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Versions: 00 01 02 03 04 RFC 5657

Network Working Group                                       L. Dusseault
Internet-Draft                                               CommerceNet
Intended status: BCP                                           R. Sparks
Expires: February 1, 2009                                        Tekelec
                                                            Jul 31, 2008

         Guidance on Interoperation and Implementation Reports

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.

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   This Internet-Draft will expire on February 1, 2009.


   Advancing a protocol to Draft Standard requires documentation of the
   interoperation and implementation of the protocol.  Historic reports
   have varied widely in form and level of content and there is little
   guidance available to new report preparers.  This document updates
   the existing processes and provides more detail on what is
   appropriate in an interoperability and implementation report.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Content Requirements . . . . . . . . . . . . . . . . . . . . .  4
   3.  Format . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Feature Coverage . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Special Cases  . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  Deployed Protocols . . . . . . . . . . . . . . . . . . . .  7
     5.2.  Undeployed Protocols . . . . . . . . . . . . . . . . . . .  8
     5.3.  Schemas, languages and formats . . . . . . . . . . . . . .  8
     5.4.  Multiple Contributors, Multiple Implementation Reports . .  8
     5.5.  Test Suites  . . . . . . . . . . . . . . . . . . . . . . .  9
     5.6.  Optional Features, extensibility features  . . . . . . . .  9
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Minimal Implementation Report  . . . . . . . . . . . . . . 10
     6.2.  Covering Exceptions  . . . . . . . . . . . . . . . . . . . 11
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 13

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1.  Introduction

   The Draft Standard level, and requirements for standards to meet it,
   are described in [RFC2026].  For Draft Standard, not only must two
   implementations interoperate, but also documentation (the report)
   must be provided to the IETF.  The entire paragraph covering this
   documentation reads

          The Working Group chair is responsible for documenting the
      specific implementations which qualify the specification for Draft
      or Internet Standard status along with documentation about testing
      of the interoperation of these implementations.  The documentation
      must include information about the support of each of the
      individual options and features.  This documentation should be
      submitted to the Area Director with the protocol action request.
      (see Section 6)

   Moving standards along the standards track can be an important signal
   to the user and implementor communities, and the process of
   submitting a standard for advancement can help improve the standard
   or the quality of implementations that participate.  However, the
   barriers seem to be high for advancement to Draft Standard, or at the
   very least confusing.  This memo may help in guiding people through
   one part of advancing specifications to Draft Standard.  It also
   changes some of the requirements made in RFC2026 in ways that are
   intended to maintain or improve the quality of reports while reducing
   the burden of creating them.

   Having and demonstrating sufficient interoperability is a gating
   requirement for advancing a protocol to Draft Standard.  Thus, the
   primary goal of an implementation report is to convince the IETF and
   the IESG that the protocol is ready for Draft Standard.  This goal
   can be met by summarizing the interoperability characteristics and by
   providing just enough detail to support that conclusion.  Side
   benefits may accrue to the community creating the report in the form
   of bugs found or fixed in tested implementations, documentation that
   can help future implementors, or ideas for other documents or future
   revisions of the protocol being tested.

   Different kinds of documentation are appropriate for widely deployed
   standards than for standards that are not yet deployed.  Different
   test approaches are appropriate for standards that are not typical
   protocols: languages, formats, schemas etc.  This memo discusses how
   reports for these standards may vary in Section 5.

   The level of detail in reports accepted in the past has varied
   widely.  An example of a submitted report that is not sufficient for
   demonstrating interoperability is (in its entirety): "A partial list

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   of implementations include: Cray SGI Netstar IBM HP Network Systems
   Convex."  This report does not state how it is known that these
   implementations interoperate (was it through public lab testing?
   internal lab testing? deployment?).  Nor does it capture whether
   implementors are aware of, or were asked about, any problem features.
   At a different extreme, reports have been submitted that contain a
   great amount of detail about the test methodology, but relatively
   little information about what worked and what failed to work.

   This memo is intended to clarify what an implementation report should
   contain and to suggest a reasonable form for most implementation
   reports.  It is not intended to rule out good ideas.  For example,
   this memo can't take into account all process variations such as
   documents going to Draft Standard twice, or consider all types of
   standards.  Whenever the situation varies significantly from what's
   described here, the IESG uses judgement in determining whether an
   implementation report meets the goals above.

2.  Content Requirements

   The implementation report MUST identify the author of the report, who
   is responsible for characterizing the interoperability quality of the
   protocol.  The report MAY identify other contributors (testers, those
   who answered surveys or those who contributed information) to share
   credit or blame.

   Some of the requirements of RFC2026 are relaxed with this update:

   o  The report MAY name exactly which implementations were tested.  A
      requirement to name implementations was implied by the description
      of the responsibility for "documenting the specific
      implementations" in RFC2026.  However, note that usually
      identifying implementations will help meet the goals of
      implementation reports.  See also the note on implementation
      independence below.

   o  The report MAY choose an appropriate level of detail to document
      feature interoperability, rather than document each individual
      feature.  See note on granularity of features below.

   o  A contributor other than a WG chair MAY submit an implementation
      report to an AD.

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   Note:  Independence of implementations is mentioned in the RFC2026
      requirements for Draft Standard status.  Independent
      implementations should be written by different people at different
      organizations using different code and protocol libraries.  If
      it's necessary to relax this definition, it can be relaxed as long
      as there is evidence to show that success is due more to the
      quality of the protocol than to out-of-band understandings or
      common code.  If there are only two implementations of an
      undeployed protocol, the report SHOULD identify the
      implementations and their "genealogy" (which libraries were used
      or where the codebase came from).  If there are many more
      implementations or the protocol is in broad deployment it is not
      necessary to call out which two of the implementations
      demonstrated interoperability of each given feature -- a reader
      may conclude that at least some of the implementations of that
      feature are independent.

   Note:  The granularity of features described in a specification is
      necessarily very detailed.  In contrast, the granularity of an
      implementation report need not be as detailed.  A report need not
      list every "MAY", "SHOULD" and "MUST" in a complete matrix across
      implementations.  A more effective approach might be to
      characterize the interoperability quality and testing approach,
      then call out any known problems in either testing or

3.  Format

   The format of implementation and interoperability reports MUST be
   ASCII text with line-breaks for readability.  It is acceptable, but
   not necessary, for a report to be formatted as an Internet Draft.

   Titles of implementation reports are strongly RECOMMENDED to contain
   one or more RFC number for consistent lookup in a simple archive.  In
   addition, the name or a common mnemonic of the standard should be in
   the title.

   Here is a simple outline that an implementation report MAY follow in
   part or in full:

   Summary:  Attest that the standard meets the requirements for Draft
      Standard and name who is attesting it.  Describe how many
      implementations were tested or surveyed.  Quickly characterize the
      deployment level and where the standard can be found in
      deployment.  Call out, and if possible, briefly describe any
      notably difficult or poorly interoperable features and explain why
      these still meet the requirement.  Assert any derivative

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      conclusions: if a high-level system is tested and shown to work,
      then we may conclude that the normative requirements of that
      system (all sub-system or lower-layer protocols, to the extent
      that a range of features is used) have also been shown to work.

   Methodology:  Describe how the information in the report was
      obtained.  This should be no longer than the summary.

   Exceptions:  This section might read "Every feature was implemented,
      tested and widely interoperable without exception and without
      question."  If that statement is not true, then this section
      should cover whether any features were thought to be problematic.
      Problematic features need not disqualify a protocol from Draft
      Standard, but this section should explain why they do not (e.g.
      optional, untestable, trace or extension features).  See example
      Section 6.2.

   Detail sections:  Any other justifying or background information can
      be included here.  In particular, any information that would have
      made the summary or methodology sections more than a few
      paragraphs long may be created as a detail section and referred

   Appendix sections:  It's not necessary to archive test material such
      as test suites, test documents, questionnaire text or
      questionnaire responses.  However, if it's easy to preserve this
      information, appendix sections allow readers to skip over it if
      they are not interested.  Preserving detailed test information can
      help people doing similar or follow-on implementation reports, and
      can also help new implementors.

4.  Feature Coverage

   What constitutes a "feature" for the purposes of an interoperability
   report has been frequently debated.  Good judgement is required in
   finding a level of detail that adequately demonstrates coverage of
   the requirements.  Statements made at too high a level will result in
   a document that can't be verified and hasn't adequately challenged
   that the testing accidentally missed an important failure to
   interoperate.  On the other hand, statements at too fine a level
   result in an exponentially-exploding matrix of requirement
   interaction that overburdens the testers and report writers.  The
   important information in the resulting report would likely be hard to
   find in the sea of detail, making it difficult to evaluate whether
   the important points of interoperability have been addressed.

   The best interoperability reports will organize statements of

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   interoperability at a level of detail just sufficient to convince the
   reader that testing has covered the full set of requirements and in
   particular that the testing was sufficient to uncover any places
   where interoperability does not exist.  Reports similar to that for
   RTP/RTCP (an excerpt appears below) are more useful than an
   exhaustive checklist of every normative statement in the

         10. Interoperable exchange of receiver report packets.

             o  PASS: Many implementations, tested UCL rat with vat,
                      Cisco IP/TV with vat/vic.

         11. Interoperable exchange of receiver report packets when
             not receiving data (ie:   the empty receiver report
             which has to be sent first in each compound RTCP packet
             when no-participants are transmitting data).

             o  PASS: Many implementations, tested UCL rat with vat,
                      Cisco IP/TV with vat/vic.


           8. Interoperable transport of RTP via TCP using the
              encapsulation defined in the audio/video profile

              o  FAIL: no known implementations. This has been
                       removed from the audio/video profile.

                               Excerpts from

   Consensus can be a good tool to help determine the appropriate level
   for such feature descriptions.  A working group can make a strong
   statement by documenting its consensus that a report sufficiently
   covers a specification and that interoperability has been

5.  Special Cases

5.1.  Deployed Protocols

   When a protocol is deployed, test-lab results are not as useful to
   the IETF as learning what is actually working in deployment.  To this
   end, it may be more informative to survey implementors or operators.

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   A questionnaire or interview can elicit information from a wider
   number of sources.  As long as it is known that independent
   implementations can work in deployment, it is more useful to discover
   what problems exist, rather than gather long and detailed checklists
   of features and options.

5.2.  Undeployed Protocols

   It is appropriate to provide finer-grained detail in reports for
   protocols that do not yet have a wealth of experience gained through
   deployment.  In particular, some complicated, flexible or powerful
   features might show interoperability problems when testers start to
   probe outside the core use cases -- even if the core use cases are
   already successfully interoperable in deployment.  RFC2026 requires
   "sufficient successful operational experience" before progressing a
   standard to Draft, and notes that

          Draft Standard may still require additional or more widespread
      field experience, since it is possible for implementations based
      on Draft Standard specifications to demonstrate unforeseen
      behavior when subjected to large-scale use in production

   When possible, reports for protocols without much deployment
   experience should anticipate common operational considerations.  For
   example, it would be appropriate to put additional emphasis on
   reporting on details for any overload or congestion management
   features the protocol may have.

5.3.  Schemas, languages and formats

   Standards that are not on-the-wire protocols may be special cases for
   implementation reports.  The IESG SHOULD use judgement in what kind
   of implementation information is acceptable for these kinds of
   standards.  ABNF (RFC 4234) is an example of a language for which an
   implementation report was filed: it is interoperable in that
   protocols are specified using ABNF and these protocols can be
   successfully implemented and syntax verified.  Implementations of
   ABNF include the RFCs that use it as well as ABNF checking software.

5.4.  Multiple Contributors, Multiple Implementation Reports

   If it's easiest to divide up the work of implementation reports by
   implementation, the result -- multiple implementation reports -- MAY
   be submitted to the sponsoring Area Director one-by-one.  Each report
   might cover one implementation, including:

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      identification of the implementation,

      an affirmation that the implementation works in testing (or
      better, in deployment) ,

      whether any features are known to interoperate poorly with other

      which optional or required features are not implemented (note that
      there are no protocol police to punish this disclosure, we should
      instead thank implementors who point out unimplemented or
      unimplementable features especially if they can explain why),

      who is submitting this report for this implementation.

   These SHOULD be collated into one document for archiving under one
   title, but can be concatenated trivially even if the result has
   several summary sections or introductions.

5.5.  Test Suites

   Some automated tests, such as automated test clients, do not test
   interoperability directly.  When specialized test implementations are
   necessary, tests can at least be constructed from real-world protocol
   or document examples.  For example:

      - ABNF [RFC4234] itself was tested by combining real-world
      examples -- uses of ABNF found in well-known RFCs -- and feeding
      those real-world examples into ABNF checkers.  As the well-known
      RFCs were themselves interoperable and in broad deployment, this
      served as both a deployment proof and an interoperability proof.

      - Atom [RFC4287] clients might be tested by finding that they
      consistently display the information in a test Atom feed,
      constructed from real-world examples that cover all the required
      and optional features.

   As a counter-example, the automated WebDAV test client Litmus
   (http://www.webdav.org/neon/litmus/) is of limited use in
   demonstrating interoperability for WebDAV because it tests
   completeness of server implementations and simple test cases.  It
   does not test real-world use or whether any real WebDAV clients
   implement a feature properly or at all.

5.6.  Optional Features, extensibility features

   Optional features need not be shown to be implemented everywhere.
   However, they do need to be implemented somewhere, and more than one

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   independent implementation is required.  If an optional feature does
   not meet this requirement, the implementation report must say so and
   explain why the feature must be kept anyway versus being evidence of
   a poor-quality standard.

   Extensibility features are particularly likely to need this kind of
   treatment.  When a protocol version 1 is released, the protocol
   version field itself is likely to be unused.  Before any other
   versions exist, it can't really be demonstrated that this particular
   field or option is implemented.

6.  Examples

   Some good, extremely brief examples of implementation reports can be
   found in the archives.



   In some cases, perfectly good implementation reports are longer than
   necessary, but may preserve helpful information:



6.1.  Minimal Implementation Report

   "A large number of SMTP implementations support SMTP pipelining,
   including: (1) Innosoft's PMDF and Sun's SIMS. (2) ISODE/
   MessagingDirect's PP. (3) ISOCOR's nPlex. (4) software.com's
   post.office. (5) Zmailer. (6) Smail. (7) The SMTP server in Windows
   2000.  SMTP pipelining has been widely deployed in these and other
   implementations for some time, and there have been no reported
   interoperability problems."

   This implementation report can also be found at http://www.ietf.org/
   IESG/Implementations/SMTP-PIPELINING-Standard-implementation but the
   entire report is already reproduced above.  Since SMTP pipelining had
   no interoperability problems, the implementation report was able to
   provide all the key information in a very terse format.  The reader
   can infer from the different vendors and platforms that the codebases
   must by and large be independent.  This implementation report would
   only be slightly improved by a positive affirmation that there have
   been probes or investigations asking about interoperability problems

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   rather than merely a lack of problem reports, and by stating who
   provided this summary report.

6.2.  Covering Exceptions

   The RFC2821bis (SMTP) implementation survey asked implementors what
   features were not implemented.  The VRFY and EXPN commands showed up
   frequently in the responses as not implemented or disabled.  That
   implementation report might have followed the advice in this
   document, had it already existed, by justifying the interoperability
   of those features up front or in an "exceptions" section if the
   outline defined in this memo were used:

   "VRFY and EXPN commands are often not implemented or are disabled.
   This does not pose an interoperability problem for SMTP because EXPN
   is an optional features and its support is never relied on.  VRFY is
   required, but in practice it is not relied on because servers can
   legitimately reply with a non-response.  These commands should remain
   in the standard because they are sometimes used by administrators
   within a domain under controlled circumstances (e.g. authenticated
   query from within the domain).  Thus, the occasional utility argues
   for keeping these features, while the lack of problems for end-users
   means that the interoperability of SMTP in real use is not in the
   least degraded."

7.  Security Considerations

   This memo introduces no new security considerations.

8.  Informative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

   [RFC4234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.

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Authors' Addresses

   Lisa Dusseault
   169 University Ave.
   Palo Alto, CA  94301

   Email: ldusseault@commerce.net

   Robert Sparks
   17210 Campbell Road
   Suite 250
   Dallas, Texas  75254-4203

   Email: RjS@nostrum.com

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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   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.

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