brian@sdcsvax.UCSD.EDU (Brian Kantor) (11/16/87)
---
RFC 987 June 1986
Mapping between X.400 and RFC 822
4.1. A textual representation of P1.ORName.
P1.ORName is structured as a set of attribute value pairs. It is
clearly necessary to be able to encode this in ASCII for
gatewaying purposes. A general encoding is given here, which may
be used as a basis for a user interface, as well as for the
defined gateway mapping.
4.1.1. Basic Representation
A series of BNF definitions of each possible attribute value
pair is given, which is given a 1:1 mapping with the X.400
encoding. The rest of the mapping then talks in terms of these
BNF components, with the mapping to X.400 encoding being
trivial.
attributevalue = c / admd / prmd / x121 / t-id / o / ou
/ ua-id / pn.g / pn.i / pn.s / pn.gq / dd.value
c = printablestring ; P1.CountryName
admd = printablestring ; P1.AdministrationDomainName
prmd = printablestring ; P1.PrivateDomainName
x121 = numericstring ; P1.X121Address
t-id = numericstring ; P1.TerminalID
o = printablestring ; P1.OrganisationName
ou = printablestring ; P1.OrganisationalUnit
ua-id = numericstring ; P1.UniqueUAIdentifier
pn.s = printablestring ; P1.PersonalName.surName
pn.g = printablestring ; P1.PersonalName.givenName
pn.i = printablestring ; P1.PersonalName.initials
pn.gq = printablestring ; P1.PersonalName.generation
Qualifier
dd.value = printablestring ; P1.DomainDefined
Attribute.value
In cases where an attribute can be encoded as either a
PrintableString or NumericString (Country, ADMD, PRMD) it is
assumed that the NumericString encoding will be adopted if
possible. This prevents the encoding of PrintableString where
the characters are all numbers. This restriction seems
preferable to the added complexity of a general solution.
Similarly, we can define a set of attribute types.
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dd.type = printablestring ; P1.DomainDefinedAttribute.type
standard-type =
"C" ; P1.CountryName
/ "ADMD" ; P1.AdministrationDomainName
/ "PRMD" ; P1.PrivateDomainName
/ "X121" ; P1.X121Address
/ "T-ID" ; P1.TerminalID
/ "O" ; P1.OrganisationName
/ "OU" ; P1.OrganisationalUnit
/ "UA-ID" ; P1.UniqueUAIdentifier
/ "S" ; P1.PersonalName.surName
/ "G" ; P1.PersonalName.givenName
/ "I" ; P1.PersonalName.initials
/ "GQ" ; P1.PersonalName.generationQualifier
standard-dd-type =
"RFC-822" ; dd.type = "RFC-822"
/ "JNT-Mail" ; dd.type = "JNT-Mail"
/ "UUCP" ; dd.type = "UUCP"
4.1.2. Encoding of Personal Name
Handling of 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 proposed here. It is
designed to cope with the common cases of O/R Name
specification where:
1. There is no generational qualifier
2. Initials contain only letters <7>.
3. Given Name does not contain full stop ("."), and is at
least two characters long.
4. If Surname contains full stop, then it may not be in
the first two characters, and either initials or given
name is present.
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Mapping between X.400 and RFC 822
The following EBNF is defined:
encoded-pn = [ given "." ] *( initial "." ) surname
given = 2*<ps-char not including ".">
initial = ALPHA
surname = printablestring
Subject to the above restriction, this is a reversible mapping.
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 CCITT guidelines suggest that Initials is used to
encode ALL initials. Therefore, the proposed 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!
4.1.3. Two encodings of P1.ORName
Given this structure, we can specify a BNF representation of an
O/R Name.
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Mapping between X.400 and RFC 822
std-orname = 1*( "/" attribute "=" value ) "/"
attribute = standard-type
/ "PN"
/ standard-dd-type
/ registered-dd-type
/ "DD." std-printablestring
value = std-printablestring
registered-dd-type
= std-printablestring
std-printablestring =
= *( std-char / std-pair )
std-char = <ps-delim, and any ps-char except "/"
and "=">
std-pair = "$" ( ps-delim / ps-char )
If the type is PN, the value is interpreted according to
EBNF.encoded-pn, and the components of P1.PersonalName derived
accordingly. If the value is registered-dd-type, if the value
is registered at the SRI NIC as an accepted Domain Defined
Attribute type, then the value should be interpreted
accordingly. This restriction maximises the syntax checking
which can be done at a gateway.
Another syntax is now defined. This is intended to be
compatible with the syntax used for 822.domains. This syntax
is not intended to be handled by users.
dmn-orname = dmn-part *( "." dmn-part )
dmn-part = attribute "$" value
attribute = standard-type
/ "~" dmn-printablestring
value = dmn-printablestring
dmn-printablestring =
= *( dmn-char / dmn-pair )
dmn-char = <ps-delim, and any ps-char except ".">
dmn-pair = "\."
For example: C$US.ADMD$ATT.~ROLE$Big\.Chief
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Mapping between X.400 and RFC 822
4.2. Mapping between EBNF.822-address and P1.ORName
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.
4.2.1. X.400 encoded in RFC 822
The std-orname syntax is used to encode O/R Name information
in the 822.local-part of EBNF.822-address. Further O/R Name
information may be associated with the 822.domain component.
This cannot be used in the general case, basically due to
character set problems, and lack of order in X.400 O/R Names.
The only way to encode the full PrintableString character set
in a domain is by use of the 822.domain-ref syntax. 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.
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)
should be 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 may
also identify the gateway from within the RFC 822 world. This
final 822.domain may be used to determine some number of O/R
Name attributes. The following O/R Name 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
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Mapping between X.400 and RFC 822
There may be multiple Organisational Units.
Associations may be defined between domain specifications, and
some set of attributes. This association proceeds
hierarchically: i.e. if a domain implies ADMD, it also implies
country. If one of the hierarchical components is omitted from
an X.400 structure, this information can be associated with the
corresponding domain (e.g. a domain can be mapped onto a
Country/ADMD/Organisation tuple). Subdomains under this are
associated according to the O/R Name hierarchy. For example:
=> "AC.UK" might be associated with
C="234", ADMD="BT", PRMD="DES"
then domain "R-D.Salford.AC.UK" maps with
C="234", ADMD="BT", PRMD="DES", O="Salford", OU="R-D"
There are two 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:
domain-syntax = ALPHA [ *alphanumhyphen alphanum ]
alphanum = <ALPHA or DIGIT>
alphanumhyphen = <ALPHA or DIGIT or HYPHEN>
Although RFC 822 allows for a more general syntax, this
restriced syntax is chosen as it is the one chosen by the
various domain service administrations.
This provides a general aliasing mechanism.
This set of mappings need only be known by the gateways
relaying between the RFC 822 world, and the O/R Name namespace
associated with the mapping in question. However, it is
desirable (for the optimal mapping of third party addresses)
for all gateways to know these mappings. A format for the
exchange of this information is defined in Appendix F.
From the standpoint of the RFC 822 Message Transfer System, the
domain specification is simply used to route the message in the
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standard manner. The standard domain mechanisms are used to
identify gateways, and are used to select appropriate gateways
for the corresponding O/R Name namespace. In most cases, this
will be done by registering the higher levels, and assuming
that the gateway can handle the lower levels.
As a further mechanism to simplify the encoding of common
cases, where the only attributes to be encoded on the LHS are
Personal Name attributes which comply with the restrictions of
4.2.2, the 822.local-part may be encoded as EBNF.encoded-pn.
An example encoding is:
/PN=J.Linnimouth/GQ=5/@Marketing.Xerox.COM
encodes the P1.ORName consisting of
P1.CountryName = "US"
P1.AdministrationDomainName = "ATT"
P1.OrganisationName = "Xerox"
P1.OrganisationalUnit = "Marketing"
P1.PersonalName.surName = "Linnimouth"
P1.PersonalName.initials = "J"
P1.PersonalName.GenerationQualifier = "5"
If the GenerationQualifier was not present, the encoding
J.Linnimouth@Marketing.Xerox.COM could be used.
Note that in this example, the first three attributes are
determined by the domain Xerox.COM. The OrganisationalUnit is
determined systematically.
There has been an implicit assumption that an RFC 822 domain is
either X.400 or RFC 822. This is pragmatic, but undesirable,
as the namespace should be structured on a logical basis which
does not necessarily correspond to the choice of Message
Transfer protocols. The restriction can be lifted, provided
that the nameservice deals with multiple message transfer
protocols. This can happen in a straightforward manner for the
UK NRS, as explained in [Kille86a]. It could also be achieved
with the DARPA Domain Nameserver scheme by use of the WKS
mechanism.
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Mapping between X.400 and RFC 822
4.2.2. 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
domains.
The general case is mapped by use of domain defined attributes.
Three are defined, according to the full environment used to
interpret the RFC 822 information.
1. Domain defined type "RFC-822". This string is to be
interpreted in the context of RFC 822, and RFC 920
[Crocker82a,Postel84a].
2. Domain defined type "JNT-Mail". This string is to be
interpreted in the context of the JNT Mail protocol,
and the NRS [Kille84a,Larmouth83a].
3. Domain defined type "UUCP". This is interpreted
according to the constraints of the UUCP world
[Horton86a].
These three are values currently known to be of use. Further
recognised values may be defined. These will be maintained in
a list at the SRI Network Information Center.
Other O/R Name attributes will be used to identify a context in
which the O/R Name will be interpreted. This might be a
Management Domain, or some part of a Management Domain which
identifies a gateway MTA. For example:
1)
C = "GB"
ADMD = "BT"
PRMD = "AC"
"JNT-Mail" = "Jimmy(a)UK.CO.BT-RESEARCH-LABS"
2)
C = "US"
ADMD = "Telemail"
PRMD = "San Fransisco"
O = "U Cal"
OU = "Berkeley"
"RFC-822" = "postel(a)usc-isib.arpa"
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Mapping between X.400 and RFC 822
Note in each case the PrintableString encoding of "@" as "(a)".
In the first example, the "JNT-Mail" domain defined attribute
is interpreted everywhere within the (Administrative or
Private) Management Domain. In the second 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.
4.2.3. 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 should proceed as follows, by first assuming case
1).
STAGE 1.
1. If the 822-address is not of the form:
local-part "@" domain
go to stage 2.
2. Attempt to parse domain as:
*( domain-syntax "." ) known-domain
Where known-domain is the longest possible match in a
list of gatewayed domains. If this fails, and the domain
does not explicitly identify the local gateway, go to
stage 2. If it succeeds, allocate the attributes
associated with EBNF.known-domain, and systematically
allocate the attributes implied by each
EBNF.domain-syntax component.
3. Map 822.local-part to ASCII, according to the
definition of Appendix A. This step should be applied:
A. If the source network cannot support
822.quoted-string (as discussed in Appendix A).
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B. If the address is an 822-P1 recipient.
This mapping is always applied in case B, as it
increases the functionality of the gateway, and does
not imply any loss of generality. Mapping case B
allows sites which cannot generate 822.quoted-string
to address recipients the gateway, without the gateway
having to know this explicitly. There is no loss of
functionality, as the quoting character of Appendix A
(#) is not in PrintableString. This seems desirable.
It should not be applied in to other addresses, as a
third party RFC#822 address containing the sequence
EBNF.atom-encoded (as defined in Appendix A) would be
transformed asymmetrically.
4. Map the result of 3) to EBNF.ps-encoded according to
section 3.
5. Parse the result of 4) according to the EBNF
EBNF.std-orname. If this parse fails, parse the result
of 4) according to the EBNF EBNF.encoded-pn. If this
also fails, go to stage 2. Otherwise, the result is a
set of type/value pairs.
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 2.
7. Ensure that the set of attributes conforms both to the
X.411 P1.ORName specification and to the restrictions
on this set given in X.400. If not go to stage 2.
8. Build the O/R Name from this information.
STAGE 2.
This will only be reached if the RFC 822 EBNF.822-address is
not a valid X.400 encoding. If the address is an 822-P1
recipient address, it must be rejected, as there is a need to
interpret such an address in X.400. For the 822-P1 return
address, and any addresses in the RFC 822 header, they should
now be encoded as RFC 822 addresses in an X.400 O/R Name:
1. Convert the EBNF.822-address to PrintableString, as
specified in chapter 3.
2. The domain defined attribute ("RFC-822", "JNT-Mail" or
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Mapping between X.400 and RFC 822
"UUCP") appropriate to the gateway should be selected,
and its value set.
3. Build the rest of the O/R Name in the local Management
Domain agreed manner, so that the O/R Name will receive
a correct global interpretation.
4.2.4. 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 P1 Recipient O/R Name is interpreted, gatewaying will be
selected if there a single special domain defined attribute
present ("RFC-822", "JNT-Mail" or "UUCP"). In this case, use
mapping A. For other O/R Names which
1. Contain the special attribute.
AND
2. Identify the local gateway with the other attributes.
Use mapping A. In other cases, use mapping B.
Mapping A
1. Map the domain defined attribute value to ASCII, as
defined in chapter 3.
2. Where appropriate (P1 recipients), interpret the string
according to the semantics implied by the domain
defined attribute.
Mapping B.
This will be used for X.400 addresses which do not use the
explicit RFC 822 encoding.
1. Noting the hierarchy specified in 4.3.1, determine the
maximum set of attributes which have an associated
domain specification. If no match is found, allocate
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Mapping between X.400 and RFC 822
the domain as the domain specification of the local
gateway, and go to step 4.
2. Following the 4.3.1 hierarchy, if each successive
component exists, and conforms to the syntax
EBNF.domain-syntax (as defined in 4.3.1), allocate the
next subdomain.
3. If the remaining components are personal-name
components, conforming to the restrictions of 4.2.2,
then EBNF.encoded-pn should be derived to form
822.local-part. In other cases the remaining
components should simply be encoded as a 822.local-part
using the EBNF.std-orname syntax. Where registered
domain defined types exist, the DD. syntax should not
be used.
4. If this step is reached for an 822-P1 recipient, then
the address is invalid. For other addresses, if the
derived 822.local-part can only be encoded by use of
822.quoted-string, the gateway may optionally use the
ASCII to 822.local-part mapping defined in Appendix A,
dependent on the mail protocols of the networks being
relayed to. Use of this encoding is discouraged.
4.3. Repeated Mappings
The mappings defined are symmetrical across a single gateway,
except in certain pathological cases (see chapter 3). However, it
is always possible to specify any valid address across a gateway.
This 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 names 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.
However, the syntax may be used to source route.
For example: X.400 -> RFC 822 -> X.400
C = "UK"
ADMD = "BT"
PRMD = "AC"
"JNT-Mail" = "/PN=Duval/DD.Title=Manager/(a)FR.PTT.Inria"
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Mapping between X.400 and RFC 822
This will be sent to an arbitrary UK Academic Community gateway
by X.400. Then by JNT Mail to another gateway determined by
the domain FR.PTT.Inria. This will then derive the X.400 O/R
Name:
C = "FR"
ADMD = "PTT"
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
/C=UK/ADMD=BT/PRMD=AC/RFC-822=jj#l#a#r#seismo.css.gov/
@monet.berkeley.edu
The second case uses the Appendix A encoding to avoid
822.quoted-text. 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.
4.4. The full P1 / 822-P1 mapping
There are two basic mappings at the P1 level:
1. 822-P1 return address <-> P1.UMPDUEnvelope.originator
2. 822-P1 recipient <-> P1.RecipientInfo
822-P1 recipients and return addresses are encoded as
EBNF.822-address. As P1.UMPDUEnvelope.originator is encoded as
P1.ORName, mapping 1) has already been specified.
P1.RecipientInfo contains a P1.ORName and additional information.
The handling of this additional information is now specified.
4.4.1. RFC 822 -> X.400
The following default settings should be made for each
component of P1.RecipientInfo.
P1.ExtensionIdentifier
This can be set systematically by the X.400 system.
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P1.RecipientInfo.perRecipientFlag
Responsibility Flag should be set. Report Request should
be set according to content return policy, as discussed
in section 5.3. User Report Request should be set to
Basic.
P1.ExplicitConversion
This optional component should be omitted.
4.4.2. X.400 -> RFC 822
The mapping only takes place in cases where
P1.RecipientInfo.perRecipientFlag Responsibility Flag is set.
The following treatment should be given to the other
P1.RecipientInfo components.
P1.ExtensionIdentifier
Not used.
P1.RecipientInfo.perRecipientFlag
If ReportRequest is Confirmed or Audit-and-Confirmed then
a delivery report indicating success should be sent by
the gateway. This report should use each
P1.ReportedRecipientInfo.SupplementaryInformation to
indicate the identity of the gateway, and the nature of
the report (i.e. only as far as the gateway). Failures
will be handled by returning RFC 822 messages, and so
User Report Request set to No report is ignored.
P1.ExplicitConversion
If present, the O/R name should be rejected, unless the
requested conversion can be achieved. None of the
currently recognised values of this parameter are
appropriate to a gateway using this specification.
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4.5. The full P2 / RFC 822 mapping
All RFC 822 addresses are assumed to use the 822.mailbox syntax.
This should include all 822.comments associated with the lexical
tokens of the 822.mailbox. All P2.ORNames are encoded within the
syntax P2.ORDescriptor, or P2.Recipient (or within Message IDs).
An asymmetrical mapping is defined between these components.
4.5.1. RFC 822 -> X.400
The following sequence is followed.
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 P2.ORName as described above.
2. A string should be built consisting of (if present):
- The 822.phrase component if it is a 822.phrase
822.route-addr construct.
- Any 822.comments, in order, retaining the
parentheses.
This string should then be encoded into T.61 (as
described in chapter 3). If the string is not null,
it should be assigned to P2.ORDescriptor.freeformName.
3. P2.ORDescriptor.telephoneNumber should be omitted.
4. In cases of converting to P2.Recipient,
P2.Recipient.replyRequest and
P2.Recipient.reportRequest should be omitted.
If the 822.group construct is present, each included
822.mailbox should be encoded as above. The 822.group should
be mapped to T.61, and a P2.ORDesciptor with only a
freeformName component built from it.
4.5.2. X.400 -> RFC 822
In the basic case, where P2.ORName is present, proceed as
follows.
1. Encode P2.ORName as EBNF.822-address.
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2a. If P2.ORDescriptor.freeformName is present, convert it
to ASCII (chapter 3), and use use this as the
822.phrase component of 822.mailbox using the
822.phrase 822.route-addr construct.
2b. If P2.ORDescriptor.freeformName 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 should be added.
3. If P2.ORDescriptor.telephoneNumber is present, this
should be placed in a trailing 822.comment.
4. If P2.Recipient.reportRequest has the
receiptNotification bit set, then an 822.comment
"(Receipt Notification Requested)" should be appended
to the address. The effort of correlating P1 and P2
information is too great to justify the gateway sending
Receipt Notifications.
5. If P2.Recipient.replyRequest is present, an 822.comment
"(Reply requested)" or "(Reply not requested)" should
be appended to the address, dependent on its value.
If P2.ORName is absent, P2.ORDescriptor.freeformName should be
converted to ASCII, and used with the RFC 822 822.group syntax:
freeformname ":" ";"
Steps 3-5 should then be followed.
4.6. Message IDs
There is a need to map both ways between 822.msg-id and
P2.IPMessageID. A mapping is defined which is symmetrical for
non-pathological cases. The mapping allows for the fact that
P2.IPMessageID.PrintableString is mandatory for the Cen/Cenelec
profile. This allows for good things to happen when messages pass
multiple times across the X.400/RFC 822 boundary. A mapping
between 822.msg-id and P1.MPDUIdentifier is defined. This allows
for X.400 error messages to reference an RFC 822 ID, which is
preferable to a gateway generated ID.
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4.6.1. P2.IPMessageID -> 822.msg-id
P2.IPMessageID.ORName is used to generate an 822.addr-spec, as
defined above. P2.IPMessageID.PrintableString is mapped to
ASCII, as defined in chapter 3. This string (if it is present
and if the value is not "RFC-822") is appended to the front of
the 822.local-part of the 822.msg-id, with "*" as a separator.
If no ORName is present, an 822.msg-id of the form
"PrintableString*@gateway-domain" is generated.
4.6.2. 822.msg-id -> P2.IPMessageID
822.local-part is parsed as:
[ printablestring "*" ] real-local-part
If EBNF.printablestring is found, it is mapped to
PrintableString, and used as P2.IPMessageID.PrintableString.
Otherwise
P2.IPMessageID.PrintableString is set to "RFC-822". This
arbitrary value allows for conformance to Cen/Cenelec. If
EBNF.real-local-part is not present, no P2.IPMessageID.ORName
is generated. Otherwise, 822.local-part is replaced with
EBNF.real-local-part, and 822.addr-spec is mapped to
P2.IPMessageID.ORName as defined above.
4.6.3. 822.msg-id -> P1.MPDUIdentifier
P1.CountryName is assigned to "", P1.AdministrationDomainName
to 822.domain (from 822.msg-id) and P1.MPDUIdentifier.IA5String
to 822.local-part (from 822.msg-id).
4.6.4. P1.MPDUIdentifier -> 822.msg-id
822.local-part is set to P1.MPDUIdentifier.IA5String, with any
CRLF mapped to SPACE. If P1.CountryName is "", 822.domain is
set to P1.AdministrationDomainName; Otherwise to
P1.AdministrationDomainName ".." P1.CountryName. If there are
any specials, the domain literal encoding should be used.
Kille [Page 38]
RFC 987 June 1986
Mapping between X.400 and RFC 822
Chapter 5 -- Protocol Elements
This chapter gives 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. This chapter is structured as
follows:
5.1. Basic RFC 822 -> X.400 mappings
5.2. A definition of some new RFC 822 elements, and their mapping
to X.400.
5.3 Some special handling associated with Return of Contents.
5.4. X.400 -> RFC 822
5.1. RFC 822 -> X.400
First, the basic functions of an 822-P1 protocol should be mapped
as follows:
822-P1 Originator
Mapped to P1.UMPDUEnvelope.originator (see chapter 4).
822-P1 Recipient
Mapped to P1.RecipientInfo (see chapter 4).
The RFC 822 headers are used to generate both a P1.UMPDUEnvelope
and a P2.Heading. The IP Message will have either one or two
P2.BodyParts which will be type P2.IA5Text with no
P2.IA5Text.repertoire component. The last P2.BodyPart will contain
the RFC 822 message body. If there are any RFC 822 headers which
indicate mapping into the P2.BodyPart, then two P2.BodyParts are
generated. If a revised version of P2 allowed for extensible
header specification, this would be seen as a preferable mapping.
The first body part will start with the line:
RFC-822-Headers:
The rest of this body part will contain all of the headers not
otherwise mapped (both 822.field-name and 822.field-body). The
order of any such headers should be preserved. Similarly,
ordering within P2.Heading and P1.UMPDUEnvelope should reflect
ordering within the RFC 822 header. No P1 or P2 optional fields
are generated unless specified.
Kille [Page 39]
RFC 987 June 1986
Mapping between X.400 and RFC 822
A pro-forma X.400 message is now specified. Some of these
defaults may be changed by the values in the RFC 822 message being
mapped. The mandatory P1 and P2 components have the following
defaults.
P1.MPDUIdentifier
The default should be unique value generated by the gateway.
P1.OriginatorORName
Always generated from 822-P1.
P1.ContentType
P1.ContentType.p2
P1.RecipientInfo
These will always be supplied from 822-P1.
P1.Trace
The last P1.TraceInformation component is generated such
that: P1.TraceInformation.GlobalDomainIdentifier is set to
the local vaglue. P1.DomainSuppliedInfo.action is set to
relayed. P1.DomainSuppliedInfo.arrival is set to the current
time. P1.DomainSuppliedInfo.previous may be set if there is
anything sensible to set it to.
P2.IPMessageID
The default should be a unique value generated by the
gateway.
The following optional parameters should be set:
P1.PerMessageFlag
The P1.PerMessageFlag.contentReturnRequest bit should be set
according to the discussion in section 5.3. The
P1.PerMessageFlag.alternateRecipientAllowed bit should be
set, as it seems desirable to maximise opportunity for
(reliable) delivery.
Kille [Page 40]
RFC 987 June 1986
Mapping between X.400 and RFC 822
The RFC 822 headings should be mapped as follows:
Received:
Fudged onto P1.TraceInformation (try not to grimace too
much). P1.DomainSuppliedInfo.action is set to relayed.
P1.DomainSuppliedInfo.arrival is set to the date-time
component P1.TraceInformation.GlobalDomainIdentifier has
P1.CountryName as a null string, and
P1..AdministrationDomainName as the domain of the receiving
host (if present - null string if not).
P1.DomainSuppliedInfo.previous has P1.CountryName as a null
string, and P1.AdministrationDomainName has the domain of
the sending host with all other information enclosed in
round parentheses. The encoding of ASCII to PrintableString
(chapter 3) should be used if needed. For example:
Received: from 44e.cs.ucl.ac.uk by vax2.Cs.Ucl.AC.UK
with SMTP id a002110; 18 Dec 85 10:40 GMT
maps to -
P1.GlobalDomainIdentifier
CountryName = ""
AdministrationDomainName = "vax2.Cs.Ucl.AC.UK"
P1.DomainSuppliedInfo
arrival = 18 Dec 85 10:40 GMT
action = relayed
previous
CountryName = ""
AdministrationDomainName =
"44e.cs.ucl.ac.uk (with SMTP id a002110)"
Date:
This is used to set the first component of
P1.TraceInformation. The mandatory components are set as
follows:
P1.GlobalDomainIdentifier
CountryName = ""
AdministrationDomainName = ""
P1.DomainSuppliedInfo
arrival = time derived from Date:
action = relayed
No optional fields are used in the trace.
Kille [Page 41]
RFC 987 June 1986
Mapping between X.400 and RFC 822
Message-Id:
Mapped to P2.IPMessageID. If the RFC 822 message does not
contain a P1-Message-ID: field, the Message-Id: field is
also mapped to P1.MPDUIdentifier. For these, and all other
fields containing msg-id the mappings of chapter 4 are used
for each msg-id.
From:
If Sender: is present, this is mapped to
P2.AuthorisingUsers. If not, it is mapped to P2.Originator.
For this, and other components containing addresses, the
mappings of chapter 4 are used for each address.
Sender:
Mapped to P2.Originator.
Reply-To:
Mapped to P2.Heading.replyToUsers.
To:
Mapped to P2.Heading.primaryRecipients
Cc:
Mapped to P2.Heading.copyRecipients.
Bcc:
Mapped to P2.Heading.blindCopyRecipients.
In-Reply-To:
Mapped to P2.Heading.inReplyTo for the first (if any)
822.msg-id component. If the field contains an 822.phrase
component, or there are multiple 822.msg-id components, the
ENTIRE field is passed in the P2.BodyPart.
References:
Mapped to P2.Heading.crossReferences.
Kille [Page 42]