draft-kucherawy-bcp97bis.xml

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<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
  <!ENTITY RFC1321 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.1321.xml">
  <!ENTITY RFC2026 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2026.xml">
  <!ENTITY RFC2104 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2104.xml">
  <!ENTITY RFC3967 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.3967.xml">
  <!ENTITY RFC4858 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.4858.xml">
  <!ENTITY RFC4897 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.4897.xml">
  <!ENTITY RFC8067 PUBLIC "" "http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8067.xml">
]>

<rfc ipr="trust200902" category="bcp" obsoletes="3967, 4897, 8067"
        docName="draft-kucherawy-bcp97bis-02">

<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>

<?rfc toc="yes" ?>
<?rfc tocdepth="4" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc compact="yes" ?>
<?rfc subcompact="no"?>

<front>
	<title abbrev="downref">
		Procedures for Standards Track Documents to Refer
		Normatively to Documents at a Lower Level
	</title>

	<author initials="M." surname="Kucherawy"
	        fullname="Murray Kucherawy"
		role="editor">

		<address>
			<email>superuser@gmail.com</email>
		</address>
	</author>

	<date year="2021"/>

	<area>General</area>

	<keyword>internet-drafts</keyword>

	<abstract>
		<t> 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 defines
		    the procedure used in these circumstances. </t>

		<t> This document merges and updates, and thus obsoletes,
		    RFC 3967, RFC 4897, and RFC 8067. </t>
	</abstract>
</front>

<middle>
	<section anchor="intro" title="Introduction">
		<t> The Internet Standards Process <xref target="RFC2026"/>
		    (BCP 9) Section 4.2.4 specifies the following:

			<figure><artwork>
  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.
			</artwork></figure></t>

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

		<t> It should also be noted that Best Current Practice
		    documents (BCPs; see <xref target="RFC2026"/>) have
		    generally been considered similar to Standards Track
		    documents in terms of what they can reference.  For
		    example, a normative reference from a BCP to an
		    Experimental RFC has been considered an
		    improper reference. </t>

		<t> This document describes a process for allowing
		    normative references to documents at lower maturity
		    levels ("downrefs"), after due notice and consideration
		    as the document progresses toward publication.  The
		    original process was defined in <xref target="RFC3967"/>
		    and later amended by <xref target="RFC4897"/> and
		    <xref target="RFC8067"/>.  This document consolidates
		    those, and presents further guidance regarding normative
		    references to non-IETF documents. </t>

		<section anchor="normative" title="Normative References">
			<t> 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 RFC, or whose contents are
			    effectively part of the RFC, as its omission
			    would leave the RFC incompletely specified.
			    An informative reference is not normative; rather,
			    it provides only additional background
			    information. </t>

			<t> 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. </t>

			<t> The rest of this section provides guidance on what
			    might (and might not) be considered normative in
			    the context of the IETF standards process. </t>

			<t> In the IETF, it is a basic assumption that
			    implementers 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. </t>

			<t> Some specific examples:
			    <list style="symbols">
				<t> 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.  The referenced
				    specification would likely include details
				    about specific key management
				    requirements, which transforms are
				    required and which are optional, etc. </t>

				<t> In YANG documents, any "import" or
				    "include" statement by definition is a
				    normative reference. </t>

				<t> 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 [RFCxxxx]
				    would be acceptable" indicates an
				    informative reference, since that cited
				    algorithm is just one of several possible
				    algorithms that could be used. </t>
			    </list> </t>
		</section>
	</section>

	<section anchor="need" title="The Need for Downward References">
		<t> There are a number of circumstances in which an
		    IETF document may need to make a normative
		    reference to a document at a lower maturity level,
		    but such a reference conflicts with Section 4.2.4
		    of <xref target="RFC2026"/>.  For example:

		    <list style="symbols">
			<t> 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 <xref target="RFC1321"/>
			    and HMAC <xref target="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. </t>

			<t> A standards document may need to refer
			    to a proprietary protocol, and the IETF
			    normally documents proprietary protocols
			    using informational RFCs. </t>

			<t> 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. </t>

			<t> There are exceptional procedural or legal
			    reasons that force the target of the
			    normative reference to be an informational
			    or historical RFC or to be at a lower
			    standards level than the referring
			    document. </t>

			<t> A BCP document may want to describe best
			    current practices for experimental or
			    informational specifications. </t>
		    </list> </t>
	</section>

	<section anchor="definitions" title="Definitions">
		<t> A reference involves two documents, the one in which the
		    reference is embedded and the document referenced.  Where
		    needed for clarity, these documents are referred to as
		    the "source document" and "target document",
		    respectively. </t>

		<t> The term "Standards-Track document", as used in this
		    specification, is assumed to include only Standards-Track
		    documents at any maturity level, plus BCPs, but not
		    documents with any other status. </t>
	</section>

	<section anchor="procedure" title="Procedure">
		<t> The following sections describe the procedures to be used
		    by authors/editors and the IESG when handling downrefs. </t>

		<section anchor="auths_eds" title="Authors and Editors">
			<t> When a Standards-Track or BCP document requires
			    a normative reference to a document of lower
			    maturity, the authors/editors should apply the
			    following very simple procedure:

			    <list style="symbols">
				<t> The reference text (i.e., in the "Normative
				    References" section of the source
				    document) is written as usual. </t>

				<t> A note is included in the reference text
				    that indicates that the reference is to a
				    target document of a lower maturity level,
				    that some caution should be used since it
				    may be less stable than the document from
				    which it is being referenced, and,
				    optionally, explaining why the
				    downref is appropriate. </t>
			    </list></t>

			<t> The Internet Engineering Steering Group (IESG)
			    may, at its discretion, specify the exact text to
			    be used, establish procedures regarding the text
			    to use, or give guidance on this text.  When
			    establishing procedures, the IESG should seek
			    appropriate community review. </t>

			<t> These annotations are part of the source
			    document.  If members of the community consider
			    either the downref or the annotation
			    text to be inappropriate, those issues can be
			    raised at any time during the document life cycle,
			    just as with any other text in the document.
			    There is no separate review of these
			    references.  For example, when the downref
			    is to a document of a lower maturity level that
			    is understood to be stable, the annotation can
			    be omitted.  Such decisions should be noted in
			    the document shepherd writeup
			    <xref target="RFC4858"/> so the IESG is aware
			    at the time of its review why the annotation
			    is absent. </t>

			<t> At the option of the author/editor, similar notes
			    may be attached to non-normative references. </t>
		</section>

		<section anchor="iesg" title="The IESG">
			<t> With appropriate community review, the IESG may
			    establish procedures for when normative downref
			    should delay a document and when downrefs should
			    be noted.  Absent specific guidance, authors and
			    reviewers should use their best judgment.  It is
			    assumed that, in a significant majority of cases,
			    noting a downref is preferable to delaying
			    publication. </t>

			<t> When a document is presented to the IESG for
			    publication that contains a downref not called out
			    by the author/editor(s) as described in the
			    previous section, it is strongly recommended
			    that the normal IETF Last Call
			    procedure will be issued, with the need for the
			    downref explicitly documented in the
			    Last Call itself.  Any community comments on the
			    appropriateness of downrefs will be considered by
			    the IESG as part of its deliberations. </t>

			<t> If, by oversight, the Last Call does not identify
			    the downref, the IESG may choose to repeat the
			    Last Call with the downref properly
			    identified.  If it elects not to do so, then any
			    future downref to the same target document is
			    subject again to the procedures described in this
			    document.  In making this decision, the IESG
			    should take into account the general discussion
			    in <xref target="need"/>. </t>

			<t> Once a specific downref to a particular document
			    has been accepted by the community (e.g., has been
			    mentioned in one or more Last Calls), an Area
			    Director may waive subsequent notices in the Last
			    Call of downrefs to it.  This should only occur
			    when the same document (and version) are being
			    referenced and when the Area Director 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
			    <xref target="RFC1321"/> and HMAC
			    <xref target="RFC2104"/> is well known among
			    cryptographers.  Such documents are added to the
			    "Downref Registry". </t>

			<t> In the case of a downref approved in this manner,
			    the annotations described above should be added
			    to the reference unless the IESG, after
			    consideration of Last Call input, concludes it is
			    inappropriate. </t>

			<t> This procedure is not to be used if the proper
			    step is to move the document to which the
			    reference is being made into the appropriate
			    category.  It is not intended as an easy way out
			    of normal process.  Rather, the procedure is
			    intended for dealing with specific cases where
			    putting particular documents into the required
			    category is problematic and unlikely ever to
			    happen. </t>
		</section>
	</section>

	<section anchor="ietf_targets" title="IETF Target Documents">
		<t> The "downward reference by annotation" model specified
		    here is applicable only to published Standards-Track RFCs
		    at lower maturity levels. </t>

		<t> Obviously, such downward references are part of the
		    relevant source document at IETF Last Call and subject to
		    comments from the community. </t>

		<t> Advancing documents, when appropriate, is still strongly
		    preferred to the use of either this procedure or the one
		    specified in <xref target="iesg"/>.  This specification
		    does not impose a specific test or requirement to
		    determine appropriateness.  This is partially because it
		    would be impossible to do so for the general case, but
		    more so because the intention is to permit the IESG and
		    the community to balance the importance of getting a
		    source document published against the time and difficulty
		    associated with upgrading a target document.  That
		    requirement is intended to be less stringent than the one
		    of <xref target="iesg"/>. </t>
	</section>

	<section anchor="external_targets" title="Non-IETF Target Documents">
		<t> A reference to a non-IETF document provides a few
		    challenges relative to the RFC series:
		    <list style="symbols">
			<t> its development may not have been as rigorous as
			    the Standards-Track document referencing it; </t>

			<t> the actual reference to it (e.g., a web link) may
			    have dubious stability; </t>

			<t> it may be subject to unexpected revision in
			    situ; or </t>

			<t> it may not be freely available. </t>
		    </list> </t>

		<t> The IESG may, at its discretion, establish policies
		    regarding external documents referenced normatively by
		    Standards-Track RFCs in light of these challenges.  Such
		    policies are to be developed with solicitation of
		    community input. </t>

		<t> At a minimum, authors/editors of source documents need to
		    secure freely available copies of the target documents for
		    use by all anticipated reviewers during the source
		    document's life cycle, which includes working group
		    participants, any member of the community that chooses to
		    participate in Last Call discussions, area review teams, 
		    IANA expert reviewers, and members of the IESG.  The
		    mechanism for acquiring access to those documents is to be
		    be specified in the shepherd writeup. </t>
	</section>

	<section anchor="registry" title="Downref Registry">
		<t> The IETF has previously established a registry of downrefs
		    to RFCs that have been previously waived by the IESG in the
		    manner described in <xref target="iesg"/>.  The registry
		    includes the name of the referenced RFC and the
		    Internet-Draft whose publication resulted it its addition
		    to the registry.  The IESG is responsible for the
		    maintenance of this registry, adding new entries to it
		    as appropriate. </t>

		<t> Going forward, new registry entries should also record
		    the reason the registry addition was made, and the name
		    of the Area Director making the new entry. </t>

		<t> Note that there is currently no registry of downrefs to
		    non-IETF documents. </t>
	</section>

	<section anchor="security" title="Security Considerations">
		<t> This document is not known to create any new
		    vulnerabilities for the Internet.  On the other hand,
		    inappropriate or excessive use of these processes might be
		    considered a downgrade attack on the quality of IETF
		    standards or, worse, on the rigorous review of security
		    aspects of standards. </t>
	</section>
</middle>

<back>
	<references title="Normative References">
		&RFC2026;
		&RFC3967;
		&RFC4897;
		&RFC8067;
	</references>

	<references title="Informative References">
		&RFC1321;
		&RFC2104;
		&RFC4858;
	</references>

	<section anchor="changes" title="Changes">
		<t> The following are the changes in this document relative
		    to the current state of BCP 97:

		    <list style="symbols">
			<t> Apply erratum #2793. </t>

			<t> Remove references to RFC 1818, which is
			    historic. </t>

			<t> Describe the downref registry's format and
			    ownership. </t>

			<t> Discuss restricted-access documents. </t>

			<t> Allow for skipping downref annotations when the
			    target document is understood to be stable. </t>

			<t> Stronger language against using this process when
			    advancing the target document is The Right Thing
			    To Do. </t>

			<t> Replace MIB guidance with YANG guidance. </t>
		    </list> </t>
	</section>

	<section anchor="ack" title="Acknowledgments">
		<t> This editor offers a salute to the authors of and
		    contributors to RFC 3967, RFC 4897, and RFC 8067: Randy
		    Bush, Thomas Narten, John Klensin, Sam Hartman, and
		    Barry Leiba. </t>

		<t> This revision benefited from contributions by
		    Mohamed Boucadair,
		    Scott Bradner,
		    Brian Carpenter,
		    Russ Housley,
		    John Klensin,
		    Michael Richardson,
		    and
		    Rich Salz. </t>
	</section>
</back>

</rfc>