Negative Caching of DNS Resolution Failures
RFC 9520, “Negative Caching of DNS Resolution Failures”, is a Proposed Standard document published in December 2023 by D. Wessels, W. Carroll, M. Thomas. It updates RFC 2308, RFC 4035, RFC 4697. The canonical text is published by the RFC Editor.
Abstract
In the DNS, resolvers employ caching to reduce both latency for end users and load on authoritative name servers. The process of resolution may result in one of three types of responses: (1) a response containing the requested data, (2) a response indicating the requested data does not exist, or (3) a non-response due to a resolution failure in which the resolver does not receive any useful information regarding the data's existence. This document concerns itself only with the third type.
RFC 2308 specifies requirements for DNS negative caching. There, caching of TYPE 2 responses is mandatory and caching of TYPE 3 responses is optional. This document updates RFC 2308 to require negative caching for DNS resolution failures.
RFC 4035 allows DNSSEC validation failure caching. This document updates RFC 4035 to require caching for DNSSEC validation failures.
RFC 4697 prohibits aggressive requerying for NS records at a failed zone's parent zone. This document updates RFC 4697 to expand this requirement to all query types and to all ancestor zones.
What “Proposed Standard” means
An entry-level standards-track specification: stable, peer-reviewed and a solid basis for implementation, though it may still evolve before becoming an Internet Standard.
The canonical text of RFC 9520 is hosted at rfc-editor.org. Available in HTML,TXT,PDF,XML.
- RFC 9518 Centralization, Decentralization, and Internet Standards
- RFC 9516 Active Operations, Administration, and Maintenance for Service Function Chaining
- RFC 9515 Revision to Registration Procedures for Multiple BMP Registries
- RFC 9525 Service Identity in TLS
- RFC 9514 Border Gateway Protocol - Link State Extensions for Segment Routing over IPv6
- RFC 9513 OSPFv3 Extensions for Segment Routing over IPv6
- RFC 9511 Attribution of Internet Probes
- RFC 9506 Explicit Host-to-Network Flow Measurements Techniques