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General Internet Engineering Task Force DNS DNSSEC DNS64 RESINFO This document specifies two DNS Resolver Information Keys (RFC 9606) for DNSSEC validation capability, "dnssecval" and DNS64 synthesis, "dns64".

Introduction RFC 9606 specifies a DNS resource record (RR) type RESINFO to allow resolvers to publish information about their capabilities and policies. This information is encoded as {key, value} pairs, with each information is unambiguously identified with a key. Keys are maintained in an IANA registry. This specification adds two new keys. The first one indicates that the resolver validates with DNSSEC . Such key may be used, for example, by a DNS client to prefer resolvers that enable DNSSEC validation. The second key is used for DNS64. DNS64 is performed by a DNS resolver together with NAT64 to allow an IPv6-only client to initiate communications by name to an IPv4-only server. The new key can be used to inform DNS clients that DNS64 is performed by the DNS resolver. Note that, per the rules for the keys defined in Section 6.4 of if there is no '=' in a key, then it is a boolean attribute, simply identified as being present, with no value. The two keys are therefore simple booleans.

Requirements Language 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 when, and only when, they appear in all capitals, as shown here.

The key "dnssecval" The name of the key is "dnssecval", for "DNSSEC validating [resolver]". The presence of this key indicates that the DNS resolver validates all answers with DNSSEC . A resolver that announces this capability in a RESINFO record MAY add DNSSEC-specific EDE (Extended DNS Error Codes, ) to the value of the "exterr" key, e.g., "Unsupported DNSKEY Algorithm", "Unsupported DS Digest Type", and "DNSSEC Bogus". Refer to the "Extended DNS Error Codes" registry for a definitive list of these EDEs.

The key "dns64" The name of the key is simply "dns64". The presence of this key indicates that the DNS resolver performs address synthesis. A resolver which supports SHOULD add the dns64 key if it performs DNS64 address synthesis.

IANA Considerations This document requests IANA to add the key "dnssecval", with the explanation text "The presence of the key name indicates that DNSSEC validation is enabled", and a reference to this document to the registry "DNS Resolver Information Keys" under the "Domain Name System (DNS) Parameters" registry group. This document requests IANA to add the key "dns64", with the explanation text "The presence of the key indicates that DNS64 address synthesis is performed", and a reference to this document to the registry "DNS Resolver Information Keys" under the "Domain Name System (DNS) Parameters" registry group.

Name	Description	Reference
dnssecval	The presence of the key name indicates that DNSSEC validation is enabled.	RFC EDITOR: replace : This_Document
dns64	The presence of the key indicates that DNS64 address synthesis is performed	RFC EDITOR: replace : This_Document

Security Considerations DNSSEC is a very important tool for the security of the DNS. Therefore it is important for users to know in advance whether the resolver they consider supports DNSSEC. It would be better to assume that every resolver validates (thus rendering this document useless) but it is not the case today. Using the RESINFO mechanism solely to inform clients about the presence of DNS64 without conveying any prefix information avoids the security problems of . As with any information published in the DNS, the keys in the RESINFO may be wrong or outdated. They should be regarded with care. The security considerations discussed in Section 7 of apply.

References Normative References Informative References

Discussions and alternatives To be deleted before publication. It has been proposed to turn "dnssecval" from a boolean into a key with value (, section 4) to indicate different ways to do DNSSEC validation. For instance, the PowerDNS resolver has several levels of validation, see . At the present stage, it is the opinion of the authors that such detailed information is both difficult to standardize (different resolvers have different knobs to turn) and difficult o use since the typical consumer will have difficulty understanding them. This draft does not suggest what to do with the information provided, it is up to the consumer. This is inline with , which goal is to provide information, not guidance.

Acknowledgements Original idea by Marco Davids.