DNS Resolver Information Key for DNS64

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Table of Contents

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.¶

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.¶

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.¶

6. References

Author's Address