Latest Delivery Designation
Not supported. A new RFC822 header (Latest-Delivery-Time:) is
provided, which may be used by the recipient for general
information, but will not be acted on by the SMTP infrastrucuture.
Message Flow Confidentiality
Not supported.
Message Origin Authentication
N/A (reception).
Message Security Labelling
Not supported.
Message Sequence Integrity
Not supported.
Multi-Destination Delivery Supported.
Multi-part Body
Supported.
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 RFC822 header (Supersedes:).
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 RFC822 header (X400-
Recipients:), associated with the recipient in question.
Physical Forwarding Prohibited
Supported by use of a comment in a new RFC822 header (X400-
Recipients:), associated with the recipient in question.
Prevention of Non-delivery notification
Supported where SMTP and NOTARY are available. In other cases
formally supported, as delivery notifications cannot be generated
by RFC822. 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 Disallowed by Originator
Redirection means MTS supported redirection, in the manner of
X.400. This service does not exist in the RFC822 world. RFC822
redirection (e.g., aliasing) is regarded as an informal
redirection mechanism, beyond the scope of this control. Messages
will be sent to RFC822, irrespective of whether this service is
requested. In practice, control of this service is not supported.
Registered Mail
N/A (PDAU).
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 service request is 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
Supported where SMTP and NOTARY are used. In principle for other
situations, this is N/A, as non-delivery notifications are not
supported. In practice, most RFC822 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 RFC822 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).
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 RFC822 lists,
this service can be regarded as supported.
Auto-Submitted Indication
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 RFC822 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 RFC822 originated mail by an X.400 UA.
Authorising User's Indication
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 X.400 service "RFC822 Header Field" is defined using the
extension facilities. This allows for any RFC822 header field to be
represented. It may be present in RFC822 originated messages which
are received by an X.400 UA.
Chapter 3 Basic Mappings
3.1. Notation
The X.400 protocols are encoded in a structured manner according to
ASN.1, whereas RFC822 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. RFC822
Structured text is defined according to the Extended Backus Naur Form
(EBNF) defined in Section 2 of RFC822 [16]. In the EBNF definitions
used in this specification, the syntax rules given in Appendix D of
RFC822 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 RFC822 messages (or of SMTP
components). 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.importance).
2. To describe the structure of IA5 or ASCII information not in
an RFC822 message.
For all new EBNF, 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 RFC822 rules.
- Around the ":" in all headers
- EBNF.labelled-integer
- EBNF.object-identifier
- EBNF.encoded-info
RFC822 folding rules are applied to all headers. Comments are never
used in these new headers.
This notation is used in a modified form to refer to NOTARY EBNF
[28]. For this EBNF, the keyword EBNF it replaces with DSN, for
example DSN.final-recipient-field fields.
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.
TA MTAAbstractService defined in Section 13 of X.411 / ISO 10021-4.
FTBP File Transfer Body Part, as defined in [27].
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] .
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 [14]. 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
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, there are two options, both
of which are conformant to this specification:
1. The mappings to IA5 defined in ITU-T Recommendation X.408
(1988) may be used [13]. These will then be encoded in
ASCII. This is the approach mandated in RFC1327.
2. This mapping may be used if the characters are not contained
within ASCII repertoire, but are all in an IANA-registered
character set. Use the encoding defined in RFC1522 [9] to
generate appropriate encoded-words. If this mapping is
used, the character set ISO-8859-1 shall be used if all of
the characters needed are available in this repertoire. In
other cases, the character set TELETEX shall be used. The
details of this character set is defined in the Appendix C
of RFC2157.
There is also a need to represent Teletex Strings in ASCII, for some
aspects of OR Address. For these, the following encoding is used:
teletex-string = *( ps-char / t61-encoded )
t61-encoded = "{" 1* t61-encoded-char "}"
t61-encoded-char = 3DIGIT
Characters in EBNF.ps-char are mapped simply. Other octets,
including control characters, are mapped using a quoting mechanism
similar to the printable string mechanism. Each octet is represented
as 3 decimal digits. For example, the Yen character (hex A5) is
represented as {165}. As the three character string, a, yen
character, b, would be represented as either "a{165}b".
The use of escape sequences follows that set down for ASN1. in ISO
8825-1, with the additional specifiction that the default G1 page is
ISO Latin 1. The page settings may be changed by escape sequences.
Changes of the settings hold within a pair of curly brackets ({}),
and the settings revert to the default after the right bracket (})
(i.e., they do not carry forward to subsequent T.61 encoding).
There are a number of places where a string may have a Teletex and/or
Printable String representation. The following EBNF 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. An example is:
"yen*{165}"
3.3.5. UTCTime
Both UTCTime and the RFC822 822.date-time syntax contain: Year,
Month, Day of Month, hour, minute, second (optional), and Timezone
(technically a time differential in UTCTime). 822.date-time also
contains an optional day of the week, but this is redundant. With
the exception of Year, 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. Such errors may be noted in an RFC822
comment, to aid detection and correction.
When mapping to X.400, the UTCTime format which specifies the
timezone offset shall be used.
When mapping to RFC822, the 822.date-time format shall include a
numeric timezone offset (e.g., -0500).
When mapping time values, the timezone shall be preserved as
specified. The date shall not be normalised to any other timezone.
RFC822, as modified by RFC1123, requires use of a four digit year.
Note that the original RFC822 uses a two digit date, which is no
longer legal. UTCTime uses a two digit date. To map a year from RFC
822 to X.400, simply use the last two digits. To map a year from
X.400 to RFC822, assume that the two digit year refers to a year in
the 10 year epoch 1980-2079.
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, a text label may be
added. It is recommended that this is done wherever possible and
that clear text labels are chosen.
A second encoding labelled-integer-2 is provided. This is used in
DSNs, where the parsing rules will treat the text as a comment. This
definition was not present in RFC1327.
labelled-integer ::= [ key-string ] "(" numericstring ")"
labelled-integer-2 ::= [ numericstring ] "(" key-string ")"
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)
Because of the use of brackets and the conflict with the RFC822
comment convention, MIXER is defines so that the EBNFobject-
identifier definition is not used in structured fields.
3.4. Encoding ASCII in Printable String
Some information in RFC822 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 shall 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 RFC822
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 shall only be used in cases where the
printable strings have been 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. 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) <-> (
3.5. RFC1522
RFC1522 defines a mechanism for encoding other character set
information into elements of RFC822 Headers. A gateway may ignore
this encoding and treat the elements as ASCII.
A preferred approach is for the gateway to interpret the RFC1522
encoding. This will not always be straightforward, because:
1. RFC1522 permits an openly extensible character set choice,
which may be broader than T.61.
2. It is not always possible to map all characters into the
equivalent X.400 field.
RFC1522 is only applied to fields which are "for information only".
A gateway which interprets header elements according to RFC1522 may
apply reasonable heuristics to minimise information loss.
Chapter 4 - Addressing and Message IDs
Addressing is the most complex aspect of X.400 <-> RFC822 gateway
and is therefore given a separate chapter. This chapter also
discusses message identifiers, as they are closely linked to
addresses. This chapter, as a side effect, also defines a textual
representation of an X.400 OR Address. This specification has much
similarity to the X.400(92) representation of addresses. This was
because early versions of this specification were a major input to
this work. This specification retains compatibility with earlier
versions. The X.400 specification of address representation can be
parsed but is not generated.
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
RFC822 address is defined by the EBNF EBNF.822-address:
822-address = [ route ] addr-spec
These definitions are taken from RFC822. In SMTP (or another 822-
MTS protocol), the originator and each recipient are considered to be
defined by such a construct. In an RFC822 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 OR Address, used by the MTS for routing, is defined
by MTS.ORAddress. In IPMS, the MTS.ORAddress is encapsulated within
IPMS.ORDescriptor.
The RFC822 822.address is mapped with IPMS.ORDescriptor, and that
RFC822 EBNF.822-address is mapped with MTS.ORAddress.
Section 4.1 defines a textual representation of an OR Address, which
is used throughout the rest of this specification. This text
representation is designed to represent an X.400 address in the LHS
(left hand side) or local part of an RFC822 address, and so this
representation gives a mechanism to represent X.400 addresses within
RFC822 addresses.
Section 4.2 describes global equivalence mapping between parts of the
X.400 and RFC822 name spaces, and defines the concept of a MIXER
Conformant Global Address Mapping (MCGAM). Gateways conforming to
this specification shall support MCGAMs.
Section 4.3 is the core part of this chapter, and defines the mapping
mechanism.
4.1. A textual representation of MTS.ORAddress
MTS.ORAddress is structured as an ordered set of attributes
(type/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.
4.1.1. Basic OR Address Representation
An OR 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 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
attribute key 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. The attribute key table
follows:
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 P 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.DomainDefineAttribute.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
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 UPA 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
UPA upa-string
I labelled-integer
X presentation-address
The EBNF for presentation-address is taken from the specification RFC
1278 "A String Encoding of Presentation Address" [23].
In most cases, the EBNF encoding maps directly to the ASN.1 encoding
of the attribute. There are a few exceptions. In cases where an
attribute can be encoded as either a PrintableString or NumericString
(Country, ADMD, PRMD), either form is mapped into the EBNF. When
generating ASN.1, the NumericString encoding shall be used if the
string contains digits and 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 example:
/CN=yen*{165}/
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.
If there is teletex attribute or teletex component only, and it
contains only characters in the printable string character set, it
shall be represented in the EBNF as if it had been encoded as
printable string. A single printable string representation shall
also be done when both forms are present and they have the same
printable string representation.
The Unformatted Postal Address has a slightly more complex mapping
onto a variant of (teletex-and-or-ps), defined as:
upa-string = [ printable-upa ] [ "*" teletex-string ]
printable-upa = printablestring *( "|" printablestring )
The optional teletex part is straightforward. There is an (optional)
sequence of printable strings which are mapped in order. For
example:
/PD-ADDRESS=The Dome|The Square|Richmond|England/
X.400 (1992) has introduced a string representation of OR Addresses
(see F.401, Annex B). This has specified a number of string keywords
for attributes. As earlier versions of this specification were an
input to this work, many of the keywords are the same. To increase
compatibility, the following alternative values shall be recognised
when mapping from RFC822 to X.400. These shall not be generated
when mapping from X.400 to RFC822. The following keyword
alternative table and the subsequent paragraph lists alternative
keywords.
Keyword Alternative
ADMD A
PRMD P
GQ Q
X121 X.121
UA-ID N-ID
PD-OFFICE-NUM PD-OFFICE NUMBER
PD-OFFICE-NUM PD-OFN
PD-EXT-ADDRESS PD-EA
PD-EXT-DELIVERY PD-ED
PD-OFFICE PD-OF
PD-STREET PD-S
PD-UNIQUE PD-U
PD-LOCAL PD-L
PD-RESTANTE PD-R
PD-BOX PD-B
PD-CODE PD-PC
PD-SERVICE PD-SN
DD DDA
NET-NUM E.164
NET-PSAP PSAP
PD-ADDRESS PD-A
When mapping from RFC822 to X.400, the keywords defined in this
paragraph shall be recognized. The ordered 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. PD-A1, PD-A2, PD-A3, PD-A4, PD-A5, PD-A6 shall be
treated as ordered lines. If present, these will be assembled
with separating line feeds to form a single physical address. In
this case PD-ADDRESS (or PD-A) shall not be present. Similarly,
there are ordered keywords for domain defined attributes: DD1,
DD2, DD3, DD4,
If ISDN is present, it may be interpreted as an E.163/164
address, using local heuristics to parse the string. X.400
defines the key, but does not give an interpretation of the
value.
For T-TY (Terminal Type), the X.400 recommended values are
preferred, but other values are allowed. These values are: tlx
(3); ttx (4); g3fax (5); g4fax (6); ia5 (7); and vtx (8).
4.1.2. Encoding of Personal Name
Handling of Personal Name and Teletex Personal Name is a common
requirement. Therefore MIXER defines an alternative to the
EBNF.standard-type syntax, which utilises the "human" conventions for
encoding these components. A syntax is defined, which is designed to
provide a clean encoding for the common cases of OR Address
specification where:
1. There is no generational qualifier
2. Initials, if present, contain only letters
3. Given Name, if present, 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 OR address personal name. To map from a string to
OR 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 OR address which follows the above restrictions, a string is
derived in the natural manner. In this case, the 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 suggests that Initials is used to encode all initials
except the surname (X.402 section 18.3.12). 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.
4.1.3. Standard Encoding of MTS.ORAddress
Given this structure, we can specify an EBNF representation of an OR
Address. The output format of addresses is defined by EBNF.std-or-
address. The more flexible input format is defined by EBNF.std-or-
address-input. The input EBNF has been added subsequent to RFC1327,
to reflect the formal incorporation of a number of heuristics. The
address element separator on input may be "/", ";", or a mixture of
these. The output format is used in all examples.
std-or-address = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "RFC-822"
/ dd-key "." std-printablestring
std-or-address-input = [ sep pair ] sep pair *( sep pair )
sep [ pair sep ]
sep = "/" / ";"
pair = input-attribute "=" value
input-attribute = attribute
/ dd-key ":" std-printablestring
standard-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 = "$" ps-char
For address generation, the standard-type is any key defined in the
key table in Section 4.1, except PN, and DD. For address parsing,
other key values from Section 4.1 are also valid. The EBNF leads to
a set of attribute/value pairs. The value is interpreted according to
the EBNF encoding defined in the table.
If the standard-type is PN, the value is interpreted according to
EBNF.encoded-pn, and the components of MTS.PersonalName and/or
MTS.TeletexPersonalName derived accordingly.
If dd-key is the recognised Domain Defined string (DD) or one of the
alternatives defined in Section 4.1, then the type and value are
interpreted according to the syntax implied from the encoding, and
aligned to either the teletex or printable string form. Key and
value shall have the same encoding.
If value is "RFC-822", then the (printable string) Domain Defined
Type of "RFC-822" is assumed. This is an optimised encoding of the
domain defined type defined by this specification.
The matching of all keywords shall be done in a case-independent
manner.
EBNF.std-or-address uses the characters "/" and "=" as delimiters.
Domain Defined Attributes and any value may contain these characters.
A quoting mechanism, using the non-printable string "$" is used to
allow these characters to be represented.
If an address of this syntax is parsed, and a country value is
present, but no ADMD, the string shall be interpreted as if an ADMD
value of single space had been specified.
4.2. Global Address Mapping
From a user perspective, the ideal mapping 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
impossible.
2 There is insufficient administrative co-operation between
the X.400 and RFC822 name registration authorities for this
to work.
Another way to view this situation is to see that there is not a full
global equivalence between X.400 and RFC822 addressing. To meet
user needs to the extent possible, this specification provides for
equivalence where there is sufficient co-operation. To be useful,
this equivalence shall be recognised and interpreted in the same way
by all gateways. Therefore, an asymmetrical mapping is defined,
which can be symmetrical where there is appropriate administrative
co-operation. Section 4.3 describes the asymetrical aspects. This
section describes a mechanism to enable the administrative co-
ordination for symmetrical mappings.
In order to achieve a symmetrical mapping there is a need to define
an administrative equivalence between parts of the OR Address and
Domain namespaces. Previous version of this specification did this
by definition of a global set of mappings. MIXER defines the concept
of a MIXER Conformant Global Address Mapping (MCGAM). This acronym
is defined so that it is very clear what is being referenced.
The X.400 and Internet Mail address spaces are hierarchical. It is
possible to define an equivalence between two points in the
hierarchies, such that addresses below that point can be derived in
an algorithmic manner. An MCGAM is a mapping from a point in one
hierarchy to a point in the other hierarchy. An "MGGAM pair" is a
pair of symmetrical mappings between two points. To define an MCGAM,
the following shall apply:
1. The authority defining the MCGAM shall have responsibility
for BOTH of the namespaces between which the MCGAM is
defined.
2. The authority defining the MCGAM is responsible to ensure
that addresses allocated below the two equivalence points
conform to the rules set out below.
3. The authority defining the MCGAM is responsible to ensure
that addresses which are generated according to the MCGAM
are routed correctly.
In general, MCGAMs will be independent. In some cases, a set of
MCGAMs may be related (e.g., where one MCGAM defines a mapping for an
organization and a second MCGAM defines an excpetion for a subtree
within the organization). In this case, the related set of MCGAMs
shall be treated as a single MCGAM for distribution purposes.
The existence of an MCGAM does not imply routability and access for
all users.
The authority defining an MCGAM may simply use this mapping locally.
This will often be the case in a "local scenario" gateway. Because
of third party addressing, a MIXER gateway will work best with the
maximum number of MCGAMs. Therefore, three mechanisms are defined
to enable publication and exchange of MCGAMs:
1. Distribution of text tables. This is described in Appendix
F of this specification.
2. Distribution by Domain Name Service. This is described in
RFC2163 [3].
3. Distribution by X.500 Directory Service. This is defined
in RFC2164 [26].
The following sections define how the MCGAM namespace equivalence is
modelled. The Internet Domain Namespace defines a simple hierarchy.
For the purposes of this mapping, only parts of the namespace where
domains conform to the EBNF domain-syntax are allowed.
domain-syntax = alphanum [ *alphanumhyphen alphanum ]
alphanum = <ALPHA or DIGIT>
alphanumhyphen = <ALPHA or DIGIT or HYPHEN>
Although RFC822 allows for a more general syntax, this restricted
syntax is used in MIXER as it is the one chosen by the various domain
service administrations. In practice, it reflects all RFC822 usage.
The following OR Address attributes are considered as a hierarchy,
and may be specified by the domain. They are (in order of the
hierarchy defined by MIXER):
Country, ADMD, PRMD, Organization, Organizational Units
There may be up to four ordered Organizational Units. This
hierarchy reflects most usage of X.400, although X.400 may be used in
other ways. In particular, it covers the Mnemonic OR Address using a
1984 compatible encoding. This is seen as the dominant form of OR
Address. MCGAMs may only be used when this hierarchy applies.
An equivalence mapping is defined between two nodes in the respective
hierarchies. For example:
=> "AC.UK" might be mapped with
PRMD="UK.AC", ADMD="GOLD 400", C="GB"
The mapping identifies that the management of these points in the
respective hierarchies is the same (or co-operate very closely). The
equivalence means that the namespaces below this equivalence point
map 1:1, except where the mapping is overridden by further
equivalence mappings lower down the hierarchy. This equivalence may
be achieved in three ways:
1. All of the nodes below this point are RFC822, and the MIXER
mapping defines the X.400 addresses for these nodes.
2. All of the nodes below this point are X.400, and the MIXER
mapping defines the RFC822 addresses for these nodes.
3. There are X.400 and RFC822 nodes below this point, and
addressing is managed in a manner which ensures the
equivalence. The rules to achieve this are defined by
MIXER.
Each of these ways gives a framework for MCGAM definition.
When an MCGAM is defined, a systematic mapping for the inferior nodes
in the two hierarchies follows. This is a 1:1 mapping between the
nodes in the subtrees. For example, given the MCGAM pair defined
above:
the domain "R-D.Salford.AC.UK" algorithmically maps with
OU="R-D", O="Salford", PRMD="UK.AC", ADMD="GOLD 400", C="GB"
Note that when an equivalence is defined, that this can be re-defined
for lower points in the hierarchy. However, it is not possible to
declare contained subtrees to be un-mappable.
The equivalence mapping also provides a mechanism to deal with
missing elements in the X.400 hierarchy (most commonly the PRMD,
which is the only element that may be ommitted when conforming to
recent versions of X.400). 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 there is an MCGAM pair between domain HNE.EGM" and "O=HNE",
"ADMD=ECQ", "C=TC", and omitted PRMD
then
"ZI.HNE.EGM" is algorithmically mapped with "OU=I", "O=HNE",
"ADMD=ECQ", "C=TC"
Attributes may have null values, and this is treated separately from
omitted attributes (while it is not ideal to make this distinction,
it is useful in practice).
4.2.1. Directory and Nameserver Mappings
When a set of MCGAMs are supported by X.500 or DNS, there is the
possibility that results will be indeterminate due to timeout.
Lookup shall be repeated until a value is determined, in order to
maintain consistent gateway operation.
Where the mapping relates to an envelope address, the gateway shall
non-deliver messages according to the associated MTA's normal timeout
policy. Where the mapping relates to addresses in the message
header, there shall be a timeout in the range of 1-4 hours or shorter
if this is required to maintain quality of service constraints. If
a mapping cannot be done in this time, address encapsulation shall be
used.
4.3. EBNF.822-address <-> MTS.ORAddress
This section defines the basic address mapping.
4.3.1. X.400 encoded in RFC822
This section defines how X.400 addresses are represented in RFC822
addresses.
The std-or-address syntax is used to encode OR Address information
in the 822.local-part of EBNF.822-address. Where there is an
applicable equivalence mapping, further OR 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 OR 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 RFC822 set, by restrictions
imposed by domain conventions and policy [10], and by the EBNF
definition in SMTP.
A generic 822.address consists of a 822.local-part and a 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 RFC822 world, and will
not be interpreted by the gateway (although they may have identified
the gateway from within the RFC822 world).
The 822.domain associated with the 822.local-part identifies the
gateway from within the RFC822 world. This final 822.domain may be
used to determine some number of OR Address attributes, where this
does not conflict with the first role. RFC822 routing to gateways
will usually be set up to facilitate the 822.domain being used for
both purposes.
In the case that there is no applicable equivalence mapping, all of
the X.400 address is encoded in the 822.local-part and the 822.domain
identifies the gateway to which the message is being sent. This
technique may be used by the RFC822 user for any X.400 address where
the equivalence mapping is not known.
In the case that there is an applicable MCGAM, the maximum number of
attributes are encoded in the 822.domain. The remaining attributes
are encoded on the LHS, using the EBNF.std-or-address syntax. For