Registration Protocols Extensions (regext) G. Brown Internet-Draft CentralNic Group plc Intended status: Experimental 16 November 2022 Expires: 20 May 2023 Extensible Provisioning Protocol (EPP) mapping for DNS Time-To-Live (TTL) values draft-regext-brown-epp-ttl-03 Abstract This document describes an extension to the Extensible Provisioning Protocol (EPP) that allows EPP clients to manage the Time-To-Live (TTL) value for domain name delegation records. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 20 May 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal 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. Brown Expires 20 May 2023 [Page 1] Internet-Draft TTL mapping for EPP November 2022 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 2. Extension elements . . . . . . . . . . . . . . . . . . . . . 3 3. EPP command mapping . . . . . . . . . . . . . . . . . . . . . 4 3.1. EPP query commands . . . . . . . . . . . . . . . . . . . 4 3.1.1. EPP command . . . . . . . . . . . . . . . . . 4 3.2. EPP transform commands . . . . . . . . . . . . . . . . . 6 3.2.1. EPP command . . . . . . . . . . . . . . . . 6 3.2.2. EPP 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 . . . . . . . . . . . . . . . . . . . 13 8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13 8.1. XML namespace . . . . . . . . . . . . . . . . . . . . . . 13 8.2. EPP extension registry . . . . . . . . . . . . . . . . . 13 9. Formal specification . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 10.1. Normative references . . . . . . . . . . . . . . . . . . 15 10.2. Informative references . . . . . . . . . . . . . . . . . 16 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]). Typically, the Time-To-Live (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 a that domain: for example, to reduce the amount of time required to complete a change of DNS servers or DNSSEC deployment of key rollover, or to allow for fast rollback of such changes. Brown Expires 20 May 2023 [Page 2] Internet-Draft TTL mapping for EPP November 2022 This document describes an EPP extension to the domain name and host object mappings (described in [RFC5731] and [RFC5732], respectively) which allows the sponsor of a domain name or host object to change the TTL associated with that object. 1.1. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. In examples, "C:" represents lines sent by a protocol client and "S:" represents lines returned by a protocol server. Indentation and white space in examples are provided only to illustrate element relationships and are not REQUIRED features of this protocol. A protocol client that is authorized to manage an existing object is described as a "sponsoring" client throughout this document. XML is case sensitive. Unless stated otherwise, XML specifications and examples provided in this document MUST be interpreted in the character case presented in order to develop a conforming implementation. EPP uses XML namespaces to provide an extensible object management framework and to identify schemas required for XML instance parsing and validation. These namespaces and schema definitions are used to identify both the base protocol schema and the schemas for managed objects. The XML namespace prefixes used in examples (such as the string ttl in xmlns:ttl) are solely for illustrative purposes. A conforming implementation MUST NOT require the use of these or any other specific namespace prefixes. 2. Extension elements This specification defines a two new elements that are included in , and commands: * , which contains a 32-bit unsigned integer indicating the TTL (expressed in seconds) which will be applied to the delegation records for the associated domain name or host object; and * , which contains a date and time after which a TTL (specified using the element) should revert to the server's default value. Brown Expires 20 May 2023 [Page 3] Internet-Draft TTL mapping for EPP November 2022 Examples: 3600 2022-12-01T08:00:00.0Z The element is OPTIONAL in , and commands. EPP servers which do not support this element MUST reject commands which contain it with a 2012 "Unimplemented option" response. Conversely, EPP servers whose policies require the use of the element MUST reject commands which do not contain it with a 2003 "Required parameter missing" response. 3. EPP command mapping 3.1. EPP query commands 3.1.1. EPP command This extension defines additional elements for EPP responses for domain and host objects. The response MAY contain an element, which MAY contain a element, which contains the following child elements: * A element showing the current TTL for the object; and * An OPTIONAL element containing the date and time after which the TTL will revert to the server's default value. The MUST NOT appear in responses if: (1) the server does not support this element, (2) the object already has the server's default TTL value, or (3) the server does not implement automatic reversion of custom TTL values. Example domain response: Brown Expires 20 May 2023 [Page 4] Internet-Draft TTL mapping for EPP November 2022 S: S: S: S: S: Command completed successfully S: S: S: S: example.com S: EXAMPLE1-REP S: S: jd1234 S: sh8013 S: sh8013 S: S: ns1.example.com S: ns1.example.net S: S: ClientX S: ClientY S: 1999-04-03T22:00:00.0Z S: ClientX S: 1999-12-03T09:00:00.0Z S: 2005-04-03T22:00:00.0Z S: 2000-04-08T09:00:00.0Z S: S: 2fooBAR S: S: S: S: S: S: 3600 S: 2022-12-01T08:30:00.0Z S: S: S: S: ABC-12345 S: 54322-XYZ S: S: S: Example host response: Brown Expires 20 May 2023 [Page 5] Internet-Draft TTL mapping for EPP November 2022 S: S: S: S: S: Command completed successfully S: S: S: S: ns1.example.com S: NS1_EXAMPLE1-REP S: S: S: 192.0.2.2 S: 192.0.2.29 S: 1080::8:800:200C:417A S: ClientY S: ClientX S: 1999-04-03T22:00:00.0Z S: ClientX S: 1999-12-03T09:00:00.0Z S: 2000-04-08T09:00:00.0Z S: S: S: S: S: 3600 S: 2022-12-01T08:30:00.0Z S: S: S: S: ABC-12345 S: 54322-XYZ S: S: S: 3.2. EPP transform commands 3.2.1. EPP command This extension defines additional elements for EPP commands for domain and host objects. The command MAY contain an element which MAY contain a element, which contains the following child elements: Brown Expires 20 May 2023 [Page 6] Internet-Draft TTL mapping for EPP November 2022 * A element showing the desired TTL for the object; and * An OPTIONAL element containing the date and time after which the TTL should revert to the server's default value. Example domain command: C: C: C: C: C: C: example.com C: 2 C: C: ns1.example.net C: ns2.example.net C: C: jd1234 C: sh8013 C: sh8013 C: C: 2fooBAR C: C: C: C: C: C: 3600 S: 2022-12-01T08:30:00.0Z C: C: C: ABC-12345 C: C: Example host command: Brown Expires 20 May 2023 [Page 7] Internet-Draft TTL mapping for EPP November 2022 C: C: C: C: C: C: ns1.example.com C: 192.0.2.2 C: 192.0.2.29 C: 1080::8:800:200C:417A C: C: C: C: C: 3600 S: 2022-12-01T08:30:00.0Z C: C: C: ABC-12345 C: C: EPP servers which do not support the element MUST reject commands which contain it with a 2012 "Unimplemented option" response. 3.2.2. EPP command This extension defines additional elements for EPP commands for domain and host objects. The command MAY contain an element which MAY contain a element, which contains the following child elements: * A element showing the desired TTL for the object; and * An OPTIONAL element containing the date and time after which the TTL should revert to the server's default value. Example domain command: Brown Expires 20 May 2023 [Page 8] Internet-Draft TTL mapping for EPP November 2022 C: C: C: C: C: C: example.com C: C: C: C: C: xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0"> C: 3600 S: 2022-12-01T08:30:00.0Z C: C: C: ABC-12345 C: C: Example host command: Brown Expires 20 May 2023 [Page 9] Internet-Draft TTL mapping for EPP November 2022 C: C: C: C: C: C: ns1.example.com C: C: 192.0.2.22 C: C: C: C: 1080::8:800:200C:417A C: C: C: ns2.example.com C: C: C: C: C: C: xmlns:ttl="urn:ietf:params:xml:ns:ttl-1.0"> C: 3600 S: 2022-12-01T08:30:00.0Z C: C: C: ABC-12345 C: C: EPP servers which do not support the element MUST reject commands which contain it with a 2012 "Unimplemented option" response. 4. Server processing of TTL values If an EPP server receives a command containing a TTL that is outside the server's permitted range (see Operational considerations and Security considerations below), it MUST reject the command with a 2004 "Parameter value range error" response. 4.1. Use of TTL values in delegation records EPP servers which implement this extension SHOULD use the values provided by EPP clients for the TTL values of NS, A, AAAA and DS records published in the DNS for the corresponding delegation. Brown Expires 20 May 2023 [Page 10] Internet-Draft TTL mapping for EPP November 2022 4.2. Relationship between host object and domain object TTL values The extension in this document allows TTL values to be configured for both domain and host objects. In domain name registries, these object types have a hierarchical relationship, in that a host object may be subordinate to a domain object: for example, the host object ns1.example.com is subordinate to the domain object example.com. When publishing A and AAAA for host objects, TTL values for host objects SHOULD take precedence over the TTL of the superordinate domain object. However, if no TTL value is configured for a subordinate host object, but a TTL value is configured for the superordinate domain object, then the domain object's TTL value SHOULD be used for the host object instead of the default TTL value. 4.3. Use of TTL values for IDN variants If a domain name has variants ([RFC6927]) that are linked to that domain, then any NS or DNAME records published for those variants MUST use the same TTL as that used for the primary domain. 5. Out-of-band changes to TTL values EPP server operators MAY, in order to address operational or security issues, make changes to TTL values out-of-band (that is, not in response to an command received from the sponsoring client). Additionally, server operators MAY implement an automatic reset of TTL values, so that they may be changed for a finite period before and after a planned change, and then revert to a standard value. In the event of changes to TTL values taking place out-of-band, EPP server operators SHOULD notify the sponsoring client using the EPP Change Poll extension ([RFC8590]). 6. Operational considerations 6.1. Operational impact of TTL values Domain registry operators must strike a balance between, on the one hand, the desire of registrants for changes to their domains to be visible in the DNS quickly, and on the other, the increased DNS query traffic that short TTLs can bring. Historically, registry operators have used a global TTL value which was applied to all delegations within their zones, which could then be tuned to an optimum value. Brown Expires 20 May 2023 [Page 11] Internet-Draft TTL mapping for EPP November 2022 Domain registry operators SHOULD implement limits on the maximum and minimum accepted TTL values that are narrower than the values permitted in the XML schema in the Formal specification (which were chosen to allow any TTL permitted in DNS records), in order to prevent scenarios where an excessively high or low TTL causes operational issues on either side of the zone cut. Similarly, EPP servers which support the element MUST reject commands (with a 2004 "parameter value range error" response) if the specified date and time is in the past, or is otherwise outside a server-defined range of acceptable values. EPP servers MAY vary the range of acceptable values for the element based on the value of the element: for example, to allow the setting of a very short TTL for a short period of time, while permitting longer TTLs to be used for longer periods, as the following table illustrates: +=================+==================+ | TTL value range | Maximum duration | +=================+==================+ | 0-60s | - | +-----------------+------------------+ | 61-299s | 3600s | +-----------------+------------------+ | 300-1099s | 43200s | +-----------------+------------------+ | 1200-3599s | 86400s | +-----------------+------------------+ | >= 3600s | any | +-----------------+------------------+ Table 1: Example TTL/Duration Policy Table In the above policy, the default TTL is one hour, and the server will reject any TTL below 60 seconds. Clients can set TTLs of between one and five minutes for a maximum of one hour, or between five minutes and thirty minutes for up to twelve hours, or between 30 minutes and one hour for up to one day. 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. Brown Expires 20 May 2023 [Page 12] Internet-Draft TTL mapping for EPP November 2022 Client implementations of this specification SHOULD ensure that the user understands that changes to a TTL are only effective in shortening transition periods if implemented a period of time -- at least equal to the current TTL -- _before_ the planned change. 7. Security considerations Many malicious actors use a technique called "fast flux DNS" to rapidly change the DNS configuration for a zone in order to evade takedown and law enforcement activity. Registry operators SHOULD take this into consideration when setting the lower limit on TTL values, since a short TTL on delegations has the potential to enhance the effectiveness of fast flux techniques on evasion. 8. IANA considerations 8.1. XML namespace This document uses URNs to describe XML namespaces and XML schemas conforming to a registry mechanism described in [RFC3688]. The following URI assignment has been made by IANA: Registration for the TTL namespace: *URI:* urn:ietf:params:xml:ns:ttl-1.0 *Registrant Contact:* See the author of this document *XML:* None. Namespace URIs do not represent an XML specification Registration for the TTL XML schema: *URI:* urn:ietf:params:xml:ns:ttl-1.0 *Registrant Contact:* See the author of this document *XML:* See the "Formal specification" section of this document 8.2. EPP extension registry The EPP extension described in this document has been registered by the IANA in the Extensions for the "Extensible Provisioning Protocol (EPP)" registry described in [RFC7451]. The details of the registration are as follows: Brown Expires 20 May 2023 [Page 13] Internet-Draft TTL mapping for EPP November 2022 *Name of Extension:* Extensible Provisioning Protocol (EPP) Mapping for DNS Time-To-Live (TTL) values *Document Status:* Experimental *Reference:* URL of this document *Registrant Name and Email Address:* See the author of this document *TLDs:* Any *IPR Disclosure:* None *Status:* Active *Notes:* None 9. Formal specification Brown Expires 20 May 2023 [Page 14] Internet-Draft TTL mapping for EPP November 2022 Extensible Provisioning Protocol v1.0 domain name extension schema for Time-To-Live (TTL) modification in all DNS responses for a domain name including delegation (NS) records and any address (A) records. 10. References 10.1. Normative references [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M. and RFC Publisher, "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . Brown Expires 20 May 2023 [Page 15] Internet-Draft TTL mapping for EPP November 2022 [RFC5731] Hollenbeck, S. and RFC Publisher, "Extensible Provisioning Protocol (EPP) Domain Name Mapping", STD 69, RFC 5731, DOI 10.17487/RFC5731, August 2009, . [RFC5732] Hollenbeck, S. and RFC Publisher, "Extensible Provisioning Protocol (EPP) Host Mapping", STD 69, RFC 5732, DOI 10.17487/RFC5732, August 2009, . [RFC7451] Hollenbeck, S. and RFC Publisher, "Extension Registry for the Extensible Provisioning Protocol", RFC 7451, DOI 10.17487/RFC7451, February 2015, . [RFC8499] Hoffman, P., Sullivan, A., Fujiwara, K., and RFC Publisher, "DNS Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, January 2019, . [RFC8590] Gould, J., Feher, K., and RFC Publisher, "Change Poll Extension for the Extensible Provisioning Protocol (EPP)", RFC 8590, DOI 10.17487/RFC8590, May 2019, . 10.2. Informative references [RFC6927] Levine, J., Hoffman, P., and RFC Publisher, "Variants in Second-Level Names Registered in Top-Level Domains", RFC 6927, DOI 10.17487/RFC6927, May 2013, . Author's Address Gavin Brown CentralNic Group plc 44 Gutter Lane London EC2V 6BR United Kingdom Phone: +44 20 33 88 0600 Email: gavin.brown@centralnic.com URI: https://www.centralnic.com Brown Expires 20 May 2023 [Page 16]