RFC2119 规范内容

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[RFC2119][]

[https://www.ietf.org/rfc/rfc2119.txt][https_www.ietf.org_rfc_rfc2119.txt]

Network Working Group                                         S. Bradner
    Request for Comments: 2119                            Harvard University
    BCP: 14                                                       March 1997
    Category: Best Current Practice
    
    
            Key words for use in RFCs to Indicate Requirement Levels
    
    Status of this Memo
    
       This document specifies an Internet Best Current Practices for the
       Internet Community, and requests discussion and suggestions for
       improvements.  Distribution of this memo is unlimited.
    
    Abstract
    
       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.
    
       Note that the force of these words is modified by the requirement
       level of the document in which they are used.
    
    1. MUST   This word, or the terms "REQUIRED" or "SHALL", mean that the
       definition is an absolute requirement of the specification.
    
    2. MUST NOT   This phrase, or the phrase "SHALL NOT", mean that the
       definition is an absolute prohibition of the specification.
    
    3. SHOULD   This word, or the adjective "RECOMMENDED", mean 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, or the phrase "NOT RECOMMENDED" mean 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 the case carefully weighed
       before implementing any behavior described with this label.
    
    
    
    
    
    Bradner                  Best Current Practice                  [Page 1]
    
    RFC 2119                     RFC Key Words                    March 1997
    
    
    5. MAY   This word, or the adjective "OPTIONAL", mean 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, though perhaps with reduced functionality. In the
       same vein an implementation which does include a particular option
       MUST be prepared to interoperate with another implementation which
       does not include the option (except, of course, for the feature the
       option provides.)
    
    6. Guidance in the use of these Imperatives
    
       Imperatives of the type defined in this memo must be used with care
       and sparingly.  In particular, they MUST only be used where it is
       actually required for interoperation or to limit behavior which has
       potential for causing harm (e.g., limiting retransmisssions)  For
       example, they must not be used to try to impose a particular method
       on implementors where the method is not required for
       interoperability.
    
    7. Security Considerations
    
       These terms are frequently used to specify behavior with security
       implications.  The effects on security of not implementing a MUST or
       SHOULD, or doing something the specification says MUST NOT or SHOULD
       NOT be done may be very subtle. Document authors should take the time
       to elaborate the security implications of not following
       recommendations or requirements as most implementors will not have
       had the benefit of the experience and discussion that produced the
       specification.
    
    8. Acknowledgments
    
       The definitions of these terms are an amalgam of definitions taken
       from a number of RFCs.  In addition, suggestions have been
       incorporated from a number of people including Robert Ullmann, Thomas
       Narten, Neal McBurnett, and Robert Elz.
    
    
    
    
    Bradner                  Best Current Practice                  [Page 2]
    
    RFC 2119                     RFC Key Words                    March 1997
    
    
    9. Author's Address
    
          Scott Bradner
          Harvard University
          1350 Mass. Ave.
          Cambridge, MA 02138
    
          phone - +1 617 495 3864
    
          email - sob@harvard.edu
    
    
    Bradner                  Best Current Practice                  [Page 3]

转载于:https://www.cnblogs.com/onelikeone/p/10996314.html

[RFC2119]: http://www.ietf.org/rfc/rfc2119.txt
[https_www.ietf.org_rfc_rfc2119.txt]: https://www.ietf.org/rfc/rfc2119.txt