| Network Working Group | S. Kille | |
| Request for Comments: 2247 | Isode Ltd. | |
| Category: Standards Track | M. Wahl | |
| Critical Angle Inc. | ||
| A. Grimstad | ||
| AT&T | ||
| R. Huber | ||
| AT&T | ||
| S. Sataluri | ||
| AT&T | ||
| January 1998 |
This document defines an algorithm by which a name registered with the
Internet Domain Name Service [2] can be represented as an LDAP distinguished
name.
LDAP-based directories provide a more general hierarchical naming framework. A primary difference in specification of distinguished names from domain names is that each component of an distinguished name has an explicit attribute type indication.
X.500 does not mandate any particular naming structure. It does contain suggested naming structures which are based on geographic and national regions, however there is not currently an established registration infrastructure in many regions which would be able to assign or ensure uniqueness of names.
The mechanism described in this document automatically provides an enterprise a distinguished name for each domain name it has obtained for use in the Internet. These distinguished names may be used to identify objects in an LDAP directory.
An example distinguished name represented in the LDAP string format [3] is "DC=CRITICAL-ANGLE,DC=COM". As with a domain name, the most significant component, closest to the root of the namespace, is written last.
This document does not define how to represent objects which do not
have domain names. Nor does this document define the procedure to
locate an enterprise's LDAP directory server, given their domain name.
Such procedures may be defined in future RFCs.
The algorithm for transforming a domain name is to begin with an empty distinguished name (DN) and then attach Relative Distinguished Names (RDNs) for each component of the domain, most significant (e.g. rightmost) first. Each of these RDNs is a single AttributeTypeAndValue, where the type is the attribute "DC" and the value is an IA5 string containing the domain name component.
Thus the domain name "CS.UCL.AC.UK" can be transformed into
DC=CS,DC=UCL,DC=AC,DC=UK
Distinguished names in which there are one or more RDNs, all containing
only the attribute type DC, can be mapped back into domain names. Note
that this document does not define a domain name equivalence for any other
distinguished names.
( 0.9.2342.19200300.100.1.25 NAME 'dc' EQUALITY caseIgnoreIA5Match
SUBSTR caseIgnoreIA5SubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.26 SINGLE-VALUE )
The value of this attribute is a string holding one component of a domain
name. The encoding of IA5String for use in LDAP is simply the characters
of the string itself. The equality matching rule is case insensitive,
as is today's DNS.
An attribute can only be present in an entry held by an LDAP server when that attribute is permitted by the entry's object class.
This section defines two object classes. The first, dcObject,
is intended to be used in entries for which there is an appropriate structural
object class. For example, if the domain represents a particular
organization, the entry would have as its structural object class 'organization',
and the 'dcObject' class would be an auxiliary class. The second,
domain, is a structural object class used for entries in which no other
information is being stored. The domain object class is typically used
for entries that are placeholders or whose domains do not correspond to
real-world entities.
The following object class, along with the dc attribute, can be added to any entry.
( 1.3.6.1.4.1.1466.344 NAME 'dcObject' SUP top AUXILIARY MUST dc )
An example entry would be:
dn: dc=critical-angle,dc=com
objectClass: top
objectClass: organization
objectClass: dcObject
dc: critical-angle
o: Critical Angle Inc.
The entry will have as its structural object class the "domain" object class.
( 0.9.2342.19200300.100.4.13 NAME 'domain' SUP top STRUCTURAL
MUST dc
MAY ( userPassword $ searchGuide $ seeAlso $ businessCategory $
x121Address $ registeredAddress $ destinationIndicator $
preferredDeliveryMethod $ telexNumber $ teletexTerminalIdentifier $
telephoneNumber $ internationaliSDNNumber $ facsimileTelephoneNumber
$
street $ postOfficeBox $ postalCode $ postalAddress $
physicalDeliveryOfficeName $ st $ l $ description $ o $
associatedName ) )
The optional attributes of the domain class are used for describing the object represented by this domain, and may also be useful when searching. These attributes are already defined for use with LDAP [4].
An example entry would be:
dn: dc=tcp,dc=critical-angle,dc=com
objectClass: top
objectClass: domain
dc: tcp
description: a placeholder entry used with SRV records
The DC attribute is used for naming entries of the domain class, and this can be represented in X.500 servers by the following name form rule.
( 1.3.6.1.4.1.1466.345 NAME 'domainNameForm' OC domain MUST ( dc ) )
| [1] | The Directory: Selected Attribute Types. ITU-T Recommendation X.520, 1993. |
| [2] | Mockapetris, P., " Domain Names - Concepts and Facilities," STD 13, RFC 1034, November 1987. |
| [3] | Kille, S., and M. Wahl, " Lightweight Directory Access Protocol (v3): UTF-8 String Representation of Distinguished Names", RFC 2253, December 1997. |
| [4] | Wahl, M., "A Summary of the X.500(96) User Schema for use with LDAP", RFC 2256, December 1997. |
An enterprise is not restricted in the information which it may store
in DNS or LDAP servers. A client which contacts an untrusted server
may have incorrect or misleading information returned (e.g. an organization's
server may claim to hold naming contexts representing domain names which
have not been delegated to that organization).
Phone: +44-181-332-9091
EMail: S.Kille@ISODE.COM
Mark Wahl
Critical Angle Inc.
4815 W. Braker Lane #502-385
Austin, TX 78759
USA
Phone: (1) 512 372 3160
EMail: M.Wahl@critical-angle.com
Al Grimstad
AT&T
Room 1C-429, 101 Crawfords Corner Road
Holmdel, NJ 07733-3030
USA
EMail: alg@att.com
Rick Huber
AT&T
Room 1B-433, 101 Crawfords Corner Road
Holmdel, NJ 07733-3030
USA
EMail: rvh@att.com
Sri Sataluri
AT&T
Room 4G-202, 101 Crawfords Corner Road
Holmdel, NJ 07733-3030
USA
EMail: sri@att.com
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