RFC 9715

IP Fragmentation Avoidance in DNS over UDP, January 2025

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Status:
INFORMATIONAL
Authors:
K. Fujiwara
P. Vixie
Stream:
IETF
Source:
dnsop (ops)

Cite this RFC: TXT  |  XML  |   BibTeX

DOI:  https://doi.org/10.17487/RFC9715

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Abstract

The widely deployed Extension Mechanisms for DNS (EDNS(0)) feature in the DNS enables a DNS receiver to indicate its received UDP message size capacity, which supports the sending of large UDP responses by a DNS server. Large DNS/UDP messages are more likely to be fragmented, and IP fragmentation has exposed weaknesses in application protocols. It is possible to avoid IP fragmentation in DNS by limiting the response size where possible and signaling the need to upgrade from UDP to TCP transport where necessary. This document describes techniques to avoid IP fragmentation in DNS.


For the definition of Status, see RFC 2026.

For the definition of Stream, see RFC 8729.




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