draft-ietf-extra-imap-status-size-02.txt   rfc8438.txt 
EXTRA S. Bosch Internet Engineering Task Force (IETF) S. Bosch
Internet-Draft Dovecot Oy Request for Comments: 8438 Dovecot Oy
Intended status: Standards Track May 29, 2018 Category: Standards Track August 2018
Expires: November 30, 2018 ISSN: 2070-1721
Internet Message Access Protocol (IMAP) - STATUS=SIZE Extension IMAP Extension for STATUS=SIZE
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
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
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Internet Standards is available in Section 2 of RFC 7841.
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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.
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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 . . . . . . . . . . . . . . 3
3. STATUS Command and Response Extensions . . . . . . . . . . . 3 3. STATUS Command and Response Extensions . . . . . . . . . . . 3
4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
This document extends Internet Message Access Protocol (IMAP) This document extends the 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
provides a more efficient means to achieve this. It extends the a more efficient means of achieving this. It extends the STATUS
STATUS command with a new "SIZE" data item, which indicates the total command with a new "SIZE" data item, which indicates the total size
size of all messages in the target mailbox. This way, this of all messages in the target mailbox. This way, this information
information can be queried with just one STATUS command. When the can be queried with just one STATUS command. When the LIST-STATUS
"LIST-STATUS" IMAP capability [LIST-STATUS] is also available, the IMAP capability [LIST-STATUS] is also available, the SIZE data item
SIZE data item can be queried for many mailboxes at once using just can be queried for many mailboxes at once using just one LIST
one LIST command. 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 an individual mailbox message sizes from the server when the size of an individual mailbox
needs to be determined. For example, a user may request detailed needs to be determined. For example, a user may request detailed
quota usage information for each mailbox to find out which specific quota usage information for each mailbox to find out which specific
mailboxes consume most of the available storage resources. Using mailboxes consume most of the available storage resources. Using
this information, the user can get an overview of which mailboxes this information, the user can get an overview of which mailboxes
need to be cleaned up to reduce quota usage. The "QUOTA" capability need to be cleaned up to reduce quota usage. The QUOTA capability
[QUOTA] is no help in that scenario, since the provided QUOTAROOT [QUOTA] is no help in that scenario, since the provided QUOTAROOT
command can only yield the "STORAGE" resource usage of a whole quota command can only yield the STORAGE resource usage of a whole quota
root, but not for each individual mailbox within that root. root, not 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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [KEYWORDS]. "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [KEYWORDS] [KEYWORDS2] when, and only when, they appear in all
capitals, as shown here.
3. STATUS Command and Response Extensions 3. STATUS Command and Response Extensions
This extension defines one new status data item for the STATUS This extension defines one new status data item for the STATUS
command and response: command and response:
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, 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. 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 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) bits to make implementations on various platforms (such as Java)
easier. easier.
Example: Example:
skipping to change at page 3, line 31 skipping to change at page 4, line 4
clients MUST be capable of receiving 63-bit SIZE data item values. 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 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) bits to make implementations on various platforms (such as Java)
easier. 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 efficiently:
C: A02 SELECT "frop" C: A02 SELECT "frop"
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * 8 EXISTS S: * 8 EXISTS
S: * 1 RECENT S: * 1 RECENT
S: * OK [UNSEEN 7] First unseen. S: * OK [UNSEEN 7] First unseen.
S: * OK [UIDVALIDITY 1364851417] UIDs valid S: * OK [UIDVALIDITY 1364851417] UIDs valid
S: * OK [UIDNEXT 242344] Predicted next UID S: * OK [UIDNEXT 242344] Predicted next UID
S: * OK [HIGHESTMODSEQ 3914] Highest S: * OK [HIGHESTMODSEQ 3914] Highest
S: A02 OK [READ-WRITE] Select completed. S: A02 OK [READ-WRITE] Select completed.
skipping to change at page 5, line 18 skipping to change at page 5, line 25
status-att-val =/ "SIZE" SP number64 status-att-val =/ "SIZE" SP number64
number64 = 1*DIGIT number64 = 1*DIGIT
; Unsigned 63-bit integer ; Unsigned 63-bit integer
; (0 <= n <= 9,223,372,036,854,775,807) ; (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 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" IANA has added "STATUS=SIZE" to the "IMAP Capabilities" registry
registry located at <http://www.iana.org/assignments/imap- located at <http://www.iana.org/assignments/imap-capabilities>.
capabilities>.
7. Acknowledgements
Thanks to Bron Gondwana, Alexey Melnikov, Stan Kalisch, and Michael
Slusarz for reviews and suggestions.
8. Normative References 7. Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[IMAP4-ABNF] [IMAP4-ABNF]
Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4 Melnikov, A. and C. Daboo, "Collected Extensions to IMAP4
ABNF", RFC 4466, DOI 10.17487/RFC4466, April 2006, ABNF", RFC 4466, DOI 10.17487/RFC4466, April 2006,
<https://www.rfc-editor.org/info/rfc4466>. <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, DOI 10.17487/RFC3501, March 2003,
<https://www.rfc-editor.org/info/rfc3501>.
[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,
Requirement Levels", BCP 14, RFC 2119, March 1997. DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[KEYWORDS2]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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. DOI 10.17487/RFC5819, March 2010,
<https://www.rfc-editor.org/info/rfc5819>.
[QUOTA] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January [QUOTA] Myers, J., "IMAP4 QUOTA extension", RFC 2087,
1997. DOI 10.17487/RFC2087, January 1997,
<https://www.rfc-editor.org/info/rfc2087>.
Acknowledgements
Thanks to Bron Gondwana, Alexey Melnikov, Stan Kalisch, and Michael
Slusarz for reviews and suggestions.
Author's Address Author's Address
Stephan Bosch Stephan Bosch
Dovecot Oy Dovecot Oy
Lars Sonckin Kaari 12 Lars Sonckin Kaari 12
Espoo 02600 Espoo 02600
Finland Finland
Email: stephan.bosch@dovecot.fi Email: stephan.bosch@dovecot.fi
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