Diff: draft-ietf-extra-imap-status-size-02.txt

	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.

	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.


	Internet-Drafts are draft documents valid for a maximum of six months	This document is a product of the Internet Engineering Task Force
	and may be updated, replaced, or obsoleted by other documents at any	(IETF). It represents the consensus of the IETF community. It has
	time. It is inappropriate to use Internet-Drafts as reference	received public review and has been approved for publication by the
	material or to cite them other than as "work in progress."	Internet Engineering Steering Group (IESG). Further information on
		Internet Standards is available in Section 2 of RFC 7841.


	This Internet-Draft will expire on November 30, 2018.	Information about the current status of this document, any errata,
		and how to provide feedback on it may be obtained at
		https://www.rfc-editor.org/info/rfc8438.

	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	(https://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
	carefully, as they describe your rights and restrictions with respect	carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must	to this document. Code Components extracted from this document must
	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 . . . . . . . . . . . . . . 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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