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Versions: 00 01 02 03 04 rfc4775                                        
Network Working Group                                         S. Bradner
Internet-Draft                                                   Harvard
Intended status: Best Current                          B. Carpenter (ed)
Practice                                                             IBM
Expires: February 5, 2007                                 August 4, 2006

           Procedures for protocol extensions and variations

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
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Copyright Notice

   Copyright (C) The Internet Society (2006).


   This document discusses procedural 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
   or variations need to be reviewed by the larger IETF community.
   Experience with IETF protocols has shown that extensibility of
   protocols without early IETF review can cause problems.  The document
   also recommends that major extensions to or variations of IETF

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   protocols only take place through normal IETF processes or in
   coordination with the IETF.

   This draft replaces draft-iesg-vendor-extensions.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  General Considerations . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Quality and Consistency  . . . . . . . . . . . . . . . . .  4
     2.2.  Registered Values and the Importance of IANA
           Assignments  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.3.  All extensions require technical review  . . . . . . . . .  5
   3.  Procedure for Review of Extensions . . . . . . . . . . . . . .  5
   4.  Some Specific Issues . . . . . . . . . . . . . . . . . . . . .  7
   5.  Intellectual Property  . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   9.  Change log [RFC Editor: please remove this section]  . . . . .  9
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     10.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     10.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
   Intellectual Property and Copyright Statements . . . . . . . . . . 11

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1.  Introduction

   For the origins of this draft, please see the Acknowledgements

   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.  In
   addition to the IETF itself, vendors, standards development
   organizations and technology fora have used those facilities.
   Although the results are often good, there is a real risk of poorly
   designed mechanisms and of 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
   IETF-wide 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 they may not be done with the full
   understanding of why the existing protocol was designed the way that
   it is - e.g., what ideas were brought up during the original
   development and rejected because of some problem with them.  Also
   such extensions could, because of a lack of understanding, negate
   some key function of the existing protocol (such as security or
   congestion control).  Generally, short-sighted design choices are

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   sometimes made, and basic underlying architectural principles of the
   protocol are sometimes violated.

   Additionally, documentation of non-IETF extensions can be hard to
   obtain, so 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 early peer review that occurs within the IETF process
   may be lacking.

   All that can be said about extensions applies with equal or greater
   force to variations - in fact, by definition, protocol variations
   damage interoperability.  They must therefore be intensely
   scrutinized.  Throughout this document, what is said about extensions
   also applies to variations.

   This document is focussed on appropriate process and practices to
   ensure that extensions developed outside the IETF will not fall into
   these traps and therefore become useless or, worse, damaging to
   interoperability.  Architectural considerations are documented

2.  General Considerations

2.1.  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 published as an Internet Draft, which must be
   sufficiently consistent in terminology and content with the
   unextended specification that these experts can readily identify the
   technical changes proposed at an early stage.

2.2.  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.
   This is hazardous; it is far too likely that someone just taking a

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   protocol value will find that the same value will later be formally
   assigned to another function, thus guaranteeing an interoperability

   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.

2.3.  All extensions require technical review

   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 or functionality 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, early 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

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   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, currently 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.

   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.  In
   some cases (e.g., [RFC3427], [I-D.andersson-rtg-gmpls-change]) the
   IETF has well defined procedures for this in place.

   Naturally, SDOs can and do develop scenarios, requirements and
   architectures based on IETF specifications.  It is only actual
   protocol changes that need to go through the IETF process.  Other
   SDOs are encouraged to communicate informally or formally with the
   IETF as early as possible, to avoid false starts.  Early technical
   review in a collaborative spirit is of great value.  Each SDO can
   "own" its ideas and discuss them in its own fora, but should start
   talking to the IETF experts about those ideas the moment the spark

   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 describing the requirements.  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

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   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, unless preliminary IETF discussion has
   already revealed serious flaws in the proposal.  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 at an early stage 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.  This should be done at an early stage, before a large
      investment of effort has taken place, in case basic prroblems are
   o  In the case of simple, minor extensions involving routine IANA
      parameter assignments, this request is satisfied as long as the
      IANA Considerations of the underlying IETF specification are
      satisfied (see [RFC2434]).  Anything beyond this requires an
      explicit protocol review by experts within the IETF.
   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.  Some Specific Issues

   It is relatively common for MIBs, which are all in effect extensions
   of the SMI data model, to be defined or extended outside the IETF.
   BCP 111 [RFC4181] offers detailed guidance for authors and reviewers.

   A number of protocols have foreseen experimental values for certain
   IANA parameters, so that experimental usages and extensions may be
   tested without need for a special parameter assignment.  It must be
   stressed that such values are not intended for production use or as a
   way to evade the type of technical review described in this document.
   See [I-D.fenner-iana-exp-2780].

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   There are certain documents that specify a change process for
   specific IETF protocols:
      The SIP change process [RFC3427]
      The (G)MPLS change process [I-D.andersson-rtg-gmpls-change]

5.  Intellectual Property

   All IETF documents fall under the IETF's intellectual property rules,
   BCP 78 [RFC3978] and BCP 79 [RFC3979], as amended.  In particular,
   there are restrictions on the production of derivative works, and
   there are rights that remain with the original authors.  Anybody
   outside the IETF considering an extension based on an IETF document
   must bear these restrictions and rights in mind.

6.  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.

7.  IANA Considerations

   The IETF 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

8.  Acknowledgements

   This document is heavily based on an earlier draft under a different
   title by Scott Bradner and Thomas Narten.

   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, Scott Brim, Dan Romascanu, Jari Arkko, Loa Andersson,...
   also made valuable comments on this document.

   This document was produced using the xml2rfc tool [RFC2629].

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9.  Change log [RFC Editor: please remove this section]

   draft-carpenter-protocol-extensions-01: 2006-08-04.  Removed
   additional architectural material, added material on MIBs,
   experimental values and IPR, reflected other comments.  Extended
   scope to cover variations as well as extensions.  Updated authorship.

   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
   draft are left to a separate document.

10.  References

10.1.  Normative References

              Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
              ICMPv6, UDP and TCP Headers",
              draft-fenner-iana-exp-2780-05 (work in progress),
              June 2006.

   [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.

   [RFC3427]  Mankin, A., Bradner, S., Mahy, R., Willis, D., Ott, J.,
              and B. Rosen, "Change Process for the Session Initiation
              Protocol (SIP)", BCP 67, RFC 3427, December 2002.

   [RFC3932]  Alvestrand, H., "The IESG and RFC Editor Documents:
              Procedures", BCP 92, RFC 3932, October 2004.

   [RFC3978]  Bradner, S., "IETF Rights in Contributions", BCP 78,
              RFC 3978, March 2005.

   [RFC3979]  Bradner, S., "Intellectual Property Rights in IETF
              Technology", BCP 79, RFC 3979, March 2005.

   [RFC4181]  Heard, C., "Guidelines for Authors and Reviewers of MIB
              Documents", BCP 111, RFC 4181, September 2005.

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10.2.  Informative References

              Andersson, L., "MPLS and GMPLS Change Process",
              draft-andersson-rtg-gmpls-change-02 (work in progress),
              December 2005.

   [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.

Authors' Addresses

   Scott Bradner
   Harvard University
   29 Oxford St.
   Cambridge, MA  02138

   Email: sob@harvard.edu

   Brian Carpenter (ed)
   8 Chemin de Blandonnet
   1214 Vernier,

   Email: brc@zurich.ibm.com

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Full 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.

   This document and the information contained herein are provided on an

Intellectual Property

   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
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   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

   The IETF invites any interested party to bring to its attention any
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