Internet Engineering Task Force (IETF)                          B. Leiba
Request for Comments: 8174                           Huawei Technologies
BCP: 14                                                         May 2017
Updates: 2119
Category: Best Current Practice
ISSN: 2070-1721

       Ambiguity of Uppercase vs Lowercase in

        RFC 2119 Key Words Words: Clarifying the Use of Capitalization

Abstract

   RFC 2119 specifies common key words that may be used in protocol
   specifications.  This document aims to reduce the ambiguity by clarifying
   that the definitions in RFC 2119 apply only to UPPERCASE usage forms of the key words have the
   defined special meanings.
   these words.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   BCPs is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8174.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Clarifying Capitalization of Key Words  . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   RFC 2119 specifies common key words, such as "MUST", "SHOULD", and "MAY",
   that may be used in protocol specifications.  It says that the key
   words "are often capitalized," capitalized", which has caused confusion about how
   to interpret non-capitalized words lowercase forms of these words, such as "must" and
   "should".

   This document updates RFC 2119 by clarifying that the specified
   definitions apply only to UPPERCASE
   usage uses of the key words have the defined special meanings. these words.  This
   document is part of BCP 14.

2.  Clarifying Capitalization of Key Words

   The following change is made to [RFC2119]:

   === OLD ===
   In many standards track documents several words are used to signify
   the requirements in the specification.  These words are often
   capitalized.  This document defines these words as they should be
   interpreted in IETF documents.  Authors who follow these guidelines
   should incorporate this phrase near the beginning of their document:

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.

   === NEW ===
   In many IETF documents, several words, when they are specific words (see below) may appear in all
   capitals
   as shown below, are used to signify the requirements in the a given specification.  These
   capitalized words can bring significant clarity and consistency to
   IETF documents because their meanings are well defined. overtly specified.  This
   document defines describes how those the capitalized words are interpreted in IETF
   documents to be interpreted.

   Please note:

   o  The meanings specified herein apply only when the words are appear in
      all capitals.

   o  These  The meanings specified herein do not apply when the words appear
      in lowercase.

   o  Using these capitalized key words can be used as defined here, but using them is not required.  Specifically,
      normative text does not require the use
      of these key words. their use.  They are used for
      clarity and consistency when that is what's wanted, but a lot of
      normative text does not use them and is still nonetheless normative.

   o  The words have the meanings specified herein only when they are in
      all capitals.

   o  When these words are not capitalized, they have their normal
      English meanings and are not affected by this document.

   Authors who follow these the guidelines above should incorporate this
   phrase near the beginning of their document:

      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
      NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
      "MAY", and "OPTIONAL" in this document are to be interpreted as
      described in BCP 14 [RFC2119] [RFC8174] when, and only when, they
      appear in all capitals, as shown here. in this paragraph.

   === END ===

3.  IANA Considerations

   This document does not require any IANA actions.

4.  Security Considerations

   This document is purely procedural; there are no related security
   considerations.

5.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

Author's Address

   Barry Leiba
   Huawei Technologies

   Phone: +1 646 827 0648
   Email: barryleiba@computer.org
   URI:   http://internetmessagingtechnology.org/