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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Bosch 3 Internet-Draft Dovecot Oy 4 Intended status: Standards Track September 15, 2017 5 Expires: March 19, 2018 7 Internet Message Access Protocol (IMAP) - STATUS=SIZE Extension 8 draft-bosch-imap-status-size-00 10 Abstract 12 This document adds a new capability called "STATUS=SIZE" to the 13 Internet Message Access Protocol (IMAP). It allows retrieving the 14 total storage size of a mailbox with a single STATUS command rather 15 than retrieving and summing the sizes of all individual messages in 16 that mailbox. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on March 19, 2018. 35 Copyright Notice 37 Copyright (c) 2017 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Conventions Used in This Document . . . . . . . . . . . . . . 2 54 3. STATUS Command and Response Extensions . . . . . . . . . . . 3 55 4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4 56 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 57 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 58 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 59 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 8.1. Normative References . . . . . . . . . . . . . . . . . . 4 61 8.2. Informative References . . . . . . . . . . . . . . . . . 5 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 64 1. Introduction 66 This document extends Internet Message Access Protocol (IMAP) 67 [IMAP4rev1] with a new capability called "STATUS=SIZE". To determine 68 the total storage size of a mailbox, an IMAP client currently needs 69 to retrieve all message sizes individually using the FETCH command 70 with the RFC822.SIZE data item. The "STATUS=SIZE" capability 71 provides a more efficient means to achieve this. It extends the 72 STATUS command with a new "SIZE" data item, which indicates the total 73 size of all messages in the target mailbox. This way, this 74 information can be queried with just one STATUS command. When the 75 "LIST-STATUS" IMAP capability [LIST-STATUS] is also available, the 76 SIZE data item can be queried for many mailboxes at once using just 77 one LIST command. 79 This capability is particularly useful for IMAP clients that do not 80 cache the state of the message store, such as most webmail clients. 81 Without the "STATUS=SIZE" capability, such clients need to fetch all 82 message sizes from the server when the size of a mailbox needs to be 83 determined, for example when the user requests detailed quota usage 84 information. The "QUOTA" capability [QUOTA] is no help in that 85 scenario, since the provided QUOTAROOT command can only yield the 86 "STORAGE" resource usage of a whole quota root, but not for a single 87 mailbox within that root. 89 2. Conventions Used in This Document 91 In examples, "C:" indicates lines sent by a client that is connected 92 to a server. "S:" indicates lines sent by the server to the client. 94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 95 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 96 document are to be interpreted as described in [KEYWORDS]. 98 3. STATUS Command and Response Extensions 100 This extension defines one new status data item for the STATUS 101 command and response: 103 SIZE 104 The total size of the mailbox in octets. This MUST be equal to 105 the sum of the values of the RFC822.SIZE FETCH message data item 106 [IMAP4rev1] of all messages in the mailbox. 108 Example: 110 C: A01 STATUS frop (MESSAGES SIZE UIDNEXT) 111 S: * STATUS frop (MESSAGES 8 SIZE 44421 UIDNEXT 242344) 112 S: A01 OK STATUS completed 114 The same information can be obtained by using the following commands, 115 albeit less efficient: 117 C: A02 SELECT "frop" 118 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 119 S: * 8 EXISTS 120 S: * 1 RECENT 121 S: * OK [UNSEEN 7] First unseen. 122 S: * OK [UIDVALIDITY 1364851417] UIDs valid 123 S: * OK [UIDNEXT 242344] Predicted next UID 124 S: * OK [HIGHESTMODSEQ 3914] Highest 125 S: A02 OK [READ-WRITE] Select completed. 126 C: A03 FETCH 1:* (RFC822.SIZE) 127 S: * 1 FETCH (RFC822.SIZE 3224) 128 S: * 2 FETCH (RFC822.SIZE 1222) 129 S: * 3 FETCH (RFC822.SIZE 444) 130 S: * 4 FETCH (RFC822.SIZE 4516) 131 S: * 5 FETCH (RFC822.SIZE 544) 132 S: * 6 FETCH (RFC822.SIZE 922) 133 S: * 7 FETCH (RFC822.SIZE 31126) 134 S: * 8 FETCH (RFC822.SIZE 2423) 135 S: A03 OK Fetch completed. 137 When the LIST-STATUS IMAP capability [LIST-STATUS] is also available, 138 the STATUS command can be combined with the LIST command to further 139 improve efficiency. This way, the sizes of many mailboxes can be 140 queried with just one LIST command. 142 Example: 144 C: A04 LIST "" % RETURN (STATUS (MESSAGES SIZE)) 145 S: * LIST () "." "INBOX" 146 S: * STATUS "INBOX" (MESSAGES 17 SIZE 16234) 147 S: * LIST () "." "frop" 148 S: * STATUS "frop" (MESSAGES 8 SIZE 44421) 149 S: A04 OK List completed. 151 4. Formal Syntax 153 The following syntax specification augments the grammar specified in 154 [IMAP4rev1]. It uses the Augmented Backus-Naur Form (ABNF) notation 155 as specified in [ABNF]. Elements not defined here are taken from 156 [IMAP4rev1]. 158 capability =/ "STATUS=SIZE" 160 status-att =/ "SIZE" 162 [FIXME: Interaction with 64BIT capability] 164 5. Security Considerations 166 There are no known additional security issues with this extension 167 beyond those described in the base protocol described in [IMAP4rev1]. 169 6. IANA Considerations 171 The IANA is requested to add "STATUS=SIZE" to the "IMAP Capabilities" 172 registry located at . 175 7. Acknowledgements 177 Thanks to Alexey Melnikov and Michael Slusarz for reviews and 178 suggestions. 180 More reviews are appreciated. 182 8. References 184 8.1. Normative References 186 [ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax 187 Specifications: ABNF", STD 68, RFC 5234, January 2008. 189 [IMAP4rev1] 190 Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 191 4rev1", RFC 3501, March 2003. 193 [KEYWORDS] 194 Bradner, S., "Key words for use in RFCs to Indicate 195 Requirement Levels", BCP 14, RFC 2119, March 1997. 197 [LIST-STATUS] 198 Melnikov, A. and T. Sirainen, "IMAP4 Extension for 199 Returning STATUS Information in Extended LIST", RFC 5819, 200 March 2010. 202 8.2. Informative References 204 [QUOTA] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January 205 1997. 207 Author's Address 209 Stephan Bosch 210 Dovecot Oy 211 Lars Sonckin Kaari 10 212 Espoo 02600 213 Finland 215 Email: stephan.bosch@dovecot.fi