LEMONADE P. Resnick Internet-Draft QUALCOMM Incorporated Expires: March 2, 2005 September 2004 Internet Message Access Protocol (IMAP) CATENATE Extension draft-ietf-lemonade-catenate-02 Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. 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 March 2, 2005. Copyright Notice Copyright (C) The Internet Society (2004). Abstract The CATENATE extension to the Internet Message Access Protocol (IMAP) allows clients to create messages on the IMAP server which may contain a combination of new data along with parts of (or entire) messages already on the server. Using this extension, the client can catenate parts of an already existing message on to a new message without having to first download the data and then upload it back to the server. Resnick Expires March 2, 2005 [Page 1] Internet-Draft IMAP CATENATE Extension September 2004 1. Introduction The CATENATE extension to the Internet Message Access Protocol (IMAP) [1] allows the client to create a message on the server which can include the text of messages (or parts of messages) that already exist on the server without having to FETCH them and APPEND them back to the server. The CATENATE command works much like the APPEND command except that, instead of a single message literal, the command can take as arguments any combination of message literals (as described in IMAP [1]) and message URLs (as described in the IMAP URL Scheme [2] specification). The server takes all of the pieces and catenates them into the output message. There are some obvious uses for the CATENATE command. The motivating use case for this command was to provide a way for a resource-constrained client to compose a message for future delivery which contains data that already exists in that client's IMAP store. Because the client does not have to download and re-upload potentially large message parts, bandwidth and processing limitations do not have as much impact. (Mechanisms for sending the message are outside of the scope of this document.) CATENATE can also be used to copy parts of a message to another mailbox for archival purposes while getting rid of undesired parts. In environments where server storage is limited, a client could get rid of large message parts by copying over only the necessary parts and then deleting the original message. CATENATE could also be used to add data to a message such as prepending message header fields or including other data by making a copy of the original and catenating the new data. 2. The CATENATE Capability A server which supports this extension returns "CATENATE" as one of the responses to the CAPABILITY command. 3. The CATENATE command Arguments: mailbox name OPTIONAL flag parenthesized list OPTIONAL date/time string one or more message parts to catenate, specified as: message literal or message (or message part) URL Resnick Expires March 2, 2005 [Page 2] Internet-Draft IMAP CATENATE Extension September 2004 Responses: no specific responses for this command Result: OK - catenate completed NO - catenate error: can't append to that mailbox, error in flags or date/time or message text, or can't fetch that data BAD - command unknown or arguments invalid The CATENATE command concatenates all of the message parts and appends them as a new message to the end of the specified mailbox. The optional flag parenthesized list and date/time string are used just as they are in the APPEND command, setting the flags and the internal date, respectively. The subsequent parameters specify the message parts that are appended sequentially to the output message. If a message literal is specified (indicated by the octet count enclosed in braces), the octets following the count are appended just as they would be with the APPEND command. If a message URL is specified, the octets of that body part are appended, as if the literal returned in a FETCH BODY response were put in place of the message part specifier. The CATENATE command does not cause the \Seen flag to be set for any catenated body part. Note: This document only describes the behavior of the CATENATE command using a message URL (as defined by [2]) which refers to a specific message or message part in the currently selected mailbox on the current IMAP server. (Because of that, the CATENATE command is valid in the selected state for purposes of this specification.) Use of a URL that refers to anything other than a message or message part from the currently selected mailbox on the current IMAP server is outside of the scope of this document, would require an extension to this specification, and a server implementing only this specification would return NO to such a request. The client is responsible for making sure that the catenated message is in the format of an RFC 2822 [3] message. This includes inserting appropriate MIME [4] boundaries between body parts if necessary. Responses behave just as the APPEND command. If the server implements the IMAP UIDPLUS extension [5], it will also return an APPENDUID response code in the tagged OK response. Two response codes are provided in section 4 which can be used in the tagged NO response if the CATENATE command fails. 4. Response Codes When a CATENATE command fails it may return a response code that Resnick Expires March 2, 2005 [Page 3] Internet-Draft IMAP CATENATE Extension September 2004 describes a reason for the failure. 4.1 BADURL Response The BADURL response code is returned if the CATENATE fails to process one of the specified URLs. Possible reasons for this are bad url syntax, unrecognized URL schema, invalid message UID, invalid body part. The BADURL response code contains the first URL specified as a parameter to the CATENATE command that has caused the operation to fail. 4.2 TOOBIG Response The TOOBIG response code is returned if the resulting message will exceed the 4Gb IMAP message limit. This might happen, for example, if the client specifies 3 URLs for 2Gb messages. Note, that even if the server doesn't return TOOBIG, it still has to be defensive against misbehaving or malicious clients that try to construct a message over 4Gb limit. The server may also wish to return the TOOBIG response code if the resulting message exceeds the server specific message size limit. 5. Formal Syntax The following syntax specification uses the Augmented Backus-Naur Form (ABNF) [6] notation. Undefined elements are defined in the formal syntax of the ABNF [6], IMAP [1], and IMAP URL [2] specifications. catenate = "CATENATE" SP mailbox [SP flag-list] [SP date-time] 1*(SP (literal / imapurl)) badurl_response_code = "BADURL" SP imapurl toobig_response_code = "TOOBIG" 6. Security Considerations The CATENATE extension does not raise any security considerations that are not present for the base protocol or in the use of IMAP URLs, and these issues are discussed in the IMAP [1] and IMAP URL [2] documents. 7 Normative References [1] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003. Resnick Expires March 2, 2005 [Page 4] Internet-Draft IMAP CATENATE Extension September 2004 [2] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997. [3] Resnick, P., "Internet Message Format", RFC 2822, April 2001. [4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [5] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1998. [6] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. Author's Address Peter W. Resnick QUALCOMM Incorporated 5775 Morehouse Drive San Diego, CA 92121-1714 US Phone: +1 858 651 4478 EMail: presnick@qualcomm.com URI: http://www.qualcomm.com/~presnick/ Resnick Expires March 2, 2005 [Page 5] Internet-Draft IMAP CATENATE Extension September 2004 Intellectual Property Statement 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. 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Disclaimer of Validity 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 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. Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Resnick Expires March 2, 2005 [Page 6]