Network Working Group J. Myers
Request for Comments: 2087 Carnegie Mellon
Category: Standards Track January 1997

IMAP4 QUOTA extension

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

1. Abstract

The QUOTA extension of the Internet Message Access Protocol [IMAP4]
permits administrative limits on resource usage (quotas) to be
manipulated through the IMAP protocol.

Table of Contents

1. Abstract........................................... 1
2. Conventions Used in this Document.................. 1
3. IntrodUCtion and Overview.......................... 2
4. Commands........................................... 2
4.1. SETQUOTA Command................................... 2
4.2. GETQUOTA Command................................... 2
4.3. GETQUOTAROOT Command............................... 3
5. Responses.......................................... 3
5.1. QUOTA Response..................................... 3
5.2. QUOTAROOT Response................................. 4
6. Formal syntax...................................... 4
7. References......................................... 5
8. Security Considerations............................ 5
9. Author's Address................................... 5

2. Conventions Used in this Document

In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.

3. Introduction and Overview

The QUOTA extension is present in any IMAP4 implementation which
returns "QUOTA" as one of the supported capabilities to the
CAPABILITY command.

An IMAP4 server which supports the QUOTA capability may support
limits on any number of resources. Each resource has an atom name
and an implementation-defined interpretation which evaluates to an
integer. Examples of such resources are:

Name Interpretation

STORAGE Sum of messages' RFC822.SIZE, in units of 1024 octets
MESSAGE Number of messages

Each mailbox has zero or more implementation-defined named "quota
roots". Each quota root has zero or more resource limits. All
mailboxes that share the same named quota root share the resource
limits of the quota root.

Quota root names do not necessarily have to match the names of
existing mailboxes.

4. Commands

4.1. SETQUOTA Command

Arguments: quota root
list of resource limits

Data: 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.

Example: C: A001 SETQUOTA "" (STORAGE 512)
S: * QUOTA "" (STORAGE 10 512)
S: A001 OK Setquota completed

4.2. GETQUOTA Command

Arguments: quota root

Data: untagged responses: QUOTA

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.

Example: C: A003 GETQUOTA ""
S: * QUOTA "" (STORAGE 10 512)
S: A003 OK Getquota completed

4.3. GETQUOTAROOT Command

Arguments: mailbox name

Data: untagged responses: QUOTAROOT, QUOTA

Result: OK - getquota completed
NO - getquota error: no such mailbox, permission denied
BAD - command unknown or arguments invalid

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.

Example: C: A003 GETQUOTAROOT INBOX
S: * QUOTAROOT INBOX ""
S: * QUOTA "" (STORAGE 10 512)
S: A003 OK Getquota completed

5. Responses

5.1. QUOTA Response

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 triplets. Each triplet conatins 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)

5.2. QUOTAROOT Response

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

6. Formal syntax

The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in RFC822 with one exception; the
delimiter used with the "#" construct is a single space (SP) and not
one or more commas.

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 astring

getquotaroot ::= "GETQUOTAROOT" SP astring

quota_list ::= "(" #quota_resource ")"

quota_resource ::= atom SP number SP number

quota_response ::= "QUOTA" SP astring SP quota_list

quotaroot_response
::= "QUOTAROOT" SP astring *(SP astring)

setquota ::= "SETQUOTA" SP astring SP setquota_list

setquota_list ::= "(" 0#setquota_resource ")"

setquota_resource ::= atom SP number

7. References

[IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4",
RFC1730, University of Washington, December 1994.

[RFC-822] Crocker, D., "Standard for the Format of ARPA Internet
Text Messages", STD 11, RFC822.

8. Security Considerations

Implementors should be careful to make sure the implementation of
these commands does not violate the site's security policy. The
resource usage of other users is likely to be considered confidential
information and should not be divulged to unauthorized persons.

9. Author's Address

John G. Myers
Carnegie-Mellon University
5000 Forbes Ave.
Pittsburgh PA, 15213-3890

EMail: jgm+@cmu.edu