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Versions: 00 01 02 03 RFC 3967

Network Working Group                                            R. Bush
Internet-Draft                                                       IIJ
Updates: 2026 (if approved)                                    T. Narten
Expires: August 16, 2004                                 IBM Corporation
                                                           April 8, 2004

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

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2004). All Rights Reserved.


   IETF procedures generally require that a standards track RFC may not
   have a normative reference to a document at a lower standards level.
   For example a standards track document may not have a normative
   reference to an informational RFC.  There are needs for exceptions to
   this rule, often caused by the IETF using informational RFCs to
   describe non-IETF standards, or IETF-specific modes of use of such
   standards. This document clarifies the procedure used in these

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1. Normative References Expected to be to Equal or Higher Level

   The Internet Standards Process [RFC2026] Section 4.2.4 specifies:

   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.

1.1 Definitions of Normative References

   Note: this section is adapted from the RFC Editor's definition of
   "normative" as given in [RFC2223bis].

   Within an RFC, references to other documents fall into two general
   categories: "normative" and "informative".  Normative references
   specify documents that must be read to understand or implement the
   subject matter in the new RFC, or whose contents are effectively part
   of the new RFC and whose omission would leave the new RFC
   incompletely specified.  An informative reference is not normative;
   rather, it provides only additional information.  For example, an
   informative reference might provide background or historical
   information, or provide an example of possible usage.  Material in an
   informative reference is not required to be read in order to
   understand subject matter in the RFC.

   In the case of protocols, a reference is normative if it refers to
   packet formats or other protocol mechanisms that are needed to fully
   implement the protocol in the current specification.  For example, if
   a protocol relies on IPsec to provide security, one cannot fully
   implement the protocol without the specification for IPsec also being
   available; hence, the reference would be normative.  In the case of
   MIB documents, an IMPORTS clause by definition is a normative

2. The Need for Downward References

   There are a number of circumstances where a normative reference to a
   document at a lower maturity level may be needed.
   o  A standards track document may need to refer to a protocol or
      algorithm developed by an external body but modified, adapted, or
      profiled by an IETF informational RFC, for example MD5 [RFC1321]
      and HMAC [RFC2104]. Note that this does not override the IETF's
      duty to see that the specification is indeed sufficiently clear to
      enable creation of interoperable implementations.

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   o  A standards document may need to refer to a proprietary protocol,
      and the IETF normally documents proprietary protocols using
      informational RFCs.
   o  A migration or co-existence document may need to define a
      standards track mechanism for migration from, and/or co-existence
      with, an historic protocol, a proprietary protocol, or possibly a
      non-standards track protocol.
   o  There are exceptional procedural or legal reasons which force the
      target of the normative reference to be an informational or
      historical RFC, or for it to be at a lower standards level than
      the referring document.
   o A BCP document may want to describe best current practices for
      experimental or informational specifications.

3. The Procedure to be Used

   For Standards Track or BCP documents requiring normative reference to
   documents of lower maturity, the normal IETF Last Call procedure will
   be issued, with the need for the downward reference explicitly
   documented in the Last Call itself.  Any community comments on the
   appropriateness of downward references will be considered by the IESG
   as part of its deliberations.  Once a specific precedent has been set
   (i.e., the same exception has been made for a particular reference a
   few times), the need for an explicit mention of the issue during Last
   Call may be waived.

   This procedure should not be used when the appropriate step to take
   is to move the document to which the reference is being made into the
   appropriate category. I.e., this is not intended as an easy way out
   of normal process. Rather, it is intended for dealing with specific
   cases where putting particular documents into the required category
   is problematical and unlikely to ever happen.

4. BCPs and Experimental Protocols

   Best Current Practice documents 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 [2026]. Recently, the
   mboned Working Group wanted to publish BCPs on multicast issues. But
   many of the protocols are Experimental and are not expected to be
   moved onto the Standards Track (e.g., [RFC2362]). Thus, the
   Experimental protocols represent what is being used, and it is useful
   to publish BCP documents that refer to them. This document
   explicitely allows BCP documents to contain normative references to
   non-Standards Track documents. Also, it should be noted that the
   current practice has been that BCPs can reference Proposed Standards,
   and because BCPs have no concept of "advancing in grade", there are

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   no down-reference issues when a BCP refers to a document on the
   Standards Track.

5. Security Considerations

   This document is not known to create any new vulnerabilities for the
   internet.  On the other hand, inappropriate or excessive use of the
   process might be considered a down-grade attack on the quality of
   IETF standards, or worse, on the rigorous review of security aspects
   of standards.

6. Acknowledgments

   This document is the result of discussion within the IESG, with
   particular contribution by Harald Alvestrand, Steve Bellovin, Scott
   Bradner, Ned Freed, Jeff Schiller, and Bert Wijnen.

Normative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

Informative References

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   [2223bis]  "Instructions to Request for Comments (RFC) Authors",

   [RFC1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
              April 1992.

   [RFC2104]  Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, February

   [RFC2362] Protocol Independent Multicast-Sparse Mode (PIM-SM):
              Protocol Specification. D. Estrin, D. Farinacci, A. Helmy,
              D. Thaler, S.  Deering, M. Handley, V. Jacobson, C. Liu,
              P. Sharma, L. Wei. June 1998.

Authors' Addresses

   Randy Bush
   5147 Crystal Springs
   Bainbridge Island, WA  98110

   Phone: +1 206 780 0431
   EMail: randy@psg.com
   URI:   http://psg.com/~randy/

   Thomas Narten
   IBM Corporation
   P.O. Box 12195
   Research Triangle Park, NC  27709-2195

   Phone: +1 919 254 7798
   EMail: narten@us.ibm.com

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