name="ttl"
        type="ttl:responseTTLType"
        minOccurs="1"
        maxOccurs="unbounded"/>
    </sequence>
  </complexType>

  <complexType name="commandTTLType">
    <simpleContent>
      <extension base="ttl:ttlOrNull">
        <attribute
          name="for"
          type="ttl:rrType"
          use="required"/>

        <attribute
          name="custom"
          type="ttl:customRRType"/>
      </extension>
    </simpleContent>
  </complexType>

  <complexType name="responseTTLType">
    <simpleContent>
      <extension base="ttl:ttlOrNull">
        <attribute
          name="for"
          type="ttl:rrType"
          use="required"/>

        <attribute
          name="custom"
          type="ttl:customRRType"/>

        <attribute
          name="min"
          type="ttl:ttlValue"/>

        <attribute
          name="default"
          type="ttl:ttlValue"/>

        <attribute
          name="max"
          type="ttl:ttlValue"/>
      </extension>
    </simpleContent>
  </complexType>

  <!--
    union type allowing the element to either contain
    nothing or a TTL value
  -->
  <simpleType name="ttlOrNull">
    <union
      memberTypes="ttl:emptyValue ttl:ttlValue"/>
  </simpleType>

  <!-- empty value type -->
  <simpleType name="emptyValue">
    <restriction base="token">
      <length value="0"/>
    </restriction>
  </simpleType>

  <!-- TTL value type -->
  <simpleType name="ttlValue">
    <restriction base="nonNegativeInteger">
      <minInclusive value="0"/>
      <maxInclusive value="2147483647"/>
    </restriction>
  </simpleType>

  <!-- resource record mnemonic type -->
  <simpleType name="rrType">
    <restriction base="token">
      <enumeration value="NS" />
      <enumeration value="DS" />
      <enumeration value="DNAME" />
      <enumeration value="A" />
      <enumeration value="AAAA" />
      <enumeration value="custom" />
    </restriction>
  </simpleType>

  <!-- custom resource record type -->
  <simpleType name="customRRType">
    <restriction base="token">
      <pattern value="A|[A-Z][A-Z0-9\-]*[A-Z0-9]"/>
    </restriction>
  </simpleType>
</schema>

9. References 📚

9.1. Normative References

• [IANA-RRTYPES] IANA, "Resource Record (RR) TYPEs", <https://www.iana.org/assignments/dns-parameters>.
• [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>.
• [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>.
• [RFC5910] Gould, J. and S. Hollenbeck, "Domain Name System (DNS) Security Extensions Mapping for the Extensible Provisioning Protocol (EPP)", RFC 5910, DOI 10.17487/RFC5910, May 2010, <https://www.rfc-editor.org/info/rfc5910>.
• [RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895, April 2013, <https://www.rfc-editor.org/info/rfc6895>.
• [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
• [XSD-DATATYPES] Biron, P., Ed. and A. Malhotra, Ed., "XML Schema Part 2: Datatypes Second Edition", W3C Recommendation, October 2004, <https://www.w3.org/TR/2004/REC-xmlschema-2-20041028/>. Latest version available at <https://www.w3.org/TR/xmlschema-2/>.

9.2. 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>.
• [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>.
• [RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237, RFC 9364, DOI 10.17487/RFC9364, February 2023, <https://www.rfc-editor.org/info/rfc9364>.
• [RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219, RFC 9499, DOI 10.17487/RFC9499, March 2024, <https://www.rfc-editor.org/info/rfc9499>.
• [SAC-025] ICANN Security and Stability Advisory Committee (SSAC), "SSAC Advisory on Fast Flux Hosting and DNS", SAC 025, January 2008, <https://www.icann.org/en/system/files/files/sac-025-en.pdf>.

Acknowledgments 🙏

The author wishes to thank the following people for their advice and feedback during the development of this document:

• James Gould
• Hugo Salgado
• Patrick Mevzek
• Rick Wilhelm
• Marc Groeneweg
• Ties de Kock
• Tim Wicinski
• Jasdip Singh

Author's Address 📮

Gavin Brown
ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90292
United States of America
Email: gavin.brown@icann.org
URI:   https://www.icann.org/