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General Internet Engineering Task Force DNS EDE This document is the specification of three new EDE (Extended DNS Errors) codes, for minimal answers, local roots and tailoring based on the client IP address.

Introduction created the EDE (Extended DNS Errors). Each error is identified by a code, and there is an IANA registry of these codes. This specification adds four codes:

• One to say that the response has been tailored from the IP address of the end-client, for instance through ECS (EDNS Client Subnet),
• One to say that the response was deliberately minimal,
• One to say that the response comes from a local root.
• One to say that the request was rejected because of rate-limiting.

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.

Tailoring This response code, TBD, means that the response has been tailored on the basis of the IP address of the client. It can be from its actual IP address in the query (DNS-based load balancing), or because of ECS (EDNS Client Subnet, ). It MAY be sent by authoritative servers or resolvers, for instance when they implement ECS. Note that the fact that the server accepts ECS can also be seen in the EDNS part of the response, but it does not mean that ECS was actually used to tailor the answer. Also, this response code is more general than just ECS. To differentiate between the type of tailoring, the EXTRA-TEXT field MAY be used. If a resolver receives this EDE from an authoritative server, it SHOULD copy it in the response sent to its client.

Minimal response This response code, TBD, means that the response was deliberately minimal. It can be because the request was using the QTYPE ANY, as documented by . Or it can be also for cases like "glue records not sent since I wanted to save bits". It MAY be sent by authoritative servers or resolvers.

Local root This response code, TBD, means that the response comes from a local root, as documented in . It MAY be sent by resolvers using a local root.

Rate-limiting This response code, TBD, means that the request was rejected because the DNS client queries too much . It MAY be sent by resolvers or authoritative name servers, probably together with a REFUSED response code.

IANA Considerations IANA is requested to allocate codes to these four EDE and to add them to the "Extended DNS Error Codes", with a reference to this document. Note that the policy for the registry "Extended DNS Error Codes" is just "First come, first served" so this document is not strictly necessary.

Security Considerations The EDE are sent with EDNS and are not signed. They should be used with care (see , section 6).

References Normative References Informative references ISC

Surveys of implementors This appendix lists the various issues open againt diverse DNS programs, to gather input from the implementors about these new EDE.

• Knot resolver
• PowerDNS, PowerDNS recursor and dnsdist
• Knot
• BIND
• Unbound

Acknowledgements Original idea by Marco Davids.