Network Working Group F. Obser Internet-Draft OpenBSD Intended status: Informational 3 November 2024 Expires: 7 May 2025 DNS Resolver Information Key for DNS64 draft-fobser-resinfo-dns64-02 Abstract This document specifies a DNS Resolver Information Key to inform DNS clients of the presence of DNS64. 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 7 May 2025. 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. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 2 2. Relation to RFC 7050 . . . . . . . . . . . . . . . . . . . . 2 3. dns64 Resolver Information Key . . . . . . . . . . . . . . . 2 Obser Expires 7 May 2025 [Page 1] Internet-Draft Resinfo DNS64 November 2024 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 6.1. Normative References . . . . . . . . . . . . . . . . . . 3 6.2. Informative References . . . . . . . . . . . . . . . . . 3 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction DNS64 [RFC6147] performed by a DNS resolver together with NAT64 [RFC6146] allows an IPv6-only client to initiate communications by name to an IPv4-only server. [RFC9606] specifies a DNS resource record (RR) type RESINFO to allow resolvers to publish information about their capabilities and policies. This can be used to inform DNS clients that DNS64 is performed by the DNS resolver. 1.1. Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Relation to RFC 7050 [RFC7050] describes a heuristic to learn the IPv6 prefix used by a NAT64 gateway. Nodes can use this information to perform local address synthesis, for example when using 464XLAT [RFC6877] as a transition mechanism. This has security implications, making [RFC7050] difficult to deploy. A modern mechanism, like PREF64 [RFC8781] is easier to deploy, leading to a desire to deprecate [RFC7050] entirely. Using the [RFC9606] RESINFO mechanism solely to inform clients about the presence of DNS64 without conveying any prefix information avoids the security problems of [RFC7050]. 3. dns64 Resolver Information Key dns64: The presence of this key indicates that the DNS resolver performs address synthesis. A resolver which supports [RFC9606] SHOULD add the dns64 key if it performs DNS64 [RFC6147] address synthesis. Obser Expires 7 May 2025 [Page 2] Internet-Draft Resinfo DNS64 November 2024 Note that, per the rules for the keys defined in Section 6.4 of [RFC6763], if there is no '=' in a key, then it is a boolean attribute, simply identified as being present, with no value. 4. Security Considerations The security considerations of [RFC9606] apply. 5. IANA Considerations The IANA is requested to add the key "dns64", with the description of "The presence of the key indicates that DNS64 address synthesis is performed", and a reference to this document. +=======+========================================+===============+ | Name | Description | Reference | +=======+========================================+===============+ | dns64 | The presence of the key indicates that | RFC EDITOR: | | | DNS64 address synthesis is performed. | THIS DOCUMENT | +-------+----------------------------------------+---------------+ Table 1 6. References 6.1. 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, . [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9606] Reddy.K, T. and M. Boucadair, "DNS Resolver Information", RFC 9606, DOI 10.17487/RFC9606, June 2024, . 6.2. Informative References Obser Expires 7 May 2025 [Page 3] Internet-Draft Resinfo DNS64 November 2024 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, April 2011, . [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van Beijnum, "DNS64: DNS Extensions for Network Address Translation from IPv6 Clients to IPv4 Servers", RFC 6147, DOI 10.17487/RFC6147, April 2011, . [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: Combination of Stateful and Stateless Translation", RFC 6877, DOI 10.17487/RFC6877, April 2013, . [RFC7050] Savolainen, T., Korhonen, J., and D. Wing, "Discovery of the IPv6 Prefix Used for IPv6 Address Synthesis", RFC 7050, DOI 10.17487/RFC7050, November 2013, . [RFC8781] Colitti, L. and J. Linkova, "Discovering PREF64 in Router Advertisements", RFC 8781, DOI 10.17487/RFC8781, April 2020, . Author's Address Florian Obser OpenBSD Email: florian+ietf@narrans.de Obser Expires 7 May 2025 [Page 4]