Network Working Group D. Cridland Internet-Draft Clues Expires: February 18, 2003 A. Melnikov ACI August 20, 2002 IMAP4rev1 QUOTA Extension draft-cridland-imap-quota-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 18, 2003. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract The QUOTA extension of the Internet Message Access Protocol IMAP4 [2] permits administrative limits on resource usage (quotas) to be manipulated through the IMAP protocol. This memo replaces RFC2087 [4], but attempts to remain backwards compatible whenever possible. Cridland & Melnikov Expires February 18, 2003 [Page 1] Internet-Draft QUOTA August 2002 1. Document Conventions In protocol examples, this document uses a prefix of "C: " to denote lines sent by the client to the server, and "S: " for lines sent by the server to the client. Lines prefixed with "// " are comments explaining the previous protocol line. These prefixes and comments are not part of the protocol. Lines without any of these prefixes are continuations of the previous line, and no line break is present in the protocol unless specifically mentioned. Again, for examples, the hierarchy separator on the server is presumed to be "/" throughout. None of these assumptions is required nor recommended by this memo. 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 RFC2119 [5]. Other capitalised words are IMAP4 [2] keywords or keywords from this document. Cridland & Melnikov Expires February 18, 2003 [Page 2] Internet-Draft QUOTA August 2002 2. Introduction and Overview The QUOTA extension is present in any IMAP4rev1 server which advertises any CAPABILITY beginning with "QUOTA=". The capability "QUOTA", with no "=", denotes a RFC2087 [4] compliant server. Some commands and responses are not present in such servers, and clients MUST NOT rely on their presence in the absence of any capability beginning "QUOTA=". Quotas can be used to restrict clients for administrative reasons, but the QUOTA extension can also be used to indicate system limits and current usage levels to clients. Although RFC2087 [4] specified an IMAP4 QUOTA extension, and this has seen deployment in servers, it has seen little deployment in clients. Since the meaning of the resources was left implementation-dependant, it was impossible for a client implementation to determine which resources were supported, and impossible to determine which mailboxes were in a given quota root, without a priori knowledge of the implementation. Cridland & Melnikov Expires February 18, 2003 [Page 3] Internet-Draft QUOTA August 2002 3. Terms 3.1 Resource A resource has a name, a formal definition. 3.1.1 Name The resource name is an atom, as defined in IMAP4 [2]. These MUST be registered with IANA, or begin with "X-", which indicates an experimental resource. Implementation specific resources MUST be registered with IANA, and begin with "V-". Supported resource names MUST be advertised as a capability, by prepending the resource name with "QUOTA=RES-". Server is not required to support all reported resource types on all quota roots. 3.1.2 Definition The resource definition or document containing it, while not visible through the protocol, SHOULD be registered with IANA. The usage of a resource MUST be represented as a 32 bit unsigned integer. 0 indicates no usage of a resource. Usage integers MUST NOT represent proportional use, such that a client can compare available resource between two separate quota roots or servers with reasonable accuracy. Limits will be specified as, and MUST be represented as, an integer. 0 indicates that any usage is prohibited. Limits may be hard or soft - that is, an implementation MAY choose, or be configured, to disallow any command if the limit on a resource is or would be exceeded. All resources which the server handles must be advertised in a CAPABILITY constisting of the resource name prefixed by "QUOTA=RES-". For compatability with RFC2087 [4], a client which discovers resources available on the server which are not advertised through this mechanism MUST treat the resource as if it were completely opaque, and without any meaning. The resources STORAGE (Section 5.1), MESSAGES (Section 5.2) and MAILBOXES (Section 5.3) are defined in this memo. 3.2 Quota Root Each mailbox has zero or more implementation-defined named "quota Cridland & Melnikov Expires February 18, 2003 [Page 4] Internet-Draft QUOTA August 2002 roots". Each quota root has zero or more resource limits (quotas). All mailboxes that share the same named quota root share the resource limits of the quota root. Quota root names need not be mailbox names, nor is there any relationship defined by this memo between a Quota root name and a mailbox name. A quota root name is an astring, as defined in IMAP4 [2]. It MUST be treated as an opaque string by any clients which do not have a priori knowledge of the server implementation. Quota roots are used since not all implementations may be able to calculate usage, or apply quotas, on arbitary mailboxes or mailbox hierarchies. A client might be able to determine how a quota root relates to the mailboxes it governs by looking at any mapping which MAY be given in a QUOTAMAP (Section 4.2.3) response. Not all resources may be limitable or calculatable for all quota roots. Further, not all resources may support all limits - some limits may be present in the underlying system. A server implementation of this memo SHOULD advise the client of such inherent limits, by generating QUOTA (Section 4.2.1) responses and SHOULD advise the client of which resources are limitable for a particular quota root. A SETQUOTA (Section 4.1.3) command MAY also round a quota limit in an implementation dependant way, if the granularity of the underlying system demands it. A client MUST be prepared for a SETQUOTA (Section 4.1.3) command to fail if a limit cannot be set. Implementation Notes This means that, for example under UNIX, a quota root may have a MESSAGES (Section 5.2) quota always set due to the number of inodes available on the filesystem, and similarly STORAGE (Section 5.1) may be rounded to the nearest block and limited by free filesystem space. Cridland & Melnikov Expires February 18, 2003 [Page 5] Internet-Draft QUOTA August 2002 4. Definitions 4.1 Commands The following commands exist for manipulation and querying quotas. 4.1.1 GETQUOTA Arguments: quota root Responses: REQUIRED untagged responses: QUOTA OPTIONAL untagged response: SUPPORTEDQUOTARES Result: OK - getquota completed NO - getquota error: no such quota root, permission denied BAD - command unknown or arguments invalid The GETQUOTA command takes the name of a quota root and returns the quota root's resource usage and limits in an untagged QUOTA response. GETQUOTA command MAY also return an untagged SUPPORTEDQUOTARES response that lists all resource types that can be set on the quota root. If the SUPPORTEDQUOTARES response is not returned by the server, this means that all resource types returned in CAPABILITY response (i.e. all capability items with "QUOTA=RES-" prefix) are applicable to the quota root. Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE [...] [...] C: G0001 GETQUOTA "!partition/sda4" S: * QUOTA "!partition/sda4" (STORAGE 104 10923847) S: * SUPPORTEDQUOTARES "!partition/sda4" STORAGE S: G0001 OK Getquota complete 4.1.2 GETQUOTAROOT Arguments: mailbox name Responses: REQUIRED untagged responses: QUOTAROOT, QUOTA OPTIONAL untagged responses: QUOTAMAP Result: OK - getquotaroot completed NO - getquotaroot error: no such mailbox, permission denied BAD - command unknown or arguments invalid Cridland & Melnikov Expires February 18, 2003 [Page 6] Internet-Draft QUOTA August 2002 The GETQUOTAROOT command takes the name of a mailbox and returns the list of quota roots for the mailbox in an untagged QUOTAROOT response. For each listed quota root, it also returns the quota root's resource usage and limits in an untagged QUOTA response and MAY return an untagged QUOTAMAP response that describes a relationship between the quota root and the mailbox (mapping). //Should we remove some information from QUOTAMAP as it is already returned in QUOTAROOT? Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE QUOTA=RES-MESSAGES [...] [...] C: G0002 GETQUOTAROOT INBOX S: * QUOTAROOT INBOX "#user/alice" "!partition/sda4" S: * QUOTAMAP "#user/alice" INBOX (USER) S: * QUOTAMAP "!partition/sda4" INBOX () S: * QUOTA "#user/alice" (MESSAGES 42 1000) S: * QUOTA "!partition/sda4" (STORAGE 104 10923847) S: G0002 OK Getquotaroot complete 4.1.3 SETQUOTA Arguments: quota root list of resource limits Responses: untagged responses: QUOTA Result: OK - setquota completed NO - setquota error: can't set that data BAD - command unknown or arguments invalid The SETQUOTA command takes the name of a mailbox quota root and a list of resource limits. The resource limits for the named quota root are changed to be the specified limits. Any previous resource limits for the named quota root are discarded. If the named quota root did not previously exist, an implementation may optionally create it and change the quota roots for any number of existing mailboxes in an implementation-defined manner. // Should we be sending untagged QUOTA responses for all side effect changes? Cridland & Melnikov Expires February 18, 2003 [Page 7] Internet-Draft QUOTA August 2002 // Quota root name must uniquely identifier mapping [if any] (different mapping must have non overlapping namespaces) Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE QUOTA=RES-MESSAGES [...] [...] C: S0000 GETQUOTA "#user/alice" S: * QUOTA "#user/alice" (STORAGE 54 111 MESSAGES 42 1000) S: S0000 OK Getquota completed C: S0001 SETQUOTA "#user/alice" (STORAGE 510) S: * QUOTA "#user/alice" (STORAGE 58 512) // The server has rounded the STORAGE quota limit requested to the nearest 512 blocks of 1024 octects, or else another client has performed a near simultaneous SETQUOTA, using a limit of 512. S: S0001 OK Rounded quota C: S0002 SETQUOTA "!partition/sda4" (STORAGE 99999999) S: * QUOTA "!partition/sda4" (STORAGE 104 10923847) // The server has not changed the quota, since this is a filesystem limit, and cannot be changed. The QUOTA response here is entirely optional. S: S0002 NO Cannot change system limit 4.1.4 DELQUOTA Arguments: quota root resource name Responses: no specific responses for this command Result: OK - delquota completed NO - delquota error: can't delete that data BAD - command unknown or arguments invalid The DELQUOTA command takes the name of a mailbox quota root and a resource name. The resource limit associated with the resource name is removed (or reset to the underlying system limit), or other resources associated with the same quote root are unaffected. (This command is different from "SETQUOTA ( 0)", because the latter discards all resources associated with the quota root). Cridland & Melnikov Expires February 18, 2003 [Page 8] Internet-Draft QUOTA August 2002 An implementation may optionally change the quota roots for any number of existing mailboxes in an implementation-defined manner. // Should we be sending untagged QUOTA responses for all side effect changes? Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE QUOTA=RES-MESSAGES [...] [...] C: S0001 DELQUOTA "#user/alice" STORAGE S: * QUOTA "#user/alice" (MESSAGES 42 1000) S: S0001 OK STORAGE limit removed. C: S0002 DELQUOTA "!partition/sda4" STORAGE S: * QUOTA "!partition/sda4" (STORAGE 104 10923847) // The server has not changed the quota, since this is a filesystem limit, and cannot be changed. The QUOTA response here is entirely optional. S: S0002 NO Cannot remove system limit 4.1.5 LISTQUOTA Arguments: quota root OPTIONAL untagged responses: QUOTAMAP Result: OK - listquota completed NO - listquota error: no such quota root, permission denied BAD - command unknown or arguments invalid The LISTQUOTA command takes the name of a quota root and returns QUOTAMAP responses for all mailboxes accessible to the user that are governed by this quota root //Client should be prepared to receive a lot of traffic, because this might be equivalent to performing Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE QUOTA=RES-MESSAGES [...] [...] C: L0001 LISTQUOTA "#user/alice" S: * QUOTAMAP "#user/alice" INBOX (USER) Cridland & Melnikov Expires February 18, 2003 [Page 9] Internet-Draft QUOTA August 2002 S: * QUOTAMAP "#user/alice" "Drafts" (USER) S: * QUOTAMAP "#user/alice" "Work/Meetings" (USER) S: * QUOTAMAP "#user/alice" "Work/Projects" (USER) S: L0001 OK 4.1.6 STATUS attribute RECOVERABLE DELETED-MESSAGES and DELETED-STORAGE status data items allow to estimate the amount of resource freed by an EXPUNGE on a mailbox. DELETED-MESSAGES status data item requests the server to return the number of messages with \Deleted flag set. //DELETED-STORAGE - Is it the sum of RFC822.SIZEs or "How match we can recover" (depending on messages with \Deleted flag it may be different) Example: S: * CAPABILITY [...] QUOTA QUOTA=RES-STORAGE QUOTA-RES-MESSAGES [...] [...] C: S0003 STATUS INBOX (MESSAGES DELETED-MESSAGES DELETED-STORAGE) S: * STATUS INBOX (MESSAGES 12 DELETED-MESSAGES 4 DELETED-STORAGE 8) // 12 messages, 4 of which would be deleted when an EXPUNGE happens. S: S0003 OK Status complete. 4.2 Responses The following responses may be sent by the server. 4.2.1 QUOTA Data: quota root name list of resource names, usages, and limits This response occurs as a result of a GETQUOTA or GETQUOTAROOT command. The first string is the name of the quota root for which this quota applies. The name is followed by a S-expression format list of the resource usage and limits of the quota root. The list contains zero or more Cridland & Melnikov Expires February 18, 2003 [Page 10] Internet-Draft QUOTA August 2002 triplets. Each triplet contains a resource name, the current usage of the resource, and the resource limit. Resources not named in the list are not limited in the quota root. Thus, an empty list means there are no administrative resource limits in the quota root. Example: S: * QUOTA "" (STORAGE 10 512): 4.2.2 QUOTAROOT Data: mailbox name zero or more quota root names This response occurs as a result of a GETQUOTAROOT command. The first string is the mailbox and the remaining strings are the names of the quota roots for the mailbox. Example: S: * QUOTAROOT INBOX "" S: * QUOTAROOT comp.mail.mime 4.2.3 QUOTAMAP Data: quota root name mailbox name OPTIONAL mapping name This response occurs as a result of a GETQUOTAROOT or LISTQUOTA command. It defines the relationship (mapping) between the quota root and the mailbox. 4.2.4 SUPPORTEDQUOTARES Data: quota root name zero or more resource names SUPPORTEDQUOTARES response occurs as a result of GETQUOTA command. It lists all resource types that can be set on the quota root. If the list of resources is missing (not empty!) this means that the server can't list supported resources and the client must try SETQUOTA. Note that SUPPORTEDQUOTARES with no resource name is different from the absent SUPPORTEDQUOTARES response. If the SUPPORTEDQUOTARES response is not returned by the server, this means that all resource types returned in CAPABILITY response (i.e. all capability items with "QUOTA=RES-" prefix) are applicable to the Cridland & Melnikov Expires February 18, 2003 [Page 11] Internet-Draft QUOTA August 2002 quota root. 4.3 Response Codes 4.3.1 OVERQUOTA OVERQUOTA response code is returned in NO tagged response to an APPEND/COPY when the addition of the message(s) puts mailbox over any one of its quota limits. Example: S: C: A003 APPEND Drafts (\Seen $MDNSent) {310} S: + Ready for literal data C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) C: From: Fred Foobar C: Subject: afternoon meeting C: To: mooch@owatagu.siam.edu C: Message-Id: C: MIME-Version: 1.0 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII C: C: Hello Joe, do you think we can meet at 3:30 tomorrow? C: S: A003 NO [OVERQUOTA] APPEND Failed 4.4 Interaction with the ACL and ACL2 extensions Both the ACL [3] and ACL2 extensions define access control lists, and specific permissions which are required for certain actions. // But how do they interact? Presumably, QUOTAMAP responses containing mailboxes which cannot be LISTed shouldn't be generated. Quota Roots which govern no mailboxes to which the client has write access should also, presumably, be hidden from the client's view? Administration rights to set quotas? Cridland & Melnikov Expires February 18, 2003 [Page 12] Internet-Draft QUOTA August 2002 5. Resource Definitions The following resources are defined in this memo. A server supporting a resource MUST advertise this as a CAPABILITY with a name consisting of the resource name prefixed by "QUOTA=RES-". A server MAY support mupltiple resource types, and MUST advertise all resources it supports. 5.1 STORAGE The physical space estimate, in units of 1024 octets, of the mailboxes governed by the quota root. This MAY not be the same as the sum of the RFC822.SIZE of the messages. Some implementations MAY include metadata sizes for the messages and mailboxes, other implementations MAY store messages in such a way that the physical space used is smaller. Additional messages MAY NOT increase the usage. Client MUST NOT use the usage figure for anything other than informational purposes, for example, they MUST NOT refuse to APPEND a message if the limit less the usage is smaller than the RFC822.SIZE divided by 1024 of the message. The usage figure may change as a result of performing actions not associated with adding new messages to the mailbox, such as SEARCH, since this may increase the amount of metadata included in the calculations. Support for this resource MUST be indicated by the server by advertising the CAPABILITY "QUOTA=RES-STORAGE". A resource named the same was also given as an example in RFC2087 [4], clients conformant to this specification connecting to servers which do not advertise "QUOTA=RES-STORAGE", yet allow a resource named STORAGE, MUST NOT assume that it is the same resource. 5.2 MESSAGES The number of messages stored within the mailboxes governed by the quota root. This MUST be an exact number, however, clients MUST NOT assume that a change in the usage indicates a change in the number of messages available, since the quota root may include mailboxes the client has no access to. Support for this resource MUST be indicated by the server by advertising the CAPABILITY "QUOTA=RES-MESSAGES". A resource named the same was also given as an example in RFC2087 [4], clients conformant to this specification connecting to servers which do not advertise "QUOTA=RES-MESSAGES", yet allow a resource Cridland & Melnikov Expires February 18, 2003 [Page 13] Internet-Draft QUOTA August 2002 named MESSAGES, MUST NOT assume that it is the same resource. 5.3 MAILBOXES The number of mailboxes governed by the quota root. This MUST be an exact number, however, clients MUST NOT assume that a change in the usage indicates a change in the number of mailboxes, since the quota root may include mailboxes the client has no access to. Support for this resource MUST be indicated by the server by advertising the CAPABILITY "QUOTA=RES-MAILBOXES". Cridland & Melnikov Expires February 18, 2003 [Page 14] Internet-Draft QUOTA August 2002 6. Quota Root Relationship Definitions Where a specific quota root relationship, or mapping, is given in a QUOTAMAP response, a client MAY make certain assumptions about which Quota Root, and therefore which Quota, will govern an existing or newly created mailbox, without having to use LISTQUOTAROOT after creation. Implementations MAY provide no mapping information at all, either for security reasons or because the mapping actually used does not fit one of the defined mappings. Relationship names are atoms, as defined in IMAP4 [2], and must be registered at IANA. Relationships which are implementation specific are of limited use for interoperability, however they MUST be registered and prefixed with "V-", along with the meaning of any parameters they list. The mapping applicable to a particular quota root and mailbox is given in the QUOTAMAP (Section 4.2.3) response. 6.1 HIER The quota root in question applies to all inferior mailboxes of the named mailbox, and a newly created inferior mailbox will be governed by the same quota root. 6.2 SINGLE The quota root in question applies only to the named mailbox, and to no other. This is mutually exclusive with HIER mappings. 6.3 USER The quota root in question applies to all mailboxes owned by the same user. The definition of ownership is implementation dependant. // Do we restrict this to the currently logged in user? 6.4 DOMAIN The quota root in question applies to all mailboxes in the current domain on at least this server. If the server doesn't support multiple domains, GLOBAL MUST be used instead. 6.5 GLOBAL The quota root in question applies to all mailboxes on at least this Cridland & Melnikov Expires February 18, 2003 [Page 15] Internet-Draft QUOTA August 2002 server. Cridland & Melnikov Expires February 18, 2003 [Page 16] Internet-Draft QUOTA August 2002 7. Formal syntax The following syntax specification uses the Augmented Backus-Naur Form (ABNF) notation as specified in ABNF [1]. Non-terminals referenced but not defined below are as defined by IMAP4 [2]. Except as noted otherwise, all alphabetic characters are case- insensitive. The use of upper or lower case characters to define token strings is for editorial clarity only. Implementations MUST accept these strings in a case-insensitive fashion. getquota = "GETQUOTA" SP quota_root_name getquotaroot = "GETQUOTAROOT" SP mailbox quota_list = "(" quota_resource *(SP quota_resource) ")" quota_resource = resource_name SP resource_usage SP resource_limit quota_response = "QUOTA" SP quota_root_name SP quota_list quotaroot_response = "QUOTAROOT" SP mailbox *(SP quota_root_name) setquota = "SETQUOTA" SP quota_root_name SP setquota_list setquota_list = "(" [setquota_resource *(SP setquota_resource)] ")" setquota_resource = resource_name SP resource_limit quota_root_name = astring resource_limit = number resource_name = "STORAGE" | "MESSAGES" | "MAILBOXES" | resource_name_priv | resource_name_vnd | resource_name_ext resource_name_priv = "X-" atom ;; Private use resource_name_vnd = "V-" atom ;; Vendor specific, must be registered with IANA resource_name_ext = atom ;; Not starting with either X- or V- and defined Cridland & Melnikov Expires February 18, 2003 [Page 17] Internet-Draft QUOTA August 2002 ;; in a Standard Track or Experimental RFC resource_names = "(" [resource_name *(SP resource_name)] ")" resource_usage = number ;; must be less than corresponding resource_limit quotamap_response = "QUOTAMAP" SP quota_root_name SP mailbox SP "(" [mapping] ")" suppres_response = "SUPPORTEDQUOTARES" SP quota_root_name [SP resource_names] mapping = "HIER" | "SINGLE" | "USER" | "DOMAIN" | "GLOBAL" | mapping_vendor | mapping_ext mapping_vendor = "V-" atom ;; Vendor specific, must be registered with IANA mapping_ext = atom ;; Must be defined by an Experimental or a Standard Track RFC delquota = "DELQUOTA" SP quota_root_name SP resource_name capability_quota = capa_quota_res | capa_quota_mapping capa_quota_res = "QUOTA=RES-" resource_name capa_quota_mapping? listquota = "LISTQUOTA" SP quota_root_name status-att =/ "DELETED-MESSAGES" | "DELETED-STORAGE" //Should this be optional unless the server implements MESSAGES/ STORAGE? resp-text-code =/ "OVERQUOTA" Cridland & Melnikov Expires February 18, 2003 [Page 18] Internet-Draft QUOTA August 2002 References [1] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [2] Crispin, M., "Internet Message Access Protocol - Version 4rev1", RFC 2060, December 1996. [3] Myers, J., "IMAP4 ACL extension", RFC 2086, January 1997. [4] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January 1997. [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Authors' Addresses Dave A. Cridland Clues Ltd EMail: dave.cridland@clues.ltd.uk URI: http://www.clues.ltd.uk/ Alexey Melnikov ACI WorldWide / MessagingDirect EMail: mel@messagingdirect.com URI: http://orthanc.ab.ca/mel/ Cridland & Melnikov Expires February 18, 2003 [Page 19] Internet-Draft QUOTA August 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. 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