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Versions: 00 draft-iab-protocol-transitions

Internet Architecture Board                                    D. Thaler
Internet-Draft                                                 Microsoft
Intended status: Informational                           October 5, 2015
Expires: April 7, 2016


                        Designing for Transition
               draft-thaler-transition-principles-00.txt

Abstract

   Over the many years since the introduction of the Internet Protocol,
   we have seen a number of transitions, throughout the protocol stack,
   from one protocol or technology to another.  Many protocols and
   technologies were not designed to enable smooth transition to
   alternatives or to easily deploy extensions, and thus some
   transitions, such as the introduction of IPv6, have been difficult.
   This document attempts to summarize some basic principles to enable
   future transitions, and also summarizes what makes for a good
   transition plan.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 7, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Transition vs. Co-existence . . . . . . . . . . . . . . . . .   4
   3.  Translation/Adaptation Location . . . . . . . . . . . . . . .   4
   4.  Translation Plans . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   A "transition" is "the process or period of changing from one state
   or condition to another.  There are several types of such
   transitions, including both technical transitions (e.g., changing a
   protocol or deploying an extension) and organizational transitions
   (e.g., changing what organization manages the IETF web site, or the
   RFC production center).  This document focuses solely on technical
   transitions, although some principles might apply to other types as
   well.

   There have been many IETF and IAB RFCs and IAB statements discussing
   transitions of various sorts.  Most are protocol-specific documents
   about specific transitions.  For example, some relevant ones in which
   the IAB has been involved include:

   o  IAB RFC 3424 [RFC3424] recommended that any technology for so-
      called "unilateral self-address fixing (UNSAF)" across NATs
      include an exit strategy/plan to transition away from such a
      mechanism.  Since the IESG, not the IAB, approves IETF documents,
      the IESG thus became the body to enforce (or not) such a
      requirement.

   o  IAB RFC 4690 [RFC4690] gave recommendations around
      internationalized domain names.  It discussed issues around the
      process of transitioning to new versions of Unicode, and this
      resulted in the creation of the IETF Precis WG to address this
      problem.

   o  The IAB statement on "Follow-up-work on NAT-PT"
      [IabIpv6TransitionStatement] pointed out gaps at the time in




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      transitioning to IPv6, and this resulted in the rechartering of
      the IETF Behave WG to solve this problem.

   More recently, the IAB has done work on more generally applicable
   principles, including two RFCs.

   IAB RFC 5218 [RFC5218] on "What Makes for a Successful Protocol?"
   studied specifically what factors contribute to, and detract from,
   the success of a protocol and it made a number of recommendations.
   It discussed two types of transitions: "initial success" (the
   transition to the technology) and extensibility (the transition to
   updated versions of it).  The principles and recommendations in that
   document are generally applicable to all technical transitions.  Some
   important principles included:

   1.  Incentive: Transition is easiest when the benefits come to those
       bearing the costs.  That is, the benefits should outweigh the
       costs at *each* entity.  Some successful cases did this by
       providing incentives (e.g., tax breaks), or by reducing costs
       (e.g., freely available source), or by imposing costs of not
       transitioning (e.g., regulation), or even by narrowing the
       scenarios of applicability to just the cases where benefits do
       outweigh costs.

   2.  Incremental Deployability: Backwards compatibility makes
       transition easier.  Furthermore, transition is easiest when
       changing only one entity still benefits that entity.  In the
       easiest case, the benefit immediately outweighs the cost and so
       entities are naturally incented to transition.  More commonly,
       the benefits only outweigh the costs once a significant number of
       other entities also transition.  Unfortunately, in such cases,
       the natural incentive is often to delay transitioning.

   3.  Total Cost: Don't underestimate the cost of things other than the
       hardware/software itself.  For example, operational tools and
       processes, personnel training, business model (accounting/
       billing) dependencies, and legal (regulation, patents, etc.)
       costs all add up.

   4.  Extensibility: Design for extensibility so that things can be
       fixed up later.

   IAB RFC 7305 [RFC7305] reported on a IAB workshop on Internet
   Technology Adoption and Transition (ITAT).  Like RFC 5218, this
   workshop also discussed economic aspects of transition, not just
   technical aspects.  Some important observations included:





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   1.  Early-Adopter Incentives: Part of Bitcoin's strategy was extra
       incentives for early adopters.  That is, providing a long-term
       advantage to early adopters can help stimulate transition even
       when the initial costs outweigh the initial benefit.

   2.  Policy Partners: Policy-making organizations of various sorts
       (RIRs, ICANN, etc.) can be important partners in enabling and
       facilitating transition.

   The remainder of this document continues the discussion in those two
   RFCs and provides some additional thoughts on the topic of transition
   strategies and plans.

2.  Transition vs. Co-existence

   We need to distinguish between a strict "flag-day" style transition
   where an old mechanism is immediately replaced with a new mechanism,
   vs. a looser co-existence based approach where transition proceeds in
   stages where a new mechanism is first added alongside an existing one
   for some overlap period, and then the old mechanism is removed at a
   later stage.

   When a new mechanism is backwards compatible with an existing
   mechanism, transition is easiest, and the difference between the two
   types of transition is not particularly significant.  However, when
   no backwards compatibility exists (such as in the IPv4 to IPv6
   transition), a transition plan must choose either a "flag day" or a
   period of co-existence.  When a large number of entities are
   involved, a flag day becomes impractical.  Coexistence, on the other
   hand, involves additional costs of maintaining two separate
   mechanisms during the overlap period which could be quite long.
   Furthermore, the longer the overlap period, the more the old
   mechanism might get further deployment and thus increase the overall
   pain of transition.

   Often the decision between a "flag day" and a sustained co-existence
   period may be difficult, such as in the case of IDNA2008 [RFC5891]
   [RFC5895] and Unicode TR46 [TR46].

3.  Translation/Adaptation Location

   A translation or adaptation layer is often required if the old and
   new mechanisms are not interoperable.  Care must be taken when
   determining where such a translator is best placed.

   Requiring a translator in the middle of the path can hamper end-to-
   end security and reliability.  For example, see the discussion of
   network-based filtering in [I-D.iab-filtering-considerations].



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   On the other hand, requiring a translation layer within an endpoint
   can be a resource issue in some cases, such as if the endpoint could
   be a constrained node [RFC7228].

   Any transition strategy for a non-backward-compatible mechanism
   should include a discussion of where it is placed and a rationale.

4.  Translation Plans

   A good transition plan includes at least the following components:

   1.  An explanation of incentives for each entity involved

   2.  A description of transition phases.  For example, there might be
       pilot, co-existence, deprecation, and removal phases, for a
       transition from one technology to another incompatible one.

   3.  A proposed timeline

   4.  A way to effectively communicate the proposed plan to the
       entities affected, and incorporate their feedback

5.  Security Considerations

   This document discusses attributes of protocol transitions.  Some
   types of transition can adversely affect security or privacy.  For
   example, requiring a translator in the middle of the path may hamper
   end-to-end security and privacy, since it creates an attractive
   target.  For further discussion of some of these issues, see
   Section 5 of [I-D.iab-filtering-considerations].

6.  IANA Considerations

   This document requires no actions by the IANA.

7.  Informative References

   [I-D.iab-filtering-considerations]
              Barnes, R., Cooper, A., Kolkman, O., and D. Thaler,
              "Technical Considerations for Internet Service Blocking
              and Filtering", draft-iab-filtering-considerations-07
              (work in progress), July 2015.

   [IabIpv6TransitionStatement]
              IAB, "Follow-up work on NAT-PT", October 2007,
              <https://www.iab.org/documents/correspondence-reports-
              documents/docs2007/follow-up-work-on-nat-pt//>.




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   [RFC3424]  Daigle, L., Ed. and IAB, "IAB Considerations for
              UNilateral Self-Address Fixing (UNSAF) Across Network
              Address Translation", RFC 3424, DOI 10.17487/RFC3424,
              November 2002, <http://www.rfc-editor.org/info/rfc3424>.

   [RFC4690]  Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and
              Recommendations for Internationalized Domain Names
              (IDNs)", RFC 4690, DOI 10.17487/RFC4690, September 2006,
              <http://www.rfc-editor.org/info/rfc4690>.

   [RFC5218]  Thaler, D. and B. Aboba, "What Makes For a Successful
              Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008,
              <http://www.rfc-editor.org/info/rfc5218>.

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891,
              DOI 10.17487/RFC5891, August 2010,
              <http://www.rfc-editor.org/info/rfc5891>.

   [RFC5895]  Resnick, P. and P. Hoffman, "Mapping Characters for
              Internationalized Domain Names in Applications (IDNA)
              2008", RFC 5895, DOI 10.17487/RFC5895, September 2010,
              <http://www.rfc-editor.org/info/rfc5895>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <http://www.rfc-editor.org/info/rfc7228>.

   [RFC7305]  Lear, E., Ed., "Report from the IAB Workshop on Internet
              Technology Adoption and Transition (ITAT)", RFC 7305,
              DOI 10.17487/RFC7305, July 2014,
              <http://www.rfc-editor.org/info/rfc7305>.

   [TR46]     Unicode Consortium, "Unicode IDNA Compatibility
              Processing", June 2015,
              <http://www.unicode.org/reports/tr46/>.

Author's Address

   Dave Thaler
   Microsoft
   One Microsoft Way
   Redmond, WA  98052
   US

   Email: dthaler@microsoft.com




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