Clarifying when Standards Track Documents may Refer Normatively to Documents at a Lower Level
RFC 3967

Document Type RFC - Best Current Practice (January 2005; Errata)
Updated by RFC 4897, RFC 8067
Was draft-ymbk-downref (individual in gen area)
Authors Thomas Narten  , Randy Bush 
Last updated 2013-03-02
Stream Internent Engineering Task Force (IETF)
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IESG IESG state RFC 3967 (Best Current Practice)
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Responsible AD Harald Alvestrand
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Network Working Group                                            R. Bush
Request for Comments: 3967                                           IIJ
BCP: 97                                                        T. Narten
Category: Best Current Practice                          IBM Corporation
                                                           December 2004

          Clarifying when Standards Track Documents may Refer
               Normatively to Documents at a Lower Level

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.

Copyright Notice

   Copyright (C) The Internet Society (2004).


   IETF procedures generally require that a standards track RFC may not
   have a normative reference to another standards track document at a
   lower maturity level or to a non standards track specification (other
   than specifications from other standards bodies).  For example, a
   standards track document may not have a normative reference to an
   informational RFC.  Exceptions to this rule are sometimes needed as
   the IETF uses informational RFCs to describe non-IETF standards or
   IETF-specific modes of use of such standards.  This document
   clarifies and updates the procedure used in these circumstances.

1.  Introduction

   The Internet Standards Process [RFC2026] Section 4.2.4 specifies the

      Standards track specifications normally must not depend on other
      standards track specifications which are at a lower maturity level
      or on non standards track specifications other than referenced
      specifications from other standards bodies.

   One intent is to avoid creating a perception that a standard is more
   mature than it actually is.

Bush & Narten            Best Current Practice                  [Page 1]
RFC 3967            Document Down-Ref Clarifications       December 2004

   It should also be noted that Best Current Practice documents
   [RFC1818] have generally been considered similar to Standards Track
   documents in terms of what they can reference.  For example, a
   normative reference to an Experimental RFC has been considered an
   improper reference per [RFC2026].

1.1.  Normative References

   Within an RFC, references to other documents fall into two general
   categories: "normative" and "informative".  Broadly speaking, a
   normative reference specifies a document that must be read to fully
   understand or implement the subject matter in the new RFC, or whose
   contents are effectively part of the new RFC, as its omission would
   leave the new RFC incompletely specified.  An informative reference
   is not normative; rather, it provides only additional background

   An exact and precise definition of what is (and is not) a normative
   reference has proven challenging in practice, as the details and
   implications can be subtle.  Moreover, whether a reference needs to
   be normative can depend on the context in which a particular RFC is
   being published in the first place.  For example, in the context of
   an IETF Standard, it is important that all dependent pieces be
   clearly specified and available in an archival form so that there is
   no disagreement over what constitutes a standard.  This is not always
   the case for other documents.

   The rest of this section provides guidance on what might (and might
   not) be considered normative in the context of the IETF standards

   In the IETF, it is a basic assumption that implementors must have a
   clear understanding of what they need to implement in order to be
   fully compliant with a standard and to be able to interoperate with
   other implementations of that standard.  For documents that are
   referenced, any document that includes key information an implementer
   needs would be normative.  For example, if one needs to understand a
   packet format defined in another document in order to fully implement
   a specification, the reference to that format would be normative.
   Likewise, if a reference to a required algorithm is made, the
   reference would be normative.

   Some specific examples:

   -  If a protocol relies on IPsec to provide security, one cannot
      fully implement the protocol unless the specification for IPsec is
      available; hence, the reference would be normative.

Bush & Narten            Best Current Practice                  [Page 2]
RFC 3967            Document Down-Ref Clarifications       December 2004

      The referenced specification would likely include details about
      specific key management requirements, which transforms are
      required and which are optional, etc.

   -  In MIB documents, an IMPORTS clause by definition is a normative

   -  When a reference to an example is made, such a reference need not
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