draft HARPOON May 92 HARPOON Rules for downgrading messages from X.400/88 to X.400/84 when MIME content-types are present in the messages Sun Aug 30 23:40:19 MET DST 1992 Harald Tveit Alvestrand SINTEF DELAB Harald.T.Alvestrand@delab.sintef.no Jim Romaguera NetConsult AG Romaguera@cosine-mhs.switch.ch Kevin Jordan Control Data Systems, Inc. kej@mercury.udev.cdc.com Status of this Memo This document is an Internet Draft. 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. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "work in progress." Please check the I-D abstract listing contained in each Internet Draft directory to learn the current status of this or any other Internet Draft. If consensus is reached in the IETF MIME-MHS Interworking Working Group, it will be submitted to the IESG asking that Alvestrand et al Expires March 28 1993 [Page 1] draft HARPOON May 92 it be recommended to the IAB as a Proposed Standard protocol specification. HARPOON stands for Holistic Approach to Reliable Provision of Open Networking, and is used solely to catch the eye of readers. Please send comments to the MIME-MHS mailing list Alvestrand et al Expires March 28 1993 [Page 2] draft HARPOON May 92 1. Introduction Interworking between X.400(88) and MIME is achieved by [MAPPING], which modifies RFC-1327 [RFC 1327], which specifies the interworking between X.400(88) and RFC-822 based mail. Interworking between X.400(88) and X.400 (84) is achieved by RFC- 1328 [RFC 1328]. That document does not describe what to do in the case where body parts arrive at the gateway that cannot be adequately represented in the X.400(84) system. This document describes how RFC-1328 must be modified in order to provide adequate support for the scenarios: SMTP(MIME) -> X.400(84) X.400(84) -> SMTP(MIME) 2. Basic approach The approach is to imagine that the connection X.400(84) <-> SMTP(MIME) never happens. This, of course, is an illusion, but can be a very useful illusion. All mail will therefore go on one of the paths X.400(84) -> X.400(88) -> SMTP(MIME) SMTP(MIME) -> X.400(88) -> X.400(84) when it goes between a MIME user and an X.400(84) user. The approach at the interface between X.400(88) and X.400(84) is: o Convert what you can o Encapsulate what you have to o Never drop a message 3. Basic fallback format For any body part that cannot be used directly in X.400(84), the following body part is made: Alvestrand et al Expires March 28 1993 [Page 3] draft HARPOON May 92 - Tag = 14 (Bilaterally defined) - Content = Octet string - First bytes of content: (in USASCII, with C escape sequences used to represent control characters): MIME-version: \r\n Content-type: \r\n Content-transfer-encoding: \r\n \r\n The preferred encoding is BINARY, because X.400 does not have any limitations to what octets it can pass in an Octet String, but this RFC does not require use of the BINARY encoding. All implementations MUST place the MIME-version: header first in the body part. Headers that are placed by [RFC-1327] and [MAPPING] into other parts of the message MUST NOT be placed in the MIME body part. Since all X.400(88) body parts can be represented in MIME by using the x400-bp MIME content-type, this conversion will never fail. In the reverse direction, any body part that starts with the token "MIME-Version:" will be subjected to conversion according to [MAPPING] before including the body part into an X.400(88) message. 4. Implications The implications are several: - People with X.400(84) readers who have the ability to save Bodypart 14 messages to file will now be able to save MIME multimedia messages - People who can use features like the "Mailcaps" file to identify what to do about a bodypart 14 can now grab MetaMail or MHN and achieve at least some multimedia functionality Alvestrand et al Expires March 28 1993 [Page 4] draft HARPOON May 92 - People with E-mail systems that drop into BP 14 when an 8-bit character comes along can now include the magic tokens by hand at the beginning of the message, and get their characters received properly by MIME users 5. Security considerations The security considerations in [MIME] and [MAPPING] (beware of trojans that can hit you if your UA automagically starts programs for you) are now relevant also for X.400(84) systems. 6. Authors' address Harald Tveit Alvestrand SINTEF DELAB N-7034 Trondheim NORWAY Harald.T.Alvestrand@delab.sintef.no Kevin E. Jordan, ARH215 Control Data Systems, Inc. 4201 Lexington Avenue N Arden Hills, MN 55126 USA Kevin.E.Jordan@mercury.oss.arh.cpg.cdc.com James A. Romaguera NetConsult AG Mettlendwaldweg 20a 3037 Herrenschwanden Switzerland Romaguera@cosine-mhs.switch.ch 7. References [MIME] N. Borenstein, N. Freed, MIME: Mechanisms for Specifying and Describing the Format of Internet Message Bodies. Internet- Draft, (January, 1992). [RFC-1327] S.E. Hardcastle-Kille, Mapping between X.400(1988) / ISO 10021 and RFC-822. Alvestrand et al Expires March 28 1993 [Page 5] draft HARPOON May 92 [RFC-1328] S.E. Hardcastle-Kille, X.400 1988 to 1984 downgrading. [MAPPING] H.T. Alvestrand, R.S. Miles, M.T. Rose, S.J. Thompson, Mapping between X.400 and RFC-822 Message Bodies Internet- Draft, (June, 1992). Alvestrand et al Expires March 28 1993 [Page 6] draft HARPOON May 92 Table of Contents Status of this Memo ........................................ 1 1 Introduction .............................................. 3 2 Basic approach ............................................ 3 3 Basic fallback format ..................................... 3 4 Implications .............................................. 4 5 Security considerations ................................... 5 6 Authors' address .......................................... 5 7 References ................................................ 5 Alvestrand et al Expires March 28 1993 [Page 7] ------------------------------ End of body part 2