RFC 2521 · EXPERIMENTAL · 1999
SUN · 14 JUN 2026
ICMP Security Failures Messages
Overview
RFC 2521, “ICMP Security Failures Messages”, is an Experimental document published in March 1999 by P. Karn, W. Simpson. The canonical text is published by the RFC Editor.
Abstract
This document specifies ICMP messages for indicating failures when using IP Security Protocols (AH and ESP). This document defines an Experimental Protocol for the Internet community.
What “Experimental” means
Describes a specification that is part of a research or development effort, published so the community can gain experience with it.
Read this RFC
The canonical text of RFC 2521 is hosted at rfc-editor.org. Available in TXT,HTML.
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