Internet Draft K. Murchison
Document: draft-murchison-lmtp-ignorequota-02.txt L. Greenfield
Expires December 15, 2002 10 June 2002
LMTP Service Extension for Ignoring Recipient Quotas
Status of this Memo
This document is an Internet-Draft and is in full conformance with
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Distribution of this memo is unlimited.
Abstract
This memo defines an extension to the LMTP service whereby a client
may ask the server to ignore a recipient's quotas when delivering a
message.
Conventions Used in the Document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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].
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0. Meta-information on this draft
This information is intended to facilitate discussion. It will be
removed when this document leaves the Internet-Draft stage.
0.1. Discussion
This draft is intended to be an extension to the Local Mail Transfer
Protocol, available from the RFC repository as
<ftp://ftp.ietf.org/rfc/rfc2033.txt>. A revised version of this
draft document will be submitted to the RFC editor as Informational
for the Internet Community.
This draft and the Local Mail Protocol Extension itself are being
discussed on the SMTP Extensions mailing list at <ietf-smtp@imc.org>.
Subscription requests can be sent to <ietf-smtp-request@imc.org>
(send an email message with the word "subscribe" in the body). More
information on the mailing list along with a WWW archive of back
messages is available at <http://www.imc.org/ietf-smtp/>.
0.2. Noted Changes
0.2.1 since -01
Editorial changes (re-submission).
0.2.2 since -00
Editorial changes.
1. Introduction
In many cases, the [LMTP] protocol is used to transfer messages to a
delivery agent which might impose some limits on the usage of system
resources by individual recipients (e.g. disk space on a mailstore).
Sometimes it may be desirable for an LMTP client to inject a message
into the mailstore regardless of these quotas (e.g. an automated
process notifying users that they are over quota).
This memo uses the mechanism defined in [ESMTP] to define an
extension to the LMTP service whereby a client may ask a server to
ignore such quotas when delivering a message.
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2. Framework for the Ignore Quota Extension
The following service extension is hereby defined:
(1) the name of the LMTP service extension is "Ignore Quota";
(2) the LHLO keyword value associated with this extension is
"IGNOREQUOTA";
(3) no parameters are allowed with this LHLO keyword value;
(4) one optional parameter using the keyword "IGNOREQUOTA" is added
to the RCPT TO command;
(5) the maximum length of a RCPT TO command line is increased by 12
characters by the possible addition of the IGNOREQUOTA keyword;
(6) no additional LMTP verbs are defined by this extension.
The remainder of this memo specifies how support for the extension
affects the behavior of an LMTP client and server.
3. The Ignore Quota service extension
When an LMTP client wishes to force delivery of a message regardless
of quotas, it first issues the LHLO command to the server. If the
LMTP server responds with code 250 to the LHLO command, and the
response includes the LHLO keyword IGNOREQUOTA, then the server sup¡
ports the Ignore Quota extension and will accept the extended ver¡
sion of the RCPT command.
The extended RCPT command is issued by an LMTP client when it wishes
to have the server ignore the recipient's quotas. The extended RCPT
command is identical to the RCPT command defined in [SMTP], except
that an IGNOREQUOTA parameter must appear after the address.
The complete syntax of this extended command is defined in [ESMTP],
with the esmtp-keyword of IGNOREQUOTA.
4. Usage Example
The following dialogue illustrates the use of the Ignore Quota ser¡
vice extension:
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S: <wait for connection>
C: <open connection to server>
S: 220 foo.oceana.com LMTP Cyrus v2.0.11 ready
C: LHLO oceana.com
S: 250-foo.oceana.com
S: 250-IGNOREQUOTA
S: 250-8BITMIME
S: 250-ENHANCEDSTATUSCODES
S: 250-AUTH DIGEST-MD5 CRAM-MD5 EXTERNAL
S: 250 PIPELINING
C: MAIL FROM:<ken@oceana.com>
S: 250 2.1.0 ok
C: RCPT TO:<test@oceana.com>
S: 250 2.1.5 ok
C: DATA
S: 354 go ahead
...
C: .
S: 452 4.2.2 Over quota
C: MAIL FROM:<ken@oceana.com>
S: 250 2.1.0 ok
C: RCPT TO:<test@oceana.com> IGNOREQUOTA
S: 250 2.1.5 ok
C: DATA
S: 354 go ahead
...
C: .
S: 250 2.1.5 Ok
C: QUIT
S: 221 2.0.0 bye
5. Security Considerations
The Ignore Quota extension described in this memo can conceivably be
used to force any or all users over their quotas and prevent further
messages from being delivered. For this reason, implementations
SHOULD try to limit the use of this extension to privileged or
trusted users. Possible means for doing so would be to either
authenticate and identify the user of the LMTP client by using the
mechanism defined in [SMTPAUTH] or restrict the use of the LMTP
client via permissions or access control lists.
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6. IANA Considerations
The registration of the LMTP "IGNOREQUOTA" extension follows:
Service Extension: Ignore Quota
LHLO Keyword: IGNOREQUOTA
Parameters: none
Verb: none
Added Behavior: defined in this memo
7. References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", Harvard University, RFC 2119, March 1997.
[LMTP] Myers, J., "Local Mail Transfer Protocol", Carnegie-Mellon
University, RFC 2033, October 1996.
[SMTP] Klensin, J., Ed., "Simple Mail Transfer Protocol", AT&T Lab¡
oratories, RFC 2821, April 2001.
[ESMTP] Klensin, J., Freed, N., Rose, M., Stefferud, E., and D.
Crocker, "SMTP Service Extensions", MCI, Innosoft Interna¡
tional, Inc., Dover Beach Consulting, Inc., Network Management
Associates, Inc., Brandenburg Consulting, RFC 1869, November
1995.
[SMTPAUTH] Myers, J., "SMTP Service Extension for Authentication",
Netscape Communications, RFC 2554, March 1999.
8. Author's Address
Kenneth Murchison
Oceana Matrix Ltd.
21 Princeton Place
Orchard Park, NY 14127
Phone: (716) 662-8973
EMail: ken@oceana.com
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Lawrence E. Greenfield
Carnegie Mellon University
5000 Forbes Ave.
Pittsburgh, PA 15213
Phone: (412) 268-4646
EMail: leg+@andrew.cmu.edu
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