As per Relevance of the word identifier, we have this rfc below:
Network Working Group S.
Request for Comments: 1838 ISODE
Category: Experimental August 1995
Use of the X.500 Directory to support mapping between X.400
and RFC 822
Status of this
This memo defines an Experimental Protocol for the
community. This memo does not specify an Internet standard of
kind. Discussion and suggestions for improvement are requested
Distribution of this memo is unlimited
This document defines how to use directory to support the
between X.400 O/R Addresses and mailboxes defined in RFC 1327 [2].
1. X.400/RFC 822
RFC 1327 defines an algorithm for maintaining a global
between X.400 and RFC 822 addresses directory [2]. RFC 1327
defines a table based mechanism for maintaining this mapping.
is substantial benefit to maintaining this mapping within
directory. In particular, this will lead to an approach for
the mapping which is both distributed and scalable
Mechanisms for representing O/R Address and Domain hierarchies
the DIT are defined in [1, 5]. These techniques are used to
two independent subtrees in the DIT, which contain the
information. The benefits of this approach are
1. The mapping information is kept in a clearly defined area
can be widely replicated in an efficient manner. The tree
constrained to hold only information needed to support
mapping. This is important as gateways need good access to
entire mapping
2. It facilitates migration from the currently deployed table-
approach
3. It handles the issues of "missing components" in a
manner
Kille Experimental [Page 1]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
An alternative approach which is not taken is to locate
information in the routing subtrees. The benefits of
would be
o It is the "natural" location, and will also help
ensure correct administrative authority for a
definition
o The tree will usually be accessed for routing, and so
will be efficient for addresses which are being routed
This is not done, as the benefits of the approach
are greater
There are three mappings, which are represented by two
located under
OU=X.400/RFC 822 Mapping, O=
These subtree roots are of object class subtree, and use
mechanism for representing subtrees defined in [4].
X.400 to RFC 822 This table gives the equivalence mapping from X.400
to RFC 822. There is an O/R Address tree under this. An
entry is
PRMD=UK.AC, ADMD=Gold 400, C=GB, CN=X.400 to RFC 822,
OU=X.400/RFC 822 Mapping, O=
RFC 822 to X.400 There is a domain tree under this. This table
the equivalence mapping from RFC 822 to X.400, and the
mapping defined in RFC 1327. An example entry is
DomainComponent=ISODE, DomainComponent=COM
CN=RFC 822 to X.400,
OU=X.400/RFC 822 Mapping, O=
The values of the table mapping are defined by use of two new
classes, as specified in Figure 1. The objects give pointers to
mapped components
Kille Experimental [Page 2]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
2. Omitted
In RFC 1327, it is possible to have omitted components in O/
Addresses on either side of the mapping. A mechanism to
such omitted components is defined in Figure 2.
The attribute at-or-address-component-type is set to the X.500
attribute type associated with the omitted component (e.g., at-prmd
name). This mechanism is for use only within the X.400 to RFC 822
subtree and for the at-associated-or-address attribute
-----------------------------------------------------------------------
rFC822ToX400Mapping OBJECT-CLASS ::= {
SUBCLASS OF {domain-component
MAY CONTAIN {
associatedORAddress
associatedX400Gateway
ID oc-rfc822-to-x400-mapping
x400ToRFC822Mapping OBJECT-CLASS ::= {
SUBCLASS OF {top
MAY CONTAIN { 10
associatedDomain
ID oc-x400-to-rfc822-mapping
associatedORAddress ATTRIBUTE ::= {
SUBTYPE OF
SINGLE
ID at-associated-or-address
20
associatedX400Gateway ATTRIBUTE ::= {
SUBTYPE OF mhs-or-
MULTI
ID at-associated-x400-gateway
associatedDomain ATTRIBUTE ::= {
SUBTYPE OF
WITH SYNTAX caseIgnoreIA5
SINGLE
ID at-associated-domain} 30
Figure 1: ObjectClasses for RFC 1327
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RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
-----------------------------------------------------------------------
omittedORAddressComponent OBJECT-CLASS ::=
SUBCLASS OF {top
MUST Contain {
}
ID oc-omitted-or-address-component
oRAddressComponentType ATTRIBUTE ::= {
SUBTYPE OF objectIdentifier 10
SINGLE
ID at-or-address-component-type
Figure 2: Omitted O/R Address
3. Mapping from X.400 to RFC 822
As an example, consider the mapping from the O/R Address
P=UK.AC; A=Gold 400; C=
This would be keyed by the directory entry
PRMD=UK.AC, ADMD=Gold 400, C=GB, CN=X.400 to RFC 822,
OU=X.400/RFC 822 Mapping, O=
and return the mapping from the associatedDomain attribute,
gives the domain which this O/R address maps to. This attribute
used to define authoritative mappings, which are placed in the
community tree. The manager of an RFC 1327 mapping shall make
appropriate entry
Functionally, mapping takes place exactly according to RFC 1327.
longest match is found by the following algorithm
1. Take the O/R Address, and derive a directory name. This will
the O/R Address as far as the lowest OU
2. Look up the entire name derived from the RFC 1327 key in the
the X.400 to RFC 822 subtree. This lookup will either succeed
or it will fail and indicate the longest possible match,
can then be looked up
3. Check for an associatedDomain attribute in the matched entry
Kille Experimental [Page 4]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
The mapping can always be achieved with two lookups
Because of the availability of aliases, some of the table
may be simplified. In addition, the directory can support
from addresses using the numeric country codes
4. Mapping from RFC 822 to X.400
There is an analogous structure for mappings in the
direction. The domain hierarchy is represented in the DIT
to RFC 1279. The domain
AC.
Is represented in the DIT as
DomainComponent=AC, DomainComponent=UK, CN=RFC 822 to X.400,
OU=X.400/RFC 822 Mapping, O=
This has associated with it the attribute associatedORAddress
as a distinguished name with a value
PRMD=UK.AC, ADMD=Gold 400, C=
The "table 3" mapping defined in RFC 1327 [2] is provided by
associatedX400Gateway attribute. This value may identify
possible associated gateways. This information is looked up at
same time as mapped O/R addresses. In effect, this provides
fallback mapping, which is found if there is no equivalence mapping
Because of the nature of the mapping a domain will map to either
gateway or a domain, but not both. Thus, there shall never be
an associatedX400Gateway and associatedORAddress attribute present
the same entry. Functionally, mapping takes place exactly
to RFC 1327. The longest match is found by the following algorithm
1. Derive a directory name from the domain part of the RFC 822
address
2. Look up this name in the RFC 822 to X.400 subtree to find
mapped value (either associatedORAddress
associatedX400Gateway.). If the lookup fails, the error
indicate the longest match, which can then be looked up
If associatedORAddress is found, this will define the mapped O/
Address. The mapping can always be achieved with two lookups. If
associatedX400Gateway is present, the address in question will
encoded as a domain defined attribute, relative to the O/R
defined by this attribute. If multiple associatedX400
Kille Experimental [Page 5]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
attributes are found, the MTA may select the one it chooses to use
Because of the availability of aliases, some of the table
may be simplified. In addition, the directory can support
from addresses using the numeric country codes
5.
Acknowledgements for work on this document are given in [3].
[1] Kille, S. "X.500 and Domains", RFC 1279,
Department of Computer Science, University College London
November 1991.
[2] Kille, S., "Mapping between X.400(1988)/ISO 10021 and RFC 822",
RFC 1327, Department of Computer Science, University
London, May 1992.
[3] Kille, S., "MHS Use of the X.500 Directory to Support
Routing", RFC 1801, ISODE Consortium, June 1995.
[4] Kille, S., "Representing Tables and Subtrees in the X.500
Directory", RFC 1837, ISODE Consortium, August 1995.
[5] Kille, S., "Representing the O/R Address Hierarchy in the X.500
Directory Information Tree", RFC 1836, ISODE Consortium,
1995.
6. Security
Security issues are not discussed in this memo
Kille Experimental [Page 6]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
7. Author's
Steve
ISODE
The
The
TW9 1
Phone: +44-81-332-9091
Internet EMail: S.Kille@ISODE.
X.400: I=S; S=Kille; O=ISODE Consortium; P=ISODE
A=Mailnet; C=FI
UFN: S. Kille, ISODE Consortium,
Kille Experimental [Page 7]
RFC 1838 RFC 822/X.400 Mapping by X.500 August 1995
A Object Identifier
-----------------------------------------------------------------------
mhs-ds OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1)
private(4) enterprises(1) isode-consortium (453) mhs-ds (7)}
mapping OBJECT IDENTIFIER ::= {mhs-ds 4}
oc OBJECT IDENTIFIER ::= {mapping 1}
at OBJECT IDENTIFIER ::= {mapping 2}
oc-rfc822-to-x400-mapping OBJECT IDENTIFIER ::= {oc 1} 10
oc-x400-to-rfc822-mapping OBJECT IDENTIFIER ::= {oc 2}
oc-omitted-or-address-component OBJECT IDENTIFIER ::= {oc 3}
at-associated-or-address OBJECT IDENTIFIER ::= {at 6}
at-associated-x400-gateway OBJECT IDENTIFIER ::= {at 3}
at-associated-domain OBJECT IDENTIFIER ::= {at 4}
at-or-address-component-type OBJECT IDENTIFIER ::= {at 7}
Figure 3: Object Identifier
Kille Experimental [Page 8]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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