RFC relevance of identifier

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Network Working Group S.
Request for Comments: 2164 Isode Ltd
Obsoletes: 1838 January 1998
Category: Standards

Use of an X.500/LDAP directory to support MIXER address

Status of this

This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited

Copyright

Copyright (C) The Internet Society (1998). All Rights Reserved

1 MIXER X.400/RFC 822

MIXER (RFC 2156) defines an algorithm for use of a set of
mapping between X.400 and RFC 822 addresses [4]. This
defines how to represent and maintain these mappings (
Conformant Global Address Mappings of MCGAMs) in an X.500 or
directory. Mechanisms for representing OR Address and
hierarchies within the DIT are defined in [5, 2]. These
are used to define two independent subtrees in the DIT, which
the mapping 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 a table-based approach

3. It handles the issues of "missing components" in a
manner

An alternative approach which is not taken is to locate
information in the routing subtrees. The benefits of
would be

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

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 proposed
greater

MCGAMs are global. A MIXER gateway may use any set of MCGAMs. A
use of the directory is to enable MIXER gateways to share MCGAMs
to share the effort of maintaining and publishing MCGAMs.
specification and MIXER also recognise that there is not a
unique location for publication of all MCGAMs. This
allows for multiple sets of MCGAMs to be published. Each set
MCGAMs is published under a single part of the directory. There
four mappings, which are represented by two subtrees located
any part of the DIT. For the examples the location defined below
used

OU=MIXER MCGAMs, O=Zydeco Plc, C=

These subtree roots are of object class subtree, and use
mechanism for representing subtrees defined in [1].

X.400 to RFC 822 This table gives the equivalence mapping from X.400
to RFC 822. There is an OR Address tree under this. An
entry is

PRMD=Isode, ADMD=Mailnet, C=FI, CN=X.400 to RFC 822,
OU=MIXER MCGAMs, O=Zydeco Plc, C=

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=MIXER MCGAMs, O=Zydeco Plc, C=

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

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

2 Omitted

In MIXER, it is possible to have omitted components in OR
on either side of the mapping. A mechanism to represent such
components is defined in Figure 2. The attribute at-or-address
component-type is set to the X.500 attribute type associated with
omitted component (e.g.,

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
associatedInternetGateway
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

associatedInternetGateway ATTRIBUTE ::= {
SUBTYPE OF
WITH SYNTAX caseIgnoreIA5
MULTI
ID at-associated-internet-gateway

Figure 1: Object Classes for MIXER

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

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 OR Address

at-prmd-name). This mechanism is for use only within the X.400
RFC 822 subtree and for the at-associated-or-address attribute

3 Mapping from X.400 to RFC 822

As an example, consider the mapping from the OR Address

P=Isode; A=Mailnet; C=

This would be keyed by the directory entry

PRMD=Isode, ADMD=Mailnet, C=FI, CN=X.400 to RFC 822,
OU=MIXER MCGAMs, O=Zydeco Plc, C=

and return the mapping from the associatedDomain attribute,
gives the domain which this OR address maps to. This attribute
used to define authoritative mappings, which are placed in the
community tree. The manager of an MCGAM shall make the
entry

The Internet gateway mapping defined in MIXER[4] is provided by
associatedInternetGateway attribute. This value may
multiple possible associated gateways. This information is looked
at the same time as mapped OR addresses. In effect, this provides
fallback mapping, which is found if there is no equivalence mapping
Because of the nature of the mapping an OR Address will map to
a gateway or a domain, but not both. Thus, there shall never be

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

an associatedDomain and associatedInternetGateway attribute
in the same entry. Functionally, mapping takes place
according to MIXER. The longest match is found by the
algorithm

1. Take the OR Address, and derive a directory name. This will
the OR Address as far as the lowest OU

2. Look up the entire name derived from the MIXER key in the in
X.400 to RFC 822 subtree. This lookup will either succeed, or
will fail and indicate the longest possible match, which can
be looked up

3. Check for an associatedDomain or
attribute in the matched entry

The mapping can always be achieved with two lookups. Because of
availability of aliases, some of the table mappings may
simplified. In addition, the directory can support mapping
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

ISODE.

Is represented in the DIT as

DomainComponent=ISODE, DomainComponent=COM, CN=RFC 822 to X.400,
OU=MIXER MCGAMs, O=Zydeco Plc, C=

This has associated with it the attribute associatedORAddress
as a distinguished name with a value: PRMD=Isode, ADMD=Mailnet, C=

The X.400 gateway mapping defined in MIXER[4] is provided by
associatedX400Gateway attribute. This value may identify
possible associated gateways. This information is looked up at
same time as mapped OR 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 MIXER. The longest match is found by the following algorithm

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

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
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 OR
defined by this attribute. If multiple associatedX400
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 Gateway Selection of

The directory information to support identification of MCGAMs
given in Figure 3. A MIXER gateway simply identifies the an
lists of MCGAM collections that it will use for lookup. These
referenced by name. A gateway is not required to use any MCGAMs
Where MCGAMs are accessed from multiple sources, it is
that all of the sources be accessed in order to determine the
which gives

mixerGateway OBJECT-CLASS ::=
KIND
SUBCLASS OF {mhs-message-transfer-agent
MUST Contain {

}
ID oc-mixer-gateway

mcgamTables ATTRIBUTE ::= { 10
WITH SYNTAX SEQUENCE OF
SINGLE
ID at-mcgam-tables

Figure 3: Object Classes for MCGAM

best match

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

6

Acknowledgements for work on this document are given in [3].

[1] Kille, S., "Representing tables and subtrees in the X.500
directory", RFC 1837, August 1995.

[2] Kille, S., "Representing the O/R Address hierarchy in the X.500
directory information tree," RFC 1836, August 1995.

[3] Kille, S., " X.400-MHS use of the X.500 directory to
X.400-MHS routing," RFC 1801, June 1995.

[4] Kille, S., "MIXER (Mime Internet X.400 Enhanced Relay):
Mapping between X.400 and RFC 822/MIME," RFC 2156, January 1998.

[5] Kille, S., Wahl, M., Grimsatd, A., Huber, R., and S. Sataluri
"Using Domains in LDAP/X.500 Distinguished Names", RFC 2247,
January 1998.

7 Security

This document specifies a means by which the X.500/LDAP
service can direct the translation between X.400 and Internet
addresses. This can indirectly affect the routing of messages
a gateway between X.400 and Internet Mail. A succesful attack
this service could cause incorrect translation of an
address (thus "forging" the originator address), or
translation of a recipient address (thus directing the mail to
unauthorized recipient, or making it appear to an
recipient, that the message was intended for recipients other
those chosen by the originator). When cryptographic
is available for directory responses, clients shall employ
mechanisms to verify the authenticity and integrity of
responses

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

8 Author's

Steve
Isode Ltd
The
The

TW9 1

Phone: +44-181-332-9091
Internet EMail: S.Kille@ISODE.

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

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}
oc-mixer-gateway ::= {oc 4}

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}
at-associated-internet-gateway OBJECT IDENTIFIER ::= {at 8}
at-mcgam-tables ::= {at 9} 20

Figure 4: Object Identifier

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RFC 2164 X.500/LDAP Directory to Support MIXER January 1998

Full Copyright

Copyright (C) The Internet Society (1998). All Rights Reserved

This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English

The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns

This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE

Kille Standards Track [Page 10]

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just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.

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