From: Unknown <> Date: Fri, 7 Mar 2008 22:05:13 +0000 (+0000) Subject: add files for 2008-03-07T22:05:13Z X-Git-Tag: imap-2007a1~3 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a1dc9ab0be949ddfa928aedab00dbbde624f2066;p=uw-imap add files for 2008-03-07T22:05:13Z --- diff --git a/docs/rfc/rfc5161.txt b/docs/rfc/rfc5161.txt new file mode 100644 index 0000000..13bbbf7 --- /dev/null +++ b/docs/rfc/rfc5161.txt @@ -0,0 +1,395 @@ + + + + + + +Network Working Group A. Gulbrandsen, Ed. +Request for Comments: 5161 Oryx Mail Systems GmbH +Category: Standards Track A. Melnikov, Ed. + Isode Limited + March 2008 + + + The IMAP ENABLE 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. + +Abstract + + Most IMAP extensions are used by the client when it wants to and the + server supports it. However, a few extensions require the server to + know whether a client supports that extension. The ENABLE extension + allows an IMAP client to say which extensions it supports. + +1. Overview + + Several IMAP extensions allow the server to return unsolicited + responses specific to these extensions in certain circumstances. + However, servers cannot send those unsolicited responses until they + know that the clients support such extensions and thus won't choke on + the extension response data. + + Up until now, extensions have typically stated that a server cannot + send the unsolicited responses until after the client has used a + command with the extension data (i.e., at that point the server knows + the client is aware of the extension). CONDSTORE ([RFC4551]), + ANNOTATE ([ANNOTATE]), and some extensions under consideration at the + moment use various commands to enable server extensions. For + example, CONDSTORE uses a SELECT or FETCH parameter, and ANNOTATE + uses a side effect of FETCH. + + The ENABLE extension provides an explicit indication from the client + that it supports particular extensions. This is done using a new + ENABLE command. + + An IMAP server that supports ENABLE advertises this by including the + word ENABLE in its capability list. + + + + +Gulbrandsen & Melnikov Standards Track [Page 1] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + + Most IMAP extensions do not require the client to enable the + extension in any way. + +2. Conventions Used in This Document + + 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]. + + Formal syntax is defined by [RFC5234] and [RFC3501]. + + Example lines prefaced by "C:" are sent by the client and ones + prefaced by "S:" by the server. The five characters [...] means that + something has been elided. + +3. Protocol Changes + +3.1. The ENABLE Command + + Arguments: capability names + + Result: OK: Relevant capabilities enabled + BAD: No arguments, or syntax error in an argument + + The ENABLE command takes a list of capability names, and requests the + server to enable the named extensions. Once enabled using ENABLE, + each extension remains active until the IMAP connection is closed. + For each argument, the server does the following: + + - If the argument is not an extension known to the server, the server + MUST ignore the argument. + + - If the argument is an extension known to the server, and it is not + specifically permitted to be enabled using ENABLE, the server MUST + ignore the argument. (Note that knowing about an extension doesn't + necessarily imply supporting that extension.) + + - If the argument is an extension that is supported by the server and + that needs to be enabled, the server MUST enable the extension for + the duration of the connection. At present, this applies only to + CONDSTORE ([RFC4551]). Note that once an extension is enabled, + there is no way to disable it. + + If the ENABLE command is successful, the server MUST send an untagged + ENABLED response (see Section 3.2). + + + + + + +Gulbrandsen & Melnikov Standards Track [Page 2] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + + Clients SHOULD only include extensions that need to be enabled by the + server. At the time of publication, CONDSTORE is the only such + extension (i.e., ENABLE CONDSTORE is an additional "CONDSTORE + enabling command" as defined in [RFC4551]). Future RFCs may add to + this list. + + The ENABLE command is only valid in the authenticated state (see + [RFC3501]), before any mailbox is selected. Clients MUST NOT issue + ENABLE once they SELECT/EXAMINE a mailbox; however, server + implementations don't have to check that no mailbox is selected or + was previously selected during the duration of a connection. + + The ENABLE command can be issued multiple times in a session. It is + additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a + single command "ENABLE a b c". When multiple ENABLE commands are + issued, each corresponding ENABLED response SHOULD only contain + extensions enabled by the corresponding ENABLE command. + + There are no limitations on pipelining ENABLE. For example, it is + possible to send ENABLE and then immediately SELECT, or a LOGIN + immediately followed by ENABLE. + + The server MUST NOT change the CAPABILITY list as a result of + executing ENABLE; i.e., a CAPABILITY command issued right after an + ENABLE command MUST list the same capabilities as a CAPABILITY + command issued before the ENABLE command. This is demonstrated in + the following example: + + C: t1 CAPABILITY + S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA + S: t1 OK foo + C: t2 ENABLE CONDSTORE X-GOOD-IDEA + S: * ENABLED X-GOOD-IDEA + S: t2 OK foo + C: t3 CAPABILITY + S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA + S: t3 OK foo again + + In the following example, the client enables CONDSTORE: + + C: a1 ENABLE CONDSTORE + S: * ENABLED CONDSTORE + S: a1 OK Conditional Store enabled + + + + + + + + +Gulbrandsen & Melnikov Standards Track [Page 3] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + +3.2. The ENABLED Response + + Contents: capability listing + + The ENABLED response occurs as a result of an ENABLE command. The + capability listing contains a space-separated listing of capability + names that the server supports and that were successfully enabled. + The ENABLED response may contain no capabilities, which means that no + extensions listed by the client were successfully enabled. + +3.3. Note to Designers of Extensions That May Use the ENABLE Command + + Designers of IMAP extensions are discouraged from creating extensions + that require ENABLE unless there is no good alternative design. + Specifically, extensions that cause potentially incompatible behavior + changes to deployed server responses (and thus benefit from ENABLE) + have a higher complexity cost than extensions that do not. + +4. Formal Syntax + + The following syntax specification uses the Augmented Backus-Naur + Form (ABNF) notation as specified in [RFC5234] including the core + rules in Appendix B.1. [RFC3501] defines the non-terminals + "capability" and "command-any". + + 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. + + capability =/ "ENABLE" + + command-any =/ "ENABLE" 1*(SP capability) + + response-data =/ "*" SP enable-data CRLF + + enable-data = "ENABLED" *(SP capability) + +5. Security Considerations + + It is believed that this extension doesn't add any security + considerations that are not already present in the base IMAP protocol + [RFC3501]. + +6. IANA Considerations + + The IANA has added ENABLE to the IMAP4 Capabilities Registry. + + + + +Gulbrandsen & Melnikov Standards Track [Page 4] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + +7. Acknowledgments + + The editors would like to thank Randy Gellens, Chris Newman, Peter + Coates, Dave Cridland, Mark Crispin, Ned Freed, Dan Karp, Cyrus + Daboo, Ken Murchison, and Eric Burger for comments and corrections. + However, this doesn't necessarily mean that they endorse this + extension, agree with all details, or are responsible for errors + introduced by the editors. + +8. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION + 4rev1", RFC 3501, March 2003. + + [RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for + Syntax Specifications: ABNF", STD 68, RFC 5234, January + 2008. + + [RFC4551] Melnikov, A. and S. Hole, "IMAP Extension for Conditional + STORE Operation or Quick Flag Changes Resynchronization", + RFC 4551, June 2006. + +9. Informative References + + [ANNOTATE] Daboo, C. and R. Gellens, "IMAP ANNOTATE Extension", Work + in Progress, August 2006. + + + + + + + + + + + + + + + + + + + + + + +Gulbrandsen & Melnikov Standards Track [Page 5] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + +Editors' Addresses + + Arnt Gulbrandsen + Oryx Mail Systems GmbH + Schweppermannstr. 8 + D-81671 Muenchen + Germany + + Fax: +49 89 4502 9758 + EMail: arnt@oryx.com + + + Alexey Melnikov + Isode Ltd + 5 Castle Business Village + 36 Station Road + Hampton, Middlesex TW12 2BX + UK + + EMail: Alexey.Melnikov@isode.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Gulbrandsen & Melnikov Standards Track [Page 6] + +RFC 5161 The IMAP ENABLE Extension March 2008 + + +Full Copyright Statement + + Copyright (C) The IETF Trust (2008). + + This document is subject to the rights, licenses and restrictions + contained in BCP 78, and except as set forth therein, the authors + retain all their rights. + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND + THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS + OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF + THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + +Intellectual Property + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at + ietf-ipr@ietf.org. + + + + + + + + + + + + +Gulbrandsen & Melnikov Standards Track [Page 7] +