One document matched: draft-hoffman-additional-key-words-00.txt

Network Working Group                                         P. Hoffman
Internet-Draft                                            VPN Consortium
Updates: 2119 (if approved)                             January 15, 2008
Expires: July 18, 2008


          Additional Key words to Indicate Requirement Levels
               draft-hoffman-additional-key-words-00.txt

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Copyright Notice

   Copyright (C) The IETF Trust (2008).

Abstract

   Some document authors want to express requirement levels using the
   traditional definitions of "MUST" and "SHOULD" from RFC 2119, but
   also want to express that there is an expectation that later versions
   of the document may change those requirements.  For example, they may
   want to express "this SHOULD be implemented now, but we expect that
   this will become a MUST requirement in a future update to this
   standard".




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   This document defines three new keywords, "MUST-", "SHOULD+", and
   "SHOULD-" to facilitate such definitions.


1.  Introduction

   RFC 2119 [RFC2119] defines keywords that are used in the RFC series.
   Using those definitions allows a document writer to specify the
   requirements level in a generally-understood manner.  However, in
   some protocols, the authors want to convey that the requirements
   levels are expected to change in the future.

   There are three requirements level changes that can be easily
   envisioned:

   o  A MUST requirement that is expected to be demoted to SHOULD in the
      future.

   o  A SHOULD requirement that is expected to be elevated to MUST in
      the future.

   o  A SHOULD requirement that is expected to be demoted to MAY in the
      future.

   RFC 4307 [RFC4307] defined new terms for these three states.  The
   purpose of defining new terms in RFC 4307 was to alert implementers
   that there was a widespread expectation that some of the
   cryptographic algorithms that were listed as SHOULD-level in the
   document were expected to become MUST-level in a few years;
   similarly, there was a widespread expectation that some of the MUST-
   level algorithms would be demoted to SHOULD-level in a few years.

   Since then, other RFCs and Internet Drafts have re-used those
   definitions.  This document provides stand-alone definitions based on
   RFC 4307, and explicitly updates RFC 2119.  It is important to note
   that this document does not change any of the definitions in RFC
   2119; it only adds new ones.


2.  Definitions of MUST-, SHOULD+, and SHOULD-

   Three new terms are defined:









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   MUST-      This term means the same as MUST.  However, the authors
              expect that this requirement will no longer be a MUST in
              a future revision of this document.  Although its status
              will be determined at a later time, it is reasonable to
              expect that if a future update this document alters the
              status of a MUST- requirement, it will remain at least a
              SHOULD or a SHOULD-.

   SHOULD+    This term means the same as SHOULD.  However, the authors
              expect that a requirement marked as SHOULD+ will be
              promoted at some future time to be a MUST.

   SHOULD-    This term means the same as SHOULD.  However, the authors
              expect a requirement marked as SHOULD- will be demoted to
              a MAY in a future version of this document.


3.  Acknowledgements

   The definitions here are based on those in RFC 4107, which was
   authored by Jeff Schiller.  The genesis for the idea of requirements
   language that includes foreshadowing of changes came from Russ
   Housley during the discussion of RFC 4107.


4.  Security Considerations

   There are no security considerations specific to the new definitions.


5.  References

5.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

5.2.  Informative References

   [RFC4307]  Schiller, J., "Cryptographic Algorithms for Use in the
              Internet Key Exchange Version 2 (IKEv2)", RFC 4307,
              December 2005.


Appendix A.  Change History

   [[ This entire section is to be removed upon publication. ]]




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   This is the first version of the document.


Author's Address

   Paul Hoffman
   VPN Consortium
   127 Segre Place
   Santa Cruz, CA  95060
   US

   Phone: 1-831-426-9827
   Email: paul.hoffman@vpnc.org






































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