About Knowledge ReferencesChapter 5 Designing the Directory Topology 93• Smart referralsSmart referrals are stored on entries within the directory itself. Smart referralspoint to Directory Servers that have knowledge of the subtree whose DNmatches the DN of the entry containing the smart referral.All referrals are returned in the format of an LDAP uniform resource locator (URL).The following sections describe the structure of an LDAP referral, and thendescribe the two referral types supported by Directory Server.The Structure of an LDAP ReferralAn LDAP referral contains information in the format of an LDAP URL. An LDAPURL contains the following information:• The host name of the server to contact• The port number of the server• The base DN (for search operations) or target DN (for add, delete, and modifyoperations).For example, a client application searches dc=example,dc=com for entries with asurname Jensen. A referral returns the following LDAP URL to the clientapplication:ldap://europe.example.com:389/ou=people,l=europe,dc=example,dc=comThe referral tells the client application to contact the host europe.example.com onport 389 and submit a search rooted atou=people,l=europe,dc=example,dc=com.The LDAP client application you use determines how a referral is handled. Someclient applications automatically retry the operation on the server to which theyhave been referred. Other client applications simply return the referral informationto the user. Most LDAP client applications provided by Netscape (such as thecommand-line utilities or the Directory Server Gateway (DSGW)) automaticallyfollow the referral. The same bind credentials you supply on the initial directoryrequest are used to access the server.Most client applications follow a limited number of referrals, or hops. The limit onthe number of referrals followed reduces the time a client application spends tryingto complete a directory lookup request and helps eliminate hung processes causedby circular referral patterns.
