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rfc:rfc6477

Internet Engineering Task Force (IETF) A. Melnikov Request for Comments: 6477 Isode Ltd Category: Informational G. Lunt ISSN: 2070-1721 SMHS Ltd

                                                          January 2012
      Registration of Military Message Handling System (MMHS)
               Header Fields for Use in Internet Mail

Abstract

 A Military Message Handling System (MMHS) processes formal messages
 ensuring release, distribution, security, and timely delivery across
 national and international strategic and tactical networks.  The MMHS
 Elements of Service are defined as a set of extensions to the ITU-T
 X.400 (1992) international standards and are specified in STANAG 4406
 Edition 2 and ACP 123.  This document specifies message header fields
 and associated processing for RFC 5322 (Internet Message Format) to
 provide a comparable messaging service.  In addition, this document
 provides for a STANAG 4406 / Internet Email Gateway that supports
 message conversion.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6477.

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect

Melnikov & Lunt Informational [Page 1] RFC 6477 MMHS Header Fields January 2012

 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................2
 2. Conventions Used in This Document ...............................3
 3. Registration Templates ..........................................3
    3.1. Header Field: MMHS-Exempted-Address ........................5
    3.2. Header Field: MMHS-Extended-Authorisation-Info .............5
    3.3. Header Field: MMHS-Subject-Indicator-Codes .................6
    3.4. Header Field: MMHS-Handling-Instructions ...................6
    3.5. Header Field: MMHS-Message-Instructions ....................7
    3.6. Header Field: MMHS-Codress-Message-Indicator ...............8
    3.7. Header Field: MMHS-Originator-Reference ....................8
    3.8. Header Field: MMHS-Primary-Precedence ......................9
    3.9. Header Field: MMHS-Copy-Precedence ........................10
    3.10. Header Field: MMHS-Message-Type ..........................10
    3.11. Header Field: MMHS-Other-Recipients-Indicator-To .........11
    3.12. Header Field: MMHS-Other-Recipients-Indicator-CC .........12
    3.13. Header Field: MMHS-Acp127-Message-Identifier .............13
    3.14. Header Field: MMHS-Originator-PLAD .......................13
 4. Formal Syntax ..................................................14
 5. Service in Comparison to ACP 123 / STANAG 4406 .................16
 6. Gatewaying with ACP 123 / STANAG 4406 ..........................16
 7. Gatewaying with ACP 127 ........................................18
 8. IANA Considerations ............................................18
 9. Security Considerations ........................................18
 10. References ....................................................19
    10.1. Normative References .....................................19
    10.2. Informative References ...................................19
 Appendix A. Acknowledgements ......................................21

1. Introduction

 [RFC5322] defines a protocol for the format of electronic messages
 exchanged on the Internet.  MMHS is a military specification defined
 in ACP 123 [ACP123] (also specified in STANAG 4406 [STANAG-4406]),
 which defines a number of extensions to the basic X.400 (1992)
 protocol for the services required by military messaging.
 This document supports translating most of the Elements of Service
 defined in ACP 123 [ACP123] to Internet message header fields (see
 Section 5 for more details).  This specification is written to extend
 the Mime Internet X.400 Enhanced Relay (MIXER) specification

Melnikov & Lunt Informational [Page 2] RFC 6477 MMHS Header Fields January 2012

 [RFC2156] to enable inter-conversion in a MIXER gateway with the
 X.400 Interpersonal Messaging System (IPMS) heading extensions
 defined in ACP 123 / STANAG 4406, Annex A.
 The document is aimed at the ability to represent MMHS messages as
 RFC 5322 messages.  All RFC 5322 header fields defined in this
 document are prefixed with the string "MMHS-" to distinguish them
 from any other header fields.
 Unless stated otherwise, all header fields described in this document
 are OPTIONAL in an Internet Message.
 This document is structured as follows: Section 3 and its subsections
 formally define new Internet header fields and show some examples.
 Section 4 provides Augmented Backus-Naur Form (ABNF) syntax for them.
 Section 5 provides some background information about which features
 of ACP 123 / STANAG 4406 were not implemented in this specification.
 Subsequent sections talk about additional requirements for gatewaying
 to/from ACP 123 / STANAG 4406 and ACP 127 [ACP127] environments,
 respectively.

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].
 The formal syntax uses the ABNF [RFC5234] notation including the core
 rules defined in Appendix B of RFC 5234 [RFC5234].

3. Registration Templates

 Header field entries are summarized below in tabular form for
 convenience of reference and presented in full in the following
 subsections.
 Any header field specified in this document MUST NOT appear more than
 once in message headers.

Melnikov & Lunt Informational [Page 3] RFC 6477 MMHS Header Fields January 2012

 +------------------------------------+----------+-------------------+
 | Header name                        | Protocol | Reference         |
 +------------------------------------+----------+-------------------+
 | MMHS-Exempted-Address              | mail     | [ACP123],         |
 |                                    |          | Appendices A1.1   |
 |                                    |          | and B.105         |
 | MMHS-Extended-Authorisation-Info   | mail     | [ACP123],         |
 |                                    |          | Appendices A1.2   |
 |                                    |          | and B.106         |
 | MMHS-Subject-Indicator-Codes       | mail     | [ACP123],         |
 |                                    |          | Appendices A1.3   |
 |                                    |          | and B.107         |
 | MMHS-Handling-Instructions         | mail     | [ACP123][ACP123], |
 |                                    |          | Appendices A1.4   |
 |                                    |          | and B.108         |
 | MMHS-Message-Instructions          | mail     | [ACP123],         |
 |                                    |          | Appendices A1.5   |
 |                                    |          | and B.109         |
 | MMHS-Codress-Message-Indicator     | mail     | [ACP123],         |
 |                                    |          | Appendices A1.6   |
 |                                    |          | and B.110         |
 | MMHS-Originator-Reference          | mail     | [ACP123],         |
 |                                    |          | Appendices A1.7   |
 |                                    |          | and  B.111        |
 | MMHS-Primary-Precedence            | mail     | [ACP123],         |
 |                                    |          | Appendices A1.8   |
 |                                    |          | and B.101         |
 | MMHS-Copy-Precedence               | mail     | [ACP123],         |
 |                                    |          | Appendices A1.9   |
 |                                    |          | and B.102         |
 | MMHS-Message-Type                  | mail     | [ACP123],         |
 |                                    |          | Appendices A1.10  |
 |                                    |          | and B.103         |
 | MMHS-Other-Recipients-Indicator-To | mail     | [ACP123],         |
 |                                    |          | Appendices A1.12  |
 |                                    |          | and B.113         |
 | MMHS-Other-Recipients-Indicator-CC | mail     | [ACP123],         |
 |                                    |          | Appendices A1.12  |
 |                                    |          | and B.113         |
 | MMHS-Acp127-Message-Identifier     | mail     | [ACP123],         |
 |                                    |          | Appendices A1.14  |
 |                                    |          | and B.116         |
 | MMHS-Originator-PLAD               | mail     | [ACP123],         |
 |                                    |          | Appendices A1.15  |
 |                                    |          | and B.117         |
 +------------------------------------+----------+-------------------+

Melnikov & Lunt Informational [Page 4] RFC 6477 MMHS Header Fields January 2012

3.1. Header Field: MMHS-Exempted-Address

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Exempted-Address header field, by its presence, indicates
 the addresses of members in an Address List (AL) that should not
 receive the message.  If this header field is absent from the
 message, all members of an AL will be considered to be valid
 recipients of the message.
 Note: there is no guarantee that the exempted addresses will not
 receive the message as the result of redirection, Distribution List
 (DL) expansion, etc.
 Example:
 MMHS-Exempted-Address:
  UK SHL CGT Samuals G <graham.samuals@shl.example.com>,
  UK SHL Duty Officer <duty@shl.example.com>

3.2. Header Field: MMHS-Extended-Authorisation-Info

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]]
 The MMHS-Extended-Authorisation-Info header field, by its presence,
 indicates either the date and the time when the message was
 officially released by the releasing officer or the date and time
 when the message was initially submitted to a communication facility
 for transmission.
 This header field SHOULD always be present in an email message that
 complies with this specification.
 Example:
 MMHS-Extended-Authorisation-Info:
   Mon, 09 Aug 2010 15:27:40 +0100
 The example above demonstrates use of folding white space (FWS
 [RFC5322]).

Melnikov & Lunt Informational [Page 5] RFC 6477 MMHS Header Fields January 2012

3.3. Header Field: MMHS-Subject-Indicator-Codes

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 A Subject Indicator Code (SIC) is a mechanism for formally
 identifying the topic of a message.  SICs are nested codes that
 provide information for message distribution after delivery to the
 recipient organization.  SICs are usually three letters or three
 letters and digits, but may be up to eight characters long.  Nations
 and organizations using SICs usually maintain a central registry.
 When present, an MMHS-Subject-Indicator-Codes header field contains
 one or more SICs, which indicates distribution information to a
 recipient or a recipient's User Agent.  This information can be used
 to perform automatic or manual local distribution of a message.  If
 the MMHS-Subject-Indicator-Codes header field is absent, then the
 local distribution will be in accordance with the message handling
 policy of the recipient's domain.
 [ACP123] specifies two optional components of the Distribution Code
 Element of Service.  The MMHS-Subject-Indicator-Codes header field
 covers only the SIC code component of distribution codes.
 Example:
 MMHS-Subject-Indicator-Codes: SDM; KKZ ; BRL
 The example above includes three SIC codes: "SDM" (GROUND/LAND
 REQUIREMENTS), "KKZ" (HELICOPTER PUBLICATIONS/MANUALS), and "BRL"
 (HILEX INCIDENTS).

3.4. Header Field: MMHS-Handling-Instructions

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Handling-Instructions header field, by its presence,
 indicates human-readable local handling instructions that require
 some manual handling by a traffic operator.  If this header field is
 absent, the message will be considered as not requiring manual
 handling by a traffic operator.

Melnikov & Lunt Informational [Page 6] RFC 6477 MMHS Header Fields January 2012

 Handling instructions (also called "transmission instructions") are a
 part of format line 4 as defined in ACP 127 [ACP127] and concern the
 sending of the message, e.g., that a particular system shall be used
 for transfer of the message.
 This header field is used to support interoperability with ACP 127
 systems.
 Example:
 MMHS-Handling-Instructions: RXFPA ZOV MINDEF
 The example above includes one ACP 131(F) handling instruction:
 "RXFPA ZOV MINDEF".  The "ZOV MINDEF" indicates that MINDEF rerouted
 the message for some reason, and the correct routing is via RXFPA.

3.5. Header Field: MMHS-Message-Instructions

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Message-Instructions header field, by its presence,
 indicates message instructions (also known as "remarks") accompanying
 the message (e.g., similar to the operating signals specified in ACP
 131 [ACP131]).  If this header field is absent, the message will be
 considered received without message instructions.
 The difference between handling instructions and message instructions
 is that the former is only for manual handling by traffic operators,
 while the latter also contains information of interest to the persons
 reading the message.
 Example:
 MMHS-Message-Instructions: MINIMIZE CONSIDERED; NO DISTRIBUTION
 The example above includes two message instructions defined by
 ACP123(B) [ACP123]: "MINIMIZE CONSIDERED" indicating that the
 originating user has considered the Minimize status of the recipients
 and "NO DISTRIBUTION" indicating that the recipients should not
 distribute the message further without the originating user's
 approval.

Melnikov & Lunt Informational [Page 7] RFC 6477 MMHS Header Fields January 2012

3.6. Header Field: MMHS-Codress-Message-Indicator

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Codress-Message-Indicator header field, by its presence,
 indicates that the message is in Codress format.  If this header
 field is absent, the message will be considered received without the
 Codress format.
 A Codress message is one in which all addresses, i.e., the sender and
 all recipients, are encrypted within the ACP 127 text (body)
 [ACP127].  The heading of any Codress message contains only the
 minimum amount of information that will enable a receiving station to
 deal properly and expeditiously with the particular transmission.
 The general rules for the preparation and transmission of Codress
 messages are given in ACP 121 [ACP121].
 This header field is used only to support interoperability with ACP
 127 systems.
 Example:
 MMHS-Codress-Message-Indicator: 23

3.7. Header Field: MMHS-Originator-Reference

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Originator-Reference header field, by its presence,
 indicates a user-defined reference called the "originator's number".
 If this header field is absent, then the message will be considered
 received without any user-defined reference.
 The originator's number is used by the originating organizational
 unit and is further qualified within national policy.
 Note: trailing and leading spaces in an originator reference are not
 allowed by syntax.
 Example:
 MMHS-Originator-Reference: IMSCOM-JIC-612-78

Melnikov & Lunt Informational [Page 8] RFC 6477 MMHS Header Fields January 2012

3.8. Header Field: MMHS-Primary-Precedence

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Primary-Precedence header field, by its presence, indicates
 the precedence level of the primary ("action") recipients.  The
 message originating domain MUST ensure that this header field is
 always present if the message contains "To:" ("action") addresses.
 The MMHS Primary Precedence Element of Service indicates the relative
 order in which Military Messages are to be handled for primary
 (action) recipients, i.e., a Military Message with a higher MMHS-
 Primary-Precedence header field value SHOULD be handled before a
 Military Message with a lower MMHS-Primary-Precedence header field
 value.
 The header field value is a non-negative integer, or one of the six
 predefined case-insensitive labels: "deferred" (same as "0"),
 "routine" (same as "1"), "priority" (same as "2"), "immediate" (same
 as "3"), "flash" (same as "4"), or "override" (same as "5"),
 optionally followed by a comment.  Note that, according to ACP 123,
 values in the range from 0 to 15 are reserved for NATO-defined
 precedence levels, and values in the range from 16 to 31 are reserved
 for national users.
 Example 1:
 MMHS-Primary-Precedence: 0 (Deferred)
 Example 2:
 MMHS-Primary-Precedence: FLASH
 Example 3:
 MMHS-Primary-Precedence: 7

Melnikov & Lunt Informational [Page 9] RFC 6477 MMHS Header Fields January 2012

3.9. Header Field: MMHS-Copy-Precedence

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Copy-Precedence header field, by its presence, indicates the
 precedence level of the copy ("information") recipients.  The message
 originating domain MUST ensure that this header field is always
 present if the message contains "Cc:" or "Bcc:" ("information")
 addresses.
 The MMHS Copy Precedence Element of Service indicates the relative
 order in which Military Messages are to be handled for copy
 (information) recipients. i.e. a Military Message with higher MMHS-
 Copy-Precedence header field value SHOULD be handled before a
 Military Message with a lower MMHS-Copy-Precedence header field
 value.
 The header field value is a non-negative integer, or one of the 6
 predefined case-insensitive labels: "deferred" (same as "0"),
 "routine" (same as "1"), "priority" (same as "2"), "immediate" (same
 as "3"), "flash" (same as "4"), or "override" (same as "5"),
 optionally followed by a comment.  Note that according to ACP 123,
 values in the range from 0 to 15 are reserved for NATO-defined
 precedence levels and values in the range from 16 to 31 are reserved
 for national users.
 Example 1:
 MMHS-Copy-Precedence: 2 (priority)
 Example 2:
 MMHS-Copy-Precedence: Priority

3.10. Header Field: MMHS-Message-Type

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Message-Type heading extension, by its presence, indicates
 whether the message is to be considered as an exercise, an operation,
 a project, or a drill.  (Note that the list of types is extensible,
 and other types can be specified using the numeric form, see below).

Melnikov & Lunt Informational [Page 10] RFC 6477 MMHS Header Fields January 2012

 It may include an optional parameter specifying the name of the
 exercise, operation, project, or drill.  If this extension is absent,
 the message will be considered to be of an undefined type.
 The header field value is a non-negative integer, or one of the four
 predefined case-insensitive labels: "exercise" (same as "0"),
 "operation" (same as "1"), "project" (same as "2"), "drill" (same as
 "3").  Note that according to ACP 123, values in the range from 0 to
 127 are reserved for NATO-defined Message Type identifiers and values
 in the range from 128 to 255 are not defined by NATO and may be used
 nationally or bilaterally.
 Example 1:
 MMHS-Message-Type: 0(exercise); identifier="CANDLE FISH"
 Example 2:
 MMHS-Message-Type: 3
 Example 3:
 MMHS-Message-Type: 2 (projet)
 Example 4:
 MMHS-Message-Type: project
 Note that some of the examples above demonstrate use of optional
 comments.  See Section 4 for the exact syntax of this header field.

3.11. Header Field: MMHS-Other-Recipients-Indicator-To

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Other-Recipients-Indicator-To header field, by its presence,
 indicates the names of primary ("action") recipients that are
 intended to receive, or have received, the message via means other
 than MMHS.  Note that the absence of both this header field and the
 MMHS-Other-Recipients-Indicator-CC header field (see Section 3.12)
 does not guarantee that all recipients are within the MMHS.
 This header field enables a recipient to determine all action
 recipients of a Military Message.  This header field is derived from
 the Other Recipient Indicator Element of Service.

Melnikov & Lunt Informational [Page 11] RFC 6477 MMHS Header Fields January 2012

 There are several reasons as to why a recipient of a Military Message
 may be identified by this header:
 1.  The recipient is not part of the MMHS.
 2.  The path to the recipient through the MMHS may not be secure;
     therefore, the originator has used alternative mechanisms to
     distribute the Military Message.
 3.  The recipient was already in receipt of the Military Message
     prior to the Military Message being inserted into the MMHS.
 Example:
 MMHS-Other-Recipients-Indicator-To: UK SHL COS; UK SHL IM
 The example above includes names of two primary recipients that
 received the message via means other than MMHS.

3.12. Header Field: MMHS-Other-Recipients-Indicator-CC

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Other-Recipients-Indicator-CC header field, by its presence,
 indicates the names of copy ("information") recipients that are
 intended to receive, or have received, the message via means other
 than MMHS.  Note that the absence of both this header field and the
 MMHS-Other-Recipients-Indicator-To header field (see Section 3.11)
 does not guarantee that all recipients are within the MMHS.
 This header field enables a recipient to determine all copy
 recipients of a Military Message.  This header field is derived from
 the Other Recipient Indicator Element of Service.
 There are several reasons as to why a recipient of a Military Message
 may be identified by this header:
 1.  The recipient is not part of the MMHS.
 2.  The path to the recipient through the MMHS may not be secure;
     therefore, the originator has used alternative mechanisms to
     distribute the Military Message.
 3.  The recipient was already in receipt of the Military Message
     prior to it being inserted into the MMHS.

Melnikov & Lunt Informational [Page 12] RFC 6477 MMHS Header Fields January 2012

 Example:
 MMHS-Other-Recipients-Indicator-CC: UK SHL LEGAD
 The example above includes 1 copy (information) recipient that
 received the message via means other than MMHS.

3.13. Header Field: MMHS-Acp127-Message-Identifier

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Acp127-Message-Identifier header field, by its presence,
 indicates an ACP 127 message identifier [ACP127] for a message that
 originated from an ACP 127 domain.  If this extension is absent, then
 the message did not encounter an ACP 127 domain.
 The MMHS-Acp127-Message-Identifier contains the contents of ACP 127
 format line 3, which consists of three space-separated fields: the
 Calling Station (DERI), Station Serial Number (SSN), and Filing Time
 (JFT) [ACP127].
 This header field is used only to support interoperability with ACP
 127 systems, it should be treated as opaque by a pure MMHS system.
 Example:
 MMHS-Acp127-Message-Identifier: RPDLE 1234 0341215

3.14. Header Field: MMHS-Originator-PLAD

 Applicable protocol: mail [RFC5322]
 Status: informational
 Author/change controller: IESG (iesg@ietf.org) on behalf of the IETF
 Specification document(s): [RFC6477]
 The MMHS-Originator-PLAD (PLAD: Plain Language Address Designator)
 header field, by its presence, indicates the plain language address
 associated with an originator for cross-referencing purposes.  If
 this header field is absent, then the message will be considered not
 to have an originator PLAD cross-reference between the MMHS and ACP
 127 domains.
 This header field is used only to support interoperability with ACP
 127 systems.

Melnikov & Lunt Informational [Page 13] RFC 6477 MMHS Header Fields January 2012

 This header field and the MMHS-Extended-Authorisation-Info header
 field provide a cross-reference for message identification in both
 ACP 127 and MMHS domains.
 Example:
 MMHS-Originator-PLAD: SACLANT

4. Formal Syntax

 The following syntax specification uses the Augmented Backus-Naur
 Form (ABNF) as described in [RFC5234].  Terms not defined here are
 taken from [RFC5322], [RFC5234], and [RFC2156].
 NZ-DIGIT       =  %x31-39
                   ; "1".."9"
 nonneg-integer = "0" / (NZ-DIGIT *DIGIT)
 military-string = 1*69( ps-char )
 quoted-military-string = DQUOTE military-string DQUOTE
 military-string-sequence = military-string
                     *( [FWS] ";" [FWS] military-string )
 Exempted-Address = "MMHS-Exempted-Address:"
                    [FWS] address-list [FWS] CRLF
 Extended-Authorisation-Info = "MMHS-Extended-Authorisation-Info:"
                               [FWS] date-time CRLF
 Subject-Indicator-Codes = "MMHS-Subject-Indicator-Codes:"
                           [FWS] sic-sequence [FWS] CRLF
 sic-sequence = sic *( [FWS] ";" [FWS] sic )
                ; ACP 123 specifies that the maximum number of
                ; SICs is 8. Use of more than 8 SICs is
                ; permitted, but additional SICs might not
                ; be transferred to ACP 123 system.
 sic = 3*8( ps-char )
 Handling-Instructions = "MMHS-Handling-Instructions:"
                         [FWS] military-string-sequence [FWS] CRLF
 Message-Instructions = "MMHS-Message-Instructions:"
                        [FWS] military-string-sequence [FWS] CRLF

Melnikov & Lunt Informational [Page 14] RFC 6477 MMHS Header Fields January 2012

 Codress-Message-Indicator = "MMHS-Codress-Message-Indicator:"
                             [FWS] nonneg-integer [FWS] CRLF
 Originator-Reference = "MMHS-Originator-Reference:"
                        [FWS] military-string [FWS] CRLF
 PrimaryPrecedence = "MMHS-Primary-Precedence:" [FWS] precedence CRLF
 CopyPrecedence = "MMHS-Copy-Precedence:" [FWS] precedence CRLF
 precedence = (nonneg-integer / std-precedence) [CFWS]
 std-precedence = "deferred" / "routine" / "priority" /
                  "immediate" / "flash" / "override"
                  ; deferred == 0
                  ; routine == 1
                  ; priority == 2
                  ; immediate == 3
                  ; flash == 4
                  ; override == 5
 MessageType = "MMHS-Message-Type:" [FWS] message-type [CFWS]
               [";" [FWS] MessageTypeParam [FWS] ] CRLF
 message-type = nonneg-integer / std-message-type
 std-message-type = "exercise" / "operation" / "project" /  "drill"
                    ; exercise  == 0
                    ; operation == 1
                    ; project == 2
                    ; drill == 3
 MessageTypeParam = "identifier" [FWS] "=" [FWS]
                    quoted-military-string
 Designator = military-string
 OtherRecipIndicatorPrimary = "MMHS-Other-Recipients-Indicator-To:"
                      [FWS] Designator *([FWS] ";" [FWS] Designator)
                      [FWS] CRLF
 OtherRecipIndicatorCopy = "MMHS-Other-Recipients-Indicator-CC:"
                      [FWS] Designator *([FWS] ";" [FWS] Designator)
                      [FWS] CRLF
 Acp127MessageIdentifier = "MMHS-Acp127-Message-Identifier:"
                           [FWS] military-string [FWS] CRLF

Melnikov & Lunt Informational [Page 15] RFC 6477 MMHS Header Fields January 2012

 OriginatorPLAD = "MMHS-Originator-PLAD:" [FWS] military-string [FWS]
                  CRLF
 address-list = <Defined in RFC 5322>

5. Service in Comparison to ACP 123 / STANAG 4406

 The service specified in this document is a subset of the
 functionality set out in Annex A1 "Military Heading Extensions" of
 [ACP123].  The majority of this functionality is supported in this
 document.  A few capabilities have been left out, which would have
 significantly increased the complexity of this specification.
 For Distribution Codes (A.1.3) only Subject Indicator Codes are
 supported and Distribution Extensions are omitted.  Authors of this
 document believe that distribution extensions are not widely used.
 Address List Indication (A.1.11) is not supported.  This complex
 extension is deprecated in [ACP123].
 Pilot Forwarding Information (A.1.13) is not supported.
 Security Information Labels (A.1.16) is not supported.  This
 extension is deprecated in favor of Annex A of [ACP123], which uses
 Enhanced Security Services (ESS) Labels [RFC2634] that can be
 supported in a directly compatible manner in S/MIME [RFC5751].
 ACP 127 Notification Requests (see Annex A.2.1 of [ACP123) and
 Responses (see Annex A.3.1 of [ACP123]) are not supported.  These
 extensions are used to request and return notifications from ACP 127
 gateways, and are not relevant to an SMTP gateway.

6. Gatewaying with ACP 123 / STANAG 4406

 The header fields defined in this specification are designed to be
 mapped with ACP 123 Annex A1 heading extensions as part of a MIXER
 mapping according to [RFC2156].  The syntax of these headings is
 defined such that mapping is mechanical.  OR Names SHOULD be mapped
 with Internet Email addresses according to [RFC2156].
 This section summarizes how a gateway between [ACP123] and [RFC5322]
 conformant to this specification operates.
 If an incoming X.400 message is encoded as P772, [RFC5322] header
 fields MUST be generated according to this specification for all ACP
 123 heading extensions where an equivalent header is defined in this
 specification.  For the three heading extensions where no mapping is
 defined, the heading extension MAY be discarded or mapped in a

Melnikov & Lunt Informational [Page 16] RFC 6477 MMHS Header Fields January 2012

 proprietary manner.  If a Distribution Extension is encoded, this MAY
 be discarded or represented as a comment (<CFWS>).  The whole message
 MAY be signed according to [RFC5652].  These rules also apply to
 heading extensions in forwarded messages.  MM-Message MUST be treated
 as a forwarded message for the purposes of MIXER mapping.  If an ACP
 127 Notification Request is present, this MAY be discarded or
 represented as a comment (<CFWS>).
 Incoming X.400 notifications are encoded according to [RFC2156].  If
 an ACP 127 Notification Response is present, this MAY be discarded or
 mapped in a proprietary manner.
 If an incoming SMTP message contains any of the header fields defined
 in this specification, the outgoing X.400 message MUST be encoded as
 P772.  The outgoing message MAY be encoded as P772 for other reasons,
 for instance, policy or characteristics such as the message
 containing a military body part.  The X.400 message might be signed
 according to ACP 123 Annex B [ACP123] or STANAG 4406 Annex G
 [STANAG-4406].  message/rfc822 body parts included in the message
 SHOULD be mapped to MM-Message and the heading mapping rules applied.
 Generated P772 messages SHOULD follow the following rules, generating
 heading extensions if needed.
 a.  Extended Authorization is required.  If the MMHS-Extended-
     Authorization-Info header field is absent, then the default value
     is taken from the Date header field.
 b.  Primary Precedence is required if the To header field is present.
     If the MMHS-Primary-Precedence header field is absent, the
     message need not be considered a Military Message and can be
     handled according to a local policy.
 c.  Copy Precedence is required if the Cc header field is present and
     there is an MMHS-Copy-Precedence header field that is different
     from the MMHS-Primary-Precedence header field.
 d.  For Message-ID fields, ACP 123 applies additional constraints
     over X.400, leading to the following rules in addition to
     [RFC2156], which SHOULD be followed by a gateway following this
     specification.
     1.  The local identifier MUST be at least 15 characters long.  If
         the [RFC2156] generated value is shorter than this, then it
         is padded with spaces to 15 characters.  This value will
         correctly reverse map.

Melnikov & Lunt Informational [Page 17] RFC 6477 MMHS Header Fields January 2012

     2.  The OR Address part is required, and it is not usually
         generated by an [RFC2156] mapping.  It is mandatory in ACP
         123.  The gateway SHOULD generate an OR Address in a manner
         that can be reverse mapped.  It MAY use the OR Address to
         encode long message ids that cannot be encoded in the local
         identifier.

7. Gatewaying with ACP 127

 The header fields defined in this specification include fields to
 carry Elements of Service specific to ACP 127 [ACP127].  This
 specification does not define a mapping of these header fields to ACP
 127.  In the absence of this mapping, it is recommended that these
 headings be mapped to ACP 123 and hence into ACP 127 following the
 Annex D (Gateway Translation) of [STANAG-4406].

8. IANA Considerations

 IANA has added the list of header fields specified in subsections of
 Section 3 to the "Permanent Message Header Field Names" registry
 defined by "Registration Procedures for Message Header Fields"
 [RFC3864].

9. Security Considerations

 Annex B of [ACP123] describes how MMHS messages can be protected in
 an X.400 environment.  Similar protection can be provided using
 S/MIME [RFC5751] and/or DKIM [RFC6376].  In particular, DKIM can be
 used to protect against alteration, deletion, or insertion of header
 fields specified in this document that can affect disposition and
 quality of service applied to processing of the protected Internet
 message by receiving gateways/endpoints that support this
 specification.  (Note that most of the header fields defined in this
 document might affect processing of the message by the receiving
 gateway/end system, MMHS-Subject-Indicator-Codes and MMHS-Primary-
 Precedence/MMHS-Copy-Precedence header fields being the most
 important examples.  For example, alteration of the MMHS-Primary-
 Precedence header field value might affect processing speed of the
 message by the recipient Message Transfer Agent (MTA).)
 When the original message header fields are digitally signed, the act
 of gatewaying messages with such header fields to/from an Internet
 environment from/to an ACP 123 environment breaks digital signatures.
 The gateway can sign the translated message itself (e.g., with DKIM),
 but a message recipient would be unable to verify that the message
 was generated by the original sender.

Melnikov & Lunt Informational [Page 18] RFC 6477 MMHS Header Fields January 2012

10. References

10.1. Normative References

 [ACP123]    CCEB, "Common Messaging Strategy and Procedures", ACP 123
             (B), May 2009, http://jcs.dtic.mil/j6/cceb/acps/acp123/.
 [ACP127]    CCEB, "Communication Instructions - Tape Relay
             Procedures", ACP 127 (G), November 1988,
             http://jcs.dtic.mil/j6/cceb/acps/acp127/.
 [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2156]   Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay):
             Mapping between X.400 and RFC 822/MIME", RFC 2156,
             January 1998.
 [RFC3864]   Klyne, G., Nottingham, M., and J. Mogul, "Registration
             Procedures for Message Header Fields", BCP 90, RFC 3864,
             September 2004.
 [RFC5234]   Crocker, D., Ed., and P. Overell, "Augmented BNF for
             Syntax Specifications: ABNF", STD 68, RFC 5234, January
             2008.
 [RFC5322]   Resnick, P., Ed., "Internet Message Format", RFC 5322,
             October 2008.
 [RFC5652]   Housley, R., "Cryptographic Message Syntax (CMS)", STD
             70, RFC 5652, September 2009.
 [RFC6376]   Crocker, D., Ed., Hansen, T., Ed., and M. Kucherawy, Ed.,
             "DomainKeys Identified Mail (DKIM) Signatures", RFC 6376,
             September 2011.

10.2. Informative References

 [ACP121]    CCEB, "Comms Instructions - General", ACP 121 (I),
             October 2010, http://jcs.dtic.mil/j6/cceb/acps/acp121/.
 [ACP131]    CCEB, "Comms Instructions - Operating Signals", ACP 131
             (F), April 2009,
             http://jcs.dtic.mil/j6/cceb/acps/acp131/.
 [RFC2634]   Hoffman, P., Ed., "Enhanced Security Services for
             S/MIME", RFC 2634, June 1999.

Melnikov & Lunt Informational [Page 19] RFC 6477 MMHS Header Fields January 2012

 [RFC5751]   Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
             Mail Extensions (S/MIME) Version 3.2 Message
             Specification", RFC 5751, January 2010.
 [STANAG-4406]
             NATO, "STANAG 4406 Edition 2: Military Message Handling
             System", STANAG 4406, March 2005.

Melnikov & Lunt Informational [Page 20] RFC 6477 MMHS Header Fields January 2012

Appendix A. Acknowledgements

 This document copies a lot of text from the "Mapping between X.400
 P772 and RFC-822" by Julian Onions and Graeme Lunt and STANAG 4406
 (2nd Edition).  So the authors of this document would like to
 acknowledge contributions made by the authors of these documents.
 Many thanks for reviews and text provided by Steve Kille, Alan Ross,
 David Wilson, James Usmar, Kathy Nuckles, Andy Trayler, Ken Carlberg,
 Chris Bonatti, Oeyvind Jonsson, Mykyta Yevstifeyev, Sean Turner,
 Stephen Farrell, Adrian Farrel, and Peter Saint-Andre.

Authors' Addresses

 Alexey Melnikov
 Isode Ltd
 5 Castle Business Village
 36 Station Road
 Hampton, Middlesex, TW12 2BX
 UK
 EMail: Alexey.Melnikov@isode.com
 Graeme Lunt
 SMHS Ltd
 Bescar Moss Farm
 Bescar Lane
 Ormskirk  L40 9QN
 UK
 EMail: graeme.lunt@smhs.co.uk

Melnikov & Lunt Informational [Page 21]

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