OpenLDAP Root Service An experimental LDAP referral service
RFC 3088

Document Type RFC - Experimental (April 2001; No errata)
Was draft-zeilenga-ldap-root (individual)
Last updated 2013-03-02
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Network Working Group                                        K. Zeilenga
Request for Comments: 3088                           OpenLDAP Foundation
Category: Experimental                                        April 2001

                         OpenLDAP Root Service
                 An experimental LDAP referral service

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.


   The OpenLDAP Project is operating an experimental LDAP (Lightweight
   Directory Access Protocol) referral service known as the "OpenLDAP
   Root Service".  The automated system generates referrals based upon
   service location information published in DNS SRV RRs (Domain Name
   System location of services resource records).  This document
   describes this service.

1. Background

   LDAP [RFC2251] directories use a hierarchical naming scheme inherited
   from X.500 [X500].  Traditionally, X.500 deployments have used a
   geo-political naming scheme (e.g., CN=Jane
   Doe,OU=Engineering,O=Example,ST=CA,C=US).  However, registration
   infrastructure and location services in many portions of the naming
   hierarchical are inadequate or nonexistent.

   The construction of a global directory requires a robust registration
   infrastructure and location service.  Use of Internet domain-based
   naming [RFC2247] (e.g., UID=jdoe,DC=eng,DC=example,DC=net) allows
   LDAP directory services to leverage the existing DNS [RFC1034]
   registration infrastructure and DNS SRV [RFC2782] resource records
   can be used to locate services [LOCATE].

Zeilenga                      Experimental                      [Page 1]
RFC 3088                 OpenLDAP Root Service                April 2001

1.1.  The Glue

   Most existing LDAP implementations do not support location of
   directory services using DNS SRV resource records.  However, most
   servers support generation of referrals to "superior" server(s).
   This service provides a "root" LDAP service which servers may use as
   their superior referral service.

   Client may also use the service directly to locate services
   associated with an arbitrary Distinguished Name [RFC2253] within the
   domain based hierarchy.

     The mechanisms used by service are experimental.  The descriptions
     provided by this document are not definitive.  Definitive
     mechanisms shall be published in a Standard Track document(s).

2. Generating Referrals based upon DNS SRV RRs

   This service returns referrals generated from DNS SRV resource
   records [RFC2782].

2.1. DN to Domain Name Mapping

   The service maps a DN [RFC2253] to a fully qualified domain name
   using the following algorithm:

       domain = null;
       foreach RDN left-to-right        // [1]

           if not multi-valued RDN and
               RDN.type == domainComponent
               if ( domain == null || domain == "." )
               {   // start
                   domain = "";
               {   // append separator
                   domain .= ".";

               if ( RDN.value == "."  )
               {   // root
                   domain = ".";

Zeilenga                      Experimental                      [Page 2]
RFC 3088                 OpenLDAP Root Service                April 2001

               {   // append domainComponent
                   domain .= RDN.value;
           domain = null;


       Distinguished Name              Domain
       -----------------------------   ------------
       DC=.                            .            [2]
       DC=example,DC=net,DC=.          .            [3]
       DC=example,DC=.,DC=net          net          [4]          [5]
       CN=Jane Doe,O=example,C=US      null
       UID=jdoe,DC=example,C=US        null
       DC=example,O=example,DC=net     net
       DC=example+O=example,DC=net     net
       DC=example,C=US+DC=net          null


   0) A later incarnation will use a Standard Track mechanism.

   1) A later incarnation of this service may use a right-to-left

   2) RFC 2247 does not state how one can map the domain representing
      the root of the domain tree to a DN.  We suggest the root of the
      domain tree be mapped to "DC=." and that this be reversable.

   3) RFC 2247 states that domain "" should be mapped to the
      DN "DC=example,DC=net", not to "DC=example,DC=net,DC=.".  As it is
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