Internet Engineering Task Force H. Hazewinkel INTERNET-DRAFT I.Net Expires July 2003 January 2003 IMAP Virtual Hosting draft-hazewinkel-imap-vhost-00.txt January 2003 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. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This memo describes an extension to the IMAP protocol in order to enable virtual hosting. The concept of virtual hosting for HTTP is used and a new IMAP command is introduced to provide the virtual hosting feature. H. Hazewinkel Expires July 2003 [Page 1] Internet Draft IMAP Virtual Hosting January 2003 Conventions 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]. Introduction The Internet Message Access Protocol (IMAP) [IMAP4] allows a client to access and manipulate electronic mail messages on a server. IMAP defines a transparent protocol as if remote mailboxes are local mailboxes. This document proposes a virtual hosting command, VHOST, for IMAP. Such a command would identify a session as part of a FQDN in a multi- domain environment. the concept of virtual hosting is taken from the HTTP protocol [HTTP] and is application in IMAP is similar. For example, a generic IMAP server runs under the hostname imap.example.com, but serves IMAP for the virtual hosts imap.example- a.com and imap.example-b.com. Currently, username must be or identified with the inclusion of their domain name otherwise usernames from one domain may not exist in the other domain. The VHOST command would enable to provide a separation of the domain name from the username. The VHOST command, which should be given before the AUTH or LOGIN command, identifies the applicable domain name for the IMAP session and the username does not require the domain name anymore. VHOST command The VHOST command indicates the domain (virtual host) for the following sessions. The domain name is specified by the one and only argument. This command may only be given in the 'Non-Authenticated' state. Arguments: virtual host that MUST be identified and is applicable for the following session or authenticated user. Response: no specific response for this command, but see 'Result' Result: OK - virtual host identification completes and an IMAP service is provided. NO - the server does not know this virtual host or the service for this virtual host is temporarely H. Hazewinkel Expires July 2003 [Page 2] Internet Draft IMAP Virtual Hosting January 2003 unavailable. BAD - command unknown or arguments invalid, no virtual host applicable. The IMAP server MUST respond with an 'OK' if it provides services for the specified virtual host. The following commands are then all done within the domain to which the virtual host belongs. The IMAP server MUST respond with a 'NO" if it is not able to identify the virtual host. The following session or commands are not provided as in the domain of the virtual host specified. The IMAP server MAY respond with a 'NO' if it is not able to provide services for the virtual host in case the service is temporarily is not available. Such an action of the server may be caused by, for instance, a not available message store. The following session or commands are not provided as in the domain of the virtual host specified. The IMAP server MUST respond with a BAD in case the request is received incorrect from the client. Capability A server which supports the VHOST command MUST announce this in a CAPABILITY response with the keyword "VHOST". If this not specified a client SHOULD NOT use the VHOST command. Formal Syntax Formal syntax is defined using ABNF [ABNF] as modified by [IMAP4]. Non-terminals referenced but not defined below are as defined by [IMAP4]. vhost_command = "VHOST" astring Security Considerations No new security issues are recognized at this moment which are already in IMAP. Other Considerations It is recognised that different domain names can also be done by H. Hazewinkel Expires July 2003 [Page 3] Internet Draft IMAP Virtual Hosting January 2003 extending the with the domain name. This creates a single level list of user identification in all the domains. A trade-off against a change in the state diagram on behalf of not changing the the AUTHENTICATE and LOGIN commands. This way the core IMAP specification does not require a change. Neither does it means that the VHOST command introduces new states or change state. As a result of this, multiple VHOST commands could be given in sequence, but the last command always determines the virtual host for the following commands. The VHOST command could, for instance, provide a mechanism to enable a service not available in case of high load on a server. In such a case the client does not receive an authentication or login error, but a message to wait some time in order to have the service available. Editors' Addresses Harrie Hazewinkel I.Net via Darwin 85 20019 Settimo Milanese (VA) Italy Phone: +39-02328631 EMail: harrie@inet.it Full Copyright statement. Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. H. Hazewinkel Expires July 2003 [Page 4] Internet Draft IMAP Virtual Hosting January 2003 The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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." References [IMAP4] Crispin, M., "Internet Message Access Protocol - Version 4rev1", RFC 2060, University of Washington, December 1996. [RFC2119] Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, Harvard University, March 1997. [RFC2234] Crocker, Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium, Demon Internet Ltd, November 1997. [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol, HTTP/1.1", RFC 2616, June 1999. H. Hazewinkel Expires July 2003 [Page 5]