RFC 8174 · BEST CURRENT PRACTICE · 2017
SUN · 14 JUN 2026
Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words
Overview
RFC 8174, “Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words”, is a Best Current Practice document published in May 2017 by B. Leiba. It updates RFC 2119. The canonical text is published by the RFC Editor.
Abstract
RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.
What “Best Current Practice” means
Documents the IETF community's recommended operational or procedural practice rather than a protocol specification.
Read this RFC
The canonical text of RFC 8174 is hosted at rfc-editor.org. Available in TXT,HTML.
Relationships to other RFCs
Other RFCs from 2017
- RFC 8173 Precision Time Protocol Version 2 Management Information Base
- RFC 8175 Dynamic Link Exchange Protocol
- RFC 8172 Considerations for Benchmarking Virtual Network Functions and Their Infrastructure
- RFC 8176 Authentication Method Reference Values
- RFC 8171 Transparent Interconnection of Lots of Links : Edge Directory Assistance Mechanisms
- RFC 8177 YANG Data Model for Key Chains
- RFC 8170 Planning for Protocol Adoption and Subsequent Transitions
- RFC 8178 Rules for NFSv4 Extensions and Minor Versions