Internet DRAFT - draft-kucherawy-received-state
draft-kucherawy-received-state
Individual submission D. Crocker
Internet-Draft Brandenburg InternetWorking
Intended status: Standards Track M. Kucherawy
Expires: July 16, 2012 Cloudmark, Inc.
January 13, 2012
Indicating Email Handling States in Trace Fields
draft-kucherawy-received-state-02
Abstract
This memo registers a trace field clause for use in indicating
transitions between handling queues or processing states, including
enacting inter- and intra-host message transitions. This might
include message quarantining, mailing list moderation, timed
delivery, queueing for further analysis, or other similar causes.
Status of This Memo
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Copyright Notice
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. New Trace Clause . . . . . . . . . . . . . . . . . . . . . . . 4
4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Mail Parameters Additional-registered-clauses
Sub-Registry . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. Mail Parameters Registered-states Sub-Registry . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Trace Field Examples . . . . . . . . . . . . . . . . . 8
A.1. Typical Delivery Without Obvious Delays . . . . . . . . . . 8
A.2. Delivery With Moderation . . . . . . . . . . . . . . . . . 9
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
[SMTP] defines the content of email message trace fields, commonly
the "Received" field. These are typically used to record an audit
trail of the path a message follows from origin to destination, with
one such field added each time a message moves from one host to the
next.
There are some cases where there may be large time gaps between trace
fields. Though this might be caused by transient communication
issues, they might also be caused by policy decisions or special
processing regarding the content of the message, authorization of
some identity on the message, or transitions between major software
components. Common examples include message quarantines (filters
that delay relaying or delivery of a message pending manual operator
action), pending content analysis, or mailing list servers that
impose moderation rules (mailing list owner action required regarding
mail from authors not subscribed to those lists).
This memo registers a new optional clause that can be used in trace
fields to indicate that a message entered such a special processing
queue for some period. This allows inspection of the trace
information to reveal that the cause for a time gap in trace fields
was an imposed delay rather than one caused by transient technical
difficulties.
The degree of granularity -- and therefore the degree of verbosity --
will vary according to the needs of the operator making use of this
specification. In normal operation, the verbosity would likely be
limited to record only "unusual" transitions, such as to a
quarantine.
Somewhat greater granularity might also include transitions of
administrative responsibility, such as between an Mail Transfer Agent
(MTA) operator and a Mailing List Manager (MLM) operator. This could
be further enhanced to note some transitions that are interesting
only when other transitions have occurred, such as noting entry to
the outbound queue only when the message is originating from an
"interesting" source, such as an MLM, since an MLM can introduce
significant delay and it could be useful to know when it completed
its processing, as distinct from the subsequent processing by the
originating MTA. In circumstances needing very fine-grained trace
information, fields might be created to note all of these
"significant" network architecture transitions.
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2. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS].
3. New Trace Clause
This memo creates a new trace field clause, called "state", which can
be used to indicate the nature of a delay imposed on relaying of a
message toward its recipient(s). It is followed by a single keyword
that provides that detail. An Mail Transfer Agent (MTA) or other
handling agent that determines a message has entered a state other
than normal queueing of messages for relaying or delivery MAY
generate a trace field including one of these clauses. That is, the
presence of this clause on a trace field is an indication of the
entry of the message into that state; a later trace field added would
indicate its departure from that state.
Appropriate use of this mechanism does not include associating meta-
data with the message, such as categorizing the message (e.g., the
notions of "is spam" or "was 8-bit, converted to 7-bit").
The following keywords are defined in this document; extensions may
define other registered keywords (see Section 5.2):
auth: The message entered a queue pending authentication of some
identifier in the message.
content: The message entered a queue pending content analysis, such
as scanning for spam or viruses.
convert: The message entered a queue pending content conversion for
passage through a gateway.
moderation: The message entered a hold pending mailing list
moderator action.
normal: The message is not in an administrative hold and is queued
for or is being handed off to the next handling agent (which may
be local delivery). This is the default interpretation when no
"state" clause is present.
other: The message entered a hold or queue for reasons not covered
by other keywords in this list, and not for transient technology
issues.
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outbound: The message entered a queue for outbound relaying. This
is typically the last case added for a single host, and the next
Received field is expected to be added by some other host.
quarantine: The message entered a hold in an isolation queue pending
operator action for local policy reasons.
timed: The message entered a hold in order to meet a requested
delivery window.
The ABNF for this clause:
State = CFWS "state" FWS queue-state-keyword *( "/" 1*value )
queue-state-keyword = ( reg-state-keyword / unreg-state-keyword )
reg-state-keyword = ( "auth" / "content" / "convert" /
"moderation" / "normal" / "other" /
"quarantine" / "timed" /
additional-state-keyword )
additional-state-keyword = unstructured
; see "IANA Considerations" below
unreg-state-keyword = unstructured
; from [MAIL]
"FWS" and "CFWS" are defined in [MAIL]; "value" is defined in [MIME].
A transfer agent making use of this extension MAY also include header
field comments to provide additional information.
Use of this clause by transfer agents is OPTIONAL.
4. Discussion
Handling agents are not expected to implement or support all of
these. Indeed, recording trace information for all of the states
described above could make the header of a message inordinately
large. Rather, an agent is encouraged to apply state annotations
only when a message enters a handling queue where substantial delay
is possible, and especially when a handoff has occurred between two
different, independent agents.
For example, an MTA receiving a message, doing message
authentication, scanning for viruses and spam, and then putting it in
an outbound queue could add four Received fields denoting each of
these states. However, where they are all done as part of a single
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system process, in a single pass, doing so would be considered
unusual (and extremely verbose). This method SHOULD NOT be applied
except when doing detailed analysis of a single component to identify
performance issues with those steps.
Rather, an agent that wishes to make a state annotation SHOULD add
only a single Received field including such annotation indicating (a)
the time of completion of its handling of the message via the date
portion of the field, and (b) the final disposition of that message
relative to that agent. For example, an MTA receiving a message that
performs various checks on the message before immediately handing it
off to a Mailing List Manager (MLM) would only record a "normal"
state, assuming it passes those checks. The MLM would then evaluate
the message and record its own state once it decides what the next
step will be for the handling of that message.
5. IANA Considerations
5.1. Mail Parameters Additional-registered-clauses Sub-Registry
This memo adds to the "Additional-registered-clauses" sub-registry of
the "Mail Parameters" registry, created by [SMTP], the following
entry:
Clause name: state
Description: Indicates special queue state entry
State Summary: state <state-name>
Reference: [this memo]
5.2. Mail Parameters Registered-states Sub-Registry
The "Mail Parameters" registry at IANA is updated by the creation of
the "Registered-states" sub-registry to contain valid state keywords
for use with this specification. Updates to this registry are
governed by the Specification Required rules of [IANA].
Registrations must include the following entries:
Name: The name of the state keyword being defined or updated
Description: A brief description of the keyword's meaning
Specification: The specification document that defines the queue
state being registered
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Use: One of "current" (the state keyword is in current use),
"deprecated" (the state keyword is in use but not recommended for
new implementations), or "historic" (the state keyword is no
longer in substantial current use).
The initial registration set is as follows:
+------------+---------------------------+---------------+---------+
| Name | Description | Specification | Use |
+------------+---------------------------+---------------+---------+
| auth | Held for message | [this memo] | current |
| | authentication | | |
+------------+---------------------------+---------------+---------+
| content | Held for message | [this memo] | current |
| | content analysis | | |
+------------+---------------------------+---------------+---------+
| convert | Held for message | [this memo] | current |
| | content conversion | | |
+------------+---------------------------+---------------+---------+
| moderation | Held for list moderation | [this memo] | current |
+------------+---------------------------+---------------+---------+
| normal | Message is not being held | [this memo] | current |
| | other than to accommodate | | |
| | typical relaying delays | | |
+------------+---------------------------+---------------+---------+
| other | Held for causes not | [this memo] | current |
| | covered by other | | |
| | registered state keywords | | |
+------------+---------------------------+---------------+---------+
| quarantine | Held for operator action | [this memo] | current |
| | due to content analysis | | |
| | or local policy | | |
+------------+---------------------------+---------------+---------+
| timed | Held to accommodate a | [this memo] | current |
| | specific requested | | |
| | delivery window | | |
+------------+---------------------------+---------------+---------+
6. Security Considerations
The use of this trace information can reveal hints as to local policy
that was in effect at the time of message handling.
7. Normative References
[IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
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[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[MAIL] Resnick, P., "Internet Message Format", RFC 5322,
October 2008.
[MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
October 2008.
Appendix A. Trace Field Examples
This section includes a sample of the new trace field clause in use.
A.1. Typical Delivery Without Obvious Delays
Typical message delivery
Received: from newyork.example.com
(newyork.example.com [192.0.2.250])
by mail-router.example.net (8.11.6/8.11.6)
with ESMTP id i7PK0sH7021929
for <recipient@example.net>;
Fri, Feb 15 2002 17:19:22 -0800
Received: from internal.example.com
(internal.example.com [192.168.0.1])
by newyork.example.com (8.11.6/8.11.6)
with ESMTP id i9MKZCRd064134
for <recipient@example.net>;
Fri, Feb 15 2002 17:19:08 -0800
Example 1: Typical message delivery with no appreciable handling
delays; only Received fields shown
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A.2. Delivery With Moderation
Message delivery after moderation
Received: from newyork.example.com
(newyork.example.com [192.0.2.250])
by mail-router.example.net (8.11.6/8.11.6)
with ESMTP id i7PK0sH7021929
for <recipient@example.net>;
Fri, Feb 15 2002 18:33:29 -0800
Received: from internal.example.com
(internal.example.com [192.168.0.1])
by newyork.example.com (8.11.6/8.11.6)
with ESMTP id i9MKZCRd064134
for <secret-list@example.com>
state moderation (sender not subscribed);
Fri, Feb 15 2002 17:19:08 -0800
Example 2: Message held for moderation; only Received fields shown
The message passed from internal.example.com to newyork.example.com
intended for a mailing list hosted at the latter. For list
administrative reasons, the message is held there for moderation. It
is finally released over an hour later and passed to the next host.
A comment after the state expression indicates the actual cause for
the administrative hold.
Appendix B. Acknowledgements
The authors wish to acknowledge the following for their reviews and
constructive criticisms of this proposal: Tony Finch, Carl S.
Gutenkunst, John Levine, Bill McQuillan, Robert A. Rosenberg, Hector
Santos, Rolf Sonneveld, and Mykyta Yevstifeyev.
Authors' Addresses
D. Crocker
Brandenburg InternetWorking
675 Spruce Dr.
Sunnyvale 94086
USA
Phone: +1.408.246.8253
EMail: dcrocker@bbiw.net
URI: http://bbiw.net
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Murray S. Kucherawy
Cloudmark, Inc.
128 King St., 2nd Floor
San Francisco, CA 94107
US
Phone: +1 415 946 3800
EMail: msk@cloudmark.com
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