YAM Working Group J. Klensin
Internet-Draft
Intended status: Informational B. Leiba
Expires: November 5, 2010 Huawei Technologies
May 4, 2010
Preliminary Evaluation of RFC5321, Simple Mail Transfer Protocol (SMTP),
for advancement from Draft Standard to Full Standard by the YAM Working
Group
draft-ietf-yam-5321bis-smtp-pre-evaluation-05
Abstract
This memo is a preliminary evaluation of RFC 5321, Simple Mail
Transfer Protocol for advancement from Draft to Full Standard. It
has been prepared by the The Yet Another Mail Working Group.
THIS INTERNET DRAFT IS NOT MEANT TO BE PUBLISHED AS AN RFC, BUT IS
WRITTEN TO FACILITATE DISCUSSION WITH THE IESG.
Status of this Memo
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This Internet-Draft will expire on November 5, 2010.
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Note to RFC Editor . . . . . . . . . . . . . . . . . . . . 3
2. Preliminary Evaluation . . . . . . . . . . . . . . . . . . . . 3
2.1. Document . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Time in Place . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Implementation and Operational Experience . . . . . . . . 3
2.4. Proposed Changes . . . . . . . . . . . . . . . . . . . . . 4
2.5. Non-Changes . . . . . . . . . . . . . . . . . . . . . . . 5
2.6. Downward references . . . . . . . . . . . . . . . . . . . 6
2.7. IESG Feedback . . . . . . . . . . . . . . . . . . . . . . 6
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 7
A.1. Changes from version -01 to -02 . . . . . . . . . . . . . 8
A.2. Changes from version -00 to -01 . . . . . . . . . . . . . 8
Appendix B. Detailed Issues List . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
A preliminary evaluation has been made of Simple Mail Tranfer
Protocol [RFC5321] by the Yet Another Mail (YAM) Working Group for
advancing it from Draft to Full Standard. The YAM WG requests
feedback from the IESG on this decision.
1.1. Note to RFC Editor
This Internet-Draft is not meant to be published as an RFC. It is
written to facilitate processing within the IESG.
2. Preliminary Evaluation
2.1. Document
Title: Simple Mail Transfer Protocol
Link: http://tools.ietf.org/html/rfc5321
2.2. Time in Place
RFC2026: _ "A specification shall remain at the Draft Standard
level for at least four (4) months, or until at least one IETF
meeting has occurred." _
Published: October 2008
2.3. Implementation and Operational Experience
RFC2026: _ "significant implementation and successful operational
experience ... characterized by a high degree of technical
maturity and by a generally held belief that the specified
protocol or service provides significant benefit to the Internet
community." _
Confidence level: Very high.
Electronic mail (historically known as "netmail" before "email" came
into common use) has been in active use in the Internet community
since the early 1970s. Although many small adjustments and
clarifications have been made, the basic transport protocol that is
now used has been changed in only two important ways since the
publication of RFC 821 in August 1982. One of those changes was the
introduction of DNS-based mail routing with the MX record with RFC
974 in January 1986 (with some small clarifications in RFC 1123 in
October 1989). The second was the introduction of a model for
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negotiating optional services with RFC 1425 in February 1993.
While many mail systems over the years have relied more on the
robustness of receiving systems in the face of deviations (or
creative interpretations of RFC 821 language in spite of changes and
clarifications over the last 27 years), the DRUMS WG work that
produced RFC 2821 [RFC2821] in April 2001 was largely an update to
clarify various provisions. With the exception of a very few edge-
case clarifications and changes in requirements levels, systems that
conform to the combination of RFC 821 [RFC0821] and RFC 1869
[RFC1869] (both Full Standards) conform to RFCs 2821 (April 2001) and
5321. Those differences represented existing practice when RFC 5321
was written and have been well-tested and widely deployed.
2.4. Proposed Changes
The YAM WG proposes making the changes listed below in a revision.
That the working group will review or consider an issue means that
when RFC 5321bis is submitted for IESG approval, either changes will
have be made for that issue or the working group will provide the
IESG a summary of why it decided not to.
Terminology: There has been ongoing controversy about the
terminology in RFC 5321 and especially changes made between 821
and 2821 or between 2821 and 5321. While we assume that 5321 is
adequate, the WG will review terminology as appropriate and may
make some adjustments.
Metalanguage: During and after IETF Last Call on 5321, some
suggestions were made about how to make metalanguage productions
easier to find and connect. A complete rewrite or restructuring
of the metalanguage should be avoided on the grounds that it would
carry a very high risk of introducing errors. Instead, resources
and tools permitting (significant manual work is now required),
the revised document will contain an index to productions and
where they are defined.
Normative References: RFC 5321 is worded in a way that makes some
references normative that are not strictly required to be. The WG
will consider whether those rewordings are appropriate. In
particular, the reference to RFC 821 will be moved to Informative
because all normative uses have been removed.
Existing Errata Reports: The working group will incorporate
corrections to accepted errata, as shown in the RFC Editor's
errata tool. Errata ID 1683 is currently the only such item. IDs
1543 and 1851 are reported, but unverified; the working group will
consider those. See Appendix B for details.
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Small Editorial Errors: Clear up various small editorial errors,
e.g., the use of "SHOULD not" in one location. YAM issue tracker
issues 5, 6, 9, 12, and 13 refer to issues of this sort. The
working group will add others that may be identified in its
detailed review. See Appendix B for details.
Clarifications: The working group will attempt to address things
that have been identified as unclear in RFC 5321. YAM issue
tracker issues 7, 8, 10, and 11 refer to issues of this sort.
There has been discussion of these on the mailing list, and the
resolutions of each may or may not result in a change in the
document. See Appendix B for details. In no case will
clarification changes be significant enough to violate "Non-
Changes", Section 2.5.
Updates to References: Section 7.1 of RFC 5321 should have
informational references to RFC 3207 (STARTTLS) and RFC 4954 (SMTP
AUTH); they will be added in 5321bis. RFC 3851 has been obsoleted
by RFC 5751; that informational reference will be updated in
5321bis. Other obsolete references that may exist will be updated
as appropriate.
2.5. Non-Changes
The YAM WG discussed and chose not to make the following changes:
1. Complete revision, rearrangement, or reformatting of metalanguage
(see #2 above).
2. Any extensions that would violate the rules for Full Standard or
otherwise require revisiting the approved interoperability report
for RFC 5321.
3. A number of extensions and changes that would have imposed
significant new requirements on SMTP, or that would have implied
incompatible changes, were proposed both during the DRUMS WG
period (leading up to RFC 2821) and during the subsequent
discussions that led to RFC 5321. In each case, the authors were
advised to prepare a specific Internet-Draft describing the
change, convince the community to progress it to Proposed
Standard, and then implement and deploy the change quickly enough
to "catch up" with the progress that started with RFC 2821. The
notion was that those changes could then be integrated with the
progression at the same maturity level. It is important to note
that, independent of any constraints imposed by the YAM charter
design, none of those proposals have appeared and been progressed
even to IETF Last Call.
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4. As agreed when RFC 5321 was reviewed, the examples will not be
revised to bring them into alignment with RFC 2606 (BCP 32)
conventions (example.com, etc.). The issues are explained in
Section 1.3 of RFC 5321. The community also noted at the time
that the relevant examples have been in use, substantially
unchanged, for more than a quarter-century with no serious claims
of confusion or other harm being caused.
5. The Security Considerations section was extensively reviewed in
2008 (during the review and approval of RFC 5321). No evidence
has appeared since then that would require further review or
additional changes.
2.6. Downward references
At Full Standard, the following references would be downward
references:
RFC 5322 if 5322bis is not progressed simultaneously with 5321bis.
(This is not expected to happen.)
RFC 4291, IP Version 6 Addressing Architecture.
RFC 3848, ESMTP and LMTP Transmission Types Registration. Note
that it is possible to rephrase RFC 5321bis to avoid this
normative reference and the WG will consider doing that.
2.7. IESG Feedback
The YAM WG requests feedback from the IESG on this decision. In
particular:
o Does the IESG believe the proposed changes are suitable during a
move from Draft to Full Standard?
o Excluding the previous proposed changes and expected IESG support
for technically substantive IETF last call feedback, does the IESG
believe any additional changes are critical to advance this
document from draft to full standard? If so, please provide
sufficient information so the WG can address these issues prior to
IETF last call or determine that the document is inappropriate for
the YAM WG to process at this time.
o Does the IESG consider the downward references acceptable for a
full standard? If not, please cite which specific downward
reference or references are problematic and why so the WG can
address these issues prior to IETF last call or determine the
document is inappropriate for the YAM WG to process at this time.
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3. IANA Considerations
This document contains no IANA actions.
4. Security Considerations
This document requests IESG feedback and does not raise any security
concerns. Security considerations for RFC 5321 have been taken into
account during the preliminary evaluation and appear in either
Section 2.4 or Section 2.5 of this document.
5. Acknowledgments
This document was prepared from a template supplied by Subramanian
Moonesamy.
Some of the information provided in this document, but not provided
in the RFC 1652 evaluation (http://www.ietf.org/id/
draft-ietf-yam-rfc1652bis-pre-evaluation-00.txt), was inspired by
brief discussions with Pasi Eronen and Subramanian Moonesamy during
IETF 76.
6. References
6.1. Normative References
[RFC5321] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
6.2. Informative References
[RFC0821] Postel, J., "Simple Mail Transfer Protocol", STD 10,
RFC 821, August 1982.
[RFC1869] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extensions", STD 10, RFC 1869,
November 1995.
[RFC2821] Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
April 2001.
Appendix A. Change Log
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A.1. Changes from version -01 to -02
o Added classes of changes for "errata" and "clarifications".
o Included YAM issue tracker numbers in the lists of possible
changes.
A.2. Changes from version -00 to -01
o Added Security Considerations and Examples to the "no change" list
in Section 2.5.
o Identified RFC 821 as a specific reference to be moved from
Normative to Informative.
o Add blanket placeholder for changes due to small editorial errors.
Appendix B. Detailed Issues List
What follows are abbreviated details of the errata and tracker issues
at the time of this writing, along with URLs to the actual entries.
They are provided here to make it easier for IESG members -- and
others -- to review them. If your browser does not automatically
turn URLs into clickable links, copy/paste should still be
convenient.
Errata ID 1543: In section 3.8, client should treat a closed
connection as a 451 response, not as 421 (current).
http://www.rfc-editor.org/errata_search.php/doc/html/rfc5321
The working group will consider this item. Discussion so far
leans toward not making the change.
Errata ID 1683: In section 4.4, missing repeat in grammar for
Additional-Registered-Clauses.
http://www.rfc-editor.org/errata_search.php/doc/html/rfc5321
This item has been accepted, and the working group will make a
change for it.
Errata ID 1851: In section 4.1.1.5, text specifying server behaviour
on a closed connection is misplaced, and should be in section
4.1.1.10 or section 3.8.
http://www.rfc-editor.org/errata_search.php/doc/html/rfc5321
The working group will consider this item.
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Tracker Issue 5: In section 6.1, reword "next subsection" to specify
the section number, for clarity.
http://trac.tools.ietf.org/wg/yam/trac/ticket/5
This item suggests an editorial change, and the working group will
consider it.
Tracker Issue 6: In section 4.4, there is extraneous text that
should be removed or corrected (probably a paste error).
http://trac.tools.ietf.org/wg/yam/trac/ticket/6
This item documents an editorial error, and the working group will
make a change for it.
Tracker Issue 7: In section 2.2.2, add a bullet saying "Future SMTP
extensions SHOULD explicitly specify if they are valid on the
Submission port."
http://trac.tools.ietf.org/wg/yam/trac/ticket/7
The working group will consider this item.
Tracker Issue 8: In section 4.1.1.3, remove text about source routes
and move text about failed recipients here.
http://trac.tools.ietf.org/wg/yam/trac/ticket/8
The working group will consider this item.
Tracker Issue 9: In section 3.9.2, there is extraneous text that
should be removed or corrected (probably a paste error).
http://trac.tools.ietf.org/wg/yam/trac/ticket/9
This item documents an editorial error, and the working group will
make a change for it.
Tracker Issue 10: In section 3.9, add a subsection for "Backup MX"
or "Plain forwarding".
http://trac.tools.ietf.org/wg/yam/trac/ticket/10
The working group will consider this item.
Tracker Issue 11: In section 3.1, a server can offer two greeting
codes to a new connection: 220 or 554. Clarify the semantics of
the 554 code.
http://trac.tools.ietf.org/wg/yam/trac/ticket/11
The working group will consider this item.
Tracker Issue 12: In examples, explicitly state that the examples
will not be changed to use RFC 2606 domain names (such as
example.com).
http://trac.tools.ietf.org/wg/yam/trac/ticket/12
This item suggests an editorial change, and the working group will
consider it.
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Tracker Issue 13: In section 4.2.5, "SHOULD not" appears, with
lowercase "not". The "NOT" should be in uppercase.
http://trac.tools.ietf.org/wg/yam/trac/ticket/13
This item documents an editorial error, and the working group will
make a change for it.
Authors' Addresses
John C Klensin
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
USA
Phone: +1 617 245 1457
Email: john+ietf@jck.com
Barry Leiba
Huawei Technologies
Phone: +1 646 827 0648
Email: barryleiba@computer.org
URI: http://internetmessagingtechnology.org/
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