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

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.

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.





















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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
  Provisions Relating to IETF Documents
  (http://trustee.ietf.org/license-info) in effect on the date of
  publication of this document.  Please review these documents
  carefully, as they describe your rights and restrictions with respect
  to this document.  Code Components extracted from this document must
  include Simplified BSD License text as described in Section 4.e of
  the Trust Legal Provisions and are provided without warranty as
  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," which has caused confusion about
  how to interpret non-capitalized words such as "must" and "should".

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

















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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 in all capitals
  as shown below, are used to signify the requirements in the
  specification.  These capitalized words can bring significant clarity
  and consistency to documents because their meanings are well defined.
  This document defines how those words are interpreted in IETF
  documents when the words are in all capitals.

  o  These 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.  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 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 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", "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.

  === END ===





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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: [email protected]
  URI:   http://internetmessagingtechnology.org/



























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