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Network Working Group E. Levinson
Request for Comments: 1895 Accurate Info. Sys., Inc.
Category: Informational February 1996
The Application/CALS-1840 Content-type
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This memorandum provides guidelines for using the United States
Department of Defense Military Standard MIL-STD-1840, "Automated
Interchange of Technical Information," with the Internet electronic
mail standards, RFC 822 and RFC 1521. Electronic mail provides a
more convenient mechanism that delivery via physical media for
certain types and quantities of data. Software already exists to
support data exchanges based on MIL-STD-1840 and it can continue to
be used in conjunction with electronic mail exchanges defined in this
document. This document defines a new media type and a MIME message
structure for exchanging data in conformance with MIL-STD-1840.
1. Introduction
The United States Department of Defense (DOD) has defined a standard,
MIL-STD-1840 [1840], for the exchange of digital data. Most
applications of that standard use 9-track tape as the transport
medium. The Application/CALS-1840 media-type is proposed to
facilitate such exchanges using the Multipurpose Internet Mail
Extensions [MIME] and network based transport media, i.e. electronic
mail [822].
This memo has been reviewed and authorized by the Continuous
Acquistion and Life-cycle Support (CALS) Industry Steering Group
(ISG). CALS is a US DOD initiative for the use and exchange of
digital data. The Industry Steering Group, which consists of members
drawn from government and industry, guides the development of CALS
standards such as [1840].
2. Definition
An [1840] exchange consists of a set of files with well defined file
names (see below). Each set consists of a declaration file and one
or more data files. The data files, in turn, consist of header
Levinson Informational [Page 1]
RFC 1895 CALS-1840 February 1996 records immediately followed by the data. The data itself may be formatted in accordance with a published specification or a contractual agreement. MIL-STD-1840 encodes the file's data type in the file name. It might seem appropriate to transform the 1840 headers into MIME headers and use the appropriate media type, essentially transforming the 1840 files into MIME body parts. There are three reasons for not doing that. First, not all of the "types" used in [1840] are registered MIME types. Second, there exists an installed base of software capable of reading the 1840 formatted files and processing the data appropriately. Finally the three existing revisions to the standard have maintained the same file structure. Consequently, a processor for the data may be able to handle any one of the standard's revisions. Thus, a single Application/CALS-1840 is being proposed and its body part body contains headers and data in the [1840] format. A set of related files constitutes a "transfer unit" in 1840 and each transfer unit shall correspond to a Multipart/Mixed MIME entity. Included in each transfer unit is a declaration file which shall be the first body part in the Multipart/Mixed entity. Several transfer units may be included in a single MIME message. Levinson Informational [Page 2]
RFC 1895 CALS-1840 February 1996 2.1 Registration Information The following form is copied from RFC 1590, Appendix A for the purpose of registering this media-type. To: IANA@isi.edu Subject: Registration of new Media Type content-type/subtype Media Type name: Application Media subtype name: CALS-1840 Required parameters: filename, version Optional parameters: None Encoding considerations: Any valid MIME encodings my be used Security considerations: Depends solely on the referenced type Published specification: This document Person & email address to contact for further information: Alan Peltzman <peltzmaa@ncr.disa.mil> +1 (703) 735-3568 Defense Information Systems Agency Center for Standards Code JIEO/JEBEB 10701 Parkridge Blvd Reston, VA 22091-4398 2.2. The Filename Parameter The filename parameter gives the transfer unit filename as defined by [1840]. The parameter's value, called <1840-name>, has the syntax given by the grammer below. 1840-name := "D" 1840-tuseq [ 1840-type 1840-dfseq ] 1840-type := letter ; limited to the set defined in ; the appropriate version of ; [1840, Table III] 1840-tuseq := 1840-seq 1840-dfseq := 1840-seq 1840-seq := alphnum alphnum alphnum alphanum := letter / digit letter := "A" / "B" / "C" / "D" / "E" / "F" / "G" / "H" / "I" / "J" / "K" / "L" / "M" / "N" / "O" / "P" / "Q" / "R" / "S" / "T" / "U" / "V" / "W" / "X" / "Y" / "Z" digit := "0" / "1" / "2" / "3" / "4" / "5" / "6" / "7" / "8" / "9" / Levinson Informational [Page 3]
RFC 1895 CALS-1840 February 1996 All Application/CALS-1840 body parts in a single Multipart/Mixed MIME entity shall have the same <1840-tuseq>. Within a single message all filename values shall be unique. Notes: 1) Tuseq and dfseq correspond to transfer unit sequence number and data file sequence number respectively. 2) The filename for a declaration file has the form "D" 1840-tuseq and for data files, the form "D" 1840-tuseq <letter> 1840-dfseq. 2.3. The Version Parameter The specversion parameter's value shall indicate the particular version of MIL-STD-1840 to which the data conforms. Valid values are: MIL-STD-1840C, 0, 199XXXXX MIL-STD-1840B, 0, 19921103 MIL-STD-1840A, 0, 19871222 Notes: (1) The value "199XXXXX" is to be replaced with the actual issue date for MIL-STD-1840C. (2) The embedded blanks in the above strings are required, hence the value must be enclosed in quote marks ("). 3. Example In the example below a single transfer unit is provided. It consists of three data files, the declaration, a contract defined file and an IGES file. The headers and data are in accordance with MIL-STD- 1840B. The content-transfer-encoding perserves the data file's fixed record length. To: you@some.org From: me@here.com Date: Fri, 03 Nov 1995 18:23:10 -0500 MIME-Version: 1.0 Content-Type: Multipart/Mixed; Boundary="DISA CFS - SFC ASID" --DISA CFS - SFC ASID Content-Type: Application/CALS-1840; filename=D001; version="MIL-STD-1840B, 0, 19921103" Content-Transfer-Encoding: Base64 [Declaration File] --DISA CFS - SFC ASID Content-Type: Application/CALS-1840; filename=D001A001; version="MIL-STD-1840B, 0, 19921103" Levinson Informational [Page 4]
RFC 1895 CALS-1840 February 1996 Content-Transfer-Encoding: Base64 [Data File -- Contract Defined including headers] --DISA CFS - SFC ASID Content-Type: Application/CALS-1840; filename=D001Q001; version="MIL-STD-1840B, 0, 19921103" Content-Transfer-Encoding: Base64 [Data File -- Raster including 1840 headers] --DISA CFS - SFC ASID-- 4. Security Considerations None of the body parts, as constitued, represent executable data. When the 1840 file format is processed the resultant data may be executable. Processing will be under the control of the process associated with Application/CALS-1840. Classified information or other information that cannot be disclosed except to authorized personnel should not be sent via the Internet without using appropriate privacy enhancements, [PEM], [MOSS], or other privacy mechanism. 5. Acknowledgments The author acknowledges the encouragement of Alan Peltzman, US DOD, DISA, and the suggestions of Richard Klobuchar, SAIC. This work was supported under U.S. Dept. of the Army, Contract DAAB07-93-D-T001 and prepared under the direction of the MIL-STD-1840 Revision C Review Team. 6. References [1840] MIL-STD-1840B, "Automated Interchange of Technical Information", US Department of Defense, 3 November 1992. [822] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, UDEL, August 1982. [MIME] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies", RFC 1521, Bellcore and Innosoft, September 1993. [MOSS] Crocker, S., Freed, N., Galvin, J., and S. Murphy, "MIME Object Security Services", RFC 1848, Cybercash, Innosoft, TIS, October 1995. Levinson Informational [Page 5]
RFC 1895 CALS-1840 February 1996 [PEM] Linn, J., "Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures", RFC 1421, IAB IRTF PSRG, IETF PEM WG, February 1993. 9. Author's Address Edward Levinson Accurate Information Systems, Inc. 2 Industrial Way Eatontown, NJ 07724-2265 USA Phone: +1 908 389 5550 EMail: ELevinson@Accurate.com Levinson Informational [Page 6]