Knowledge References and Referrals

A knowledge reference provides the names and addresses of the various naming contexts held in another partition. For example, in Figure 2-7, Server B uses knowledge references to point to the c=us and c=uk naming contexts on Server A. When Server B is asked for information residing on Server A, it sends back one or more referrals to Server A. Clients can then use these referrals to contact Server A.

Typically, each directory server contains both superior and subordinate knowledge references. Superior knowledge references point upward in the DIT toward the root. They tie the partitioned naming context to its parent. Subordinate knowledge references point downward in the DIT to other partitions.

For example, in Figure 2-8, Server B holds four naming contexts, two of which are superior to the others. These two superior naming contexts use subordinate knowledge references to point to their subordinate naming contexts. Conversely, the naming context on Server A has an immediate superior residing on Server B. Server A therefore uses a superior knowledge reference to point to its parent on Server B.

Figure 2-8 Using Knowledge References to Point to Naming Contexts

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Naming contexts that start at the top of the DIT obviously cannot have a knowledge reference to a superior naming context.

Note: There are presently no Internet standards for enforcing the validity of knowledge references, and Oracle Internet Directory does not do so. It is up to the administrator to ensure consistency among knowledge references within an enterprise network. Oracle Corporation recommends that permission for managing knowledge reference entries be restricted, as is the case with any other privileged administrative function such as schema or access control.

There are two kinds of referrals:

• Smart referrals

  These are returned to the client when the knowledge reference entry is in the scope of the search. It points the client to the server that stores the requested information.

  For example, suppose that:

  • Server A holds the naming context
    ou=server development,c=us,o=acme, and has a knowledge reference to Server B

  • Server B holds the naming context ou=sales,c=us,o=acme

  When a client sends a request to Server A for information in ou=sales,c=us,o=acme, Server A provides the user with a referral to Server B.

• Default referrals

  These are returned when the base object is not in the directory, and the operation is performed in a naming context on another server. A default referral typically sends the client to a server that has more detailed information about the directory partitioning arrangement.

  For example, suppose that Server A holds:

  • The naming context c=us,o=acme

  • A knowledge reference to Server PQR that has more knowledge about the overall directory partitioning arrangement

  Now suppose that a client requests information on c=uk,o=acme. When Server A finds that it does not have the c=uk,o=acme naming context, it provides the client with a referral to Server PQR. From there, the client can find the server holding the requested naming context.

  See Also: "Managing Knowledge References and Referrals"