IP Fragmentation Avoidance in DNS over UDP
RFC 9715, “IP Fragmentation Avoidance in DNS over UDP”, is an Informational document published in January 2025 by K. Fujiwara, P. Vixie. The canonical text is published by the RFC Editor.
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.
What “Informational” means
Published for the general information of the community. It does not define an IETF standard and carries no standards-track status.
The canonical text of RFC 9715 is hosted at rfc-editor.org. Available in HTML,TXT,PDF,XML.
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