Registration Protocols Extensions (regext) G. Brown
Internet-Draft CentralNic Group plc
Intended status: Standards Track 1 August 2023
Expires: 2 February 2024
Extensible Provisioning Protocol (EPP) mapping for DNS Time-To-Live
(TTL) values
draft-ietf-regext-epp-ttl-01
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
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Copyright (c) 2023 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
2. Extension elements . . . . . . . . . . . . . . . . . . . . . 4
3. EPP command mapping . . . . . . . . . . . . . . . . . . . . . 4
3.1. EPP query commands . . . . . . . . . . . . . . . . . . . 4
3.1.1. EPP <info> command . . . . . . . . . . . . . . . . . 4
3.2. EPP transform commands . . . . . . . . . . . . . . . . . 6
3.2.1. EPP <create> command . . . . . . . . . . . . . . . . 6
3.2.2. EPP <update> command . . . . . . . . . . . . . . . . 8
4. Server processing of TTL values . . . . . . . . . . . . . . . 10
4.1. Use of TTL values in delegation records . . . . . . . . . 10
4.2. Relationship between host object and domain object TTL
values . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.3. Use of TTL values for IDN variants . . . . . . . . . . . 11
5. Out-of-band changes to TTL values . . . . . . . . . . . . . . 11
6. Operational considerations . . . . . . . . . . . . . . . . . 11
6.1. Operational impact of TTL values . . . . . . . . . . . . 11
6.2. When the TTL should be changed . . . . . . . . . . . . . 12
7. Security considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 12
8.1. XML namespace . . . . . . . . . . . . . . . . . . . . . . 12
8.2. EPP extension registry . . . . . . . . . . . . . . . . . 13
9. Formal syntax . . . . . . . . . . . . . . . . . . . . . . . . 13
10. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Change from 00 to 01 . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative references . . . . . . . . . . . . . . . . . . 15
11.2. Informative references . . . . . . . . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
The principal output of any domain name provisioning system is a DNS
zone file, which contains the delegation record(s) for names
registered within a zone (such as a top-level domain). These records
include, at minimum, one or more NS records, but may also include A
and/or AAAA glue records, DS records, and DNAME records for IDN
variants ([RFC6927]).
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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 used for that domain: 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 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.
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:secs) are solely for illustrative purposes. A conforming
implementation MUST NOT require the use of these or any other
specific namespace prefixes.
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2. Extension elements
This specification defines a new element, <ttl:secs>, that is
included in <info> responses, and <create> and <update> commands.
The <ttl:secs> element takes two forms. The first contains a 32-bit
unsigned integer indicating the TTL (expressed in seconds) which will
be applied to the DNS records for the associated domain name or host
object.
Example:
<ttl:secs>3600</secs>
The second form, which contains no content, indicates that (a) in
<info> responses, no specific value has been set for the object, or
(b) in <create> and <update> commands, that the client wishes to
remove a previously set value, in favour of the default value. Note
that this does no mean that no TTL is published in DNS records (since
this is not possible), rather, that the server-determined default TTL
is (or should be) used for that object.
Example:
<ttl:secs/>
3. EPP command mapping
3.1. EPP query commands
3.1.1. EPP <info> command
This extension defines an additional element for EPP <info> responses
for domain and host objects.
When a server receives a domain or host <info> command from a client
which included the extension namespace in the <svcExtension> element
of the <login> command, the response MUST contain an <extension>
element, which MUST contain a <ttl:infData> element. This element
contains a single <ttl:secs> element.
Example domain <info> response:
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S: <?xml version="1.0" encoding="utf-8" standalone="no"?>
S: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
S: <response>
S: <result code="1000">
S: <msg>Command completed successfully</msg>
S: </result>
S: <resData>
S: <domain:infData
S: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
S: <domain:name>example.com</domain:name>
S: <domain:roid>EXAMPLE1-REP</domain:roid>
S: <domain:status s="ok" />
S: <domain:registrant>jd1234</domain:registrant>
S: <domain:contact type="admin">sh8013</domain:contact>
S: <domain:contact type="tech">sh8013</domain:contact>
S: <domain:ns>
S: <domain:hostObj>ns1.example.com</domain:hostObj>
S: <domain:hostObj>ns1.example.net</domain:hostObj>
S: </domain:ns>
S: <domain:clID>ClientX</domain:clID>
S: <domain:crID>ClientY</domain:crID>
S: <domain:crDate>1999-04-03T22:00:00.0Z</domain:crDate>
S: <domain:upID>ClientX</domain:upID>
S: <domain:upDate>1999-12-03T09:00:00.0Z</domain:upDate>
S: <domain:exDate>2005-04-03T22:00:00.0Z</domain:exDate>
S: <domain:trDate>2000-04-08T09:00:00.0Z</domain:trDate>
S: <domain:authInfo>
S: <domain:pw>2fooBAR</domain:pw>
S: </domain:authInfo>
S: </domain:infData>
S: </resData>
S: <extension>
S: <ttl:infData
S: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S: <ttl:secs>3600</ttl:secs>
S: </ttl:infData>
S: </extension>
S: <trID>
S: <clTRID>ABC-12345</clTRID>
S: <svTRID>54322-XYZ</svTRID>
S: </trID>
S: </response>
S: </epp>
Example host <info> response:
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S:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
S: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
S: <response>
S: <result code="1000">
S: <msg>Command completed successfully</msg>
S: </result>
S: <resData>
S: <host:infData
S: xmlns:host="urn:ietf:params:xml:ns:host-1.0">
S: <host:name>ns1.example.com</host:name>
S: <host:roid>NS1_EXAMPLE1-REP</host:roid>
S: <host:status s="linked"/>
S: <host:status s="clientUpdateProhibited"/>
S: <host:addr ip="v4">192.0.2.2</host:addr>
S: <host:addr ip="v4">192.0.2.29</host:addr>
S: <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
S: <host:clID>ClientY</host:clID>
S: <host:crID>ClientX</host:crID>
S: <host:crDate>1999-04-03T22:00:00.0Z</host:crDate>
S: <host:upID>ClientX</host:upID>
S: <host:upDate>1999-12-03T09:00:00.0Z</host:upDate>
S: <host:trDate>2000-04-08T09:00:00.0Z</host:trDate>
S: </host:infData>
S: </resData>
S: <extension>
S: <ttl:infData
S: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
S: <ttl:secs>3600</ttl:secs>
S: </ttl:infData>
S: </extension>
S: <trID>
S: <clTRID>ABC-12345</clTRID>
S: <svTRID>54322-XYZ</svTRID>
S: </trID>
S: </response>
S: </epp>
3.2. EPP transform commands
3.2.1. EPP <create> command
This extension defines an additional element for EPP <create>
commands for domain and host objects.
The <create> command MAY contain an <extension> element which MAY
contain a <ttl:create> element. This element contains a single
<ttl:secs> element.
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Example domain <create> command:
C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C: <command>
C: <create>
C: <domain:create
C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
C: <domain:name>example.com</domain:name>
C: <domain:period unit="y">2</domain:period>
C: <domain:ns>
C: <domain:hostObj>ns1.example.net</domain:hostObj>
C: <domain:hostObj>ns2.example.net</domain:hostObj>
C: </domain:ns>
C: <domain:registrant>jd1234</domain:registrant>
C: <domain:contact type="admin">sh8013</domain:contact>
C: <domain:contact type="tech">sh8013</domain:contact>
C: <domain:authInfo>
C: <domain:pw>2fooBAR</domain:pw>
C: </domain:authInfo>
C: </domain:create>
C: </create>
C: <extension>
C: <ttl:create
C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C: <ttl:secs>3600</ttl:secs>
C: </ttl:create>
C: </extension>
C: <clTRID>ABC-12345</clTRID>
C: </command>
C: </epp>
Example host <create> command:
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C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C: <command>
C: <create>
C: <host:create
C: xmlns:host="urn:ietf:params:xml:ns:host-1.0">
C: <host:name>ns1.example.com</host:name>
C: <host:addr ip="v4">192.0.2.2</host:addr>
C: <host:addr ip="v4">192.0.2.29</host:addr>
C: <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
C: </host:create>
C: </create>
C: <extension>
C: <ttl:create
C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C: <ttl:secs>3600</ttl:secs>
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 that is
outside the server's permitted range, it MUST reject the command with
a 2306 "Parameter value policy error" response.
3.2.2. EPP <update> command
This extension defines an additional element for EPP <update>
commands for domain and host objects.
The <update> command MAY contain an <extension> element which MAY
contain a <ttl:update> element. This element contains a single
<ttl:secs> element.
Example domain <update> command:
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C: <?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0"
C: xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
C: <command>
C: <update>
C: <domain:update
C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
C: <domain:name>example.com</domain:name>
C: </domain:update>
C: </update>
C: <extension>
C: <ttl:update>
C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C: <ttl:secs>3600</ttl:secs>
C: </ttl:update>
C: </extension>
C: <clTRID>ABC-12345</clTRID>
C: </command>
C: </epp>
Example host <update> command:
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C:<?xml version="1.0" encoding="UTF-8" standalone="no"?>
C: <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
C: <command>
C: <update>
C: <host:update
C: xmlns:host="urn:ietf:params:xml:ns:host-1.0">
C: <host:name>ns1.example.com</host:name>
C: <host:add>
C: <host:addr ip="v4">192.0.2.22</host:addr>
C: <host:status s="clientUpdateProhibited"/>
C: </host:add>
C: <host:rem>
C: <host:addr ip="v6">1080::8:800:200C:417A</host:addr>
C: </host:rem>
C: <host:chg>
C: <host:name>ns2.example.com</host:name>
C: </host:chg>
C: </host:update>
C: </update>
C: <extension>
C: <ttl:update>
C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
C: <ttl:secs>3600</ttl:secs>
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 that
is outside the server's permitted range, it MUST reject the command
with a 2306 "Parameter value policy error" response.
4. Server processing of TTL values
4.1. Use of TTL values in delegation records
EPP servers which implement this extension SHOULD use the values
provided by EPP clients for the TTL values of NS and DS records
published in the DNS for domain objects, and A and AAAA records
published in the DNS for host objects.
EPP servers that use the "host attribute" model (described in section
1.1 of [RFC5731]) SHOULD use the TTL of the domain object when
publishing NS, A and AAAA records derived from host attributes.
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4.2. Relationship between host object and domain object TTL values
The extension in this document allows TTL values to be configured for
both domain and host objects. In domain name registries, these
object types have a hierarchical relationship, in that a host object
may be subordinate to a domain object: for example, the host object
ns1.example.com is subordinate to the domain object example.com.
When publishing A and AAAA for host objects, TTL values for host
objects SHOULD take precedence over the TTL of the superordinate
domain object. However, if no TTL value is specified for a
subordinate host object, but a TTL value _is_ specified for the
superordinate domain object, then the domain object's TTL value MAY
be used for the host object instead of the default TTL value.
4.3. Use of TTL values for IDN variants
If a domain name has variants ([RFC6927]) that are linked to that
domain, then any NS or DNAME records published for those variants MAY
use the same TTL as that used for the primary domain.
5. Out-of-band changes to TTL values
EPP server operators MAY, in order to address operational or security
issues, make changes to TTL values out-of-band (that is, not in
response to an <update> command received from the sponsoring client).
Additionally, server operators MAY implement an automatic reset of
TTL values, so that they may be changed for a finite period before
and after a planned change, and then revert to a standard value.
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 servrers to
notify clients of changes to objects under their sponsorship.
6. Operational considerations
6.1. Operational impact of TTL values
Domain registry operators must strike a balance between, on the one
hand, the desire of registrants for changes to their domains to be
visible in the DNS quickly, and on the other, the increased DNS query
traffic that short TTLs can bring. Historically, registry operators
have used a global TTL value which was applied to all delegations
within their zones, which could then be tuned to an optimum value.
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Domain registry operators SHOULD implement limits on the maximum and
minimum accepted TTL values that are narrower than the values
permitted in the XML schema in the Formal 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 5 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).
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
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 has
the potential to enhance the effectiveness of fast flux techniques on
evasion.
8. IANA considerations
8.1. XML namespace
This document uses URNs to describe XML namespaces and XML schemas
conforming to a registry mechanism described in [RFC3688]. The
following URI assignment has been made by IANA:
Registration for the TTL namespace:
*URI:* urn:ietf:params:xml:ns:epp:ttl-1.0
*Registrant Contact:* See the author of this document
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*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:* 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:* 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
9. Formal syntax
The formal syntax presented here is a complete schema representation
of the extension suitable for automated validation of EPP XML
instances.
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<?xml version="1.0" encoding="UTF-8"?>
<schema
targetNamespace="urn:ietf:params:xml:ns:epp:ttl-1.0"
xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
xmlns="http://www.w3.org/2001/XMLSchema"
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="create" type="ttl:seconds"/>
<element name="update" type="ttl:seconds"/>
<element name="infData" type="ttl:seconds"/>
<complexType name="seconds">
<choice>
<element name="secs" type="ttl:nonNegativeInteger"/>
<element name="secs"/>
</choice>
</complexType>
<simpleType name="nonNegativeInteger">
<restriction base="nonNegativeInteger">
<minInclusive value="0"/>
<maxInclusive value="2147483647"/>
</restriction>
</simpleType>
</schema>
10. Change Log
This section is to be removed before publishing as an RFC.
10.1. 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).
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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 4.1 (thanks Hugo Salgado).
7. Added a Change Log (Section 10).
11. References
11.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5731] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Domain Name Mapping", STD 69, RFC 5731,
DOI 10.17487/RFC5731, August 2009,
<https://www.rfc-editor.org/info/rfc5731>.
[RFC5732] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Host Mapping", STD 69, RFC 5732, DOI 10.17487/RFC5732,
August 2009, <https://www.rfc-editor.org/info/rfc5732>.
[RFC7451] Hollenbeck, S., "Extension Registry for the Extensible
Provisioning Protocol", RFC 7451, DOI 10.17487/RFC7451,
February 2015, <https://www.rfc-editor.org/info/rfc7451>.
[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>.
11.2. Informative references
Brown Expires 2 February 2024 [Page 15]
Internet-Draft TTL mapping for EPP August 2023
[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>.
[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
CentralNic Group plc
44 Gutter Lane
London
EC2V 6BR
United Kingdom
Email: gavin.brown@centralnic.com
URI: https://www.centralnic.com
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