Network node directories

A network node provides distributed directory services to the end nodes it serves.

An example of a network node directory is shown in Figure 1.

Figure 1. Network Node Directory

A network node locates a remote LU as follows:

  1. The network node receives a request to locate an LU. The request can be any of the following:
    • The name of a destination LU sent by an end node or a LEN node to its network node server
    • An LU name specified in a LOCATE search request from an end node
    • An LU name specified in a BIND request from a LEN node
    • An LU name specified by a TP on the network node
  2. If the destination LU is not located in the network node - but appears in its directory - the network node sends a directed search request to the destination network node server to verify the location of the LU.

    If the LU is not in the network node directory, the node initiates a search of the network by sending a broadcast search to every adjacent network node.

  3. Each node in turn propagates the broadcast and returns replies indicating success or failure.

For its future needs, a network node caches information obtained from successful broadcast searches.

An APPN end node can also receive (and respond to) LOCATE search requests from its network node server to search for, or confirm the continued presence of, specific LUs in the end node.

Each APPN end node registers its LUs with its network node server by sending the network node a registration message. In this way, the network node maintains current directory information for the end nodes in its domain. A LEN node cannot register LUs with its network node server. Therefore, all LUs on the LEN node must be predefined, through configuration, to the network node server.