draft-ietf-extra-imap-status-size-01.txt   draft-ietf-extra-imap-status-size-02.txt 
EXTRA S. Bosch EXTRA S. Bosch
Internet-Draft Dovecot Oy Internet-Draft Dovecot Oy
Intended status: Standards Track March 24, 2018 Intended status: Standards Track May 29, 2018
Expires: September 25, 2018 Expires: November 30, 2018
Internet Message Access Protocol (IMAP) - STATUS=SIZE Extension Internet Message Access Protocol (IMAP) - STATUS=SIZE Extension
draft-ietf-extra-imap-status-size-01 draft-ietf-extra-imap-status-size-02
Abstract Abstract
This document adds a new capability called "STATUS=SIZE" to the This document adds a new capability called "STATUS=SIZE" to the
Internet Message Access Protocol (IMAP). It allows retrieving the Internet Message Access Protocol (IMAP). It allows retrieving the
total storage size of a mailbox with a single STATUS command rather total storage size of a mailbox with a single STATUS command rather
than retrieving and summing the sizes of all individual messages in than retrieving and summing the sizes of all individual messages in
that mailbox. that mailbox.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 25, 2018. This Internet-Draft will expire on November 30, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2 2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. STATUS Command and Response Extensions . . . . . . . . . . . 3 3. STATUS Command and Response Extensions . . . . . . . . . . . 3
4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. Normative References . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
This document extends Internet Message Access Protocol (IMAP) This document extends Internet Message Access Protocol (IMAP)
[IMAP4rev1] with a new capability called "STATUS=SIZE". To determine [IMAP4rev1] with a new capability called "STATUS=SIZE". To determine
the total storage size of a mailbox, an IMAP client currently needs the total storage size of a mailbox, an IMAP client currently needs
to retrieve all message sizes individually using the FETCH command to retrieve all message sizes individually using the FETCH command
with the RFC822.SIZE data item. The "STATUS=SIZE" capability with the RFC822.SIZE data item. The "STATUS=SIZE" capability
provides a more efficient means to achieve this. It extends the provides a more efficient means to achieve this. It extends the
STATUS command with a new "SIZE" data item, which indicates the total STATUS command with a new "SIZE" data item, which indicates the total
size of all messages in the target mailbox. This way, this size of all messages in the target mailbox. This way, this
information can be queried with just one STATUS command. When the information can be queried with just one STATUS command. When the
"LIST-STATUS" IMAP capability [LIST-STATUS] is also available, the "LIST-STATUS" IMAP capability [LIST-STATUS] is also available, the
SIZE data item can be queried for many mailboxes at once using just SIZE data item can be queried for many mailboxes at once using just
one LIST command. one LIST command.
This capability is particularly useful for IMAP clients that do not This capability is particularly useful for IMAP clients that do not
cache the state of the message store, such as most webmail clients. cache the state of the message store, such as most webmail clients.
Without the "STATUS=SIZE" capability, such clients need to fetch all Without the "STATUS=SIZE" capability, such clients need to fetch all
message sizes from the server when the size of a mailbox needs to be message sizes from the server when the size of an individual mailbox
determined, for example when the user requests detailed quota usage needs to be determined. For example, a user may request detailed
information. The "QUOTA" capability [QUOTA] is no help in that quota usage information for each mailbox to find out which specific
scenario, since the provided QUOTAROOT command can only yield the mailboxes consume most of the available storage resources. Using
"STORAGE" resource usage of a whole quota root, but not for a single this information, the user can get an overview of which mailboxes
mailbox within that root. need to be cleaned up to reduce quota usage. The "QUOTA" capability
[QUOTA] is no help in that scenario, since the provided QUOTAROOT
command can only yield the "STORAGE" resource usage of a whole quota
root, but not for each individual mailbox within that root.
2. Conventions Used in This Document 2. Conventions Used in This Document
In examples, "C:" indicates lines sent by a client that is connected In examples, "C:" indicates lines sent by a client that is connected
to a server. "S:" indicates lines sent by the server to the client. to a server. "S:" indicates lines sent by the server to the client.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS]. document are to be interpreted as described in [KEYWORDS].
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SIZE SIZE
The total size of the mailbox in octets. This is not strictly The total size of the mailbox in octets. This is not strictly
required to be an exact value, but it MUST be equal to or greater required to be an exact value, but it MUST be equal to or greater
than the sum of the values of the RFC822.SIZE FETCH message data than the sum of the values of the RFC822.SIZE FETCH message data
item [IMAP4rev1] of all messages in the mailbox. When the "QUOTA" item [IMAP4rev1] of all messages in the mailbox. When the "QUOTA"
capability [QUOTA] is also supported, this value SHOULD be equal capability [QUOTA] is also supported, this value SHOULD be equal
to the storage usage value used to enforce the "STORAGE" resource to the storage usage value used to enforce the "STORAGE" resource
limit for this mailbox. This way, the client can directly infer limit for this mailbox. This way, the client can directly infer
the quota usage. the quota usage.
Since the total storage size of a mailbox can easily exceed 4 GB,
clients MUST be capable of receiving 63-bit SIZE data item values.
The message size is chosen to be at most 63 bits wide rather than 64
bits to make implementations on various platforms (such as Java)
easier.
Example: Example:
C: A01 STATUS frop (MESSAGES SIZE UIDNEXT) C: A01 STATUS frop (MESSAGES SIZE UIDNEXT)
S: * STATUS frop (MESSAGES 8 SIZE 44421 UIDNEXT 242344) S: * STATUS frop (MESSAGES 8 SIZE 44421 UIDNEXT 242344)
S: A01 OK STATUS completed S: A01 OK STATUS completed
The same information can be obtained by using the following commands, The same information can be obtained by using the following commands,
albeit less efficient: albeit less efficient:
C: A02 SELECT "frop" C: A02 SELECT "frop"
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C: A04 LIST "" % RETURN (STATUS (MESSAGES SIZE)) C: A04 LIST "" % RETURN (STATUS (MESSAGES SIZE))
S: * LIST () "." "INBOX" S: * LIST () "." "INBOX"
S: * STATUS "INBOX" (MESSAGES 17 SIZE 16234) S: * STATUS "INBOX" (MESSAGES 17 SIZE 16234)
S: * LIST () "." "frop" S: * LIST () "." "frop"
S: * STATUS "frop" (MESSAGES 8 SIZE 44421) S: * STATUS "frop" (MESSAGES 8 SIZE 44421)
S: A04 OK List completed. S: A04 OK List completed.
4. Formal Syntax 4. Formal Syntax
The following syntax specification augments the grammar specified in The following syntax specification augments the grammar specified in
[IMAP4rev1]. It uses the Augmented Backus-Naur Form (ABNF) notation [IMAP4rev1] and [IMAP4-ABNF]. It uses the Augmented Backus-Naur Form
as specified in [ABNF]. Elements not defined here are taken from (ABNF) notation as specified in [ABNF]. Elements not defined here
[IMAP4rev1]. are taken from [IMAP4rev1] and [IMAP4-ABNF].
capability =/ "STATUS=SIZE" capability =/ "STATUS=SIZE"
status-att =/ "SIZE" status-att =/ "SIZE"
status-att-val =/ "SIZE" SP number64
number64 = 1*DIGIT
; Unsigned 63-bit integer
; (0 <= n <= 9,223,372,036,854,775,807)
5. Security Considerations 5. Security Considerations
There are no known additional security issues with this extension There are no known additional security issues with this extension
beyond those described for the base protocol [IMAP4rev1] and for the beyond those described for the base protocol [IMAP4rev1] and for the
LIST-STATUS extension [LIST-STATUS]. LIST-STATUS extension [LIST-STATUS].
6. IANA Considerations 6. IANA Considerations
The IANA is requested to add "STATUS=SIZE" to the "IMAP Capabilities" The IANA is requested to add "STATUS=SIZE" to the "IMAP Capabilities"
registry located at <http://www.iana.org/assignments/imap- registry located at <http://www.iana.org/assignments/imap-
capabilities>. capabilities>.
7. Acknowledgements 7. Acknowledgements
Thanks to Bron Gondwana, Alexey Melnikov, Stan Kalisch, and Michael Thanks to Bron Gondwana, Alexey Melnikov, Stan Kalisch, and Michael
Slusarz for reviews and suggestions. Slusarz for reviews and suggestions.
8. References 8. Normative References
8.1. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[IMAP4-ABNF]
Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
ABNF", RFC 4466, DOI 10.17487/RFC4466, April 2006,
<https://www.rfc-editor.org/info/rfc4466>.
[IMAP4rev1] [IMAP4rev1]
Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, March 2003. 4rev1", RFC 3501, March 2003.
[KEYWORDS] [KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[LIST-STATUS] [LIST-STATUS]
Melnikov, A. and T. Sirainen, "IMAP4 Extension for Melnikov, A. and T. Sirainen, "IMAP4 Extension for
Returning STATUS Information in Extended LIST", RFC 5819, Returning STATUS Information in Extended LIST", RFC 5819,
March 2010. March 2010.
8.2. Informative References
[QUOTA] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January [QUOTA] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January
1997. 1997.
Author's Address Author's Address
Stephan Bosch Stephan Bosch
Dovecot Oy Dovecot Oy
Lars Sonckin Kaari 10 Lars Sonckin Kaari 12
Espoo 02600 Espoo 02600
Finland Finland
Email: stephan.bosch@dovecot.fi Email: stephan.bosch@dovecot.fi
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