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
draft-ymbk-downref-02.txt
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Abstract
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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circumstances.
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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
reference.
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",
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
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