Network Working Group                                            R. Bush
Internet-Draft                                                       IIJ
Updates: 2026 (if approved)                                    T. Narten
Expires: August 16, 2004 January 2005                                    IBM Corporation
                                                           April 8,
                                                           July 19, 2004

   Clarifying when Standards Track Documents may Refer Normatively to
                       Documents at a Lower Level
                       draft-ymbk-downref-02.txt
                       draft-ymbk-downref-03.txt

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3667.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on August 16, December 11, 2004.

Copyright Notice

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

Abstract

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

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

   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

   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  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 and whose in the sense that its
   omission would leave the new RFC incompletely specified.  An
   informative reference is not normative; rather, it provides only additional
   additional, background information.

   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. Morever, 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 an
   informative reference might provide background or historical
   information, or provide an example of possible usage.  Material IETF
   Standard's context, it is important that all dependent pieces be
   clearly specified and available in an
   informative reference archival form, so that there is
   no disagreement over what constitutes a standard. This is not required to always
   the case for other documents.

   The rest of this section provides guidance on what might (and might
   not) be read in order to
   understand subject matter considered normative in the RFC. context of the IETF standards
   process.

   In the case IETF, it is a basic assumption that implementors must have a
   clear understanding of protocols, what they need to implement in order to be
   fully compliant with a reference is normative if it refers standard and to
   packet formats or be able to interoperate with
   other protocol mechanisms implementations of that standard. For documents that are needed
   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 protocol in reference to that format would be normative.
   Likewise, if a reference to a required algorithm is made, the current specification.  For example,
   reference would be normative.

   Some specific examples:

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

      - in the case of MIB documents, an IMPORTS clause by definition is
        a normative reference.

      - when a reference to an example is made, such a reference need
        not be normative. For example, text such as "an algorithm such
        as the one specified in [RFCxxx] would be acceptable" indicates
        an informative reference, since that cited algorithm is just one
        of several possible algorithms that could be used.

2. The Need for Downward References

   There are a number of circumstances where an IETF document may need
   to make a normative reference to a document at a lower maturity level may be needed.
   level, but such a reference is in conflict with Section 4.2.4 of
   [RFC2026]. For example:

   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.
   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 down reference to a particular document has been set
   (i.e.,
   accepted by the same exception community (e.g., has been made for a particular reference a
   few times), the need for mentioned in several Last
   Calls), an explicit mention of Area Director may waive subsequent notices in the issue during Last
   Call may be waived. of down references to it. This should only occur when the same
   document (and version) are being referenced and when the AD believes
   that the document's use is an accepted part of the community's
   understanding of the relevant technical area.  For example, the use
   of MD5 [RFC1321] and HMAC [RFC2104] is well known among
   cryptographers.

   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
   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.
   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.

5. Acknowledgments

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

Normative References

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

Informative References

   [RFC1818] Best Current Practices, J. Postel, T. Li, Y. Rekhter. RFC
              1818, August 1995.

   [2223bis]  "Instructions to Request for Comments (RFC) Authors",
              draft-rfc-editor-rfc2223bis-07.txt.

   [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
              1997.

   [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
   IIJ
   5147 Crystal Springs
   Bainbridge Island, WA  98110
   US

   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
   US

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

Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.

Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgment

   Funding for the RFC Editor function is currently provided by the
   Internet Society.