Mapping between X.400(1988) / ISO 10021 and RFC 822
draft-ietf-kille-x_400mapping-04
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draft-ietf-kille-x_400mapping-04
Network Working Group S.E. Hardcastle-Kille
Internet Draft University College London
November 1991
Mapping between X.400(1988) / ISO 10021 and RFC 822
Status of this Memo:
This document describes a set of mappings which will enable
interworking between systems operating the CCITT X.400
(1988) Recommendations on Message Handling Systems / ISO IEC
10021 Message Oriented Text Interchange Systems (MOTIS)
[CCITT/ISO88a], and systems using the RFC 822 mail protocol
[Crocker82a] or protocols derived from RFC 822. The
approach aims to maximise the services offered across the
boundary, whilst not requiring unduly complex mappings. The
mappings should not require any changes to end systems. This
document is a revision based on RFCs 987, 1026, 1138, and
1148[Kille86a,Kille87a] which it obsoletes.
This document specifies a mapping between two protocols.
This specification should be used when this mapping is
performed on the DARPA Internet or in the UK Academic
Community. This specification may be modified in the light
of implementation experience, but no substantial changes are
expected.
This draft document will be submitted to the RFC editor as
a protocol specification. Distribution of this memo is
unlimited. Please send comments to the author.
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Table of Contents
1 - Overview ...................................... 6
1.1 - X.400 ......................................... 6
1.2 - RFC 822 ....................................... 6
1.3 - The need for conversion ....................... 7
1.4 - General approach .............................. 7
1.5 - Gatewaying Model .............................. 8
1.6 - X.400 (1984) .................................. 11
1.7 - Compatibility with previous versions .......... 12
1.8 - Aspects not covered ........................... 12
1.9 - Subsetting .................................... 12
1.10 - Document Structure ........................... 13
1.11 - Acknowledgements ............................. 13
2 - Service Elements .............................. 14
2.1 - The Notion of Service Across a Gateway ........ 14
2.2 - RFC 822 ....................................... 15
2.3 - X.400 ......................................... 19
3 - Basic Mappings ................................ 30
3.1 - Notation ...................................... 30
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3.2 - ASCII and IA5 ................................. 32
3.3 - Standard Types ................................ 32
3.4 - Encoding ASCII in Printable String ............ 35
4 - Addressing .................................... 37
4.1 - A textual representation of MTS.ORAddress ..... 37
4.2 - Basic Representation .......................... 37
4.3 - EBNF.822-address <-> MTS.ORAddress ............ 44
4.4 - Repeated Mappings ............................. 57
4.5 - Directory Names ............................... 59
4.6 - MTS Mappings .................................. 60
4.7 - IPMS Mappings ................................. 65
5 - Detailed Mappings ............................. 70
5.1 - RFC 822 -> X.400 .............................. 70
5.2 - Return of Contents ............................ 78
5.3 - X.400 -> RFC 822 .............................. 79
Appendix A - Mappings Specific to SMTP ..................... 107
Appendix B - Mappings specific to the JNT Mail ............. 108
1 - Introduction .................................. 108
2 - Domain Ordering ............................... 108
3 - Addressing .................................... 108
4 - Acknowledge-To: .............................. 108
5 - Trace ......................................... 109
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6 - Timezone specification ........................ 109
7 - Lack of 822-MTS originator specification ...... 109
Appendix C - Mappings specific to UUCP Mail ................ 111
Appendix D - Object Identifier Assignment .................. 112
Appendix E - BNF Summary ................................... 113
Appendix F - Format of address mapping tables .............. 123
1 - Global Mapping Information .................... 123
2 - Syntax Definitions ............................ 124
3 - Table Lookups ................................. 125
4 - Domain -> O/R Address format .................. 125
5 - O/R Address -> Domain format .................. 126
6 - Domain -> O/R Address of Gateway table ........ 126
Appendix G - Mapping with X.400(1984) ...................... 127
Appendix H - RFC 822 Extensions for X.400 access ........... 129
Appendix I - Conformance ................................... 130
Appendix J - Change History: RFC 987, 1026, 1138,
1148 .................................................. 132
1 - Introduction .................................. 132
2 - Service Elements .............................. 132
3 - Basic Mappings ................................ 133
4 - Addressing .................................... 133
5 - Detailed Mappings ............................. 133
6 - Appendices .................................... 134
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Appendix K - Change History: RFC 1148 to this Document
............................................................ 135
1 - General ....................................... 135
2 - Basic Mappings ................................ 135
3 - Addressing .................................... 135
4 - Detailed Mappings ............................. 136
5 - Appendices .................................... 136
Hardcastle-Kille [page 5]
Chapter 1 -- Overview
1.1. X.400
This document relates to the CCITT 1988 X.400 Series
Recommendations / ISO IEC 10021 on the Message Oriented Text
Interchange Service (MOTIS). This ISO/CCITT standard is referred
to in this document as "X.400", which is a convenient shorthand.
Any reference to the 1984 CCITT Recommendations will be explicit.
X.400 defines an Interpersonal Messaging System (IPMS), making
use of a store and forward Message Transfer System. This
document relates to the IPMS, and not to wider application of
X.400. It is expected that X.400 will be implemented very
widely.
1.2. RFC 822
RFC 822 evolved as a messaging standard on the DARPA (the US
Defense Advanced Research Projects Agency) Internet. It
specifies and end to end message format. It is used in
conjunction with a number of different message transfer protocol
environments.
SMTP Networks
On the DARPA Internet and other TCP/IP networks, RFC 822 is
used in conjunction with two other standards: RFC 821, also
known as Simple Mail Transfer Protocol (SMTP) [Postel82a],
and RFC 920 which is a Specification for domains and a
distributed name service [Postel84a].
UUCP Networks
UUCP is the UNIX to UNIX CoPy protocol, which is usually
used over dialup telephone networks to provide a simple
message transfer mechanism. There are some extensions to
RFC 822, particularly in the addressing. They use domains
which conform to RFC 920, but not the corresponding domain
nameservers [Horton86a].
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Bitnet
Some parts of Bitnet and related networks use RFC 822
related protocols, with EBCDIC encoding.
JNT Mail Networks
A number of X.25 networks, particularly those associated
with the UK Academic Community, use the JNT (Joint Network
Team) Mail Protocol, also known as Greybook [Kille84a].
This is used with domains and name service specified by the
JNT NRS (Name Registration Scheme) [Larmouth83a].
The mappings specified here are appropriate for all of these
networks.
1.3. The need for conversion
There is a large community using RFC 822 based protocols for mail
services, who will wish to communicate with users of the IPMS
provided by X.400 systems. This will also be a requirement in
cases where communities intend to make a transition to use of an
X.400 IPMS, as conversion will be needed to ensure a smooth
service transition. It is expected that there will be more than
one gateway, and this specification will enable them to behave in
a consistent manner. Note that the term gateway is used to
describe a component performing the protocol mappings between RFC
822 and X.400. This is standard usage amongst mail implementors,
but should be noted carefully by transport and network service
implementors.
Consistency between gateways is desirable to provide:
1. Consistent service to users.
2. The best service in cases where a message passes through
multiple gateways.
1.4. General approach
There are a number of basic principles underlying the details of
the specification. These principles are goals, and are not
achieved in all aspects of the specification.
1. The specification should be pragmatic. There should not be
a requirement for complex mappings for "Academic" reasons.
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Complex mappings should not be required to support trivial
additional functionality.
2. Subject to 1), functionality across a gateway should be as
high as possible.
3. It is always a bad idea to lose information as a result of
any transformation. Hence, it is a bad idea for a gateway
to discard information in the objects it processes. This
includes requested services which cannot be fully mapped.
4. All mail gateways actually operate at exactly one level
above the layer on which they conceptually operate. This
implies that the gateway must not only be cognisant of the
semantics of objects at the gateway level, but also be
cognisant of higher level semantics. If meaningful
transformation of the objects that the gateway operates on
is to occur, then the gateway needs to understand more than
the objects themselves.
5. Subject to 1), the specification should be reversible. That
is, a double transformation should bring you back to where
you started.
1.5. Gatewaying Model
1.5.1. X.400
X.400 defines the IPMS Abstract Service in X.420/ISO 10021-7 ,
[CCITT/ISO88b] which comprises of three basic services:
1. Origination
2. Reception
3. Management
Management is a local interaction between the user and the IPMS,
and is therefore not relevant to gatewaying. The first two
services consist of operations to originate and receive the
following two objects:
1. IPM (Interpersonal Message). This has two components: a
heading, and a body. The body is structured as a sequence
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of body parts, which may be basic components (e.g., IA5
text, or G3 fax), or IP Messages. The heading consists of
fields containing end to end user information, such as
subject, primary recipients (To:), and importance.
2. IPN (Inter Personal Notification). A notification about
receipt of a given IPM at the UA level.
The Origination service also allows for origination of a probe,
which is an object to test whether a given IPM could be correctly
received.
The Reception service also allows for receipt of Delivery Reports
(DR), which indicate delivery success or failure.
These IPMS Services utilise the Message Transfer (MT)
Abstract Service [CCITT/ISO88c]. The MT Abstract Service
provides the following three basic services:
1. Submission (used by IPMS Origination)
2. Delivery (used by IPMS Reception)
3. Administration (used by IPMS Management)
Administration is a local issue, and so does not affect this
standard. Submission and delivery relate primarily to the MTS
Message (comprising Envelope and Content), which carries an IPM
or IPN (or other uninterpreted contents). There is also an
Envelope, which includes an ID, an originator, and a list of
recipients. Submission also includes the probe service, which
supports the IPMS Probe. Delivery also includes Reports, which
indicate whether a given MTS Message has been delivered or not.
The MTS is REFINED into the MTA (Message Transfer Agent)
Service, which defines the interaction between MTAs, along with
the procedures for distributed operation. This service provides
for transfer of MTS Messages, Probes, and Reports.
1.5.2. RFC 822
RFC 822 is based on the assumption that there is an underlying
service, which is here called the 822-MTS service. The 822-MTS
service provides three basic functions:
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1. Identification of a list of recipients.
2. Identification of an error return address.
3. Transfer of an RFC 822 message.
It is possible to achieve 2) within the RFC 822 header. Some
822-MTS protocols, in particular SMTP, can provide additional
functionality, but as these are neither mandatory in SMTP, nor
available in other 822-MTS protocols, they are not considered
here. Details of aspects specific to two 822-MTS protocols are
given in Appendices B and C. An RFC 822 message consists of a
header, and content which is uninterpreted ASCII text. The
header is divided into fields, which are the protocol elements.
Most of these fields are analogous to P2 heading fields, although
some are analogous to MTS Service Elements or MTA Service
Elements.
1.5.3. The Gateway
Given this functional description of the two services, the
functional nature of a gateway can now be considered. It would
be elegant to consider the 822-MTS service mapping onto the MTS
Service Elements and RFC 822 mapping onto an IPM, but reality
just does not fit. Another elegant approach would be to treat
this document as the definition of an X.400 Access Unit (AU).
Again, reality does not fit. It is necessary to consider that
the IPM format definition, the IPMS Service Elements, the MTS
Service Elements, and MTA Service Elements on one side are mapped
into RFC 822 + 822-MTS on the other in a slightly tangled manner.
The details of the tangle will be made clear in Chapter 5.
Access to the MTA Service Elements is minimised.
The following basic mappings are thus defined. When going
from RFC 822 to X.400, an RFC 822 message and the associated
822-MTS information is always mapped into an IPM (MTA, MTS, and
IPMS Services). Going from X.400 to RFC 822, an RFC 822 message
and the associated 822-MTS information may be derived from:
1. A Report (MTA, and MTS Services)
2. An IPN (MTA, MTS, and IPMS services)
3. An IPM (MTA, MTS, and IPMS services)
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Probes (MTA Service) must be processed by the gateway, as
discussed in Chapter 5. MTS Messages containing Content Types
other than those defined by the IPMS are not mapped by the
gateway, and should be rejected at the gateway.
1.5.4. Repeated Mappings
The primary goal of this specification is to support single
mappings, so that X.400 and RFC 822 users can communicate with
maximum functionality.
The mappings specified here are designed to work where a
message traverses multiple times between X.400 and RFC 822. This
is often essential, particularly in the case of distribution
lists. However, in general, this will lead to a level of service
which is the lowest common denominator (approximately the
services offered by RFC 822).
Some RFC 822 networks may wish to use X.400 as an
interconnection mechanism (typically for policy reasons), and
this is fully supported.
Where an X.400 messages transfers to RFC 822 and then back
to X.400, there is no expectation of X.400 services which do not
have an equivalent service in standard RFC 822 being preserved -
although this may be possible in some cases.
1.6. X.400 (1984)
Much of this work is based on the initial specification of RFC
987 and in its addendum RFC 1026, which defined a mapping between
X.400(1984) and RFC 822. A basic decision is that the mapping
defined in this document is to the full 1988 version of X.400,
and not to a 1984 compatible subset. New features of X.400(1988)
can be used to provide a much cleaner mapping than that defined
in RFC 987. This is important, to give good support to
communities which will utilise full X.400 at an early date. To
interwork with 1984 systems, Appendix G shall be followed.
If a message is being transferred to an X.400(1984) system
by way of X.400(1988) MTA it will give a slightly better service
to follow the rules of Appendix G.
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1.7. Compatibility with previous versions
The changes between this an older versions of the document are
given in Appendices I and J. These are RFCs 987, 1026, 1138,
and 1148. This document is a revision of RFC 1148 [Kille90a].
As far as possible, changes have been made in a compatible
fashion.
1.8. Aspects not covered
There have been a number of cases where RFC 987 was used in a
manner which was not intended. This section is to make clear
some limitations of scope. In particular, this specification
does not specify:
- Extensions of RFC 822 to provide access to all X.400
services
- X.400 user interface definition
- Mapping X.400 to extended versions of RFC 822, with support
for multimedia content.
The first two of these are really coupled. To map the X.400
services, this specification defines a number of extensions to
RFC 822. As a side effect, these give the 822 user access to
SOME X.400 services. However, the aim on the RFC 822 side is to
preserve current service, and it is intentional that access is
not given to all X.400 services. Thus, it will be a poor choice
for X.400 implementors to use RFC 987(88) as an interface - there
are too many aspects of X.400 which cannot be accessed through
it. If a text interface is desired, a specification targeted at
X.400, without RFC 822 restrictions, would be more appropriate.
Some optional and limited extensions in this area have proved
useful, and are defined in Appendix G.
1.9. Subsetting
This proposal specifies a mapping which is appropriate to
preserve services in existing RFC 822 communities.
Implementations and specifications which subset this
specification are strongly discouraged.
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1.10. Document Structure
This document has five chapters:
1. Overview - this chapter.
2. Service Elements - This describes the (end user) services
mapped by a gateway.
3. Basic mappings - This describes some basic notation used in
Chapters 3-5, the mappings between character sets, and some
fundamental protocol elements.
4. Addressing - This considers the mapping between X.400 O/R
names and RFC 822 addresses, which is a fundamental gateway
component.
5. Detailed Mappings - This describes the details of all other
mappings.
There are also eleven appendices.
WARNING:
THE REMAINDER OF THIS SPECIFICATION IS TECHNICALLY DETAILED.
IT WILL NOT MAKE SENSE, EXCEPT IN THE CONTEXT OF RFC 822 AND
X.400 (1988). DO NOT ATTEMPT TO READ THIS DOCUMENT UNLESS
YOU ARE FAMILIAR WITH THESE SPECIFICATIONS.
1.11. Acknowledgements
The work in this specification was substantially based on RFC 987
and RFC 1148, which had input from many people, who are credited
in the respective documents.
A number of comments from people on RFC 1148 lead to this
document. In particular, there were comments and suggestions
from: Maurice Abraham (HP); Harald Alvestrand (Sintef); Peter
Cowen (X-Tel); Jim Craigie (JNT); Christian Huitema (Inria); Erik
Huizer (SURFnet); Neil Jones (DEC); Ignacio Martinez (IRIS);
Julian Onions (X-Tel); Simon Poole (SWITCH); Clive Roberts (Data
General); Pete Vanderbilt (SUN); Alan Young (Concurrent).
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Chapter 2 - Service Elements
This chapter considers the services offered across a gateway
built according to this specification. It gives a view of the
functionality provided by such a gateway for communication with
users in the opposite domain. This chapter considers service
mappings in the context of SINGLE transfers only, and not
repeated mappings through multiple gateways.
2.1. The Notion of Service Across a Gateway
RFC 822 and X.400 provide a number of services to the end user.
This chapter describes the extent to which each service can be
supported across an X.400 <-> RFC 822 gateway. The cases
considered are single transfers across such a gateway, although
the problems of multiple crossings are noted where appropriate.
2.1.1. Origination of Messages
When a user originates a message, a number of services are
available. Some of these imply actions (e.g., delivery to a
recipient), and some are insertion of known data (e.g.,
specification of a subject field). This chapter describes, for
each offered service, to what extent it is supported for a
recipient accessed through a gateway. There are three levels of
support:
Supported
The corresponding protocol elements map well, and so the
service can be fully provided.
Not Supported
The service cannot be provided, as there is a complete
mismatch.
Partial Support
The service can be partially fulfilled.
In the first two cases, the service is simply marked as
"Supported" or "Not Supported". Some explanation may be given if
there are additional implications, or the (non) support is not
intuitive. For partial support, the level of partial support is
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summarised. Where partial support is good, this will be
described by a phrase such as "Supported by use of.....". A
common case of this is where the service is mapped onto a non-
standard service on the other side of the gateway, and this would
have lead to support if it had been a standard service. In many
cases, this is equivalent to support. For partial support, an
indication of the mechanism is given, in order to give a feel for
the level of support provided. Note that this is not a
replacement for Chapter 5, where the mapping is fully specified.
If a service is described as supported, this implies:
- Semantic correspondence.
- No (significant) loss of information.
- Any actions required by the service element.
An example of a service gaining full support: If an RFC 822
originator specifies a Subject: field, this is considered to be
supported, as an X.400 recipient will get a subject indication.
In many cases, the required action will simply be to make the
information available to the end user. In other cases, actions
may imply generating a delivery report.
All RFC 822 services are supported or partially supported
for origination. The implications of non-supported X.400
services is described under X.400.
2.1.2. Reception of Messages
For reception, the list of service elements required to support
this mapping is specified. This is really an indication of what
a recipient might expect to see in a message which has been
remotely originated.
2.2. RFC 822
RFC 822 does not explicitly define service elements, as distinct
from protocol elements. However, all of the RFC 822 header
fields, with the exception of trace, can be regarded as
corresponding to implicit RFC 822 service elements.
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2.2.1. Origination in RFC 822
A mechanism of mapping, used in several cases, is to map the RFC
822 header into a heading extension in the IPM (InterPersonal
Message). This can be regarded as partial support, as it makes
the information available to any X.400 implementations which are
interested in these services. Communities which require
significant RFC 822 interworking are recommended to require that
their X.400 User Agents are able to display these heading
extensions. Support for the various service elements (headers)
is now listed.
Date:
Supported.
From:
Supported. For messages where there is also a sender field,
the mapping is to "Authorising Users Indication", which has
subtly different semantics to the general RFC 822 usage of
From:.
Sender:
Supported.
Reply-To:
Supported.
To: Supported.
Cc: Supported.
Bcc: Supported.
Message-Id:
Supported.
In-Reply-To:
Supported, for a single reference. Where multiple
references are given, partial support is given by mapping to
"Cross Referencing Indication". This gives similar
semantics.
References:
Supported.
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Keywords:
Supported by use of a heading extension.
Subject:
Supported.
Comments:
Supported by use of an extra body part.
Encrypted:
Supported by use of a heading extension.
Resent-*
Supported by use of a heading extension. Note that
addresses in these fields are mapped onto text, and so are
not accessible to the X.400 user as addresses. In
principle, fuller support would be possible by mapping onto
a forwarded IP Message, but this is not suggested.
Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are supported by use of
heading extensions.
2.2.2. Reception by RFC 822
This considers reception by an RFC 822 User Agent of a message
originated in an X.400 system and transferred across a gateway.
The following standard services (headers) may be present in such
a message:
Date:
From:
Sender:
Reply-To:
To:
Cc:
Bcc:
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Message-Id:
In-Reply-To:
References:
Subject:
The following non-standard services (headers) may be present.
These are defined in more detail in Chapter 5 (5.3.4, 5.3.6,
5.3.7):
Autoforwarded:
Content-Identifier:
Conversion:
Conversion-With-Loss:
Delivery-Date:
Discarded-X400-IPMS-Extensions:
Discarded-X400-MTS-Extensions:
DL-Expansion-History:
Deferred-Delivery:
Expiry-Date:
Importance:
Incomplete-Copy:
Language:
Latest-Delivery-Time:
Message-Type:
Obsoletes:
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Original-Encoded-Information-Types:
Originator-Return-Address:
Priority:
Reply-By:
Requested-Delivery-Method:
Sensitivity:
X400-Content-Type:
X400-MTS-Identifier:
X400-Originator:
X400-Received:
X400-Recipients:
2.3. X.400
2.3.1. Origination in X.400
When mapping services from X.400 to RFC 822 which are not
supported by RFC 822, new RFC 822 headers are defined. It is
intended that these fields will be registered, and that co-
operating RFC 822 systems may use them. Where these new fields
are used, and no system action is implied, the service can be
regarded as being partially supported. Chapter 5 describes how
to map X.400 services onto these new headers. Other elements are
provided, in part, by the gateway as they cannot be provided by
RFC 822.
Some service elements are marked N/A (not applicable).
There are five cases, which are marked with different comments:
N/A (local)
These elements are only applicable to User Agent / Message
Transfer Agent interaction and so they cannot apply to RFC
822 recipients.
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N/A (PDAU)
These service elements are only applicable where the
recipient is reached by use of a Physical Delivery Access
Unit (PDAU), and so do not need to be mapped by the gateway.
N/A (reception)
These services are only applicable for reception.
N/A (prior)
If requested, this service must be performed prior to the
gateway.
N/A (MS)
These services are only applicable to Message Store (i.e., a
local service).
Finally, some service elements are not supported. In
particular, the new security services are not mapped onto RFC
822. Unless otherwise indicated, the behaviour of service
elements marked as not supported will depend on the criticality
marking supplied by the user. If the element is marked as
critical for transfer or delivery, a non-delivery notification
will be generated. Otherwise, the service request will be
ignored.
2.3.1.1. Basic Interpersonal Messaging Service
These are the mandatory IPM services as listed in Section 19.8 of
X.400 / ISO/IEC 10021-1, listed here in the order given. Section
19.8 has cross references to short definitions of each service.
Access management
N/A (local).
Content Type Indication
Supported by a new RFC 822 header (Content-Type:).
Converted Indication
Supported by a new RFC 822 header (X400-Received:).
Delivery Time Stamp Indication
N/A (reception).
IP Message Identification
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Supported.
Message Identification
Supported, by use of a new RFC 822 header
(X400-MTS-Identifier). This new header is required, as
X.400 has two message-ids whereas RFC 822 has only one (see
previous service).
Non-delivery Notification
Not supported, although in general an RFC 822 system will
return error reports by use of IP messages. In other
service elements, this pragmatic result can be treated as
effective support of this service element.
Original Encoded Information Types Indication
Supported as a new RFC 822 header
(Original-Encoded-Information-Types:).
Submission Time Stamp Indication
Supported.
Typed Body
Some types supported. IA5 is fully supported.
ForwardedIPMessage is supported, with some loss of
information. Other types get some measure of support,
dependent on X.400 facilities for conversion to IA5. This
will only be done where content conversion is not
prohibited.
User Capabilities Registration
N/A (local).
2.3.1.2. IPM Service Optional User Facilities
This section describes support for the optional (user selectable)
IPM services as listed in Section 19.9 of X.400 / ISO/IEC 10021-
1, listed here in the order given. Section 19.9 has cross
references to short definitions of each service.
Additional Physical Rendition
N/A (PDAU).
Alternate Recipient Allowed
Not supported. There is no RFC 822 service equivalent to
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prohibition of alternate recipient assignment (e.g., an RFC
822 system may freely send an undeliverable message to a
local postmaster). Thus, the gateway cannot prevent
assignment of alternative recipients on the RFC 822 side.
This service really means giving the user control as to
whether or not an alternate recipient is allowed. This
specification requires transfer of messages to RFC 822
irrespective of this service request, and so this service is
not supported.
Authorising User's Indication
Supported.
Auto-forwarded Indication
Supported as new RFC 822 header (Auto-Forwarded:).
Basic Physical Rendition
N/A (PDAU).
Blind Copy Recipient Indication
Supported.
Body Part Encryption Indication
Supported by use of a new RFC 822 header
(Original-Encoded-Information-Types:), although in most
cases it will not be possible to map the body part in
question.
Content Confidentiality
Not supported.
Content Integrity
Not supported.
Conversion Prohibition
Supported. In this case, only messages with IA5 body parts,
other body parts which contain only IA5, and Forwarded IP
Messages (subject recursively to the same restrictions),
will be mapped.
Conversion Prohibition in Case of Loss of Information
Supported.
Counter Collection
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N/A (PDAU).
Counter Collection with Advice
N/A (PDAU).
Cross Referencing Indication
Supported.
Deferred Delivery
N/A (prior). This service should always be provided by the
MTS prior to the gateway. A new RFC 822 header
(Deferred-Delivery:) is provided to transfer information on
this service to the recipient.
Deferred Delivery Cancellation
N/A (local).
Delivery Notification
Supported. This is performed at the gateway. Thus, a
notification is sent by the gateway to the originator. If
the 822-MTS protocol is JNT Mail, a notification may also be
sent by the recipient UA.
Delivery via Bureaufax Service
N/A (PDAU).
Designation of Recipient by Directory Name
N/A (local).
Disclosure of Other Recipients
Supported by use of a new RFC 822 header (X400-Recipients:).
This is descriptive information for the RFC 822 recipient,
and is not reverse mappable.
DL Expansion History Indication
Supported by use of a new RFC 822 header
(DL-Expansion-History:).
DL Expansion Prohibited
Distribution List means MTS supported distribution list, in
the manner of X.400. This service does not exist in the RFC
822 world. RFC 822 distribution lists should be regarded as
an informal redistribution mechanism, beyond the scope of
this control. Messages will be sent to RFC 822,
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irrespective of whether this service is requested.
Theoretically therefore, this service is supported, although
in practice it may appear that it is not supported.
Express Mail Service
N/A (PDAU).
Expiry Date Indication
Supported as new RFC 822 header (Expiry-Date:). In general,
no automatic action can be expected.
Explicit Conversion
N/A (prior).
Forwarded IP Message Indication
Supported, with some loss of information. The message is
forwarded in an RFC 822 body, and so can only be interpreted
visually.
Grade of Delivery Selection
N/A (PDAU)
Importance Indication
Supported as new RFC 822 header (Importance:).
Incomplete Copy Indication
Supported as new RFC 822 header (Incomplete-Copy:).
Language Indication
Supported as new RFC 822 header (Language:).
Latest Delivery Designation
Not supported. A new RFC 822 header (Latest-Delivery-Time:)
is provided, which may be used by the recipient.
Message Flow Confidentiality
Not supported.
Message Origin Authentication
N/A (reception).
Message Security Labelling
Not supported.
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Message Sequence Integrity
Not supported.
Multi-Destination Delivery
Supported.
Multi-part Body
Supported, with some loss of information, in that the
structuring cannot be formalised in RFC 822.
Non Receipt Notification Request
Not supported.
Non Repudiation of Delivery
Not supported.
Non Repudiation of Origin
N/A (reception).
Non Repudiation of Submission
N/A (local).
Obsoleting Indication
Supported as new RFC 822 header (Obsoletes:).
Ordinary Mail
N/A (PDAU).
Originator Indication
Supported.
Originator Requested Alternate Recipient
Not supported, but is placed as comment next to address
(X400-Recipients:).
Physical Delivery Notification by MHS
N/A (PDAU).
Physical Delivery Notification by PDS
N/A (PDAU).
Physical Forwarding Allowed
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
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question.
Physical Forwarding Prohibited
Supported by use of a comment in a new RFC 822 header
(X400-Recipients:), associated with the recipient in
question.
Prevention of Non-delivery notification
Supported, as delivery notifications cannot be generated by
RFC 822. In practice, errors will be returned as IP
Messages, and so this service may appear not to be supported
(see Non-delivery Notification).
Primary and Copy Recipients Indication
Supported
Probe
Supported at the gateway (i.e., the gateway services the
probe).
Probe Origin Authentication
N/A (reception).
Proof of Delivery
Not supported.
Proof of Submission
N/A (local).
Receipt Notification Request Indication
Not supported.
Redirection Allowed by Originator
Redirection means MTS supported redirection, in the manner
of X.400. This service does not exist in the RFC 822 world.
RFC 822 redirection (e.g., aliasing) should be regarded as
an informal redirection mechanism, beyond the scope of this
control. Messages will be sent to RFC 822, irrespective of
whether this service is requested. Theoretically therefore,
this service is supported, although in practice it may
appear that it is not supported.
Registered Mail
N/A (PDAU).
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Registered Mail to Addressee in Person
N/A (PDAU).
Reply Request Indication
Supported as comment next to address.
Replying IP Message Indication
Supported.
Report Origin Authentication
N/A (reception).
Request for Forwarding Address
N/A (PDAU).
Requested Delivery Method
N/A (local). The services required must be dealt with at
submission time. Any such request is made available through
the gateway by use of a comment associated with the
recipient in question.
Return of Content
In principle, this is N/A, as non-delivery notifications are
not supported. In practice, most RFC 822 systems will
return part or all of the content along with the IP Message
indicating an error (see Non-delivery Notification).
Sensitivity Indication
Supported as new RFC 822 header (Sensitivity:).
Special Delivery
N/A (PDAU).
Stored Message Deletion
N/A (MS).
Stored Message Fetching
N/A (MS).
Stored Message Listing
N/A (MS).
Stored Message Summary
N/A (MS).
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Subject Indication
Supported.
Undeliverable Mail with Return of Physical Message
N/A (PDAU).
Use of Distribution List
In principle this applies only to X.400 supported
distribution lists (see DL Expansion Prohibited).
Theoretically, this service is N/A (prior). In practice,
because of informal RFC 822 lists, this service can be
regarded as supported.
2.3.2. Reception by X.400
2.3.2.1. Standard Mandatory Services
The following standard IPM mandatory user facilities are
required for reception of RFC 822 originated mail by an X.400 UA.
Content Type Indication
Delivery Time Stamp Indication
IP Message Identification
Message Identification
Non-delivery Notification
Original Encoded Information Types Indication
Submission Time Stamp Indication
Typed Body
2.3.2.2. Standard Optional Services
The following standard IPM optional user facilities are required
for reception of RFC 822 originated mail by an X.400 UA.
Authorising User's Indication
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Blind Copy Recipient Indication
Cross Referencing Indication
Originator Indication
Primary and Copy Recipients Indication
Replying IP Message Indication
Subject Indication
2.3.2.3. New Services
A new service "RFC 822 Header Field" is defined using the
extension facilities. This allows for any RFC 822 header field
to be represented. It may be present in RFC 822 originated
messages, which are received by an X.400 UA.
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Chapter 3 Basic Mappings
3.1. Notation
The X.400 protocols are encoded in a structured manner according
to ASN.1, whereas RFC 822 is text encoded. To define a detailed
mapping, it is necessary to refer to detailed protocol elements
in each format. A notation to achieve this is described in this
section.
3.1.1. RFC 822
Structured text is defined according to the Extended Backus Naur
Form (EBNF) defined in Section 2 of RFC 822 [Crocker82a]. In the
EBNF definitions used in this specification, the syntax rules
given in Appendix D of RFC 822 are assumed. When these EBNF
tokens are referred to outside an EBNF definition, they are
identified by the string "822." appended to the beginning of the
string (e.g., 822.addr-spec). Additional syntax rules, to be
used throughout this specification, are defined in this chapter.
The EBNF is used in two ways.
1. To describe components of RFC 822 messages (or of 822-MTS
components). In this case, the lexical analysis defined in
Section 3 of RFC 822 shall be used. When these new EBNF
tokens are referred to outside an EBNF definition, they are
identified by the string "EBNF." appended to the beginning
of the string (e.g., EBNF.bilateral-info).
2. To describe the structure of IA5 or ASCII information not in
an RFC 822 message. In these cases, tokens will either be
self delimiting, or be delimited by self delimiting tokens.
Comments and LWSP are not used as delimiters, except for the
following cases, where LWSP may be inserted according to RFC
822 rules.
- Around the ":" in all headers
- EBNF.labelled-integer
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- EBNF.object-identifier
- EBNF.encoded-info
RFC 822 folding rules are applied to all headers.
3.1.2. ASN.1
An element is referred to with the following syntax, defined in
EBNF:
element = service "." definition *( "." definition )
service = "IPMS" / "MTS" / "MTA"
definition = identifier / context
identifier = ALPHA *< ALPHA or DIGIT or "-" >
context = "[" 1*DIGIT "]"
The EBNF.service keys are shorthand for the following service
specifications:
IPMS IPMSInformationObjects defined in Annex E of X.420 / ISO
10021-7.
MTS MTSAbstractService defined in Section 9 of X.411 / ISO
10021-4.
MTA MTAAbstractService defined in Section 13 of X.411 / ISO
10021-4.
The first EBNF.identifier identifies a type or value key in the
context of the defined service specification. Subsequent
EBNF.identifiers identify a value label or type in the context of
the first identifier (SET or SEQUENCE). EBNF.context indicates a
context tag, and is used where there is no label or type to
uniquely identify a component. The special EBNF.identifier
keyword "value" is used to denote an element of a sequence.
For example, IPMS.Heading.subject defines the subject element of
the IPMS heading. The same syntax is also used to refer to
element values. For example,
MTS.EncodedInformationTypes.[0].g3Fax refers to a value of
MTS.EncodedInformationTypes.[0] .
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3.2. ASCII and IA5
A gateway will interpret all IA5 as ASCII. Thus, mapping between
these forms is conceptual.
3.3. Standard Types
There is a need to convert between ASCII text, and some of the
types defined in ASN.1 [CCITT/ISO88d]. For each case, an EBNF
syntax definition is given, for use in all of this specification,
which leads to a mapping between ASN.1, and an EBNF construct.
All EBNF syntax definitions of ASN.1 types are in lower case,
whereas ASN.1 types are referred to with the first letter in
upper case. Except as noted, all mappings are symmetrical.
3.3.1. Boolean
Boolean is encoded as:
boolean = "TRUE" / "FALSE"
3.3.2. NumericString
NumericString is encoded as:
numericstring = *DIGIT
3.3.3. PrintableString
PrintableString is a restricted IA5String defined as:
printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char
This can be used to represent real printable strings in EBNF.
3.3.4. T.61String
In cases where T.61 strings are only used for conveying human
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interpreted information, the aim of a mapping is to render the
characters appropriately in the remote character set, rather than
to maximise reversibility. For these cases, the mappings to IA5
defined in CCITT Recommendation X.408 (1988) shall be used
[CCITT/ISO88a]. These will then be encoded in ASCII.
There is also a need to represent Teletex Strings in ASCII,
for some aspects of O/R Address. For these, the following
encoding is used:
teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT
Common characters are mapped simply. Other octets are mapped
using a quoting mechanism similar to the printable string
mechanism. Each octet is represented as 3 decimal digits.
There are a number of places where a string may have a Teletex
and/or Printable String representation. The following BNF is
used to represent this.
teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]
The natural mapping is restricted to EBNF.ps-char, in order to
make the full BNF easier to parse.
3.3.5. UTCTime
Both UTCTime and the RFC 822 822.date-time syntax contain: Year
(lowest two digits), Month, Day of Month, hour, minute, second
(optional), and Timezone. 822.date-time also contains an
optional day of the week, but this is redundant. Therefore a
symmetrical mapping can be made between these constructs.
Note:
In practice, a gateway will need to parse various illegal
variants on 822.date-time. In cases where 822.date-time
cannot be parsed, it is recommended that the derived UTCTime
is set to the value at the time of translation.
When mapping to X.400, the UTCTime format which specifies the
timezone offset shall be used.
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When mapping to RFC 822, the 822.date-time format shall include a
numeric timezone offset (e.g., +0000).
When mapping time values, the timezone shall be preserved as
specified. The date shall not be normalised to any other
timezone.
3.3.6. Integer
A basic ASN.1 Integer will be mapped onto EBNF.numericstring. In
many cases ASN.1 will enumerate Integer values or use ENUMERATED.
An EBNF encoding labelled-integer is provided. When mapping from
EBNF to ASN.1, only the integer value is mapped, and the
associated text is discarded. When mapping from ASN.1 to EBNF,
addition of an appropriate text label is strongly encouraged.
labelled-integer ::= [ key-string ] "(" numericstring ")"
key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">
3.3.7. Object Identifier
Object identifiers are represented in a form similar to that
given in ASN.1. The order is the same as for ASN.1 (big-endian).
The numbers are mandatory, and used when mapping from the ASCII
to ASN.1. The key-strings are optional. It is recommended that
as many strings as possible are generated when mapping from ASN.1
to ASCII, to facilitate user recognition.
object-identifier ::= oid-comp object-identifier
| oid-comp
oid-comp ::= [ key-string ] "(" numericstring ")"
An example representation of an object identifier is:
joint-iso-ccitt(2) mhs (6) ipms (1) ep (11) ia5-text (0)
or
(2) (6) (1)(11)(0)
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3.4. Encoding ASCII in Printable String
Some information in RFC 822 is represented in ASCII, and needs to
be mapped into X.400 elements encoded as printable string. For
this reason, a mechanism to represent ASCII encoded as
PrintableString is needed.
A structured subset of EBNF.printablestring is now defined.
This shall be used to encode ASCII in the PrintableString
character set.
ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"
The 822.3DIGIT in EBNF.ps-encoded-char must have range 0-127, and
is interpreted in decimal as the corresponding ASCII character.
Special encodings are given for: at sign (@), percent (%),
exclamation mark/bang (!), double quote ("), underscore (_), left
bracket ((), and right bracket ()). These characters, with the
exception of round brackets, are not included in PrintableString,
but are common in RFC 822 addresses. The abbreviations will ease
specification of RFC 822 addresses from an X.400 system. These
special encodings shall be interpreted in a case insensitive
manner, but always generated in lower case.
A reversible mapping between PrintableString and ASCII can
now be defined. The reversibility means that some values of
printable string (containing round braces) cannot be generated
from ASCII. Therefore, this mapping must only be used in cases
where the printable strings may only be derived from ASCII (and
will therefore have a restricted domain). For example, in this
specification, it is only applied to a Domain Defined Attribute
which will have been generated by use of this specification and a
value such as "(" would not be possible.
To encode ASCII as PrintableString, the EBNF.ps-encoded
syntax is used, with all EBNF.ps-restricted-char mapped directly.
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All other 822.CHAR are encoded as EBNF.ps-encoded-char.
To encode PrintableString as ASCII, parse PrintableString as
EBNF.ps-encoded, and then reverse the previous mapping. If the
PrintableString cannot be parsed, then the mapping is being
applied in to an inappropriate value, and an error shall be given
to the procedure doing the mapping. In some cases, it may be
preferable to pass the printable string through unaltered.
Some examples are now given. Note the arrows which indicate
asymmetrical mappings:
PrintableString ASCII
'a demo.' <-> 'a demo.'
foo(a)bar <-> foo@bar
(q)(u)(p)(q) <-> "_%"
(a) <-> @
(A) -> @
(l)a(r) <-> (a)
(126) <-> ~
( -> (
(l) <-> (
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Chapter 4 - Addressing
Addressing is probably the trickiest problem of an X.400 <-> RFC
822 gateway. Therefore it is given a separate chapter. This
chapter, as a side effect, also defines a textual representation
of an X.400 O/R Address.
Initially we consider an address in the (human) mail user
sense of "what is typed at the mailsystem to reference a mail
user". A basic RFC 822 address is defined by the EBNF
EBNF.822-address:
822-address = [ route ] addr-spec
In an 822-MTS protocol, the originator and each recipient are be
considered to be defined by such a construct. In an RFC 822
header, the EBNF.822-address is encapsulated in the 822.address
syntax rule, and there may also be associated comments. None of
this extra information has any semantics, other than to the end
user.
The basic X.400 O/R Address, used by the MTS for routing, is
defined by MTS.ORAddress. In IPMS, the MTS.ORAddress is
encapsulated within IPMS.ORDescriptor.
It can be seen that RFC 822 822.address must be mapped with
IPMS.ORDescriptor, and that RFC 822 EBNF.822-address must be
mapped with MTS.ORAddress.
4.1. A textual representation of MTS.ORAddress
MTS.ORAddress is structured as a set of attribute value pairs.
It is clearly necessary to be able to encode this in ASCII for
gatewaying purposes. All components shall be encoded, in order
to guarantee return of error messages, and to optimise third
party replies.
4.2. Basic Representation
An O/R Address has a number of structured and unstructured
attributes. For each unstructured attribute, a key and an
encoding is specified. For structured attributes, the X.400
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attribute is mapped onto one or more attribute value pairs. For
domain defined attributes, each element of the sequence will be
mapped onto a triple (key and two values), with each value having
the same encoding. The attributes are as follows, with 1984
attributes given in the first part of the table. For each
attribute, a reference is given, consisting of the relevant
sections in X.402 / ISO 10021-2, and the extension identifier for
88 only attributes:
Attribute (Component) Key Enc Ref Id
84/88 Attributes
MTS.CountryName C P 18.3.3
MTS.AdministrationDomainName ADMD P 18.3.1
MTS.PrivateDomainName PRMD P 18.3.21
MTS.NetworkAddress X121 N 18.3.7
MTS.TerminalIdentifier T-ID N 18.3.23
MTS.OrganizationName O P/T 18.3.9
MTS.OrganizationalUnitNames.value OU P/T 18.3.10
MTS.NumericUserIdentifier UA-ID N 18.3.8
MTS.PersonalName PN P/T 18.3.12
MTS.PersonalName.surname S P/T 18.3.12
MTS.PersonalName.given-name G P/T 18.3.12
MTS.PersonalName.initials I P/T 18.3.12
MTS.PersonalName
.generation-qualifier GQ P/T 18.3.12
MTS.DomainDefinedAttribute.value DD P/T 18.1
88 Attributes
MTS.CommonName CN P/T 18.3.2 1
MTS.TeletexCommonName CN P/T 18.3.2 2
MTS.TeletexOrganizationName O P/T 18.3.9 3
MTS.TeletexPersonalName PN P/T 18.3.12 4
MTS.TeletexPersonalName.surname S P/T 18.3.12 4
MTS.TeletexPersonalName.given-name G P/T 18.3.12 4
MTS.TeletexPersonalName.initials I P/T 18.3.12 4
MTS.TeletexPersonalName
.generation-qualifier GQ P/T 18.3.12 4
MTS.TeletexOrganizationalUnitNames
.value OU P/T 18.3.10 5
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MTS.TeletexDomainDefinedAttribute
.value DD P/T 18.1 6
MTS.PDSName PD-SERVICE P 18.3.11 7
MTS.PhysicalDeliveryCountryName PD-C P 18.3.13 8
MTS.PostalCode PD-CODE P 18.3.19 9
MTS.PhysicalDeliveryOfficeName PD-OFFICE P/T 18.3.14 10
MTS.PhysicalDeliveryOfficeNumber PD-OFFICE-NUM P/T 18.3.15 11
MTS.ExtensionORAddressComponents PD-EXT-ADDRESS P/T 18.3.4 12
MTS.PhysicalDeliveryPersonName PD-PN P/T 18.3.17 13
MTS.PhysicalDeliveryOrganizationName PD-O P/T 18.3.16 14
MTS.ExtensionPhysicalDelivery
AddressComponents PD-EXT-DELIVERY P/T 18.3.5 15
MTS.UnformattedPostalAddress PD-ADDRESS P/T 18.3.25 16
MTS.StreetAddress PD-STREET P/T 18.3.22 17
MTS.PostOfficeBoxAddress PD-BOX P/T 18.3.18 18
MTS.PosteRestanteAddress PD-RESTANTE P/T 18.3.20 19
MTS.UniquePostalName PD-UNIQUE P/T 18.3.26 20
MTS.LocalPostalAttributes PD-LOCAL P/T 18.3.6 21
MTS.ExtendedNetworkAddress
.e163-4-address.number NET-NUM N 18.3.7 22
MTS.ExtendedNetworkAddress
.e163-4-address.sub-address NET-SUB N 18.3.7 22
MTS.ExtendedNetworkAddress
.psap-address NET-PSAP X 18.3.7 22
MTS.TerminalType T-TY I 18.3.24 23
The following keys identify different EBNF encodings, which are
associated with the ASCII representation of MTS.ORAddress.
Key Encoding
P printablestring
N numericstring
T teletex-string
P/T teletex-and-or-ps
I labelled-integer
X presentation-address
The BNF for presentation-address is taken from the specification
"A String Encoding of Presentation Address" [Kille89a].
In most cases, the EBNF encoding maps directly to the ASN.1
encoding of the attribute. There are a few exceptions. In cases
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where an attribute can be encoded as either a PrintableString or
NumericString (Country, ADMD, PRMD), either form is mapped into
the BNF. When generating ASN.1, the NumericString encoding shall
be used if the string contains only digits.
There are a number of cases where the P/T (teletex-and-or-ps)
representation is used. Where the key maps to a single
attribute, this choice is reflected in the encoding of the
attribute (attributes 10-21). For most of the 1984 attributes
and common name, there is a printablestring and a teletex
variant. This pair of attributes is mapped onto the single
component here. This will give a clean mapping for the common
cases where only one form of the name is used.
Recently, ISO has undertaken work to specify a string form
of O/R Address [CCITT/ISO91a]. This has specified a number of
string keywords for attributes. As RFC 1148 was an input to this
work, many of the keywords are the same. To increase
compatability, the following alternative values shall be
recognised when mapping from RFC 822 to X.400. These shall not
be generated when mapping from X.400 to RFC 822.
Keyword Alternative
ADMD A
PRMD P
GQ Q
X121 X.121
UA-ID N-ID
PD-OFFICE-NUMBER PD-OFFICE NUMBER
When mapping from RFC 822 to X.400, the keywords: OU1, OU2, OU3,
and OU4, shall be recognised. If these are present, no keyword
OU shall be present. These will be treated as ordered values of
OU.
4.2.1. Encoding of Personal Name
Handling of Personal Name and Teletex Personal Name based purely
on the EBNF.standard-type syntax defined above is likely to be
clumsy. It seems desirable to utilise the "human" conventions
for encoding these components. A syntax is defined, which is
designed to provide a clean encoding for the common cases of O/R
Address specification where:
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1. There is no generational qualifier
2. Initials contain only letters
3. Given Name does not contain full stop ("."), and is at least
two characters long.
4. Surname does not contain full stop in the first two
characters.
5 If Surname is the only component, it does not contain full
stop.
The following EBNF is defined:
encoded-pn = [ given "." ] *( initial "." ) surname
given = 2*<ps-char not including ".">
initial = ALPHA
surname = printablestring
This is used to map from any string containing only printable
string characters to an O/R address personal name. To map from a
string to O/R Address components, parse the string according to
the EBNF. The given name and surname are assigned directly. All
EBNF.initial tokens are concatenated without intervening full
stops to generate the initials component.
For an O/R address which follows the above restrictions, a
string is derived in the natural manner. In this case, the
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mapping will be reversible.
For example:
GivenName = "Marshall"
Surname = "Rose"
Maps with "Marshall.Rose"
Initials = "MT"
Surname = "Rose"
Maps with "M.T.Rose"
GivenName = "Marshall"
Initials = "MT"
Surname = "Rose"
Maps with "Marshall.M.T.Rose"
Note that X.400 suggest that Initials is used to encode ALL
initials. Therefore, the defined encoding is "natural" when
either GivenName or Initials, but not both, are present. The
case where both are present can be encoded, but this appears to
be contrived!
4.2.2. Standard Encoding of MTS.ORAddress
Given this structure, we can specify a BNF representation of an
O/R Address.
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std-or-address = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "RFC-822"
/ registered-dd-type
/ dd-key "." std-printablestring
standard-type = key-string
registered-dd-type
= key-string
dd-key = key-string
value = std-printablestring
std-printablestring
= *( std-char / std-pair )
std-char = <"{", "}", "*", and any ps-char
except "/" and "=">
std-pair = "$" ps-char
The standard-type is any key defined in the table in Section 4.2,
except PN, and DD. The BNF leads to a set of attribute/value
pairs. The value is interpreted according to the EBNF encoding
defined in the table.
If the standard-type is PN, the value is interpreted
according to EBNF.encoded-pn, and the components of
MTS.PersonalName and/or MTS.TeletexPersonalName derived
accordingly.
If dd-key is the recognised Domain Defined string (DD), then
the type and value are interpreted according to the syntax
implied from the encoding, and aligned to either the teletex or
printable string form. Key and value shall have the same
encoding.
If value is "RFC-822", then the (printable string) Domain
Defined Type of "RFC-822" is assumed. This is an optimised
encoding of the domain defined type defined by this
specification.
The matching of all keywords shall be done in a case-
independent manner.
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EBNF.std-or-address uses the characters "/" and "=" as
delimiters. Domain Defined Attributes and any value may contain
these characters. A quoting mechanism, using the non-printable
string "$" is used to allow these characters to be represented.
If the value is registered-dd-type, the value is registered
at the IANA as an accepted Domain Defined Attribute type, then
the value shall be interpreted accordingly. This restriction
maximises the syntax checking which can be done at a gateway.
4.3. EBNF.822-address <-> MTS.ORAddress
Ideally, the mapping specified would be entirely symmetrical and
global, to enable addresses to be referred to transparently in
the remote system, with the choice of gateway being left to the
Message Transfer Service. There are two fundamental reasons why
this is not possible:
1. The syntaxes are sufficiently different to make this
awkward.
2. In the general case, there would not be the necessary
administrative co-operation between the X.400 and RFC 822
worlds, which would be needed for this to work.
Therefore, an asymmetrical mapping is defined, which can be
symmetrical where there is appropriate administrative control.
4.3.1. X.400 encoded in RFC 822
The std-or-address syntax is used to encode O/R Address
information in the 822.local-part of EBNF.822-address. In some
cases, further O/R Address information is associated with the
822.domain component. This cannot be used in the general case,
due to character set problems, and to the variants of X.400 O/R
Addresses which use different attribute types. The only way to
encode the full PrintableString character set in a domain is by
use of the 822.domain-ref syntax (i.e. 822.atom). This is likely
to cause problems on many systems. The effective character set
of domains is in practice reduced from the RFC 822 set, by
restrictions imposed by domain conventions and policy, and by
restrictions in RFC 821.
A generic 822.address consists of a 822.local-part and a
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sequence of 822.domains (e.g., <@domain1,@domain2:user@domain3>).
All except the 822.domain associated with the 822.local-part
(domain3 in this case) are considered to specify routing within
the RFC 822 world, and will not be interpreted by the gateway
(although they may have identified the gateway from within the
RFC 822 world).
The 822.domain associated with the 822.local-part
identifies the gateway from within the RFC 822 world. This final
822.domain may be used to determine some number of O/R Address
attributes, where this does not conflict with the first role.
RFC 822 routing to gateways will usually be set up to facilitate
the 822.domain being used for both purposes. The following O/R
Address attributes are considered as a hierarchy, and may be
specified by the domain. They are (in order of hierarchy):
Country, ADMD, PRMD, Organisation, Organisational Unit
There may be multiple Organisational Units.
A global mapping is defined between domain specifications,
and some set of attributes. This association proceeds
hierarchically. For example, if a domain implies ADMD, it also
implies country. Subdomains under this are associated according
to the O/R Address hierarchy. For example:
=> "AC.UK" might be associated with
C="GB", ADMD="GOLD 400", PRMD="UK.AC"
then domain "R-D.Salford.AC.UK" maps with
C="GB", ADMD="GOLD 400", PRMD="UK.AC", O="Salford", OU="R-D"
There are three basic reasons why a domain/attribute mapping
might be maintained, as opposed to using simply subdomains:
1. As a shorthand to avoid redundant X.400 information. In
particular, there will often be only one ADMD per country,
and so it does not need to be given explicitly.
2. To deal with cases where attribute values do not fit the
syntax:
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domain-syntax = alphanum [ *alphanumhyphen alphanum ]
alphanum = <ALPHA or DIGIT>
alphanumhyphen = <ALPHA or DIGIT or HYPHEN>
Although RFC 822 allows for a more general syntax, this
restricted syntax is chosen as it is the one chosen by the
various domain service administrations.
3. To deal with missing elements in the hierarchy. A domain
may be associated with an omitted attribute in conjunction
with several present ones. When performing the algorithmic
insertion of components lower in the hierarchy, the omitted
value shall be skipped. For example, if "HNE.EGM" is
associated with "C=TC", "ADMD=ECQ", "PRMD=HNE", and omitted
organisation, then "ZI.HNE.EGM" is mapped with "C=TC",
"ADMD=ECQ", "PRMD=HNE", "OU=ZI". Attributes may have null
values, and this is treated separately from omitted
attributes (whilst it would be bad practice to treat these
two cases differently, they must be allowed for).
This set of mappings needs be known by the gateways
relaying between the RFC 822 world, and the O/R Address space
associated with the mapping in question. There needs to be a
single global definition of this set of mappings. A mapping
implies an adminstrative equivalence between the two parts of the
namespaces which are mapped together. To correctly route in all
cases, it is necessary for all gateways to know the mapping. To
facilitate distribution of a global set of mappings, a format for
the exchange of this information is defined in Appendix F.
The remaining attributes are encoded on the LHS, using the
EBNF.std-or-address syntax. For example:
/I=J/S=Linnimouth/GQ=5/@Marketing.Widget.COM
encodes the MTS.ORAddress consisting of:
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MTS.CountryName = "TC"
MTS.AdministrationDomainName = "BTT"
MTS.OrganizationName = "Widget"
MTS.OrganizationalUnitNames.value = "Marketing"
MTS.PersonalName.surname = "Linnimouth"
MTS.PersonalName.initials = "J"
MTS.PersonalName.generation-qualifier = "5"
The first three attributes are determined by the domain
Widget.COM. Then, the first element of OrganizationalUnitNames
is determined systematically, and the remaining attributes are
encoded on the LHS. In an extreme case, all of the attributes
will be on the LHS. As the domain cannot be null, the RHS will
simply be a domain indicating the gateway.
The RHS (domain) encoding is designed to deal cleanly with
common addresses, and so the amount of information on the RHS is
maximised. In particular, it covers the Mnemonic O/R Address
using a 1984 compatible encoding. This is seen as the dominant
form of O/R Address. Use of other forms of O/R Address, and
teletex encoded attributes will require an LHS encoding.
There is a further mechanism to simplify the encoding of
common cases, where the only attributes to be encoded on the LHS
is a (non-Teletex) Personal Name attributes which comply with the
restrictions of 4.2.1. To achieve this, the 822.local-part shall
be encoded as EBNF.encoded-pn. In the previous example, if the
GenerationQualifier was not present, the encoding
J.Linnimouth@Marketing.Widget.COM would result.
From the standpoint of the RFC 822 Message Transfer System,
the domain specification is simply used to route the message in
the standard manner. The standard domain mechanisms are used to
select appropriate gateways for the corresponding O/R Address
space. In most cases, this will be done by registering the
higher levels, and assuming that the gateway can handle the lower
levels.
4.3.2. RFC 822 encoded in X.400
In some cases, the encoding defined above may be reversed, to
give a "natural" encoding of genuine RFC 822 addresses. This
depends largely on the allocation of appropriate management
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domains.
The general case is mapped by use of domain defined
attributes. A Domain defined type "RFC-822" is defined. The
associated attribute value is an ASCII string encoded according
to Section 3.3.3 of this specification. The interpretation of the
ASCII string depends on the context of the gateway.
1. In the context of RFC 822, and RFC 920
[Crocker82a,Postel84a], the string can be used directly.
2. In the context of the JNT Mail protocol, and the NRS
[Kille84a,Larmouth83a], the string shall be interpreted
according to Mailgroup Note 15 [Kille84b].
3. In the context of UUCP based systems, the string shall be
interpreted as defined in [Horton86a].
Other O/R Address attributes will be used to identify a
context in which the O/R Address will be interpreted. This might
be a Management Domain, or some part of a Management Domain which
identifies a gateway MTA. For example:
C = "GB"
ADMD = "GOLD 400"
PRMD = "UK.AC"
O = "UCL"
OU = "CS"
"RFC-822" = "Jimmy(a)WIDGET-LABS.CO.UK"
OR
C = "TC"
ADMD = "Wizz.mail"
PRMD = "42"
"rfc-822" = "postel(a)venera.isi.edu"
Note in each case the PrintableString encoding of "@" as "(a)".
In the second example, the "RFC-822" domain defined attribute is
interpreted everywhere within the (Private) Management Domain.
In the first example, further attributes are needed within the
Management Domain to identify a gateway. Thus, this scheme can
be used with varying levels of Management Domain co-operation.
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There is a limit of 128 characters in the length of value of
a domain defined attribute, and an O/R Address can have a
maxmimum of four domain defined attributes. Where the printable
string generated from the RFC 822 address exceeeds this value,
additional domain defined attributes are used to enable up to 512
characters to be encoded. These attributes shall be filled
completely before the next one is started. The DDA keywords
are: RFC822C1; RFC822C2; RFC822C3. Longer addresses cannot be
encoded.
There is, analagous with 4.3.1, a means to associate parts
of the O/R Address hierarchy with domains. There is an analogous
global mapping, which in most cases will be the inverse of the
domain to O/R address mapping. The mapping is maintained
separately, as there may be differences (e.g., two alternate
domain names map to the same set of O/R address components).
4.3.3. Component Ordering
In most cases, ordering of O/R Address components is not
significant for the mappings specified. However, Organisational
Units (printable string and teletex forms) and Domain Defined
Attributes are specified as SEQUENCE in MTS.ORAddress, and so
their order may be significant. This specification needs to take
account of this:
1. To allow consistent mapping into the domain hierarchy
2. To ensure preservation of order over multiple mappings.
There are three places where an order is specified:
1. The text encoding (std-or-address) of MTS.ORAddress as used
in the local-part of an RFC 822 address. An order is needed
for those components which may have multiple values
(Organisational Unit, and Domain Defined Attributes). When
generating an 822.std-or-address, components of a given type
shall be in hierarchical order with the most significant
component on the RHS. If there is an Organisation
Attribute, it shall be to the right of any Organisational
Unit attributes. These requirements are for the following
reasons:
- Alignment to the hierarchy of other components in RFC
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822 addresses (thus, Organisational Units will appear
in the same order, whether encoded on the RHS or LHS).
Note the differences of JNT Mail as described in
Appendix B.
- Backwards compatibility with RFC 987/1026.
- To ensure that gateways generate consistent addresses.
This is both to help end users, and to generate
identical message ids.
Further, it is recommended that all other attributes are
generated according to this ordering, so that all attributes
so encoded follow a consistent hierarchy. When generating
822.msg-id, this order shall be followed.
2. For the Organisational Units (OU) in MTS.ORAddress, the
first OU in the SEQUENCE is the most significant, as
specified in X.400.
3. For the Domain Defined Attributes in MTS.ORAddress, the
First Domain Defined Attribute in the SEQUENCE is the most
significant.
Note that although this ordering is mandatory for this
mapping, there are NO implications on ordering significance
within X.400, where this is a Management Domain issue.
4.3.4. RFC 822 -> X.400
There are two basic cases:
1. X.400 addresses encoded in RFC 822. This will also include
RFC 822 addresses which are given reversible encodings.
2. "Genuine" RFC 822 addresses.
The mapping shall proceed as follows, by first assuming case 1).
STAGE I.
1. If the 822-address is not of the form:
local-part "@" domain
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take the domain which will be routed on and apply step 2 of
stage 1 to derive (a possibly null) set of attributes. Then
go to stage II.
NOTE:It may be appropriate to reduce a source route address
to this form by removal of all bar the last domain. In
terms of the design intentions of RFC 822, this would
be an incorrect action. However, in most real cases,
it will do the "right" thing and provide a better
service to the end user. This is a reflection on the
excessive and inappropriate use of source routing in
RFC 822 based systems. Either approach, or the
intermediate approach of stripping only domain
references which reference the local gateway are
conformant to this specification.
2. Attempt to parse EBNF.domain as:
*( domain-syntax "." ) known-domain
Where EBNF.known-domain is the longest possible match in the
set of globally defined mappings (see Appendix F). If this
fails, and the EBNF.domain does not explicitly identify the
local gateway, go to stage II. If the domain explicitly
identifies the gateway, allocate no attributes. Otherwise,
allocate the attributes associated with EBNF.known-domain.
For each component, systematically allocate the attributes
implied by each EBNF.domain-syntax component. If this new
component exceed an upper bound (ADMD: 16; PRMD: 16; O: 64;
OU: 32) or it would lead to more than four OUs, then go to
stage II with the attributes derived.
At this stage, a set of attributes has been derived, which
will give appropriate routing within X.400. If any of the
later steps of Stage I force use of Stage II, then these
attributes should be used in Stage II.
3. If the 822.local-part contains any characters not in
PrintableString, go to stage II.
4. If the 822.local-part uses the 822.quoted-string encoding,
remove this quoting. If this unquoted 822.local-part has
leading space, trailing space, or two adjacent space go to
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stage II.
5. Parse the (unquoted) 822.local-part according to the EBNF
EBNF.std-or-address. If this parse fails, parse the local-
part according to the EBNF EBNF.encoded-pn. If this parse
fails, go to stage II. The result is a set of type/value
pairs. If the values generated conflict with those derived
in step 2 (e.g., a duplicated country attribute), the domain
is assumed to be a remote gateway. In this case, take only
the LHS derived attributes, together with any RHS dericed
attributes which are more significant thant the most
signicant attribute which is duplicated (e.g., if there is a
duplicate PRMD, but no LHS derived ADMD and country, then
the ADMD and country should be taken from the RHS).
therwise add LHS and RHS derived attributes together.
6. Associate the EBNF.attribute-value syntax (determined from
the identified type) with each value, and check that it
conforms. If not, go to stage II.
7. Ensure that the set of attributes conforms both to the
MTS.ORAddress specification and to the restrictions on this
set given in X.400, and that no upper bounds are exceeded
for any attribute. If not go to stage II.
8. Build the O/R Address from this information.
STAGE II.
This will only be reached if the RFC 822 EBNF.822-address is not
a valid X.400 encoding. This implies that the address must refer
to a recipient on an RFC 822 system. Such addresses shall be
encoded in an X.400 O/R Address using a domain defined attribute.
1. Convert the EBNF.822-address to PrintableString, as
specified in Chapter 3.
2. Generate the "RFC-822" domain defined attribute from this
string.
3. Build the rest of the O/R Address in the manner described
below.
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It may not be possible to encode the domain defined attribute due
to length restrictions. If the limit is exceeded by a mapping at
the MTS level, then the gateway shall reject the message in
question. If this occurs at the IPMS level, then the action will
depend on the policy being taken for IPMS encoding, which is
discussed in Section 5.1.3.
If Stage I has identified a set of attributes, use these to build
the remainder of the address. The administrative equivalence of
the mappings will ensure correct routing throug X.400 to a
gateway back to RFC 822.
If Stage I has not identified a set of attributes, the
remainder of the O/R address effectively identifies a source
route to a gateway from the X.400 side. There are three cases,
which are handled differently:
822-MTS Return Address
This shall be set up so that errors are returned through the
same gateway. Therefore, the O/R Address of the local
gateway shall be used.
IPMS Addresses
These are optimised for replying. In general, the message
may end up anywhere within the X.400 world, and so this
optimisation identifies a gateway appropriate for the RFC
822 address being converted. The 822.domain to which the
address would be routed is used to select an appropriate
gateway. A globally defined set of mappings is used, which
identifies (the O/R Address components of) appropriate
gateways for parts of the domain namespace. The longest
possible match on the 822.domain defines which gateway to
use. The table format for distribution of this information
is defined in Appendix F.
This global mapping is used for parts of the RFC 822
namespace which do not have an administrative equivalence
with any part of the X.400 namespace, but for which it is
desirable to identify a preferred X.400 gateway in order to
optimise routing.
If no mapping is found for the 822.domain, a default value
(typically that of the local gateway) is used. It is never
appropriate to ignore the globally defined mappings. In
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some cases, it may be appropriate to locally override the
globally defined mappings (e.g., to identify a gateway close
to a recipient of the message). This is likely to be where
the global mapping identifies a public gateway, and the
local gateway has an agreement with a private gateway which
it prefers to use.
822-MTS Recipient
As the RFC 822 and X.400 worlds are fully connected, there
is no technical reason for this situation to occur. In some
cases, routing may be configured to connect two parts of the
RFC 822 world using X.400. The information that this part
of the domain space should be routed by X.400 rather than
remaining within the RFC 822 world will be configured
privately into the gateway in question. The O/R address
shall then be generated in the same manner as for an IPMS
address, using the globally defined mappings. It is to
support this case that the definition of the global domain
to gateway mapping is important, as the use of this mapping
will lead to a remote X.400 address, which can be routed by
X.400 routing procedures. The information in this mapping
shall not be used as a basis for deciding to convert a
message from RFC 822 to X.400.
4.3.4.1. Heuristics for mapping RFC 822 to X.400
RFC 822 users will often use an LHS encoded address to identify
an X.400 recipient. Becuase the syntax is fairly complex, a
number of heuristics may be applied to facilitate this form of
usage. A gateway should take care not to be overly "clever" with
heuristics, as this may cause more confusion than a more
mechanical approach. The heuristics are as follows:
1. Ignore the omission of a trailing "/" in the std-or syntax.
2. If there is no ADMD component, and both country and PRMD are
present, the value of /ADMD= / (single space) is assumed.
3. Parse the unquoted local part according to the EBNF colon-
or-address. This may facilitate users used to this
delimiter.
colon-or-address = 1*(attribute "=" value ";" *(LWSP-char))
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The remaining heuristic relates to ordering of address
components. The ordering of attributes may be inverted or mixed.
For this reason, the following heuristics may be applied:
4. If there is an Organisation attribute to the left of any Org
Unit attribute, assume that the hierarchy is inverted.
4.3.5. X.400 -> RFC 822
There are two basic cases:
1. RFC 822 addresses encoded in X.400.
2. "Genuine" X.400 addresses. This may include symmetrically
encoded RFC 822 addresses.
When a MTS Recipient O/R Address is interpreted, gatewaying will
be selected if there is a single "RFC-822" domain defined
attribute present and the local gateway is identified by the
remainder of the O/R Address. In this case, use mapping A. For
other O/R Addresses which
1. Contain the special attribute.
AND
2. Identifies the local gateway or any other known gateway with
the other attributes.
use mapping A. In other cases, use mapping B.
NOTE:
A pragmatic approach would be to assume that any O/R
Address with the special domain defined attribute identifies
an RFC 822 address. This will usually work correctly, but is
in principle not correct. Use of this approach is
conformant to this specification.
Mapping A
1. Map the domain defined attribute value to ASCII, as defined
in Chapter 3.
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Mapping B.
This is used for X.400 addresses which do not use the explicit
RFC 822 encoding.
1. For all string encoded attributes, remove any leading or
trailing spaces, and replace adjacent spaces with a single
space.
The only attribute which is permitted to have zero length is
the ADMD. mapped to single space. This should be
mapped onto a single space.
These transformations are for lookup only. If an
EBNF.std-or-address mapping is used as in 4), then the
orginal values should be used.
2. Map numeric country codes to the two letter values.
3. Noting the hierarchy specified in 4.3.1, determine the
maximum set of attributes which have an associated domain
specification in the globally defined mapping. If no match
is found, allocate the domain as the domain specification of
the local gateway, and go to step 5.
Note: It might be appropriate to use a non-local domain.
This would be selected by a global mapping analagous to
the one described at the end of 4.3.4. This is not
done, primarily because use of RFC 822 to connect X.400
systems is not expected to be significant.
In cases where the address refers to an X.400 UA, it is
important that the generated domain will correctly route to
a gateway. In general, this is achieved by carefully co-
ordinating RFC 822 routing with the definition of the global
mappings, as there is no easy way for the gateway to make
this check. One rule that shall be used is that domains
with only one component will not route to a gateway. If the
generated domain does not route correctly, the address is
treated as if no match is found.
4. Following the 4.3.1 hierarchy, noting any omitted
components implied by the mapping used in 3). If each
successive component exists, and conforms to the syntax
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EBNF.domain-syntax (as defined in 4.3.1), allocate the next
subdomain. At least one attribute of the X.400 address
shall not be mapped onto subdomain, as 822.local-part cannot
be null.
5. If the remaining components are personal-name components,
conforming to the restrictions of 4.2.1, then EBNF.encoded-
pn is derived to form 822.local-part. In other cases the
remaining components are simply encoded as 822.local-part
using the EBNF.std-or-address syntax. If necessary, the
822.quoted-string encoding is used. The following are
examples of legal quoting: "a b".c@x; "a b.c"@x. Either
form may be generated, but the latter is preferred.
If the derived 822.local-part can only be encoded by use of
822.quoted-string, then use of the mapping defined
in[Kille89b] may be appropriate. Use of this mapping is
discouraged.
4.4. Repeated Mappings
There are two types of repeated mapping:
1. A recursive mapping, where the repeat is within one gateway
2 A source route, where the repetition occurs across multiple
gateways
4.4.1. Recursive Mappings
It is possible to supply an address which is recurive at a single
gateway. For example:
C = "XX"
ADMD = "YY"
O = "ZZ"
"RFC-822" = "Smith(a)ZZ.YY.XX"
This is mapped first to an RFC 822 address, and then back to the
X.400 address:
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C = "XX"
ADMD = "YY"
O = "ZZ"
Surname = "Smith"
In some situations this type of recursion may be frequent. It is
important that where this occurs, that no unnecessary protocol
conversion occurs. This will minimise loss of service.
4.4.2. Source Routes
The mappings defined are symmetrical and reversible across a
single gateway. The symmetry is particularly useful in cases of
(mail exploder type) distribution list expansion. For example,
an X.400 user sends to a list on an RFC 822 system which he
belongs to. The received message will have the originator and
any 3rd party X.400 O/R Addresses in correct format (rather than
doubly encoded). In cases (X.400 or RFC 822) where there is
common agreement on gateway identification, then this will apply
to multiple gateways.
When a message traverses multiple gateways, the mapping will
always be reversible, in that a reply can be generated which will
correctly reverse the path. In many cases, the mapping will also
be symmetrical, which will appear clean to the end user. For
example, if countries "AB" and "XY" have RFC 822 networks, but
are interconnected by X.400, the following may happen: The
originator specifies:
Joe.Soap@Widget.PTT.XY
This is routed to a gateway, which generates:
C = "XY"
ADMD = "PTT"
PRMD = "Griddle MHS Providers"
Organisation = "Widget Corporation"
Surname = "Soap"
Given Name = "Joe"
This is then routed to another gateway where the mapping is
reversed to give:
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Joe.Soap@Widget.PTT.XY
Here, use of the gateway is transparent.
Mappings will only be symmetrical where mapping tables are
defined. In other cases, the reversibility is more important, due
to the (far too frequent) cases where RFC 822 and X.400 services
are partitioned.
The syntax may be used to source route. THIS IS STRONGLY
DISCOURAGED. For example:
X.400 -> RFC 822 -> X.400
C = "UK"
ADMD = "Gold 400"
PRMD = "UK.AC"
"RFC-822" = "/PN=Duval/DD.Title=Manager/(a)Inria.ATLAS.FR"
This will be sent to an arbitrary UK Academic Community gateway
by X.400. Then it will be sent by JNT Mail to another gateway
determined by the domain Inria.ATLAS.FR (FR.ATLAS.Inria). This
will then derive the X.400 O/R Address:
C = "FR"
ADMD = "ATLAS"
PRMD = "Inria"
PN.S = "Duval"
"Title" = "Manager"
Similarly:
RFC 822 -> X.400 -> RFC 822
"/C=UK/ADMD=BT/PRMD=AC/RFC-822=jj(a)seismo.css.gov/"@monet.berkeley.edu
This will be sent to monet.berkeley.edu by RFC 822, then to the
AC PRMD by X.400, and then to jj@seismo.css.gov by RFC 822.
4.5. Directory Names
Directory Names are an optional part of O/R Name, along with O/R
Address. The RFC 822 addresses are mapped onto the O/R Address
component. As there is no functional mapping for the Directory
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Name on the RFC 822 side, a textual mapping is used. There is no
requirement for reversibility in terms of the goals of this
specification. There may be some loss of functionality in terms
of third party recipients where only a directory name is given,
but this seems preferable to the significant extra complexity of
adding a full mapping for Directory Names.
Note:There is ongoing work on specification of a "user friendly"
format for directory names. If this is adopted as an
internet standard, it will be recommended, but not required,
for use here.
4.6. MTS Mappings
The basic mappings at the MTS level are:
1) 822-MTS originator ->
MTS.PerMessageSubmissionFields.originator-name
MTS.OtherMessageDeliveryFields.originator-name ->
822-MTS originator
2) 822-MTS recipient ->
MTS.PerRecipientMessageSubmissionFields
MTS.OtherMessageDeliveryFields.this-recipient-name ->
822-MTS recipient
822-MTS recipients and return addresses are encoded as
EBNF.822-address.
The MTS Originator is always encoded as MTS.OriginatorName,
which maps onto MTS.ORAddressAndOptionalDirectoryName, which in
turn maps onto MTS.ORName.
4.6.1. RFC 822 -> X.400
From the 822-MTS Originator, use the basic ORAddress mapping, to
generate MTS.PerMessageSubmissionFields.originator-name
(MTS.ORName), without a DirectoryName.
For recipients, the following settings are made for each
component of MTS.PerRecipientMessageSubmissionFields.
recipient-name
This is derived from the 822-MTS recipient by the basic
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ORAddress mapping.
originator-report-request
This is be set according to content return policy, as
discussed in Section 5.2.
explicit-conversion
This optional component is omitted, as this service is not
needed
extensions
The default value (no extensions) is used
4.6.2. X.400 -> RFC 822
The basic functionality is to generate the 822-MTS originator and
recipients. There is information present on the X.400 side,
which cannot be mapped into analogous 822-MTS services. For this
reason, new RFC 822 fields are added for the MTS Originator and
Recipients. The information discarded at the 822-MTS level will
be present in these fields. In some cases a (positive) delivery
report will be gerated.
4.6.2.1. 822-MTS Mappings
Use the basic ORAddress mapping, to generate the 822-MTS
originator (return address) from
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName). If
MTS.ORName.directory-name is present, it is discarded. (Note
that it will be presented to the user, as described in 4.6.2.2).
The 822-MTS recipient is conceptually generated from
MTS.OtherMessageDeliveryFields.this-recipient-name. This is done
by taking MTS.OtherMessageDeliveryFields.this-recipient-name, and
generating an 822-MTS recipient according to the basic ORAddress
mapping, discarding MTS.ORName.directory-name if present.
However, if this model was followed exactly, there would be no
possibility to have multiple 822-MTS recipients on a single
message. This is unacceptable, and so layering is violated. The
mapping needs to use the MTA level information, and map each
value of MTA.PerRecipientMessageTransferFields.recipient-name,
where the responsibility bit is set, onto an 822-MTS recipient.
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4.6.2.2. Generation of RFC 822 Headers
Not all per-recipient information can be passed at the 822-MTS
level. For this reason, two new RFC 822 headers are created, in
order to carry this information to the RFC 822 recipient. These
fields are "X400-Originator:" and "X400-Recipients:".
The "X400-Originator:" field is set to the same value as the
822-MTS originator. In addition, if
MTS.OtherMessageDeliveryFields.originator-name (MTS.ORName)
contains MTS.ORName.directory-name then this Directory Name shall
be represented in an 822.comment.
Recipient names, taken from each value of
MTS.OtherMessageDeliveryFields.this-recipient-name and
MTS.OtherMessageDeliveryFields.other-recipient-names are made
available to the RFC 822 user by use of the "X400-Recipients:"
field. By taking the recipients at the MTS level, disclosure of
recipients will be dealt with correctly. However, this conflicts
with a desire to optimise mail transfer. There is no problem
when disclosure of recipients is allowed. Similarly, there is no
problem if there is only one RFC 822 recipient, as the
"X400-Recipients field is only given one address.
There is a problem if there are multiple RFC 822 recipients,
and disclosure of recipients is prohibited. Two options are
allowed:
1. Generate one copy of the message for each RFC 822 recipient,
with the "X400-Recipients field correctly set to the
recipient of that copy. This is functionally correct, but
is likely to be more expensive.
2. Discard the per-recipient information, and insert a field:
X400-Recipients: non-disclosure:;
This is the recommended option.
A third option of ignoring the disclosure flag is not allowed.
If any MTS.ORName.directory-name is present, it shall be
represented in an 822.comment.
If
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MTS.OtherMessageDeliveryFields.orignally-intended-recipient-name
is present, then there has been redirection, or there has been
distribution list expansion. Distribution list expansion is a
per-message option, and the information associated with this is
represented by the "DL-Expansion-History:" field descrined in
Section 5.3.6. Other information is represented in an
822.comment associated associated with
MTS.OtherMessageDeliveryFields.this-recipient-name, The message
may be delivered to different RFC 822 recipients, and so several
addresses in the "X400-Recipients:" field may have such comments.
The non-commented recipient is the RFC 822 recipient. The EBNF of
the comment is:
redirect-comment =
[ "Originally To:" ] mailbox "Redirected"
[ "Again" ] "on" date-time
"To:" redirection-reason
redirection-reason =
"Recipient Assigned Alternate Recipient"
/ "Originator Requested Alternate Recipient"
/ "Recipient MD Assigned Alternate Recipient"
It is derived from
MTA.PerRecipientMessageTransferFields.extension.redirection-history.
An example of this is:
X400-Recipients: postmaster@widget.com (Originally To:
sales-manager@sales.widget.com Redirected
on Thu, 30 May 91 14:39:40 +0100 To: Originator Assigned
Alternate Recipient postmaster@sales.widget.com Redirected
Again on Thu, 30 May 91 14:41:20 +0100 To: Recipient MD
Assigned Alternate Recipient)
In addition the following per-recipient services from
MTS.OtherMessageDeliveryFields.extensions are represented in
comments if they are used. None of these services can be
provided on RFC 822 networks, and so in general these will be
informative strings associated with other MTS recipients. In some
cases, string values are defined. For the remainder, the string
value shall be chosen by the implementor. If the parameter has
a default value, then no comment shall be inserted when the
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parameter has that default value.
requested-delivery-method
physical-forwarding-prohibited
"(Physical Forwarding Prohibited)".
physical-forwarding-address-request
"(Physical Forwarding Address Requested)".
physical-delivery-modes
registered-mail-type
recipient-number-for-advice
physical-rendition-attributes
physical-delivery-report-request
"(Physical Delivery Report Requested)".
proof-of-delivery-request
"(Proof of Delivery Requested)".
4.6.2.3. Delivery Report Generation
If MTA.PerRecipientMessageTransferFields.per-recipient-indicators
requires a positive delivery notification, this shall be
generated by the gateway. Supplementary Information shall be set
to indicate that the report is gateway generated.
4.6.3. Message IDs (MTS)
A mapping from 822.msg-id to MTS.MTSIdentifier is defined. The
reverse mapping is not needed, as MTS.MTSIdentifier is always
mapped onto new RFC 822 fields. The value of
MTS.MTSIdentifier.local-part will facilitate correlation of
gateway errors.
To map from 822.msg-id, apply the standard mapping to
822.msg-id, in order to generate an MTS.ORAddress. The Country,
ADMD, and PRMD components of this are used to generate
MTS.MTSIdentifier.global-domain-identifier.
MTS.MTSIdentifier.local-identifier is set to the 822.msg-id,
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including the braces "<" and ">". If this string is longer than
MTS.ub-local-id-length (32), then it is truncated to this length.
The reverse mapping is not used in this specification. It
would be applicable where MTS.MTSIdentifier.local-identifier is
of syntax 822.msg-id, and it algorithmically identifies
MTS.MTSIdentifier.
4.7. IPMS Mappings
All RFC 822 addresses are assumed to use the 822.mailbox syntax.
This includes all 822.comments associated with the lexical tokens
of the 822.mailbox. In the IPMS O/R Names are encoded as
MTS.ORName. This is used within the IPMS.ORDescriptor,
IPMS.RecipientSpecifier, and IPMS.IPMIdentifier. An asymmetrical
mapping is defined between these components.
4.7.1. RFC 822 -> X.400
To derive IPMS.ORDescriptor from an RFC 822 address.
1. Take the address, and extract an EBNF.822-address. This can
be derived trivially from either the 822.addr-spec or
822.route-addr syntax. This is mapped to MTS.ORName as
described above, and used as IMPS.ORDescriptor.formal-name.
2. A string shall be built consisting of (if present):
- The 822.phrase component if the 822.address is an
822.phrase 822.route-addr construct.
- Any 822.comments, in order, retaining the parentheses.
This string is then encoded into T.61 use a human oriented
mapping (as described in Chapter 3). If the string is not
null, it is assigned to IPMS.ORDescriptor.free-form-name.
3. IPMS.ORDescriptor.telephone-number is omitted.
If IPMS.ORDescriptor is being used in IPMS.RecipientSpecifier,
IPMS.RecipientSpecifier.reply-request and
IPMS.RecipientSpecifier.notification-requests are set to default
values (none and false).
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If the 822.group construct is present, any included
822.mailbox is encoded as above to generate a separate
IPMS.ORDescriptor. The 822.group is mapped to T.61, and a
IPMS.ORDescriptor with only an free-form-name component built
from it.
4.7.2. X.400 -> RFC 822
Mapping from IPMS.ORDescriptor to RFC 822 address. In the basic
case, where IPMS.ORDescriptor.formal-name is present, proceed as
follows.
1. Encode IPMS.ORDescriptor.formal-name (MTS.ORName) as
EBNF.822-address.
2a. If IPMS.ORDescriptor.free-form-name is present, convert it
to ASCII (Chapter 3), and use this as the 822.phrase
component of 822.mailbox using the 822.phrase 822.route-addr
construct.
2b. If IPMS.ORDescriptor.free-form-name is absent. If
EBNF.822-address is parsed as 822.addr-spec use this as the
encoding of 822.mailbox. If EBNF.822-address is parsed as
822.route 822.addr-spec, then a 822.phrase taken from
822.local-part is added.
3 If IPMS.ORDescriptor.telephone-number is present, this is
placed in an 822.comment, with the string "Tel ". The
normal international form of number is used. For example:
(Tel +44-1-387-7050)
4. If IPMS.ORDescriptor.formal-name.directory-name is present,
then a text representation is placed in a trailing
822.comment.
5. If IPMS.RecipientSpecifier.report-request has any non-
default values, then an 822.comment "(Receipt Notification
Requested)", and/or "(Non Receipt Notification Requested)",
and/or "(IPM Return Requested)" is appended to the address.
The effort of correlating P1 and P2 information is too great
to justify the gateway sending Receipt Notifications.
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6. If IPMS.RecipientSpecifier.reply-request is True, an
822.comment "(Reply requested)" is appended to the address.
If IPMS.ORDescriptor.formal-name is absent,
IPMS.ORDescriptor.free-form-name is converted to ASCII, and used
as 822.phrase within the RFC 822 822.group syntax. For example:
Free Form Name ":" ";"
Steps 3-6 are then followed.
4.7.3. IP Message IDs
There is a need to map both ways between 822.msg-id and
IPMS.IPMIdentifier. This allows for X.400 Receipt Notifications,
Replies, and Cross References to reference an RFC 822 Message ID,
which is preferable to a gateway generated ID. A reversible and
symmetrical mapping is defined. This allows for good things to
happen when messages pass multiple times across the X.400/RFC 822
boundary.
An important issue with messages identifiers is mapping to
the exact form, as many systems use these ids as uninterpreted
keys. The use of table driven mappings is not always
symmetrical, particularly in the light of alternative domain
names, and alternative management domains. For this reason, a
purely algorithmic mapping is used. A mapping which is simpler
than that for addresses can be used for two reasons:
- There is no major requirement to make message IDs "natural"
- There is no issue about being able to reply to message IDs.
(For addresses, creating a return path which works is more
important than being symmetrical).
The mapping works by defining a way in which message IDs
generated on one side of the gateway can be represented on the
other side in a systematic manner. The mapping is defined so
that the possibility of clashes is is low enough to be treated as
impossible.
4.7.3.1. 822.msg-id represented in X.400
IPMS.IPMIdentifier.user is omitted. The
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IPMS.IPMIdentifier.user-relative-identifier is set to a printable
string encoding of the 822.msg-id with the angle braces ("<" and
">") removed. The upper bound on this component is 64. The
options for handling this are discussed in Section 5.1.3.
4.7.3.2. IPMS.IPMIdentifier represented in RFC 822
The 822.domain of 822.msg-id is set to the value "MHS". The
822.local-part of 822.msg-id is built as
[ printablestring ] "*" [ std-or-address ]
with EBNF.printablestring being the
IPMS.IPMIdentifier.user-relative-identifier, and std-or-address
being an encoding of the IPMS.IPMIdentifier.user. If necessary,
the 822.quoted-string encoding is used. For example:
<"147*/S=Dietrich/O=Siemens/ADMD=DBP/C=DE/"@MHS>
4.7.3.3. 822.msg-id -> IPMS.IPMIdentifier
If the 822.local-part can be parsed as:
[ printablestring ] "*" [ std-or-address ]
and the 822.domain is "MHS", then this ID was X.400 generated.
If EBNF.printablestring is present, the value is assigned to
IPMS.IPMIdentifier.user-relative-identifier. If
EBNF.std-or-address is present, the O/R Address components
derived from it are used to set IPMS.IPMIdentifier.user.
Otherwise, this is an RFC 822 generated ID. In this case,
set IPMS.IPMIdentifier.user-relative-identifier to a printable
string encoding of the 822.msg-id without the angle braces.
4.7.3.4. IPMS.IPMIdentifier -> 822.msg-id
If IPMS.IPMIdentifier.user is absent, and
IPMS.IPMIdentifier.user-relative-identifier mapped to ASCII and
angle braces added parses as 822.msg-id, then this is an RFC 822
generated ID.
Otherwise, the ID is X.400 generated. Use the
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IPMS.IPMIdentifier.user to generate an EBNF.std-or-address form
string. Build the 822.local-part of the 822.msg-id with the
syntax:
[ printablestring ] "*" [ std-or-address ]
The printablestring is taken from
IPMS.IPMIdentifier.user-relative-identifier. Use
822.quoted-string if necessary. The 822.msg-id is generated with
this 822.local-part, and "MHS" as the 822.domain.
4.7.3.5. Phrase form
In "InReply-To:" and "References:", the encoding 822.phrase may
be used as an alternative to 822.msg-id. To map from 822.phrase
to IPMS.IPMIdentifier, assign
IPMS.IPMIdentifier.user-relative-identifier to the phrase. When
mapping from IPMS.IPMIdentifier for "In-Reply-To:" and
"References:", if IPMS.IPMIdentifier.user is absent and
IPMS.IPMIdentifier.user-relative-identifier does not parse as
822.msg-id, generate an 822.phrase rather than adding the domain
MHS.
4.7.3.6. RFC 987 backwards compatibility
The mapping defined here is different to that used in RFC 987, as
the RFC 987 mapping lead to changed message IDs in many cases.
Fixing the problems is preferable to retaining backwards
compatibility. An implementation of this standard is encouraged
to recognise message IDs generated by RFC 987. This is not
required.
RFC 987 generated encodings may be recognised as follows.
When mapping from X.400 to RFC 822, if the
IPMS.IPMIdentifier.user-relative-identifier is "RFC-822" the id
is RFC 987 generated. When mapping from RFC 822 to X.400, if the
822.domain is not "MHS", and the 822.local-part can be parsed as
[ printablestring ] "*" [ std-or-address ]
then it is RFC 987 generated. In each of these cases, it is
recommended to follow the RFC 987 rules.
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Chapter 5 - Detailed Mappings
This chapter specifies detailed mappings for the functions
outlined in Chapters 1 and 2. It makes extensive use of the
notations and mappings defined in Chapters 3 and 4.
5.1. RFC 822 -> X.400
5.1.1. Basic Approach
A single IP Message is generated from an RFC 822 message The RFC
822 headers are used to generate the IPMS.Heading. The IP
Message will have one IA5 IPMS.BodyPart containing the RFC 822
message body.
Some RFC 822 fields cannot be mapped onto a standard IPM
Heading field, and so an extended field is defined in Section
5.1.2. This is then used for fields which cannot be mapped onto
existing services.
The message is submitted to the MTS, and the services
required can be defined by specifying
MTS.MessageSubmissionEnvelope. A few parameters of the MTA
Abstract service are also specified, which are not in principle
available to the MTS User. Use of these services allows RFC 822
MTA level parameters to be carried in the analogous X.400 service
elements. The advantages of this mapping far outweigh the
layering violation.
5.1.2. X.400 Extension Field
An IPMS Extension is defined:
rfc-822-field HEADING-EXTENSION
VALUE RFC822FieldList
::= id-rfc-822-field-list
RFC822FieldList ::= SEQUENCE OF RFC822Field
RFC822Field ::= IA5String
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The Object Identifier id-rfc-822-field-list is defined in
Appendix D.
To encode any RFC 822 Header using this extension, an
RFC822Field element is built using the 822.field omitting the
trailing CRLF (e.g., "Fruit-Of-The-Day: Kiwi Fruit"). Structured
fields shall be unfolded. There shall be no space before the
":". The reverse mapping builds the RFC 822 field in a
straightforward manner. This RFC822Field is appended to the
RFC822FieldList, which is added to the IPM Heading as an
extension field.
5.1.3. Generating the IPM
The IPM (IPMS Service Request) is generated according to the
rules of this section. The IPMS.IPM.body usually consists of one
IPMS.BodyPart of type IPMS.IA5TextBodyPart with
IPMS.IA5TextBodyPart.parameters.repertoire set to the default
(ia5) which contains the body of the RFC 822 message. The
exception is where there is a "Comments:" field in the RFC 822
header.
If no specific 1988 features are used, the IPM generated is
encoded as content type 2. Otherwise, it is encoded as content
type 22. The latter will always be the case if extension heading
fields are generated.
When generating the IPM, the issue of upper bounds must be
considered. At the MTS and MTA level, this specification is
strict about enforcing upper bounds. Three options are available
at the IPM level. Use of any of these options conforms to this
standard.
1. Ignore upper bounds, and generate messages in the natural
manner. This assumes that if any truncation is done, it
will happen at the recipient UA. This will maximise
transfer of information, but is likely break some recipient
UAs.
2. Reject any inbound message which would cause a message
violating constraints to be generated. This will be robust,
but may prevent useful communication.
3. Truncate fields to the upper bounds specified in X.400.
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This will prevent problems with UAs which enforce upper
bounds, but will sometimes discard useful information.
These options have different advantages and disadvantages, and
the choice will depend on the exact application of the gateway.
The rest of this section concerns IPMS.IPM.heading
(IPMS.Heading). The only mandatory component of IPMS.Heading is
the IPMS.Heading.this-IPM (IPMS.IPMIdentifier). A default is
generated by the gateway. With the exception of "Received:", the
values of multiple fields are merged (e.g., If there are two
"To:" fields, then the mailboxes of both are merged to generate a
single list which is used in the IPMS.Heading.primary-recipients.
Information shall be generated from the standard RFC 822 Headers
as follows:
Date:
Ignore (Handled at MTS level)
Received:
Ignore (Handled at MTA level)
Message-Id:
Mapped to IPMS.Heading.this-IPM. For these, and all other
fields containing 822.msg-id the mappings of Chapter 4 are
used for each 822.msg-id.
From:
If Sender: is present, this is mapped to
IPMS.Heading.authorizing-users. If not, it is mapped to
IPMS.Heading.originator. For this, and other components
containing addresses, the mappings of Chapter 4 are used for
each address.
Sender:
Mapped to IPMS.Heading.originator.
Reply-To:
Mapped to IPMS.Heading.reply-recipients.
To: Mapped to IPMS.Heading.primary-recipients
Cc: Mapped to IPMS.Heading.copy-recipients.
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Bcc: Mapped to IPMS.Heading.blind-copy-recipients.
In-Reply-To:
If there is one value, it is mapped to
IPMS.Heading.replied-to-IPM, using the 822.phrase or
822.msg-id mapping as appropriate. If there are several
values, they are mapped to IPMS.Heading.related-IPMs, along
with any values from a "References:" field.
References:
Mapped to IPMS.Heading.related-IPMs.
Keywords:
Mapped onto a heading extension.
Subject:
Mapped to IPMS.Heading.subject. The field-body uses the
human oriented mapping referenced in Chapter 3 from ASCII to
T.61.
Comments:
Generate an IPMS.BodyPart of type IPMS.IA5TextBodyPart with
IPMS.IA5TextBodyPart.parameters.repertoire set to the
default (ia5), containing the value of the fields, preceded
by the string "Comments: ". This body part shall precede
the other one.
Encrypted:
Mapped onto a heading extension.
Resent-*
Mapped onto a heading extension.
Note that it would be possible to use a ForwardedIPMessage
for these fields, but the semantics are (arguably) slightly
different, and it is probably not worth the effort.
Other Fields
In particular X-* fields, and "illegal" fields in common
usage (e.g., "Fruit-of-the-day:") are mapped onto a heading
extension, unless covered by another section or appendix of
this specification. The same treatment is applied to RFC
822 fields where the content of the field does not conform
to RFC 822 (e.g., a Date: field with unparseable syntax).
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5.1.4. Mappings to the MTS Abstract Service
The MTS.MessageSubmissionEnvelope comprises
MTS.PerMessageSubmissionFields, and
MTS.PerRecipientMessageSubmissionFields. The mandatory
parameters are defaulted as follows.
MTS.PerMessageSubmissionFields.originator-name
This is always generated from 822-MTS, as defined in
Chapter 4.
MTS.PerMessageSubmissionFields.content-type
Set to the value implied by the encoding of the IPM (2 or
22).
MTS.PerRecipientMessageSubmissionFields.recipient-name
These will always be supplied from 822-MTS, as defined in
Chapter 4.
Optional components are omitted, and default components
defaulted, with two exceptions. For
MTS.PerMessageSubmissionFields.per-message-indicators, the
following settings are made:
- Alternate recipient is allowed, as it seems desirable to
maximise the opportunity for (reliable) delivery.
- Content return request is set according to the issues
discussed in Section 5.2.
MTS.PerMessageSubmissionFields.original-encoded-information-types
is a set of one element BuiltInEncodedInformationTypes.ia5-text.
The MTS.PerMessageSubmissionFields.content-correlator is encoded
as IA5String, and contains the Subject:, Message-ID:, Date:, and
To: fields (if present). This includes the strings "Subject:",
"Date:", "To:", "Message-ID:", and appropriate folding. This
shall be truncated to MTS.ub-content-correlator-length (512)
characters. In addition, if there is a "Subject:" field, the
MTS.PerMessageSubmissionFields.content-identifier, is set to a
printable string representation of the contents of it. If the
length of this string is greater than MTS.ub-content-id-length
(16), it should be truncated to 13 characters and the string
"..." appended. Both are used, due to the much larger upper bound
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of the content correlator, and that the content id is available
in X.400(1984).
5.1.5. Mappings to the MTA Abstract Service
There is a need to map directly onto some aspects of the MTA
Abstract service, for the following reasons:
- So the the MTS Message Identifier can be generated from the
RFC 822 Message-ID:.
- So that the submission date can be generated from the
822.Date.
- To prevent loss of trace information
- To prevent RFC 822/X.400 looping caused by distribution
lists or redirects
The following mappings are defined.
Message-Id:
If this is present, the
MTA.PerMessageTransferFields.message-identifier is generated
from it, using the mappings described in Chapter 4.
Date:
This is used to set the first component of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement). The 822-MTS originator is
mapped into an MTS.ORAddress, and used to derive
MTA.TraceInformationElement.global-domain-identifier. The
optional components of
MTA.TraceInformationElement.domain-supplied-information are
omitted, and the mandatory components are set as follows:
MTA.DomainSuppliedInformation.arrival-time
This is set to the date derived from Date:
MTA.DomainSuppliedInformation.routing-action
Set to relayed.
The first element of
MTA.PerMessageTransferFields.internal-trace-information is
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generated in an analogous manner, although this can be
dropped later in certain circumstances (see the procedures
for "Received:").
Received:
All RFC 822 trace is used to derive
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information.
Processing of Received: lines follows processing of Date:,
and is be done from the the bottom to the top of the RFC 822
header (i.e., in chronological order). When other trace
elements are processed (X400-Received: in all cases and Via:
if Appendix B is supported), the relative ordering shall be
retained correctly. The initial element of
MTA.PerMessageTransferFields.trace-information will be
generated already (from Date:).
Consider the Received: field in question. If the "by" part
of the received is present, use it to derive an
MTS.GlobalDomainIdentifier. If this is different from the
one in the last element of
MTA.PerMessageTransferFields.trace-information
(MTA.TraceInformationElement.global-domain-identifier)
create a new MTA.TraceInformationElement, and optionally
remove
MTA.PerMessageTransferFields.internal-trace-information.
This removal shall be done in cases where the message is
being transferred to another MD where there is no bilateral
agreement to preserve internal trace beyond the local MD.
The trace creation is as for internal trace described below,
except that no MTA field is needed.
Then add a new element (MTA.InternalTraceInformationElement)
to MTA.PerMessageTransferFields.internal-trace-information,
creating this if needed. This shall be done, even if
inter-MD trace is created. The
MTA.InternalTraceInformationElement.global-domain-identifier
is set to the value derived. The
MTA.InternalTraceInformationElement.mta-supplied-information
(MTA.MTASuppliedInformation) is set as follows:
MTA.MTASuppliedInformation.arrival-time
Derived from the date of the Received: line
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MTA.MTASuppliedInformation.routing-action
Set to relayed
The MTA.InternalTraceInformationElement.mta-name is taken
from the "by" component of the "Received:" field, truncated
to MTS.ub-mta-name-length (32). For example:
Received: from computer-science.nottingham.ac.uk by
vs6.Cs.Ucl.AC.UK via Janet with NIFTP id aa03794;
28 Mar 89 16:38 GMT
Generates the string
vs6.Cs.Ucl.AC.UK
Note that before transferring the message to some ADMDs,
additional trace stripping may be required, as the implied path
through multiple MDs would violate ADMD policy. This will
depend on bilateral agreement with the ADMD.
5.1.6. Mapping New Fields
This specification defines a number of new fields for Reports,
Notifications and IP Messages in Section 5.3. As this
specification only aims to preserve existing services, a gateway
conforming to this specification does not need to map all of
these fields to X.400.
Two extended fields must be mapped, in order to prevent
looping. "DL-Expansion-History:" is mapped to
MTA.PerMessageTransferFields.extensions.dl-expansion-history
X400-Received: must be mapped to
MTA.PerMessageTransferFields.trace-information and
MTA.PerMessageTransferFields.internal-trace-information.
Some field that shall not be mapped, and should be
discarded. The following cannot be mapped back:
- Discarded-X400-MTS-Extensions:
- Message-Type:
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- Discarded-X400-IPMS-Extensions:
The following may cause problems, due to other information
not being mapped back (e.g., extension numbers), or due to
changes made on the RFC 822 side due to list expansion:
- X400-Content-Type:
- X400-Originator:
- X400-Recipients:
- X400-MTS-Identifier:
Other fields may be either discarded or mapped to X.400. It
is usually desirable and beneficial to do map, particularly to
facilitate support of a message traversing multiple gateways.
These mappings may be onto MTA, MTS, or IPMS services. The level
of support for this reverse mapping should be indicated in the
gateway conformace statement.
5.2. Return of Contents
It is not clear how widely supported the X.400 return of contents
service will be. Experience with X.400(1984) suggests that
support of this service may not be universal. As this service is
expected in the RFC 822 world, two approaches are specified. The
choice will depend on the use of X.400 return of contents withing
the X.400 community being serviced by the gateway.
In environments where return of contents is widely
supported, content return can be requested as a service. The
content return service can then be passed back to the end (RFC
822) user in a straightforward manner.
In environments where return of contents is not widely
supported, a gateway must make special provision to handle return
of contents. For every message passing from RFC 822 -> X.400,
content return request will not be requested, and report request
always will be. When the delivery report comes back, the gateway
can note that the message has been delivered to the recipient(s)
in question. If a non-delivery report is received, a meaningful
report (containing some or all of the original message) can be
sent to the 822-MTS originator. If no report is received for a
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recipient, a (timeout) failure notice shall be sent to the
822-MTS originator. The gateway may retransmit the X.400 message
if it wishes. When this approach is taken, routing must be set
up so that error reports are returned through the same MTA.
This approach may be difficult to use in conjunction with some
routing strategies.
5.3. X.400 -> RFC 822
5.3.1. Basic Approach
A single RFC 822 message is generated from the incoming IP
Message, Report, or IP Notification. All IPMS.BodyParts are
mapped onto a single RFC 822 body. Other services are mapped
onto RFC 822 header fields. Where there is no appropriate
existing field, new fields are defined for IPMS, MTS and MTA
services.
The gateway mechanisms will correspond to MTS Delivery. As
with submission, there are aspects where the MTA (transfer)
services are also used. In particular, there is an optimisation
to allow for multiple 822-MTS recipients.
5.3.2. RFC 822 Settings
An RFC 822 Service requires to have a number of mandatory fields
in the RFC 822 Header. Some 822-MTS services mandate
specification of an 822-MTS Originator. Even in cases where this
is optional, it is usually desirable to specify a value. The
following defaults are defined, which shall be used if the
mappings specified do not derive a value:
822-MTS Originator
If this is not generated by the mapping (e.g., for a
Delivery Report), a value pointing at a gateway
administrator shall be assigned.
Date:
A value will always be generated
From:If this is not generated by the mapping, it is assigned
equal to the 822-MTS Originator. If this is gateway
generated, an appropriate 822.phrase shall be added.
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At least one recipient field
If no recipient fields are generated, a field "To: list:;",
shall be added.
This will ensure minimal RFC 822 compliance. When generating RFC
822 headers, folding may be used. It is recommended to do this,
following the guidelines of RFC 822.
5.3.3. Basic Mappings
5.3.3.1. Encoded Information Types
This mapping from MTS.EncodedInformationTypes is needed in
several disconnected places. EBNF is defined as follows:
encoded-info = 1#encoded-type
encoded-type = built-in-eit / object-identifier
built-in-eit = "Undefined" ; undefined (0)
/ "Telex" ; tLX (1)
/ "IA5-Text" ; iA5Text (2)
/ "G3-Fax" ; g3Fax (3)
/ "TIF0" ; tIF0 (4)
/ "Teletex" ; tTX (5)
/ "Videotex" ; videotex (6)
/ "Voice" ; voice (7)
/ "SFD" ; sFD (8)
/ "TIF1" ; tIF1 (9)
MTS.EncodedInformationTypes is mapped onto EBNF.encoded-info.
MTS.EncodedInformationTypes.non-basic-parameters is ignored.
Built in types are mapped onto fixed strings (compatible with
X.400(1984) and RFC 987), and other types are mapped onto
EBNF.object-identifier.
5.3.3.2. Global Domain Identifier
The following simple EBNF is used to represent
MTS.GlobalDomainIdentifier:
global-id = std-or-address
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This is encoded using the std-or-address syntax, for the
attributes within the Global Domain Identifier.
5.3.4. Mappings from the IP Message
Consider that an IPM has to be mapped to RFC 822. The IPMS.IPM
comprises an IPMS.IPM.heading and IPMS.IPM.body. The heading is
considered first. Some EBNF for new fields is defined:
ipms-field = "Obsoletes" ":" 1#msg-id
/ "Expiry-Date" ":" date-time
/ "Reply-By" ":" date-time
/ "Importance" ":" importance
/ "Sensitivity" ":" sensitivity
/ "Autoforwarded" ":" boolean
/ "Incomplete-Copy" ":"
/ "Language" ":" language
/ "Message-Type" ":" message-type
/ "Discarded-X400-IPMS-Extensions" ":" 1#oid
importance = "low" / "normal" / "high"
sensitivity = "Personal" / "Private" /
"Company-Confidential"
language = 2*ALPHA [ language-description ]
language-description = printable-string
message-type = "Delivery Report"
/ "InterPersonal Notification"
/ "Multiple Part"
The mappings and actions for the IPMS.Heading is now specified
for each element. Addresses, and Message Identifiers are mapped
according to Chapter 4. Other mappings are explained, or are
straightforward (algorithmic).
IPMS.Heading.this-IPM
Mapped to "Message-ID:".
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IPMS.Heading.originator
If IPMS.Heading.authorizing-users is present this is mapped
to Sender:, if not to "From:".
IPMS.Heading.authorizing-users
Mapped to "From:".
IPMS.Heading.primary-recipients
Mapped to "To:".
IPMS.Heading.copy-recipients
Mapped to "Cc:".
IPMS.Heading.blind-copy-recipients
Mapped to "Bcc:".
IPMS.Heading.replied-to-ipm
Mapped to "In-Reply-To:".
IPMS.Heading.obsoleted-IPMs
Mapped to the extended RFC 822 field "Obsoletes:"
IPMS.Heading.related-IPMs
Mapped to "References:".
IPMS.Heading.subject
Mapped to "Subject:". The contents are converted to ASCII
(as defined in Chapter 3). Any CRLF are not mapped, but are
used as points at which the subject field must be folded.
IPMS.Heading.expiry-time
Mapped to the extended RFC 822 field "Expiry-Date:".
IPMS.Heading.reply-time
Mapped to the extended RFC 822 field "Reply-By:".
IPMS.Heading.reply-recipients
Mapped to "Reply-To:".
IPMS.Heading.importance
Mapped to the extended RFC 822 field "Importance:".
IPMS.Heading.sensitivity
Mapped to the extended RFC 822 field "Sensitivity:".
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IPMS.Heading.autoforwarded
Mapped to the extended RFC 822 field "Autoforwarded:".
The standard extensions (Annex H of X.420 / ISO 10021-7) are
mapped as follows:
incomplete-copy
Mapped to the extended RFC 822 field "Incomplete-Copy:".
language
Mapped to the extended RFC 822 field "Language:", filling in
the two letter code. The language-description may filled in
with a human readable description of the language, and it is
recommended to do this.
If the RFC 822 extended header is found, this shall be
mapped onto an RFC 822 header, as described in Section 5.1.2.
If a non-standard extension is found, it shall be discarded,
unless the gateway understands the extension and can perform an
appropriate mapping onto an RFC 822 header field. If extensions
are discarded, the list is indicated in the extended RFC 822
field "Discarded-X400-IPMS-Extensions:".
The IPMS.Body is mapped into the RFC 822 message body. Each
IPMS.BodyPart is converted to ASCII as follows:
IPMS.IA5Text
The mapping is straightforward (see Chapter 3).
IPMS.MessageBodyPart
The X.400 -> RFC 822 mapping is recursively applied, to
generate an RFC 822 Message. If present, the
IPMS.MessageBodyPart.parameters.delivery-envelope is used
for the MTS Abstract Service Mappings. If present, the
IPMS.MessageBodyPart.parameters.delivery-time is mapped to
the extended RFC 822 field "Delivery-Date:".
Other
If other body parts can be mapped to IA5, either by use of
mappings defined in X.408 [CCITT88a], or by other reasonable
mappings, this shall be done unless content conversion is
prohibited.
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If some or all of the body parts cannot be converted there
are three options. All of these conform to this standard. A
different choice may be made for the case where no body part can
be converted:
1. The first option is to reject the message, and send a non-
delivery notification. This must always be done if
conversion is prohibited.
2. The second option is to map a missing body part to something
of the style:
*********************************
There was a foobar here
The widget gateway ate it
*********************************
This will allow some useful information to be transferred.
As the recipient is likely to be a human (IPMS), then
suitable action will usually be possible.
3. Finally both may be done. In this case, the supplementary
information in the (positive) Delivery Report shall make
clear that something was sent on to the recipient with
substantial loss of information.
Where there is more than one IPMS.BodyPart, the mapping
defined by Rose and Stefferud in [Rose85a], is used to map the
separate IPMS.BodyParts in the single RFC 822 message body. If
this is done, a "Message-Type:" field with value "Multiple part"
shall be added, which will indicate to a receiving gateway that
the message may be unfolded according to RFC 934.
Note:There is currently work ongoing to produce an upgrade to RFC
934, which also allows for support of body parts with non-
ASCII content. When this work is released as an RFC, this
specification will be updated to refer to it instead for RFC
934.
For backwards compatibility with RFC 987, the following
procedures shall also be followed. If there are two IA5 body
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parts, and the first starts with the string "RFC-822-Headers:" as
the first line, then the remainder of this body part shall be
appended to the RFC 822 header.
An example message, illustrating a number of aspects is
given below.
Return-Path: <@mhs-relay.ac.uk:stephen.harrison@gosip-uk.hmg.gold-400.gb>
Received: from mhs-relay.ac.uk by bells.cs.ucl.ac.uk via JANET with NIFTP
id <7906-0@bells.cs.ucl.ac.uk>; Thu, 30 May 1991 18:24:55 +0100
X400-Received: by mta "mhs-relay.ac.uk" in /PRMD=uk.ac/ADMD= /C=gb/; Relayed;
Thu, 30 May 1991 18:23:26 +0100
X400-Received: by /PRMD=HMG/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 30 May 1991 18:20:27 +0100
Message-Type: Multiple Part
Date: Thu, 30 May 1991 18:20:27 +0100
X400-Originator: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
X400-MTS-Identifier:
[/PRMD=HMG/ADMD=GOLD 400/C=GB/;PC1000-910530172027-57D8]
Original-Encoded-Information-Types: ia5, undefined
X400-Content-Type: P2-1984 (2)
Content-Identifier: Email Problems
From: Stephen.Harrison@gosip-uk.hmg.gold-400.gb (Tel +44 71 217 3487)
Message-ID: <PC1000-910530172027-57D8*@MHS>
To: Jim Craigie <NTIN36@gec-b.rutherford.ac.uk>
(Receipt Notification Requested) (Non Receipt Notification Requested),
Tony Bates <tony@ean-relay.ac.uk> (Receipt Notification Requested),
Steve Kille <S.Kille@cs.ucl.ac.uk> (Receipt Notification Requested)
Subject: Email Problems
Sender: Stephen.Harrison@gosip-uk.hmg.gold-400.gb
------------------------------ Start of body part 1
Hope you gentlemen.......
Regards,
Stephen Harrison
UK GOSIP Project
..... continued on next page
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------------------------------ Start of forwarded message 1
From: Urs Eppenberger <Eppenberger@verw.switch.ch>
Message-ID:
<562*/S=Eppenberger/OU=verw/O=switch/PRMD=SWITCH/ADMD=ARCOM/C=CH/@MHS>
To: "Stephen.Harrison" <Stephen.Harrison@gosip-uk.hmg.gold-400.gb>
Cc: kimura@bsdarc.bsd.fc.nec.co.jp
Subject: Response to Email link
- ------------------------------ Start of body part 1
Dear Mr Harrison......
- ------------------------------ End of body part 1
------------------------------ End of forwarded message 1
5.3.5. Mappings from an IP Notification
A message is generated, with the following fields:
From:
Set to the MTS.MessageDeliveryEnvelope.other-
fields.originator-name.
To: Set to the IPMS.IPN.ipm-originator.
Subject:
Set to the string "X.400 Inter-Personal Notification".
Message-Type:
Set to "InterPersonal Notification"
References:
Set to IPMS.IPN.subject-ipm
The following EBNF is defined for the body of the Message. This
format is defined to ensure that all information from an
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interpersonal notification is available to the end user in a
uniform manner.
ipn-body-format = ipn-description <CRLF>
[ ipn-extra-information <CRLF> ]
ipn-content-return
ipn-description = ipn-receipt / ipn-non-receipt
ipn-receipt = "Your message to:" preferred-recipient <CRLF>
"was received at" receipt-time <CRLF> <CRLF>
"This notification was generated"
acknowledgement-mode <CRLF>
"The following extra information was given:" <CRLF>
ipn-suppl <CRLF>
ipn-non-receipt "Your message to:"
preferred-recipient <CRLF>
ipn-reason
ipn-reason = ipn-discarded / ipn-auto-forwarded
ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>
ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]
ipn-extra-information =
"The following information types were converted:"
encoded-info
ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"
<CRLF> <CRLF> message
preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring
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discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated"
acknowledgement-mode = "Manually" / "Automatically"
The mappings for elements of the common fields of IPMS.IPN
(IPMS.CommonFields) onto this structure and the message header
are:
subject-ipm
Mapped to "References:"
ipm-originator
Mapped to "To:".
ipm-preferred-recipient
Mapped to EBNF.preferred-recipient
conversion-eits
Mapped to EBNF.encoded-info in EBNF.ipn-extra-information
The mappings for elements of IPMS.IPN.non-receipt-fields
(IPMS.NonReceiptFields) are:
non-receipt-reason
Used to select between EBNF.ipn-discarded and
EBNF.ipn-auto-forwarded
discard-reason
Mapped to EBNF.discard-reason
auto-forward-comment
Mapped to EBNF.auto-comment
returned-ipm
If present, the second option of EBNF.ipn-content-return is
chosen, and an RFC 822 mapping of the message included.
Otherwise the first option is chosen.
The mappings for elements of IPMS.IPN.receipt-fields
(IPMS.ReceiptFields) are:
receipt-time
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Mapped to EBNF.receipt-time
acknowledgement-mode
Mapped to EBNF.acknowledgement-mode
suppl-receipt-info
Mapped to EBNF.ipn-suppl
An example notification is:
From: Steve Kille <steve@cs.ucl.ac.uk>
To: Julian Onions <jpo@computer-science.nottingham.ac.uk>
Subject: X.400 Inter-personal Notification
Message-Type: InterPersonal Notification
References: <1229.614418325@UK.AC.NOTT.CS>
Date: Wed, 21 Jun 89 08:45:25 +0100
Your message to: Steve Kille <steve@cs.ucl.ac.uk>
was automatically forwarded.
The following comment was made:
Sent on to a random destination
The following information types were converted: g3fax
The Original Message is not available
5.3.6. Mappings from the MTS Abstract Service
This section describes the MTS mappings for User Messages (IPM
and IPN). This mapping is defined by specifying the mapping of
MTS.MessageDeliveryEnvelope. The following extensions to RFC 822
are defined to support this mapping:
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mts-field = "X400-MTS-Identifier" ":" mts-msg-id
/ "X400-Originator" ":" mailbox
/ "X400-Recipients" ":" 1#mailbox
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Content-Type" ":" mts-content-type
/ "Content-Identifier" ":" printablestring
/ "Priority" ":" priority
/ "Originator-Return-Address" ":" 1#mailbox
/ "DL-Expansion-History" ":" mailbox ";" date-time ";"
/ "Conversion" ":" prohibition
/ "Conversion-With-Loss" ":" prohibition
/ "Requested-Delivery-Method" ":"
1*( labelled-integer )
/ "Delivery-Date" ":" date-time
/ "Discarded-X400-MTS-Extensions" ":"
1#( oid / labelled-integer )
prohibition = "Prohibited" / "Allowed"
mts-msg-id = "[" global-id ";" *text "]"
mts-content-type = "P2" / labelled-integer
/ object-identifer
priority = "normal" / "non-urgent" / "urgent"
The mappings for each element of MTS.MessageDeliveryEnvelope can
now be considered.
MTS.MessageDeliveryEnvelope.message-delivery-identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
MTS.MessageDeliveryEnvelope.message-delivery-time
Discarded, as this time will be represented in an
appropriate trace element.
The mappings for elements of
MTS.MessageDeliveryEnvelope.other-fields
(MTS.OtherMessageDeliveryFields) are:
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content-type
Mapped to the extended RFC 822 field "X400-Content-Type:".
The string "P2" is retained for backwards compatibility with
RFC 987. This shall not be generated, and either the
EBNF.labelled-integer or EBNF.object-identifier encoding
used.
originator-name
Mapped to the 822-MTS originator, and to the extended RFC
822 field "X400-Originator:". This is described in
Section 4.6.2.
original-encoded-information-types
Mapped to the extended RFC 822 field
"Original-Encoded-Information-Types:".
priority
Mapped to the extended RFC 822 field "Priority:".
delivery-flags
If the conversion-prohibited bit is set, add an extended RFC
822 field "Conversion:".
this-recipient-name and other-recipient-names
originally-intended-recipient-name
The handling of these elements is described in
Section 4.6.2.
converted-encoded-information-types
Discarded, as it will always be IA5 only.
message-submission-time
Mapped to Date:.
content-identifier
Mapped to the extended RFC 822 field "Content-Identifier:".
If any extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are
present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. The extensions
(MTS.MessageDeliveryEnvelope.other-fields.extensions) are mapped
as follows.
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conversion-with-loss-prohibited
If set to
MTS.ConversionWithLossProhibited.conversion-with-loss-prohibited,
then add the extended RFC 822 field "Conversion-With-Loss:".
requested-delivery-method
Mapped to the extended RFC 822 field
"Requested-Delivery-Method:".
originator-return-address
Mapped to the extended RFC 822 field
"Originator-Return-Address:".
physical-forwarding-address-request
physical-delivery-modes
registered-mail-type
recipient-number-for-advice
physical-rendition-attributes
physical-delivery-report-request
physical-forwarding-prohibited
These elements are only appropriate for physical delivery.
They are represented as comments in the "X400-Recipients:"
field, as described in Section 4.6.2.2.
originator-certificate
message-token
content-confidentiality-algorithm-identifier
content-integrity-check
message-origin-authentication-check
message-security-label
proof-of-delivery-request
These elements imply use of security services not available
in the RFC 822 environment. If they are marked as critical
for transfer or delivery, then the message shall be
rejected. Otherwise they are discarded.
redirection-history
This is described in Section 4.6.2.
dl-expansion-history
Each element is mapped to the extended RFC 822 field
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"DL-Expansion-History:". They shall be ordered in the
message header, so that the most recent expansion comes
first (same order as trace).
If any MTS (or MTA) Extensions not specified in X.400 are
present, and they are marked as critical for transfer or
delivery, then the message shall be rejected. If they are not so
marked, they can safely be discarded. The list of discarded
fields shall be indicated in the extended header
"Discarded-X400-MTS-Extensions:".
5.3.7. Mappings from the MTA Abstract Service
There are some mappings at the MTA Abstract Service level which
are done for IPM and IPN. These can be derived from
MTA.MessageTransferEnvelope. The reasons for the mappings at
this level, and the violation of layering are:
- Allowing for multiple recipients to share a single RFC 822
message
- Making the X.400 trace information available on the RFC 822
side
- Making any information on deferred delivery available
The 822-MTS recipients are calculated from the full list of X.400
recipients. This is all of the members of
MTA.MessageTransferEnvelope.per-recipient-fields being passed
through the gateway, where the responsibility bit is set. In
some cases, a different RFC 822 message would be calculated for
each recipient, due to differing service requests for each
recipient. As discussed in 4.6.2..2, this specification allows
either for multiple messages to be generated, or for the per-
recipient information to be discarded.
The following EBNF is defined for extended RFC 822 headers:
mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time
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x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time
md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time
md-or-mta = "MD" global-id
/ "MTA" mta
Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"
Note the EBNF.mta is encoded as 822.word. If the character
set does no allow encoding as 822.atom, the 822.quoted-string
encoding is used.
If MTA.PerMessageTransferFields.deferred-delivery-time is
present, it is used to generate a Deferred-Delivery: field. For
some reason, X.400 does not make this information available at
the MTS level on delivery. X.400 profiles, and in particular the
CEN/CENELEC profile for X.400(1984) [Systems85a], specify that
this element must be supported at the first MTA. If it is not,
the function may optionally be implemented by the gateway: that
is, the gateway may hold the message until the time specified in
the protocol element. Thus, the value of this element will
usually be in the past. For this reason, the extended RFC 822
field is primarily for information.
Merge MTA.PerMessageTransferFields.trace-information, and
MTA.PerMessageTransferFields.internal-trace-information to
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produce a single ordered trace list. If Internal trace from
other management domains has not been stripped, this may require
complex interleaving. Where an element of internal trace and
external trace are identical, except for the MTA in the internal
trace, only the internal trace element shall be presented. Use
this to generate a sequence of "X400-Received:" fields. The only
difference between external trace and internal trace will be the
extra MTA information in internal trace elements.
When generating an RFC 822 message all trace fields (X400-
Received and Received) shall be at the beginning of the header,
before any other fields. Trace shall be in chronological order,
with the most recent element at the front of the message. This
ordering is determined from the order of the fields, not from
timestamps in the trace, as there is no guarantee of clock
synchronisation. A simple example trace (external) is:
X400-Received: by /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ; Relayed ;
Tue, 20 Jun 89 19:25:11 +0100
A more complex example (internal):
X400-Received: by mta "UK.AC.UCL.CS" in /PRMD=UK.AC/ADMD=Gold 400/C=GB/ ;
deferred until Tue, 20 Jun 89 14:24:22 +0100 ;
converted (undefined, g3fax) ";" attempted /ADMD=Foo/C=GB/ ;
Relayed, Expanded, Redirected ; Tue, 20 Jun 89 19:25:11 +0100
5.3.8. Mappings from Report Delivery
Delivery reports are mapped at the MTS service level. This means
that only reports destined for the MTS user will be mapped. Some
additional services are also taken from the MTA service.
5.3.8.1. MTS Mappings
A Delivery Report service will be represented as
MTS.ReportDeliveryEnvelope, which comprises of per-report-fields
(MTS.PerReportDeliveryFields) and per-recipient-fields.
A message is generated with the following fields:
From:
An administrator at the gateway system. This is also the
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822-MTS originator.
To: A mapping of the
MTA.ReportTransferEnvelope.report-destination-name. This is
also the 822-MTS recipient.
Message-Type:
Set to "Delivery Report".
Subject:
The EBNF for the subject line is:
subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]
status = "success" / "failure" / "success and failures"
destination = mailbox / "MTA" word
The format of the body of the message is defined to ensure
that all information is conveyed to the RFC 822 user in a
consistent manner. The format is structured as if it was a
message coming from X.400, with the description in one body part,
and a forwarded message (return of content) in the second. This
structure is useful to the RFC 822 recipient, as it enables the
original message to be extracted. The first body part is
structured as follows:
1. A few lines giving keywords to indicate the original
message.
2. A human summary of the status of each recipient being
reported on.
3. A clearly marked section which contains detailed information
extracted from the report. This is marked clearly, as it
will not be comprehensible to the average user. It is
retained, as it may be critical to diagnosing an obscure
problem.
This section may be omitted in positive DRs, and it is
recommended that this is appropriate for most gateways.
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dr-body-format = dr-summary <CRLF>
dr-recipients <CRLF>
dr-administrator-info-envelope <CRLF>
dr-content-return
dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"
/ "The Orginal Message is not returned with positive reports"
dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>
dr-recipients = *(dr-recipient <CRLF> <CRLF>)
dr-recipient = dr-recip-success / dr-recip-failure
dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time
dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word
dr-administrator-info-envelope = 3*( "*" text <CRLF> )
dr-administrator-info =
"**** The following information is directed towards"
"the local administrator" <CRLF>
"**** and is not intended for the end user" <CRLF> <CRLF>
"DR generated by:" report-point <CRLF>
"at" date-time <CRLF> <CRLF>
"Converted to RFC 822 at" mta <CRLF>
"at" date-time <CRLF> <CRLF>
"Delivery Report Contents:" <CRLF> <CRLF>
drc-field-list <CRLF>
"***** End of administration information"
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drc-field-list = *(drc-field <CRLF>)
drc-field = "Subject-Submision-Identifier" ":"
mts-msg-id
/ "Content-Identifier" ":" printablestring
/ "Content-Type" ":" mts-content-type
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "Originator-and-DL-Expansion-History" ":"
dl-history
/ "Reporting-DL-Name" ":" mailbox
/ "Content-Correlator" ":" content-correlator
/ "Recipient-Info" ":" recipient-info
/ "Subject-Intermediate-Trace-Information" ":"
x400-trace
recipient-info = mailbox "," std-or ";"
report-type
[ "converted eits" encoded-info ";" ]
[ "originally intended recipient"
mailbox "," std-or ";" ]
[ "last trace" [ encoded-info ] date-time ";" ]
[ "supplementary info" <"> printablestring <"> ";" ]
[ "redirection history" 1#redirection ";"
[ "physical forwarding address"
printablestring ";" ]
report-type = "SUCCESS" drc-success
/ "FAILURE" drc-failure
drc-success = "delivered at" date-time ";"
[ "type of MTS user" labelled-integer ";" ]
drc-failure = "reason" labelled-integer ";"
[ "diagnostic" labelled-integer ";" ]
report-point = [ "mta" word "in" ] global-id
content-correlator = *word
dl-history = 1#( mailbox "(" date-time ")")
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The format is defined as a fixed definition of an the outer level
(EBNF.dr-body-format). The element
EBNF.dr-administrator-info-envelope, provides a means of
encapsulating a section of the header in a manner which is clear
to the end user. Each line of this section begins with "*".
Each element of EBNF.text within
%EBNF.dr-administrator-info-envelope must not contain <CRLF>.
This is used to wrap up EBNF.dr-administrator-info, which will
generate a sequenece of lines not starting with "*". EBNF.drc-
fields may be folded using the RFC 822 folding rules.
The elements of MTS.ReportDeliveryEnvelope.per-report-fields
are mapped as follows onto extended RFC 822 fields:
subject-submission-identifier
Mapped to EBNF.drc-field (Subject-Submission-Identifier)
content-identifier
Mapped to EBNF.drc-field (Content-Identifier). This should
also be used in EBNF.dr-summary if there is no Content
Correlator present.
content-type
Mapped to EBNF.drc-field (Content-Type)
original-encoded-information-types
Mapped to EBNF.drc-field (Encoded-Info)
The extensions from
MTS.ReportDeliveryEnvelope.per-report-fields.extensions are
mapped as follows:
originator-and-DL-expansion-history
Mapped to EBNF.drc-field (Originator-and-DL-Expansion-
History)
reporting-DL-name
Mapped to EBNF.drc-field (Reporting-DL-Name)
content-correlator
Mapped to EBNF.content-correlator, provided that the
encoding is IA5String (this will always be the case). This
is used in EBNF.dr-summary and EBNF.drc-field-list. In the
former, LWSP may be added, in order to improve the layout of
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the message.
message-security-label
reporting-MTA-certificate
report-origin-authentication-check
These security parameters will not be present unless there
is an error in a remote MTA. If they are present, they
shall be discarded in preference to discarding the whole
report.
For each element of
MTS.ReportDeliveryEnvelope.per-recipient-fields, a value of
EBNF.dr-recipient, and an EBNF.drc-field (Recipient-Info) is
generated. The components are mapped as follows.
actual-recipient-name
Used to generate the first EBNF.mailbox and EBNF.std-or in
EBNF.recipient-info. Both RFC 822 and X.400 forms are
given, as there may be a problem in the mapping tables. It
also generates the EBNF.mailbox in EBNF.dr-recip-success or
EBNF.dr-recip-failure.
report
If it is MTS.Report.delivery, then set EBNF.dr-recipient to
EBNF.dr-recip-success, and similarly set EBNF.report-type,
filling in EBNF.drc-success. If it is a failure, set
EBNF.dr-recipient to EBNF.dr-recip-failure, making a human
interpretation of the reason and diagnostic codes, and
including any supplementary information. EBNF.drc-failure
is filled in systematically.
converted-encoded-information-types
Set EBNF.drc-field ("converted eits")
originally-intended-recipient
Set the second ("originally intended recipient") mailbox and
std-or in EBNF.drc-field.
supplementary-info
Set EBNF.drc-field ("supplementary info"), and include this
information in EBNF.dr-recip-failure.
redirection-history
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Set EBNF.drc-field ("redirection history")
physical-forwarding-address
Set ENBF.drc-field ("physical forwarding address")
recipient-certificate
Discard
proof-of-delivery
Discard
Any unknown extensions shall be discarded, irrespective of
criticality.
The original message, or an extract from it, shall be
included in the delivery port if it is available. The original
message will usually be available at the gateway, as discussed in
Section 5.2.
5.3.8.2. MTA Mappings
The single 822-MTS recipient is constructed from
MTA.ReportTransferEnvelope.report-destination-name, using the
mappings of Chapter 4. Unlike with a user message, this
information is not available at the MTS level.
The following additional mappings are made:
MTA.ReportTransferEnvelope.report-destination-name
This is used to generate the To: field.
MTA.ReportTransferEnvelope.identifier
Mapped to the extended RFC 822 field "X400-MTS-Identifier:".
It may also be used to derive a "Message-Id:" field.
MTA.ReportTransferEnvelope.trace-information
and
MTA.ReportTransferEnvelope.internal-trace-information
Mapped onto the extended RFC 822 field "X400-Received:", as
described in Section 5.3.7. The first element is also used
to generate the "Date:" field, and the EBNF.failure-point.
MTA.PerRecipientReportTransferFields.last-trace-information
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Mapped to EBNF.recipient-info (last trace)
MTA.PerReportTransferFields.subject-intermediate-trace-
information Mapped to EBNF.drc-field (Subject-Intermediate-
Trace-Information). These fields are ordered so that the
most recent trace element comes first.
5.3.8.3. Example Delivery Reports
Example Delivery Report 1:
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Return-Path: <postmaster@cs.ucl.ac.uk>
Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
via Delivery Reports Channel id <27699-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:39 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for H.Hildegard@bbn.com
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:48:39 +0000
Message-ID: <"bells.cs.u.694:07.01.91.15.48.34"@cs.ucl.ac.uk>
Content-Identifier: Greetings.
------------------------------ Start of body part 1
This report relates to your message: Greetings.
of Thu, 7 Feb 1991 15:48:20 +0000
Your message was not delivered to
H.Hildegard@bbn.com for the following reason:
Bad Address
MTA 'bbn.com' gives error message (USER) Unknown user name in
"H.Hildegard@bbn.com"
***** The following information is directed towards the local administrator
***** and is not intended for the end user
*
* DR generated by mta bells.cs.ucl.ac.uk
* in /PRMD=uk.ac/ADMD=gold 400/C=gb/
* at Thu, 7 Feb 1991 15:48:34 +0000
*
* Converted to RFC 822 at bells.cs.ucl.ac.uk
* at Thu, 7 Feb 1991 15:48:40 +0000
*
..... continued on next page
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* Delivery Report Contents:
*
* Subject-Submission-Identifier:
* [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1803.665941698@UK.AC.UCL.CS>]
* Content-Identifier: Greetings.
* Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;
* arrival Thu, 7 Feb 1991 15:48:20 +0000 action Relayed
* Subject-Intermediate-Trace-Information: /PRMD=uk.ac/ADMD=gold 400/C=gb/;
* arrival Thu, 7 Feb 1991 15:48:18 +0000 action Relayed
* Recipient-Info: H.Hildegard@bbn.com,
* /RFC-822=H.Hildegard(a)bbn.com/OU=cs/O=ucl/PRMD=uk.ac/ADMD=gold 400/C=gb/;
* FAILURE reason Unable-To-Transfer (1);
* diagnostic Unrecognised-ORName (0);
* last trace (ia5) Thu, 7 Feb 1991 15:48:18 +0000;
* supplementary info "MTA 'bbn.com' gives error message (USER)
* Unknown user name in "H.Hildegard@bbn.com"";
****** End of administration information
The Original Message follows:
------------------------------ Start of forwarded message 1
Received: from glenlivet.cs.ucl.ac.uk by bells.cs.ucl.ac.uk
with SMTP inbound id <27689-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:48:21 +0000
To: H.Hildegard@bbn.com
Subject: Greetings.
Phone: +44-71-380-7294
Date: Thu, 07 Feb 91 15:48:18 +0000
Message-ID: <1803.665941698@UK.AC.UCL.CS>
From: Steve Kille <S.Kille@cs.ucl.ac.uk>
Steve
------------------------------ End of forwarded message 1
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Example Delivery Report 2:
Return-Path: <postmaster@cs.ucl.ac.uk>
Received: from cs.ucl.ac.uk by bells.cs.ucl.ac.uk
via Delivery Reports Channel id <27718-0@bells.cs.ucl.ac.uk>;
Thu, 7 Feb 1991 15:49:11 +0000
X400-Received: by mta bells.cs.ucl.ac.uk in /PRMD=uk.ac/ADMD=gold 400/C=gb/;
Relayed; Thu, 7 Feb 1991 15:49:08 +0000
X400-Received: by /PRMD=DGC/ADMD=GOLD 400/C=GB/; Relayed;
Thu, 7 Feb 1991 15:48:40 +0000
From: UCL-CS MTA <postmaster@cs.ucl.ac.uk>
To: S.Kille@cs.ucl.ac.uk
Subject: Delivery Report (failure) for
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
Message-Type: Delivery Report
Date: Thu, 7 Feb 1991 15:49:11 +0000
Message-ID: <"DLE/910207154840Z/000"@cs.ucl.ac.uk>
Content-Identifier: A useful mess...
This report relates to your message: A useful mess...
Your message was not delivered to
j.nosuchuser@dle.cambridge.DGC.gold-400.gb
for the following reason:
Bad Address
DG 21187: (CEO POA) Unknown addressee.
***** The following information is directed towards the local administrator
***** and is not intended for the end user
*
..... continued on next page
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* DR generated by /PRMD=DGC/ADMD=GOLD 400/C=GB/
* at Thu, 7 Feb 1991 15:48:40 +0000
*
* Converted to RFC 822 at bells.cs.ucl.ac.uk
* at Thu, 7 Feb 1991 15:49:12 +0000
*
* Delivery Report Contents:
*
* Subject-Submission-Identifier:
* [/PRMD=uk.ac/ADMD=gold 400/C=gb/;<1796.665941626@UK.AC.UCL.CS>]
* Content-Identifier: A useful mess...
* Recipient-Info: j.nosuchuser@dle.cambridge.DGC.gold-400.gb,
* /I=j/S=nosuchuser/OU=dle/O=cambridge/PRMD=DGC/ADMD=GOLD 400/C=GB/;
* FAILURE reason Unable-To-Transfer (1);
* diagnostic Unrecognised-ORName (0);
* supplementary info "DG 21187: (CEO POA) Unknown addressee.";
****** End of administration information
The Original Message is not available
5.3.9. Probe
This is an MTS internal issue. Any probe shall be serviced by
the gateway, as there is no equivalent RFC 822 functionality.
The value of the reply is dependent on whether the gateway could
service an MTS Message with the values specified in the probe.
The reply shall make use of MTS.SupplementaryInformation to
indicate that the probe was serviced by the gateway.
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Appendix A - Mappings Specific to SMTP
This Appendix is specific to the Simple Mail Transfer Protocol
(RFC 821). It describes specific changes in the context of this
protocol. When servicing a probe, as described in section 5.3.9,
use may be made of the SMTP VRFY command to increase the accuracy
of information contained in the delivery report.
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Appendix B - Mappings specific to the JNT Mail
This Appendix is specific to the JNT Mail Protocol. It
describes specific changes in the context of this
protocol.
1. Introduction
There are five aspects of a gateway which are JNT Mail Specific.
These are each given a section of this appendix.
2. Domain Ordering
When interpreting and generating domains, the UK NRS domain
ordering shall be used, both in headers, and in text generated
for human description.
3. Addressing
A gateway which maps to JNT Mail should recognise the Domain
Defined Attribute JNT-MAIL. The value associated with this
attribute should be interpreted according to the JNT Mail
Specification. This DDA shall never be generated by a gateway.
For this reason, the overflow mechanism is not required.
4. Acknowledge-To:
This field has no direct functional equivalent in X.400.
However, it can be supported to an extent, and can be used to
improve X.400 support.
If an Acknowledge-To: field is present when going from JNT
Mail to X.400, there are two different situations. The first
case is where there is one address in the Acknowledge-To: field,
and it is equal to the 822-MTS return address. In this case,
the
MTS.PerRecipientSubmissionFields.originator-request-report.report
shall be set for each recipient, and the Acknowledge-To: field
discarded. Here, X.400 can provide the equivalent service.
In all other cases two actions are taken.
1. Acknowledgement(s) may be generated by the gateway. The
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text of these acknowledgements shall indicate that they are
generated by the gateway, and do not correspond to delivery.
2. The Acknowledge-To: field shall be passed as an extension
heading.
When going from X.400 to JNT Mail, in cases where
MTA.PerRecipientMessageTransferFields.per-recipient-indicators.
originator-report bit is set for all recipients (i.e., there is a
user request for a positive delivery report for every recipeint),
generate an Acknowledge-To: field containing the
MTS.OtherMessageDeliveryFields.originator-name. Receipt
notification requests are not mapped onto Acknowledge-To:, as no
association can be guaranteed between IPMS and MTS level
addressing information.
5. Trace
JNT Mail trace uses the Via: syntax. When going from JNT Mail to
X.400, a mapping similar to that for Received: is used. No
MTS.GlobalDomainIdentifier of the site making the trace can be
derived from the Via:, so a value for the gateway is used. The
trace text, including the "Via:", is unfolded, truncated to
MTS.ub-mta-name-length (32), and mapped to
MTA.InternalTraceInformationElement.mta-name. There is no JNT
Mail specific mapping for the reverse direction.
6. Timezone specification
The extended syntax of zone defined in the JNT Mail Protocol
shall be used in the mapping of UTCTime defined in Chapter 3.
7. Lack of 822-MTS originator specification
In JNT Mail the default mapping of the
MTS.OtherMessageDeliveryFields.originator-name is to the Sender:
field. This can cause a problem when going from X.400 to JNT
Mail if the mapping of IPMS.Heading has already generated a
Sender: field. To overcome this, new extended JNT Mail field is
defined. This is chosen to align with the JNT recommendation for
interworking with full RFC 822 systems [Kille84b].
original-sender = "Original-Sender" ":" mailbox
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If an IPM has no IPMS.Heading.authorizing-users component and
IPMS.Heading.originator.formal-name is different from
MTS.OtherMessageDeliveryFields.originator-name, map
MTS.OtherMessageDeliveryFields.originator-name, onto the Sender:
field.
If an IPM has a IPMS.Heading.authorizing-users component, and
IPMS.Heading.originator.formal-name is different from
MTS.OtherMessageDeliveryFields.originator-name,
MTS.OtherMessageDeliveryFields.originator-name is mapped onto the
Sender: field, and IPMS.Heading.originator mapped onto the
Original-Sender: field.
In other cases the
MTS.OtherMessageDeliveryFields.originator-name, is already
correctly represented.
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Appendix C - Mappings specific to UUCP Mail
Gatewaying of UUCP and X.400 is handled by first gatewaying
the UUCP address into RFC 822 syntax (using RFC 976) and
then gatewaying the resulting RFC 822 address into X.400.
For example, an X.400 address
Country US
Organisation Xerox
Personal Name John Smith
might be expressed from UUCP as
inthop!gate!gatehost.COM!/C=US/O=Xerox/PN=John.Smith/
(assuming gate is a UUCP-ARPA gateway and gatehost.COM is an
ARPA-X.400 gateway) or
inthop!gate!Xerox.COM!John.Smith
(assuming that Xerox.COM and /C=US/O=Xerox/ are equivalent.)
In the other direction, a UUCP address Smith@ATT.COM, integrated
into 822, would be handled as any other 822 address. A non-integrated
address such as inthop!dest!user might be handled through a pair of
gateways:
Country US
ADMD ATT
PRMD ARPA
Organisation GateOrg
RFC-822 inthop!dest!user@gatehost.COM
or through a single X.400 to UUCP gateway:
Country US
ADMD ATT
PRMD UUCP
Organisation GateOrg
RFC-822 inthop!dest!user
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Appendix D - Object Identifier Assignment
An object identifier is needed for the extension IPMS element.
The following value shall be used.
rfc-987-88 OBJECT IDENTIFIER ::=
{ccitt data(9) pss(2342) ucl(234219200300) rfc-987-88(200)}
id-rfc-822-field-list OBJECT IDENTIFIER ::= {rfc987-88 field(1)}
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Appendix E - BNF Summary
boolean = "TRUE" / "FALSE"
numericstring = *DIGIT
printablestring = *( ps-char )
ps-restricted-char = 1DIGIT / 1ALPHA / " " / "'" / "+"
/ "," / "-" / "." / "/" / ":" / "=" / "?"
ps-delim = "(" / ")"
ps-char = ps-delim / ps-restricted-char
ps-encoded = *( ps-restricted-char / ps-encoded-char )
ps-encoded-char = "(a)" ; (@)
/ "(p)" ; (%)
/ "(b)" ; (!)
/ "(q)" ; (")
/ "(u)" ; (_)
/ "(l)" ; "("
/ "(r)" ; ")"
/ "(" 3DIGIT ")"
teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT
teletex-and-or-ps = [ printablestring ] [ "*" teletex-string ]
labelled-integer ::= [ key-string ] "(" numericstring ")"
key-string = *key-char
key-char = <a-z, A-Z, 0-9, and "-">
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object-identifier ::= oid-comp object-identifier
| oid-comp
oid-comp ::= [ key-string ] "(" numericstring ")"
encoded-info = 1#encoded-type
encoded-type = built-in-eit / object-identifier
built-in-eit = "Undefined" ; undefined (0)
/ "Telex" ; tLX (1)
/ "IA5-Text" ; iA5Text (2)
/ "G3-Fax" ; g3Fax (3)
/ "TIF0" ; tIF0 (4)
/ "Teletex" ; tTX (5)
/ "Videotex" ; videotex (6)
/ "Voice" ; voice (7)
/ "SFD" ; sFD (8)
/ "TIF1" ; tIF1 (9)
encoded-pn = [ given "." ] *( initial "." ) surname
given = 2*<ps-char not including ".">
initial = ALPHA
surname = printablestring
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std-or-address = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "RFC-822"
/ registered-dd-type
/ dd-key "." std-printablestring
standard-type = key-string
registered-dd-type
= key-string
dd-key = key-string
value = std-printablestring
std-printablestring
= *( std-char / std-pair )
std-char = <"{", "}", "*", and any ps-char
except "/" and "=">
std-pair = "$" ps-char
dmn-or-address = dmn-part *( "." dmn-part )
dmn-part = attribute "$" value
attribute = standard-type
/ "~" dmn-printablestring
value = dmn-printablestring
/ "@"
dmn-printablestring =
= *( dmn-char / dmn-pair )
dmn-char = <"{", "}", "*", and any ps-char
except ".">
dmn-pair = "\."
global-id = std-or-address
mta-field = "X400-Received" ":" x400-trace
/ "Deferred-Delivery" ":" date-time
/ "Latest-Delivery-Time" ":" date-time
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x400-trace = "by" md-and-mta ";"
[ "deferred until" date-time ";" ]
[ "converted" "(" encoded-info ")" ";" ]
[ "attempted" md-or-mta ";" ]
action-list
";" arrival-time
md-and-mta = [ "mta" mta "in" ] global-id
mta = word
arrival-time = date-time
md-or-mta = "MD" global-id
/ "MTA" mta
Action-list = 1#action
action = "Redirected"
/ "Expanded"
/ "Relayed"
/ "Rerouted"
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dr-body-format = dr-summary <CRLF>
dr-recipients <CRLF>
dr-administrator-info-envelope <CRLF>
dr-content-return
dr-content-return = "The Original Message is not available"
/ "The Original Message follows:"
/ "The Orginal Message is not returned with positive reports"
dr-summary = "This report relates to your message:" <CRLF>
content-correlator <CRLF> <CRLF>
"of" date-time <CRLF> <CRLF>
dr-recipients = *(dr-recipient <CRLF> <CRLF>)
dr-recipient = dr-recip-success / dr-recip-failure
dr-recip-success =
"Your message was successfully delivered to:"
mailbox "at" date-time
dr-recip-failure = "Your message was not delivered to:"
mailbox <CRLF>
"for the following reason:" *word
dr-administrator-info-envelope = 3*( "*" text <CRLF> )
dr-administrator-info =
"**** The following information is directed towards"
"the local administrator" <CRLF>
"**** and is not intended for the end user" <CRLF> <CRLF>
"DR generated by:" report-point <CRLF>
"at" date-time <CRLF> <CRLF>
"Converted to RFC 822 at" mta <CRLF>
"at" date-time <CRLF> <CRLF>
"Delivery Report Contents:" <CRLF> <CRLF>
drc-field-list <CRLF>
"***** End of administration information"
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drc-field-list = *(drc-field <CRLF>)
drc-field = "Subject-Submision-Identifier" ":"
mts-msg-id
/ "Content-Identifier" ":" printablestring
/ "Content-Type" ":" mts-content-type
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "Originator-and-DL-Expansion-History" ":"
dl-history
/ "Reporting-DL-Name" ":" mailbox
/ "Content-Correlator" ":" content-correlator
/ "Recipient-Info" ":" recipient-info
/ "Subject-Intermediate-Trace-Information" ":"
x400-trace
recipient-info = mailbox "," std-or ";"
report-type
[ "converted eits" encoded-info ";" ]
[ "originally intended recipient"
mailbox "," std-or ";" ]
[ "last trace" [ encoded-info ] date-time ";" ]
[ "supplementary info" <"> printablestring <"> ";" ]
[ "redirection history" 1#redirection ";"
[ "physical forwarding address"
printablestring ";" ]
report-type = "SUCCESS" drc-success
/ "FAILURE" drc-failure
drc-success = "delivered at" date-time ";"
[ "type of MTS user" labelled-integer ";" ]
drc-failure = "reason" labelled-integer ";"
[ "diagnostic" labelled-integer ";" ]
report-point = [ "mta" word "in" ] global-id
content-correlator = *word
dl-history = 1#( mailbox "(" date-time ")")
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mts-field = "X400-MTS-Identifier" ":" mts-msg-id
/ "X400-Originator" ":" mailbox
/ "X400-Recipients" ":" 1#mailbox
/ "Original-Encoded-Information-Types" ":"
encoded-info
/ "X400-Content-Type" ":" mts-content-type
/ "Content-Identifier" ":" printablestring
/ "Priority" ":" priority
/ "Originator-Return-Address" ":" 1#mailbox
/ "DL-Expansion-History" ":" mailbox ";" date-time ";"
/ "Conversion" ":" prohibition
/ "Conversion-With-Loss" ":" prohibition
/ "Requested-Delivery-Method" ":"
1*( labelled-integer )
/ "Delivery-Date" ":" date-time
/ "Discarded-X400-MTS-Extensions" ":"
1#( oid / labelled-integer )
prohibition = "Prohibited" / "Allowed"
mts-msg-id = "[" global-id ";" *text "]"
mts-content-type = "P2" / labelled-integer
/ object-identifer
priority = "normal" / "non-urgent" / "urgent"
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ipn-body-format = ipn-description <CRLF>
[ ipn-extra-information <CRLF> ]
ipn-content-return
ipn-description = ipn-receipt / ipn-non-receipt
ipn-receipt = "Your message to:" preferred-recipient <CRLF>
"was received at" receipt-time <CRLF> <CRLF>
"This notification was generated"
acknowledgement-mode <CRLF>
"The following extra information was given:" <CRLF>
ipn-suppl <CRLF>
ipn-non-receipt "Your message to:"
preferred-recipient <CRLF>
ipn-reason
ipn-reason = ipn-discarded / ipn-auto-forwarded
ipn-discarded = "was discarded for the following reason:"
discard-reason <CRLF>
ipn-auto-forwarded = "was automatically forwarded." <CRLF>
[ "The following comment was made:"
auto-comment ]
ipn-extra-information =
"The following information types were converted:"
encoded-info
ipn-content-return = "The Original Message is not available"
/ "The Original Message follows:"
<CRLF> <CRLF> message
preferred-recipient = mailbox
receipt-time = date-time
auto-comment = printablestring
ipn-suppl = printablestring
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discard-reason = "Expired" / "Obsoleted" /
"User Subscription Terminated"
acknowledgement-mode = "Manually" / "Automatically"
ipms-field = "Obsoletes" ":" 1#msg-id
/ "Expiry-Date" ":" date-time
/ "Reply-By" ":" date-time
/ "Importance" ":" importance
/ "Sensitivity" ":" sensitivity
/ "Autoforwarded" ":" boolean
/ "Incomplete-Copy" ":"
/ "Language" ":" language
/ "Message-Type" ":" message-type
/ "Discarded-X400-IPMS-Extensions" ":" 1#oid
importance = "low" / "normal" / "high"
sensitivity = "Personal" / "Private" /
"Company-Confidential"
language = 2*ALPHA [ language-description ]
language-description = printable-string
message-type = "Delivery Report"
/ "InterPersonal Notification"
/ "Multiple Part"
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redirect-comment =
[ "Originally To:" ] mailbox "Redirected"
[ "Again" ] "on" date-time
"To:" redirection-reason
redirection-reason =
"Recipient Assigned Alternate Recipient"
/ "Originator Requested Alternate Recipient"
/ "Recipient MD Assigned Alternate Recipient"
subject-line = "Delivery-Report" "(" status ")"
[ "for" destination ]
status = "success" / "failure" / "success and failures"
destination = mailbox / "MTA" word
extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "Content-Return" ":" prohibition
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Appendix F - Format of address mapping tables
1. Global Mapping Information
The consistent operation of gateways which follow this
specification relies of the existence of three globally defined
mappings:
1. Domain Name Space -> O/R Address Space
2. O/R Address Space -> Domain Name Space
3. Domain Name Space -> O/R Address of preferred gateway
All gateways conforming to this specification shall have access
to these mappings. The gateway may use standardised or private
mechanisms to access this mapping information.
One means of distributing this information is in three
files. This appendix defines a format for these files. Other
standardised mechanisms to distribute the mapping information are
expected. In particular, mechanisms for using the Domain Name
Scheme, and X.500 are planned.
The definition of global mapping information is being co-
ordinated by the COSINE-MHS project, on behalf of the Internet
and other X.400 and RFC 822 users. For information on accessing
this information contact:
COSINE MHS Project Team
SWITCH
Weinburgstrasse 18
8001 Zuerich
Switzerland
tel: +41 1 262 3143
fax: +41 1 262 3151
email:
C=ch;ADMD=arcom;PRMD=switch;O=switch;OU=cosine-mhs;S=project-team
or
project-team@cosine-mhs.switch.ch
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2. Syntax Definitions
An address syntax is defined, which is compatible with the syntax
used for 822.domains. By representing the O/R addresses as
domains, all lookups can be mechanically implemented as domain ->
domain mappings. This syntax defined is initially for use in
table format, but the syntax is defined in a manner which makes
it suitable to be adapted for use with the Domain Name Service.
This syntax allows for a general representation of O/R addresses,
so that it can be used in other applications. Not all attributes
are used in the table formats defined.
To allow the mapping of null attributes to be represented,
the pseudo-value "@" (not a printable string character) is used
to indicate omission of a level in the hierarchy. This is
distinct from the form including the element with no value,
although a correct X.400 implementation will interpret both in
the same manner.
This syntax is not intended to be handled by users.
dmn-or-address = dmn-part *( "." dmn-part )
dmn-part = attribute "$" value
attribute = standard-type
/ "~" dmn-printablestring
value = dmn-printablestring
/ "@"
dmn-printablestring =
= *( dmn-char / dmn-pair )
dmn-char = <"{", "}", "*", and any ps-char
except ".">
dmn-pair = "\."
An example usage:
~ROLE$Big\.Chief.ADMD$ATT.C$US
PRMD$DEC.ADMD$@.C$US
The first example illustrates quoting of a ".", and the second
omission of the ADMD level. There must be a strict ordering of
all components in this table, with the most significant
components on the RHS. This allows the encoding to be treated
as a domain.
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Various further restrictions are placed on the usage of
dmn-or-address in the address space mapping tables.
1. Only C, ADMD, PRMD, O, and up to four OUs may be used.
2. No components shall be omitted from this hierarchy, although
the hierarchy may terminate at any level. If the mapping is
to an omitted component, the "@" syntax is used.
3. Table Lookups
When determining a match, there are aspects which apply to all
lookups. Matches are always case independent. The key for all
three tables is a domain. The longest possible match shall be
obtained. Suppose the table has two entries with the following
keys:
K.L
J.K.L
Domain "A.B.C" will not return any matches. Domain "I.J.K.L"
will match the entry "J.K.L:.
4. Domain -> O/R Address format
The BNF is:
domain-syntax "#" dmn-or-address "#"
Note that the trailing "#" is used for clarity, as the dmn-or-
address syntax might lead to values with trailing blanks. Lines
staring with "#" are comments.
For example:
AC.UK#PRMD$UK\.AC.ADMD$GOLD 400.C$GB#
XEROX.COM#O$Xerox.ADMD$ATT.C$US#
GMD.DE#O$@.PRMD$GMD.ADMD$DBP.C$DE#
A domain is looked up to determine the top levels of an O/R
Address. Components of the domain which are not matched are used
to build the remainder of the O/R address, as described in
Section 4.3.4.
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5. O/R Address -> Domain format
The syntax of this table is:
dmn-or-address "#" domain-syntax "#"
For example:
#
# Mapping table
#
PRMD$UK\.AC.ADMD$GOLD 400.C$GB#AC.UK#
The O/R Address is used to generate a domain key. It is
important to order the components correctly, and to fill in
missing components in the hierarchy. Use of this mapping is
described in Section 4.3.2.
6. Domain -> O/R Address of Gateway table
This uses the same format as the domain -> O/R address mapping.
In this case, the two restrictions (omitted components and
restrictions on components) do not apply. Use of this mapping is
described in Section 4.3.4.
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Appendix G - Mapping with X.400(1984)
This appendix defines modification to the mapping for use with
X.400(1984).
The X.400(1984) protocols are a proper subset of
X.400(1988). When mapping from X.400(1984) to RFC 822, no
changes to this specification are needed.
When mapping from RFC 822 to X.400(1984), no use can be made
of 1988 specific features. No use of such features is made at
the MTS level. One feature is used at the IPMS level, and this
must be replaced by the RFC 987 approach. All header information
which would usually be mapped into the rfc-822-heading-list
extension, together with any Comments: field in the RFC 822
header is mapped into a single IA5 body part, which is the first
body part in the message. This body part will start with the
string "RFC-822-Headers:" as the first line. The headers then
follow this line. This specification requires correct reverse
mapping of this format, either from 1988 or 1984.
In an environment where RFC 822 is of major importance, it
may be desirable for downgrading to consider the case where the
message was originated in an RFC 822 system, and mapped according
to this specification. The rfc-822-heading-list extension may be
mapped according to this appendix.
When parsing std-or, the following restrictions must be
observed:
- Only the 84/88 attributes identified in the table in
Section 4.2 are present.
- No teletex encoding is allowed.
If an address violates this, it should be treated as an RFC 822
address, which will usually lead to encoding as a DDA "RFC-822".
It is possible that null attributes may be present in an O/R
Address. This is not legal in 1988, except for ADMD where the
case is explicitly described in Section 4.3.5. Null attributes
are deprecated (the attribute should be omitted), and should
therefore be unusual. However, some systems generate them and
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rely on them. Therefore, any null attribute shall be enoded
using the std-or encoding (e.g., /O=/).
If a non-Teletex Common Name (CN) is present, it should be
mapped onto a Domain Defined Attribute "Common". This is in line
with RFC XXXX on X.400 1988 to 1984 downgrading [Hardcastle-
K91a].
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Appendix H - RFC 822 Extensions for X.400 access
This appendix defines a number of optional mappings which may be
provided to give access from RFC 822 to a number of X.400
services. These mappings are beyond the basic scope of this
specification. There has been a definite demand to use extended
RFC 822 as a mechanism to acccess X.400, and these extensions
provide access to certain features. If this functionality is
provided, this appendix shall be followed. The following
headings are defined:
extended-heading =
"Prevent-NonDelivery-Report" ":"
/ "Generate-Delivery-Report" ":"
/ "Alternate-Recipient" ":" prohibition
/ "Disclose-Recipients" ":" prohibition
/ "Content-Return" ":" prohibition
Prevent-NonDelivery-Report and Generate-Delivery-Report allow
setting of
MTS.PerRecipientSubmissionFields.originator-report-request. The
setting will be the same for all recipients.
Alternate-Recipient, Disclose-Recipients, and Content-Return
allow for override of the default settings for
MTS.PerMessageIndicators.
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Appendix I - Conformance
This appendix defines a number of options, which a conforming
gateway should specify. Conformance to this specification shall
not be claimed if any of the mandatory features are not
implemented. In particular:
- Formats for all fields shall be followed.
- Formats for subject lines, delivery reports and IPNs shall
be followed. A system which followed the syntax, but
translated text into a language other than english would be
conformant.
- RFC 1137 shall not be followed when mapping to SMTP or to
JNT Mail
- All mappings of trace shall be implemented.
- There must be a mechanism to access all three global
mappings.
A gateway should specify:
- Which 822-MTS protocols are supported. The relevant
appendices must be followed to claim support of a given
protocol: SMTP (A); JNT Mail (B); UUCP (C).
- The means by which it can access the global mappings.
Currently, the tables of the formats define in Appendix F
is the only means available.
- The approach taken when upper bounds are exceeded at the IPM
level (5.1.3)
- The approach taken to return of contents (5.2)
- The approach taken to body parts which cannot be converted
(5.3.4)
- The approach taken to multiple copies vs non-disclosure
(4.6.2.2)
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The following are optional parts of this specification. A
conforming implementation should specify which of these it
supports.
- Support of X.400(1984), following Appendix G.
- Generation of extended RFC 822 fields is mandatory.
Optionally, they may be parsed and mapped back to X.400. A
gateway should should indicate if this is done.
- Support for the extension mappings of Appendix H.
- Support for the ordered OU mappings (OU1 etc.).
- Which address interpretation heuristics are supported
(4.3.4.1)
- If RFC 987 generated message ids are handled in a backwards
compatible manner (4.7.3.6)
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Appendix J - Change History: RFC 987, 1026, 1138, 1148
RFC 987 was the original document, and contained the key elements
of this specification. It was specific to X.400(1984). RFC 1026
specified a small number of necessary changes to RFC 987.
RFC 1138 was based on the RFC 987 work. It contained an
editorial error, and was reissued a few months later as RFC 1148.
RFC 1148 will be referred to here, as it is the document which is
widely referred to elsewhere. The major goal of RFC 1148 was to
upgrade RFC 987 to X.400(1988). It did this, but did not
obsolete RFC 987, which was recommended for use with X.400(1984).
This appendix summarises the changes made in going from RFC 987
to RFC 1148.
RFC 1148 noted the following about its upgrade from RFC 987:
Unnecessary change is usually a bad idea. Changes on the RFC 822
side are avoided as far as possible, so that RFC 822 users do
not see arbitrary differences between systems conforming to this
specification, and those following RFC 987. Changes on the X.400
side are minimised, but are more acceptable, due to the mapping
onto a new set of services and protocols.
1. Introduction
The model has shifted from a protocol based mapping to a service
based mapping. This has increased the generality of the
specification, and improved the model. This change affects the
entire document.
A restriction on scope has been added.
2. Service Elements
- The new service elements of X.400 are dealt with.
- A clear distinction is made between origination and
reception
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3. Basic Mappings
- Add teletex support
- Add object identifier support
- Add labelled integer support
- Make PrintableString <-> ASCII mapping reversible
- The printable string mapping is aligned to the NBS mapping
derived from RFC 987.
4. Addressing
- Support for new addressing attributes
- The message ID mapping is changed to not be table driven
5. Detailed Mappings
- Define extended IPM Header, and use instead of second body
part for RFC 822 extensions
- Realignment of element names
- New syntax for reports, simplifying the header and
introducing a mandatory body format (the RFC 987 header
format was unusable)
- Drop complex autoforwarded mapping
- Add full mapping for IP Notifications, defining a body
format
- Adopt an MTS Identifier syntax in line with the O/R Address
syntax
- A new format for X400 Trace representation on the RFC 822
side
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6. Appendices
- Move Appendix on restricted 822 mappings to a separate RFC
- Delete Phonenet and SMTP Appendixes
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Appendix K - Change History: RFC 1148 to this Document
1. General
- The scope of the document was changed to cover X.400(1984),
and so obsolete RFC 987.
- Changes were made to allow usage to connect RFC 822 networks
using X.400
- Text was tightened to be clear about optional and mandatory
aspects
- A good deal of clarification
- A number of minor EBNF errors
- Better examples are given
- Further X.400 upper bounds are handled correctly
2. Basic Mappings
- The encoding of object identifier is changed slightly
3. Addressing
- A global mapping of domain to preferred gateway is
introduced.
- An overflow mechanism is defined for RFC 822 addresses of
greater than 128 bytes
- Changes were made to improve compatability with the PDAM on
writing O/R Addresses.
+ The PD and Terminal Type keywords were aligned to the
PDAM. It is believed that minimal use has been made of
the RFC 1148 keywords.
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+ P and A are allowed as alternate keys for PRMD and ADMD
+ Where keywords are different, the PDAM keywords are
alternatives on input. This is mandatory.
4. Detailed Mappings
- The format of the Subject: lines is defined.
- Illegal use (repetition) of the heading EXTENSION is
corrected, and a new object identifier assigned.
- The Delivery Report format is extensively revised in light
of operational experience.
- The handling of redirects is significantly changed, as the
previous mechanism did not work.
5. Appendices
- An SMTP appendix is added, allowing optional use of the VRFY
command to improve probe information.
- Handling of JNT Mail Acknowledge-To is changed slightly.
- A DDA JNT-MAIL is allowed on input.
- The format definitions of Appendix F are explained further,
and a third table definition added.
- An appendix on use with X.400(1984) is added.
- Optional extensions are defined to give RFC 822 access to
further X.400 facilities.
- An appendix on conformance is added.
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SECURITY CONSIDERATIONS
Security considerations are not discussed in this RFC.
AUTHOR'S ADDRESS
Steve Kille
Department of Computer Science
University College London
Gower Street
WC1E 6BT
England
Phone: +44-71-380-7294
EMail: S.Kille@CS.UCL.AC.UK
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References
CCITT88a.
CCITT, "CCITT Recommendations X.408," Message Handling
Systems: Encoded Information Type Conversion Rules, December
1988.
CCITT/ISO88a.
CCITT/ISO, "CCITT Recommendations X.400/ ISO IS 10021-1,"
Message Handling: System and Service Overview , December
1988.
CCITT/ISO88b.
CCITT/ISO, "CCITT Recommendations X.420/ ISO IS 10021-7,"
Message Handling Systems: Interpersonal Messaging System,
December 1988.
CCITT/ISO88c.
CCITT/ISO, "CCITT Recommendations X.411/ ISO IS 10021-4,"
Message Handling Systems: Message Transfer System: Abstract
Service Definition and Procedures, December 1988.
CCITT/ISO88d.
CCITT/ISO, "Specification of Abstract Syntax Notation One
(ASN.1)," CCITT Recommendation X.208 / ISO IS 8824, December
1988.
CCITT/ISO91a.
CCITT/ISO, "Representation of O/R Addresses for Human
Usage," PDAM to CCITT X.401 / ISO/IEC 10021-2, February
1991.
Crocker82a.
D.H. Crocker, "Standard of the Format of ARPA Internet Text
Messages," RFC 822, August 1982.
Hardcastle-K91a.
S.E. Hardcastle-Kille, "X.400 1988 to 1984 downgrading," RFC
XXXXX, August 1991.
Horton86a.
M.R. Horton, "UUCP Mail Interchange Format Standard," RFC
976, February 1986.
Hardcastle-Kille [page 138]
Internet Draft
Mapping between X.400(1988) and RFC 822 November 1991
Kille84b.
S.E. Kille, "Gatewaying between RFC 822 and JNT Mail," JNT
Mailgroup Note 15, May 1984.
Kille84a.
S.E. Kille (Editor), JNT Mail Protocol (revision 1.0), Joint
Network Team, Rutherford Appleton Laboratory, March 1984.
Kille86a.
S.E. Kille, "Mapping Between X.400 and RFC 822," UK Academic
Community Report (MG.19) / RFC 987, June 1986.
Kille87a.
S.E. Kille, "Addendum to RFC 987," UK Academic Community
Report (MG.23) / RFC 1026, August 1987.
Kille89a.
S.E. Kille, "A String Encoding of Presentation Address," UCL
Research Note 89/14, March 1989.
Kille89b.
S.E. Kille, "Mapping between full RFC 822 and RFC 822 with
restricted encoding," RFC 1137, October 1989.
Kille90a.
S.E. Kille, "Mapping Between X.400(1988) / ISO 10021 and RFC
822," RFC 1148, March 1990.
Larmouth83a.
J. Larmouth, "JNT Name Registration Technical Guide,"
Salford University Computer Centre, April 1983.
Postel84a.
J. Postel and J. Reynolds, "Domain Requirements," RFC 920,
October 1984.
Postel82a.
J.B. Postel, "SIMPLE MAIL TRANSFER PROTOCOL," RFC 821,
August 1982.
Rose85a.
M.T. Rose and E.A. Stefferud, "Proposed Standard for Message
Encapsulation," RFC 934, January 1985.
Hardcastle-Kille [page 139]
Internet Draft
Mapping between X.400(1988) and RFC 822 November 1991
Systems85a.
CEN/CENELEC/Information Technology/Working Group on Private
Message Handling Systems, "FUNCTIONAL STANDARD A/3222,"
CEN/CLC/IT/WG/PMHS N 17, October 1985.
Hardcastle-Kille [page 140]