Network Working Group R. Bush Internet-Draft IIJ Updates: 2026 (if approved) T. Narten Expires:August 16, 2004January 2005 IBM CorporationApril 8,July 19, 2004 Clarifying when Standards Track Documents may Refer Normatively to Documents at a Lower Leveldraft-ymbk-downref-02.txtdraft-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 onAugust 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 toaanother standards track document at a lower maturity level or to a non standardslevel.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 describenon-IETFnon- 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 DefinitionsIt 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 ReferencesNote: 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 documentsBroadly 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 RFCand whosein the sense that its omission would leave the new RFC incompletely specified. An informative reference is not normative; rather, it provides onlyadditionaladditional, 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 aninformative reference might provide background or historical information, or provide an example of possible usage. MaterialIETF Standard's context, it is important that all dependent pieces be clearly specified and available in aninformative referencearchival form, so that there is no disagreement over what constitutes a standard. This is notrequired toalways the case for other documents. The rest of this section provides guidance on what might (and might not) beread in order to understand subject matterconsidered normative in theRFC.context of the IETF standards process. In thecaseIETF, it is a basic assumption that implementors must have a clear understanding ofprotocols,what they need to implement in order to be fully compliant with areference is normative if it refersstandard and topacket formats orbe able to interoperate with otherprotocol mechanismsimplementations of that standard. For documents that areneededreferenced, 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, theprotocol inreference to that format would be normative. Likewise, if a reference to a required algorithm is made, thecurrent 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.InThe 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 maturitylevel 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 specificprecedentdown reference to a particular document has beenset (i.e.,accepted by thesame exceptioncommunity (e.g., has beenmade for a particular reference a few times), the need formentioned in several Last Calls), anexplicit mention ofArea Director may waive subsequent notices in theissue duringLast Callmay 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 theinternet.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. 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