Network Working Group B. Carpenter (ed) Internet-Draft IBM Expires: December 18, 2006 June 16, 2006 Procedures for protocol extensions draft-carpenter-protocol-extensions-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 December 18, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document discusses issues related to the extensibility of IETF protocols, including when it is reasonable to extend IETF protocols with little or no review, and when extensions need to be reviewed by the larger IETF community. Experience with IETF protocols has shown that extensibility of protocols without IETF review can cause problems. The document also recommends that major extensions to IETF protocols only take place through normal IETF processes or in coordination with the IETF. Carpenter (ed) Expires December 18, 2006 [Page 1] Internet-Draft Procedures for protocol extensions June 2006 This draft replaces draft-iesg-vendor-extensions. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. General Considerations . . . . . . . . . . . . . . . . . . . . 4 2.1. Interoperability as a Goal . . . . . . . . . . . . . . . . 4 2.2. Quality and Consistency . . . . . . . . . . . . . . . . . 4 2.3. Registered Values and the Importance of IANA Assignments . . . . . . . . . . . . . . . . . . . . . . . 4 2.4. Major versus Minor Extensions . . . . . . . . . . . . . . 5 3. Procedure for Review of Extensions . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 7. Change log [RFC Editor: please remove this section] . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 10 Carpenter (ed) Expires December 18, 2006 [Page 2] Internet-Draft Procedures for protocol extensions June 2006 1. Introduction For the origins of this draft, please see the Acknowledgements section. It is posted as a personal draft although the material was historically developed in the IESG. BCP 9 [RFC2026] is the current definition of the IETF standards track. It is implicitly presumed that this process will apply not only to the initial definition of a protocol, but also to any subsequent updates, such that continued interoperability can be guaranteed. However, it is not always clear whether extensions to a protocol fall within this presumption, especially when they originate outside the IETF community. This document lays down procedures for such extensions. When developing protocols, IETF working groups typically include mechanisms whereby these protocols can be extended in the future. Vendors, standards development organizations and technology fora have used those facilities. Sometimes the result is a poorly designed mechanism and non-interoperability. It is of course a good principle to design extensiblity into protocols; one common definition of a successful protocol is one that becomes widely used in ways not originally anticipated. Well- designed extensibility mechanisms facilitate the evolution of protocols and help make it easier to roll-out incremental changes in an interoperable fashion. At the same time, experience has shown that extensibility features should be limited to what is clearly necessary when the protocol is developed and any later extensions should be done carefully and with a full understanding of the base protocol, existing implementations, and current operational practice. However, it is not the purpose of this document to describe the architectural principles of sound extensibility design. When extensions to IETF protocols are made within the IETF, the normal IETF process is followed, including the normal process for review and approval by the IESG. It is presumed that this will ensure that extensions developed in this way will respect all applicable architectural principles and technical criteria. When extensions to IETF protocols are made outside the IETF, experience has shown that documentation of these extensions can be hard to obtain, short-sighted design choices are sometimes made, basic underlying architectural principals of the protocol are sometimes violated, assessing the quality of the specification is hard and achieving interoperability can be hard. Also, there is a risk that mutually incompatible extensions may be developed independently. Simply put, the peer review that occurs within the Carpenter (ed) Expires December 18, 2006 [Page 3] Internet-Draft Procedures for protocol extensions June 2006 IETF process is lacking. This document is focussed on appropriate process and practices to ensure that extensions developed outside the IETF will not fall into this trap and therefore become useless or, worse, damaging to the Internet. However, some general considerations are listed first. 2. General Considerations 2.1. Interoperability as a Goal An extension is of little value if it is not interoperable with the unextended protocol, i.e. the extended protocol correctly supports all mandatory and optional features of the unextended protocol, and implementations of the base protocol operate correctly in the presence of the extensions. This places requirements on both the base protocol (design for extensibility) and on the extension. These architectural considerations are outside the scope of the present draft. 2.2. Quality and Consistency In order to be adequately reviewed by relevant experts, a proposed extension must be documented in a clear and well-written specification, which must be sufficiently consistent in terminology and content with the unextended specification that these experts can readily identify the technical changes proposed. 2.3. Registered Values and the Importance of IANA Assignments An extension is often likely to make use of additional values added to an existing IANA registry (in many cases, simply by adding a new "TLV" (type-length-value) field). It is essential that such new values are properly registered by the applicable procedures, including expert review where applicable (see BCP 26, [RFC2434]). Extensions may even need to create new IANA registries in some cases. Experience shows that the importance of this is often underestimated during extension design; designers sometimes assume that a new codepoint is theirs for the asking, or even simply for the taking. However, in many cases IANA assignment requests trigger a thorough technical review of the proposal by a designated IETF expert reviewer. Requests are sometimes refused after such a review. Thus, extension designers must pay particular attention to any needed IANA assignments and to the applicable criteria. Carpenter (ed) Expires December 18, 2006 [Page 4] Internet-Draft Procedures for protocol extensions June 2006 2.4. Major versus Minor Extensions Some extensions may be considered minor (e.g. adding a straightforward new TLV to an application protocol, which will only impact a subset of hosts) and some may be considered major (e.g. adding a new IP option type, which will potentially impact every node on the Internet). This is essentially a matter of judgement. It could be argued that anything requiring at most Expert Review in [RFC2434] is probably minor, and anything beyond that is major. However, even an apparently minor extension may have unforeseen consequences on interoperability. Thus, the distinction between major and minor is less important than ensuring that the right amount of technical review takes place in either case. For example, RADIUS [RFC2865] is designed to carry attributes and allow definition of new attributes. But it is important that discussion of new attributes involve the IETF community of experts knowledgeable about the protocol's architecture and existing usage in order to fully understand the implications of a proposed extension. Adding new attributes without such discussion creates a high risk of interoperability failure. For this reason among others, the IETF has an active RADIUS Extensions working group at the time of writing. Thus the only safe rule is that, even if an extension appears minor to the person proposing it, review by subject matter experts is always advisable. The proper forum for such review is the IETF, either in the relevant Working Group, or by individual IETF experts if no such WG exists. 3. Procedure for Review of Extensions Extensions to IETF protocols developed within the IETF will be subject to the normal IETF process, exactly like new designs. Extensions to IETF protocols discussed in an IRTF Research Group may well be the prelude to regular IETF discussion. However, a Research Group may desire to specify an experimental extension before the work is mature enough for IETF processing. In this case, the Research Group is required to involve appropriate IETF or IANA experts in their process to avoid oversights. Extensions to IETF protocols described in Independent Submissions to the RFC Editor are subject to IESG review as described in BCP 92 [RFC3932]. A possible outcome is that the IESG advises the RFC Editor that full IETF processing is needed, or that relevant IANA procedures have not been followed. Carpenter (ed) Expires December 18, 2006 [Page 5] Internet-Draft Procedures for protocol extensions June 2006 Where vendors or other Standards Development Organisations (SDOs) see a requirement for extending an IETF protocol, their first step should be to select the most appropriate of the above three routes. Regular IETF process is most likely to be suitable, assuming sufficient interest can be found in the IETF community. IRTF process is unlikely to be suitable unless there is a genuine research context for the proposed extension. In the case of an SDO that identifies a requirement for a standardised extension, a standards development process within the IETF (while maintaining appropriate liaison) is strongly recommended in preference to publishing a non-IETF standard. Otherwise, the implementor community will be faced with a standard split into two or more parts in different styles, obtained from different sources, with no unitary control over quality, compatibility, interoperability, and intellectual property conditions. Note that, since participation in the IETF is open, there is no formality or restriction for particpants in other SDOs choosing to work in the IETF as well. Vendors that identify a requirement for an extension are strongly recommended to start informal discussion in the IETF and to publish a preliminary Internet Draft. This will allow the vendor, and the community, to evaluate whether there is community interest and whether there are any major or fundamental issues. However, in the case of a vendor that identifies a requirement for a proprietary extension that does not generate interest in the IETF (or IRTF) communities, an Independent Submission to the RFC Editor is strongly recommended in preference to publishing a proprietary document. Not only does this bring the draft to the attention of the community; it also ensures a minimum of community review [RFC3932], and (if published) makes the proprietary extension available to the whole community. If, despite these strong recommendations, a vendor or SDO does choose to publish its own specification for an extension to an IETF protocol, the following guidance applies: o Extensions to IETF protocols should be well, and publicly, documented, and reviewed by the IETF community to be sure that the extension does not undermine basic assumptions and safeguards designed into the protocol, such as security functions, or undermine its architectural integrity. o Therefore, vendors and other SDOs are formally requested to submit any such proposed publications for IETF review, by an established liaison channel if it exists, or by direct communication with the IESG. o In the case of simple, minor extensions involving routine IANA parameter assignments, this request is satsified as long as the IANA Considerations of the underlying IETF specification are Carpenter (ed) Expires December 18, 2006 [Page 6] Internet-Draft Procedures for protocol extensions June 2006 satisfied (see [RFC2434]). Anything beyond this requires an explicit protocol review process. o Note that, like IETF specifications, such proposed publications must include an IANA considerations section to ensure that protocol parameter assignments that are needed to deploy extensions are not made until after a proposed extension has received adequate review, and then to ensure that IANA has precise guidance on how to make those assignments. 4. Security Considerations An extension must not introduce new security risks without also providing an adequate counter-measure, and in particular it must not inadvertently defeat security measures in the unextended protocol. This aspect must always be considered during IETF review. 5. IANA Considerations The IESG requests IANA to pay attention to the requirements of this document when requested to make protocol parameter assignments for vendors or other SDOs, i.e. to respect the IANA Considerations of all RFCs that contain them, and the general considerations of BCP 26 [RFC2434]. 6. Acknowledgements This document is heavily based on an earlier draft under a different title by Scott Bradner and Thomas Narten. Final authorship attributions remain to be determined. That earlier draft stated: The initial version of this document was put together by the IESG in 2002. Since then, it has been reworked in response to feedback from John Loughney, Henrik Levkowetz, Mark Townsley, Randy Bush, Bernard Aboba and others. Ted Hardie and Thomas Narten made valuable comments on this version. This document was produced using the xml2rfc tool[RFC2629]. 7. Change log [RFC Editor: please remove this section] draft-carpenter-protocol-extensions-00: original version, 2006-06-16. Derived from draft-iesg-vendor-extensions-02.txt dated 2004-06-04 by focussing on procedural issues; the more architectural issues in that Carpenter (ed) Expires December 18, 2006 [Page 7] Internet-Draft Procedures for protocol extensions June 2006 draft are left to the IAB. 8. References 8.1. Normative References [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC3932] Alvestrand, H., "The IESG and RFC Editor Documents: Procedures", BCP 92, RFC 3932, October 2004. 8.2. Informative References [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. Carpenter (ed) Expires December 18, 2006 [Page 8] Internet-Draft Procedures for protocol extensions June 2006 Author's Address Brian Carpenter (ed) IBM 8 Chemin de Blandonnet 1214 Vernier, Switzerland Email: brc@zurich.ibm.com Carpenter (ed) Expires December 18, 2006 [Page 9] Internet-Draft Procedures for protocol extensions June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Carpenter (ed) Expires December 18, 2006 [Page 10]