RFC 3514 · INFORMATIONAL · 2003
WED · 17 JUN 2026
The Security Flag in the IPv4 Header
Overview
RFC 3514, “The Security Flag in the IPv4 Header”, is an Informational document published in April 2003 by S. Bellovin. The canonical text is published by the RFC Editor.
Abstract
Firewalls, packet filters, intrusion detection systems, and the like often have difficulty distinguishing between packets that have malicious intent and those that are merely unusual. We define a security flag in the IPv4 header as a means of distinguishing the two cases. This memo provides information for the Internet community.
What “Informational” means
Published for the general information of the community. It does not define an IETF standard and carries no standards-track status.
Read this RFC
The canonical text of RFC 3514 is hosted at rfc-editor.org. Available in TXT,HTML.
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