+This mechanism allows for hierarchical directory services to to be
+constructed.
+
+A referral object has an structural object class of
+{{EX:referral}} and has the same {{TERM[expand]DN}} as the
+delegated subtree. Generally, the referral object will also
+provide the auxiliary object class {{EX:extensibleObject}}.
+This allows the entry to contain appropriate {{TERM[expand]RDN}}
+values. This is best demonstrated by example.
+
+If the server {{EX:a.example.net}} holds {{EX:dc=example,dc=net}}
+and wished to delegate the subtree {{EX:ou=subtree,dc=example,dc=net}}
+to another server {{EX:b.example.net}}, the following named referral
+object would be added to {{EX:a.example.net}}:
+
+> dn: dc=subtree, dc=example, dc=net
+> objectClass: referral
+> objectClass: extensibleObject
+> dc: subtree
+> ref: ldap://b.example.net/dc=subtree,dc=example,dc=net/
+
+The server uses this information to generate referrals and
+search continuations to subordinate servers.
+
+For those familiar with X.500, a {{named referral}} object is
+similar to an X.500 knowledge reference held in a {{subr}}
+{{TERM:DSE}}.
+
+!if 0
+H2: Immediate Superior Knowledge Information
+
+Immediate superior knowledge information may be provided in the
+entry at the root of a delegated subtree. The knowledge information
+is contained with {{EX:ref}} operational attribute.
+
+Extending the example above, a {{ref}} attribute can be added
+to the entry {{EX:dc=subtree,dc=example,dc=net}} in server B indicating
+that A holds the immediate superior naming context.
+
+> dn: dc=subtree, dc=example, dc=net
+> changetype: modify
+> add: ref
+> ref: ldap://a.example.net/
+
+The server uses this information to generate referrals to
+management operations.
+
+For those familiar with X.500, this use of the {{EX:ref}} attribute
+is similar to an X.500 knowledge reference held in a
+{{immSupr}} {{TERM:DSE}}.
+!endif
+
+
+H2: Superior Knowledge Information
+
+Superior knowledge information may be specified using the
+{{EX:referral}} directive. The value is a list of {{TERM:URI}}s
+referring to superior directory services. For servers without
+immediate superiors, such as for {{EX:a.example.net}} in the example
+above, the server can be configured to use directory service with
+{{global knowledge}}, such as the {{OpenLDAP Root Service}}
+({{URL:http://www.openldap.org/faq/index.cgi?file=393}}).
+
+> referral ldap://root.openldap.org/
+
+However, as {{EX:a.example.net}} is the {{immediate superior}}
+to {{EX:b.example.net}}, {{a.example.net}} would be configured
+as follows:
+
+> referral ldap://a.example.net/
+
+The server uses this information to generate referrals to
+operations acting upon operations not within or subordinate
+to any of the naming contexts held by the server.
+
+For those familiar with X.500, this use of the {{EX:ref}} attribute
+is similar to an X.500 knowledge reference held in a
+{{Supr}} {{TERM:DSE}}.