Internet DRAFT - draft-ietf-regext-epp-ttl
draft-ietf-regext-epp-ttl
Registration Protocols Extensions (regext) G. Brown
Internet-Draft ICANN
Intended status: Standards Track 1 March 2024
Expires: 2 September 2024
Extensible Provisioning Protocol (EPP) mapping for DNS Time-To-Live
(TTL) values
draft-ietf-regext-epp-ttl-06
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.
About this draft
This note is to be removed before publishing as an RFC.
The source for this draft, and an issue tracker, may can be found at
https://github.com/gbxyz/epp-ttl-extension.
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 2 September 2024.
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.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.2. Extension elements . . . . . . . . . . . . . . . . . . . 4
1.2.1. The <ttl:ttl> element . . . . . . . . . . . . . . . . 4
1.2.1.1. Element content . . . . . . . . . . . . . . . . . 5
1.2.1.2. Supported DNS record types . . . . . . . . . . . 5
1.2.1.3. Examples . . . . . . . . . . . . . . . . . . . . 6
1.3. The <ttl:info> element . . . . . . . . . . . . . . . . . 6
1.3.1. Example . . . . . . . . . . . . . . . . . . . . . . . 7
2. EPP command mapping . . . . . . . . . . . . . . . . . . . . . 7
2.1. EPP query commands . . . . . . . . . . . . . . . . . . . 7
2.1.1. EPP <info> command . . . . . . . . . . . . . . . . . 7
2.1.1.1. Default mode . . . . . . . . . . . . . . . . . . 7
2.1.1.2. Policy mode . . . . . . . . . . . . . . . . . . . 11
2.1.1.3. Unextended <info> command . . . . . . . . . . . . 14
2.2. EPP transform commands . . . . . . . . . . . . . . . . . 15
2.2.1. EPP <create> command . . . . . . . . . . . . . . . . 15
2.2.2. EPP <update> command . . . . . . . . . . . . . . . . 17
3. Server processing of TTL values . . . . . . . . . . . . . . . 19
3.1. Permitted record types . . . . . . . . . . . . . . . . . 19
3.2. Use of TTL values in delegation records . . . . . . . . . 19
4. Out-of-band changes to TTL values . . . . . . . . . . . . . . 19
5. Operational considerations . . . . . . . . . . . . . . . . . 19
5.1. Operational impact of TTL values . . . . . . . . . . . . 19
5.2. When TTL values should be changed . . . . . . . . . . . . 20
6. Security considerations . . . . . . . . . . . . . . . . . . . 20
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 20
7.1. XML namespace . . . . . . . . . . . . . . . . . . . . . . 20
7.2. EPP extension registry . . . . . . . . . . . . . . . . . 21
8. Formal syntax . . . . . . . . . . . . . . . . . . . . . . . . 21
9. Implementation status . . . . . . . . . . . . . . . . . . . . 25
9.1. Verisign EPP SDK . . . . . . . . . . . . . . . . . . . . 25
9.2. Pepper EPP Client . . . . . . . . . . . . . . . . . . . . 25
10. Change log . . . . . . . . . . . . . . . . . . . . . . . . . 25
10.1. Change from 05 to 06 . . . . . . . . . . . . . . . . . . 25
10.2. Change from 04 to 05 . . . . . . . . . . . . . . . . . . 26
10.3. Change from 04 to 05 . . . . . . . . . . . . . . . . . . 26
10.4. Change from 03 to 04 . . . . . . . . . . . . . . . . . . 26
10.5. Change from 02 to 03 . . . . . . . . . . . . . . . . . . 26
10.6. Change from 01 to 02 . . . . . . . . . . . . . . . . . . 26
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10.7. Change from 00 to 01 . . . . . . . . . . . . . . . . . . 27
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1. Normative references . . . . . . . . . . . . . . . . . . 27
12.2. Informative references . . . . . . . . . . . . . . . . . 28
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 29
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
typically include one or more NS records, but may also include DS
records for domains secured with DNSSEC ([RFC9364]), and DNAME
records for IDN variants ([RFC6927]). Where glue (see Section 7 of
[RFC8499]) is required, A and/or AAAA records may also be published
for nameservers.
Typically, the Time-To-Live value (TTL, see Section 5 of [RFC8499])
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 values used for that domain's
delegation: for example, to reduce the amount of time required to
complete a change of DNS servers, DNSSEC deployment or key rollover,
or to allow for fast rollback of such changes.
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 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 co-ordinate to manage TTL values in
response to changes in operational or security requirements.
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.
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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 ttl:create) are solely for illustrative purposes. A conforming
implementation MUST NOT require the use of these or any other
specific namespace prefixes.
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.
The <ttl:ttl> element may have the following attributes, depending on
whether it appears in a command or response frame:
1. "for", which is REQUIRED in both commands and responses, and
which 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";
2. 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.
3. "min", which MUST NOT be present in commands frames but MAY be
present in response frames (see Section 2.1.1), and which is used
by the server to indicate the lowest value that may be set;
4. "default", which MUST NOT be present in commands frames but MAY
be present in response frames (see Section 2.1.1), and which is
used by the server to indicate the default value;
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5. "max", which MUST NOT be present in commands frames but MAY be
present in response frames (see Section 2.1.1), and which is used
by the server to indicate the highest value that may be set;
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 "for" and "custom" attributes of
<ttl:ttl> elements.
The regular expression which is used to validate the values of the
"custom" attribute is based on the expression found in Section 1.3 of
[RFC6895], and is intended to match any existing and future RRTYPE
mnemonic registered with the IANA: this eliminates the need to update
this document in the event that a new DNS record that exists above a
zone cut is specified.
Nevertheless, EPP servers which 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 actually published in the DNS for domain and
host objects.
A server which receives a <create> or <update> command which includes
an invalid DNS record type MUST respond with a 2004 "Parameter value
range" 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 registry implements IDN variants using DNAME
records).
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1.2.1.2.1. Glue records
Servers which implement host objects ([RFC5732]) MAY allow clients to
specify TTL values for A and AAAA records for host objects. These
servers MUST reject commands which attempt to set TTL values for
these record types for domain objects using a 2004 "Parameter value
range" error.
EPP servers which 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. Examples
1.2.1.3.1. Explicit TTL value (<create> or <update> command)
<ttl:ttl for="NS">3600<ttl:ttl>
1.2.1.3.2. Explicit TTL value (<info> policy mode)
<ttl:ttl
for="NS"
min="60"
default="86400"
max="172800">3600<ttl:ttl>
1.2.1.3.3. Empty value indicating default TTL (<create> or <update>
command, <info> default mode)
<ttl:ttl for="NS"/>
1.2.1.3.4. Custom record type (<create> or <update> command, <info>
default mode)
<ttl:ttl
for="custom"
custom="DELEG">3600<ttl:ttl>
1.3. The <ttl:info> element
The <ttl:info> element is used to by clients to request that the
server include additional information in <info> responses for domain
and host objects.
It has a single OPTIONAL attribute, policy, which takes a boolean
value with a default value of false.
The semantics of this element are described in Section 2.1.1.
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1.3.1. Example
<ttl:info policy="true"/>
2. EPP command mapping
2.1. EPP query commands
2.1.1. EPP <info> command
This extension defines an additional element for EPP <info> commands
and responses for domain and host objects.
The EPP <info> command is extended to support two different "modes".
The first "default" mode requests the inclusion of all non-default
TTL values in the response. The second "policy" mode requests the
inclusion of TTL information for all supported DNS record types in
the response, along with the minimum, default and maximum values for
those records.
2.1.1.1. Default mode
If a server receives an <info> command for a domain or host object
which includes a <ttl:info> element without a policy attribute, or
with a policy attribute that is 0 or false, then the response MUST
contain an <extension> element, which MUST contain a <ttl:infData>
element, which MUST contain <ttl> records for all DNS record types
that have non-default TTL values. These elements SHOULD NOT have the
min, default and max attributes.
Example domain <info> command with a <ttl:info> element with a policy
attribute that is false:
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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: <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>
Example domain <info> response to a command with a <ttl:info> element
with a policy attribute that is false:
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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: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>
Example host <info> command with a <ttl:info> element with a policy
attribute that is false:
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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: <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>
Example domain <info> response to a command with a <ttl:info> element
with a policy attribute that is false:
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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="ok"/>
S: <host:addr ip="v4">192.0.2.2</host:addr>
S: <host:addr ip="v6">1080::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">3600</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
If a server receives an <info> command for a domain or host object
which includes a <ttl:info> element with a policy attribute that is
present and is 1 or true, then the response MUST contain an
<extension> element, which MUST contain a <ttl:infData> element,
which MUST include <ttl:ttl> records for all supported DNS record
types, irrespective of whether those record types are actually in use
by the object in question. These elements MUST have the min, default
and max attributes.
Example domain <info> command requesting the server policies:
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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: <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>
Example domain <info> response providing the server policies:
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
<response>
<result code="1000">
<msg>Command completed successfully</msg>
</result>
<resData>
<domain:infData
xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
<domain:name>example.com</domain:name>
<domain:roid>EXAMPLE1-REP</domain:roid>
<domain:status s="ok"/>
<domain:ns>
<domain:hostObj>ns1.example.com</domain:hostObj>
<domain:hostObj>ns1.example.net</domain:hostObj>
</domain:ns>
<domain:clID>ClientX</domain:clID>
<domain:crID>ClientX</domain:crID>
<domain:crDate>2023-11-08T10:14:55.0Z</domain:crDate>
<domain:exDate>2024-11-08T10:14:55.0Z</domain:exDate>
</domain:infData>
</resData>
<extension>
<ttl:infData
xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
<ttl:ttl for="NS"
min="3600"
default="86400"
max="172800">172800</ttl:ttl>
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<ttl:ttl for="DS"
min="60"
default="86400"
max="172800">300</ttl:ttl>
</ttl:infData>
<secDNS:infData
xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1">
<secDNS:dsData>
<secDNS:keyTag>12345</secDNS:keyTag>
<secDNS:alg>13</secDNS:alg>
<secDNS:digestType>2</secDNS:digestType>
<secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest>
</secDNS:dsData>
</secDNS:infData>
</extension>
<trID>
<clTRID>ABC-12345</clTRID>
<svTRID>54322-XYZ</svTRID>
</trID>
</response>
</epp>
Example host <info> command requesting 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>
Example host <info> response providing the server policies:
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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="ok"/>
S: <host:addr ip="v4">192.0.2.2</host:addr>
S: <host:addr ip="v6">1080::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>
2.1.1.3. Unextended <info> command
If a server receives an <info> command which does not contain a
<ttl:info> element, then the response MUST NOT contain a
<ttl:infData> element.
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2.2. EPP transform commands
2.2.1. EPP <create> command
This extension defines an additional element for EPP <create>
commands for domain and host objects.
The <command> element of the <create> command frame MAY contain an
<extension> element which MAY contain a <ttl:create> element. This
element MUST contain one or more <ttl:ttl> records as described in
Section 1.2.
Example domain <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: <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>
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="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: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>
If an EPP server receives a <create> command containing a TTL value
that is outside the server's permitted range, it MUST reject the
command with a 2306 "Parameter value policy error" response.
2.2.2. EPP <update> command
This extension defines an additional element for EPP <update>
commands for domain and host objects.
The <command> element of the <update> command frame MAY contain an
<extension> element which MAY contain a <ttl:update> element. This
element MUST contain one or more <ttl:ttl> records as described in
Section 1.2.
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: <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>
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>
If an EPP server receives an <update> command containing a TTL value
that is outside the server's permitted range, it MUST reject the
command with a 2306 "Parameter value policy error" response.
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3. Server processing of TTL values
3.1. Permitted record types
Servers MAY restrict the supported DNS record types in accordance
with their own operational needs. For example, a server MAY allow
clients to specify TTL values for DS records only.
A server which receives a <create> or <update> command which includes
a restricted record type MUST respond with a 2306 "Parameter value
policy" error.
3.2. 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 records published in the
DNS for domain and and objects.
EPP servers that use the "host attribute" model SHOULD use any A and/
or AAAA TTL values specified for the domain object when publishing
NS, A and AAAA records derived from host attributes.
4. 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).
Server operators MAY also implement automatic reset of TTL values, so
that they revert to the default value a certain amount of time after
an update has been made.
If a TTL value is changed out-of-band, EPP server operators MAY
notify the sponsoring client using the EPP Change Poll extension
([RFC8590]), which provides a generalised method for EPP servers to
notify clients of changes to objects under their sponsorship.
5. Operational considerations
5.1. 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 syntax (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.
Section 4 describes how server operators MAY unilaterally change TTL
values in order 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 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.
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.
6. Security considerations
Some malicious actors use a technique called "fast flux DNS"
([SAC-025]) 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 may
enhance the effectiveness of fast flux techniques on evasion.
7. IANA considerations
7.1. 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:epp:ttl-1.0
*Registrant Contact:* See the author of this document
*XML:* None. Namespace URIs do not represent an XML specification
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Registration for the TTL XML schema:
*URI:* urn:ietf:params:xml:schema:epp:ttl-1.0
*Registrant Contact:* See the author of this document
*XML:* See the "Formal syntax" section of this document
7.2. 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:* Standards Track
*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
8. Formal syntax
The formal syntax presented here is a complete schema representation
of the extension suitable for automated validation of EPP XML
instances.
<?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
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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">
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<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>
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</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>
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9. Implementation status
This section is to be removed before publishing as an RFC.
9.1. Verisign EPP SDK
*Organization:* Verisign Inc.
*Name:* Verisign EPP SDK
*Description:* The Verisign EPP SDK includes both a full client
implementation and a full server stub implementation of this
specification.
*Level of maturity:* Development
*Coverage:* All aspects of the protocol are implemented.
*Licensing:* GNU Lesser General Public License
*Contact:* jgould@verisign.com
*URL:* https://www.verisign.com/en_US/channel-resources/domain-
registry-products/epp-sdks
9.2. Pepper EPP Client
*Name:* Pepper EPP Client
*Description:* The Pepper EPP client will fully implement this
specification.
*Level of maturity:* Development
*Coverage:* All aspects of the protocol will be implemented.
*Licensing:* Perl Artistic License
*Contact:* The author of this document.
*URL:* https://github.com/gbxyz/pepper
10. Change log
This section is to be removed before publishing as an RFC.
10.1. Change from 05 to 06
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1. Changed how <info> commands work so that a <ttl:info> element is
required in order for <ttl> elements to be included in the
response. Thanks to Jim Gould for this feedback.
10.2. Change from 04 to 05
1. removed the erroneous required="true" attribute from the min,
default and max attributes of the responseTTLType type (thanks
JG).
2. fixed the reference to RFC 6895 (thanks HS).
10.3. Change from 04 to 05
1. Add the the Verisign EPP SDK to Section 9.
2. Add the <ttl:info> element and document how it affects server
<info> responses.
3. Updated examples to exercise more of the schema.
4. Minor schema issue fixed.
10.4. Change from 03 to 04
1. Changed the for attribute to be an enumeration and added the
custom attribute.
2. Added the min, default and max attributes.
3. Apply feedback from Jim Gould.
10.5. Change from 02 to 03
1. Rolled back the "straw man" syntax from 02. ttl:ttl now has a for
attribute which can be any DNS record type. Section 1.2.1.2
describes how the set of supported record types may be limited.
2. Removed the global/explicit models and just use the explicit
model.
3. Removed the cascading effect where a TTL set on a domain affects
subordinate hosts.
10.6. Change from 01 to 02
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1. Renamed the ttl:seconds XSD type to ttl:container, and the
ttl:nonNegativeInteger type to ttl:ttlType, to permit multiple
TTL values.
2. Converted XML instances from artwork to source code.
10.7. Change from 00 to 01
1. Incorporate feedback from Jim Gould.
2. Add wording to describe how TTL values are jointly managed by
both clients and servers.
3. Fix minimum/maximum TTL value and schema namespace (thanks
Patrick Mevzek).
4. Moved text on how the server should handle impermissible TTL
values from the top of Section 4 to Sections 3.2.1 and 3.2.2
(thanks Rick Wilhelm).
5. Namespace changed from urn:ietf:params:xml:ns:ttl-1.0 to
urn:ietf:params:xml:ns:epp:ttl-1.0.
6. Added discussion on EPP servers which use the host attribute
model in Section 3.2 (thanks Hugo Salgado).
7. Added a Change Log (Section 10).
11. Acknowledgements
The author wishes to thank the following people for their advice and
feedback during the development of this document:
1. Hugo Salgado;
2. Patrick Mevzek;
3. Rick Wilhelm;
4. James Gould;
5. Marc Groeneweg;
6. Ties de Kock.
12. References
12.1. Normative references
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[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>.
[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>.
12.2. 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>.
[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>.
[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>.
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[RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237,
RFC 9364, DOI 10.17487/RFC9364, February 2023,
<https://www.rfc-editor.org/info/rfc9364>.
[SAC-025] ICANN Security and Stability Advisory Committee (SSAC),
"SSAC Advisory on Fast Flux Hosting and DNS", SAC 25,
January 2008,
<https://www.icann.org/en/system/files/files/sac-
025-en.pdf>.
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/
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