Network Working Group                                         S. Bradner
Internet-Draft                                        Harvard University
                                                             August 1996

        Key words for use in RFCs to Indicate Requirement Levels


                    <draft-bradner-key-words-00.txt>

Status of this Memo

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Abstract
   In many standards track documents several words are used to signify
   the requirements of the specification.  These words are often
   capitalized.  This document defines these words as they should be
   interpreted in IETF documents.  Note that the force of these words is
   modified by the requirement level of the document itself.

1. MUST   This word, or the adjective "REQUIRED", means that the
   definition is an absolute requirement of the specification.

2. MUST NOT   This phrase means that the definition is an absolute
   prohibition of the specification.

3. SHOULD   This word, or the adjective "RECOMMENDED", means that there
   may exist valid reasons in particular circumstances to ignore a
   particular item, but the full implications must be understood and
   carefully weighed before choosing a different course.

4. SHOULD NOT   This phrase means that there may exist valid reasons in
   particular circumstances when the particular behavior is acceptable
   or even useful, but the full implications should be understood and



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Internet-Draft                RFC Key Words                  August 1996


   the case carefully weighed before implementing any behavior described
   with this label.

5. MAY   This word, or the adjective "OPTIONAL", means that an item is
   truly optional.  One vendor may choose to include the item because a
   particular marketplace requires it or because the vendor feels that
   it enhances the product while another vendor may omit the same item.
   An implementation which does not include a particular option MUST be
   prepared to interoperate with another implementation which does
   include the option.

6. Security Considerations
   These terms are frequently used to specify options or behavior in a
   way to maximize security risks but security itself is not addressed
   in this memo.

7. Acknowledgments
   The definitions of these terms are an amalgam of definitions taken
   from a number of RFCs.

8. Author's Address
   Scott Bradner
   Harvard University
   1350 Mass. Ave.
   Cambridge, MA 02138

   phone - +1 617 495 3864

   email - sob@harvard.edu






















Bradner                                                         [Page 2]