< draft-ymbk-downref-02.txt   draft-ymbk-downref-03.txt >
Network Working Group R. Bush Network Working Group R. Bush
Internet-Draft IIJ Internet-Draft IIJ
Updates: 2026 (if approved) T. Narten Updates: 2026 (if approved) T. Narten
Expires: August 16, 2004 IBM Corporation Expires: January 2005 IBM Corporation
April 8, 2004 July 19, 2004
Clarifying when Standards Track Documents may Refer Normatively to Clarifying when Standards Track Documents may Refer Normatively to
Documents at a Lower Level Documents at a Lower Level
draft-ymbk-downref-02.txt draft-ymbk-downref-03.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed, 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 and any of which I become aware will be disclosed, in accordance with
RFC 3667. RFC 3667.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other Task Force (IETF), its areas, and its working groups. Note that other
skipping to change at page 1, line 35 skipping to change at page 1, line 35
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This Internet-Draft will expire on August 16, 2004. This Internet-Draft will expire on December 11, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract Abstract
IETF procedures generally require that a standards track RFC may not IETF procedures generally require that a standards track RFC may not
have a normative reference to a document at a lower standards level. have a normative reference to another standards track document at a
For example a standards track document may not have a normative lower maturity level or to a non standards track specification (other
reference to an informational RFC. There are needs for exceptions to than specifications from other standards bodies). For example a
this rule, often caused by the IETF using informational RFCs to standards track document may not have a normative reference to an
describe non-IETF standards, or IETF-specific modes of use of such informational RFC. There are needs for exceptions to this rule,
standards. This document clarifies the procedure used in these 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 and updates the procedure used in these
circumstances. circumstances.
1. Normative References Expected to be to Equal or Higher Level 1. Normative References Expected to be to Equal or Higher Level
The Internet Standards Process [RFC2026] Section 4.2.4 specifies: The Internet Standards Process [RFC2026] Section 4.2.4 specifies:
Standards track specifications normally must not depend on other Standards track specifications normally must not depend on other
standards track specifications which are at a lower maturity level standards track specifications which are at a lower maturity level
or on non standards track specifications other than referenced or on non standards track specifications other than referenced
specifications from other standards bodies. specifications from other standards bodies.
One intent is to avoid creating a perception that a standard is more One intent is to avoid creating a perception that a standard is more
mature than it actually is. mature than it actually is.
1.1 Definitions of Normative References 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].
Note: this section is adapted from the RFC Editor's definition of 1.1 Normative References
"normative" as given in [RFC2223bis].
Within an RFC, references to other documents fall into two general Within an RFC, references to other documents fall into two general
categories: "normative" and "informative". Normative references categories: "normative" and "informative". Broadly speaking, a
specify documents that must be read to understand or implement the normative reference specifies a document that must be read to fully
subject matter in the new RFC, or whose contents are effectively part understand or implement the subject matter in the new RFC, or whose
of the new RFC and whose omission would leave the new RFC contents are effectively part of the new RFC in the sense that its
incompletely specified. An informative reference is not normative; omission would leave the new RFC incompletely specified. An
rather, it provides only additional information. For example, an informative reference is not normative; rather, it provides only
informative reference might provide background or historical additional, background information.
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 An exact and precise definition of what is (and is not) a normative
packet formats or other protocol mechanisms that are needed to fully reference has proven challenging in practice, as the details and
implement the protocol in the current specification. For example, if implications can be subtle. Morever, whether a reference needs to be
a protocol relies on IPsec to provide security, one cannot fully normative can depend on the context in which a particular RFC is
implement the protocol without the specification for IPsec also being being published in the first place. For example, in an IETF
available; hence, the reference would be normative. In the case of Standard's context, it is important that all dependent pieces be
MIB documents, an IMPORTS clause by definition is a normative clearly specified and available in an archival form, so that there is
reference. 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
process.
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 without the specification for IPsec
also being available; hence, the reference would be normative.
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 2. The Need for Downward References
There are a number of circumstances where a normative reference to a There are a number of circumstances where an IETF document may need
document at a lower maturity level may be needed. to make a normative reference to a document at a lower maturity
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 o A standards track document may need to refer to a protocol or
algorithm developed by an external body but modified, adapted, or algorithm developed by an external body but modified, adapted, or
profiled by an IETF informational RFC, for example MD5 [RFC1321] profiled by an IETF informational RFC, for example MD5 [RFC1321]
and HMAC [RFC2104]. Note that this does not override the IETF's and HMAC [RFC2104]. Note that this does not override the IETF's
duty to see that the specification is indeed sufficiently clear to duty to see that the specification is indeed sufficiently clear to
enable creation of interoperable implementations. enable creation of interoperable implementations.
o A standards document may need to refer to a proprietary protocol, o A standards document may need to refer to a proprietary protocol,
and the IETF normally documents proprietary protocols using and the IETF normally documents proprietary protocols using
informational RFCs. informational RFCs.
o A migration or co-existence document may need to define a o A migration or co-existence document may need to define a
standards track mechanism for migration from, and/or co-existence standards track mechanism for migration from, and/or co-existence
with, an historic protocol, a proprietary protocol, or possibly a with, an historic protocol, a proprietary protocol, or possibly a
non-standards track protocol. non-standards track protocol.
o There are exceptional procedural or legal reasons which force the o There are exceptional procedural or legal reasons which force the
target of the normative reference to be an informational or target of the normative reference to be an informational or
historical RFC, or for it to be at a lower standards level than historical RFC, or for it to be at a lower standards level than
the referring document. the referring document.
o A BCP document may want to describe best current practices for
o A BCP document may want to describe best current practices for
experimental or informational specifications. experimental or informational specifications.
3. The Procedure to be Used 3. The Procedure to be Used
For Standards Track or BCP documents requiring normative reference to For Standards Track or BCP documents requiring normative reference to
documents of lower maturity, the normal IETF Last Call procedure will documents of lower maturity, the normal IETF Last Call procedure will
be issued, with the need for the downward reference explicitly be issued, with the need for the downward reference explicitly
documented in the Last Call itself. Any community comments on the documented in the Last Call itself. Any community comments on the
appropriateness of downward references will be considered by the IESG appropriateness of downward references will be considered by the IESG
as part of its deliberations. Once a specific precedent has been set as part of its deliberations.
(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 Once a specific down reference to a particular document has been
Call may be waived. accepted by the community (e.g., has been mentioned in several Last
Calls), an Area Director may waive subsequent notices in the Last
Call 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 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 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 appropriate category. I.e., this is not intended as an easy way out
of normal process. Rather, it is intended for dealing with specific of normal process. Rather, it is intended for dealing with specific
cases where putting particular documents into the required category cases where putting particular documents into the required category
is problematical and unlikely to ever happen. is problematical and unlikely to ever happen.
4. BCPs and Experimental Protocols 4. Security Considerations
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 This document is not known to create any new vulnerabilities for the
internet. On the other hand, inappropriate or excessive use of the Internet. On the other hand, inappropriate or excessive use of the
process might be considered a down-grade attack on the quality of process might be considered a down-grade attack on the quality of
IETF standards, or worse, on the rigorous review of security aspects IETF standards, or worse, on the rigorous review of security aspects
of standards. of standards.
6. Acknowledgments 5. Acknowledgments
This document is the result of discussion within the IESG, with This document is the result of discussion within the IESG, with
particular contribution by Harald Alvestrand, Steve Bellovin, Scott particular contribution by Harald Alvestrand, Steve Bellovin, Scott
Bradner, Ned Freed, Jeff Schiller, and Bert Wijnen. Bradner, Ned Freed, Allison Mankin, Jeff Schiller, and Bert Wijnen.
Normative References Normative References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996. 3", BCP 9, RFC 2026, October 1996.
Informative References Informative References
[RFC1818] Best Current Practices, J. Postel, T. Li, Y. Rekhter. RFC
1818, August 1995.
[2223bis] "Instructions to Request for Comments (RFC) Authors", [2223bis] "Instructions to Request for Comments (RFC) Authors",
draft-rfc-editor-rfc2223bis-07.txt. draft-rfc-editor-rfc2223bis-07.txt.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
April 1992. April 1992.
[RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, February Hashing for Message Authentication", RFC 2104, February
1997. 1997.
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