Provides classes and interfaces for the directory "lookup"services. The client-server framework allows a user on his/her ITX application, which contain directory service component, to transparently find other users in the ITX network by query through the directory server. The directory service layer is completely hidden from the ITX application layer, so that only the signaling layer is responsible for interfacing with the directory service. Alternatively, ITX application layer can directly use the functionality of the directory service by getting its handle through the signaling component.

The main interface to use the directory service is `cnrg.itx.ds.DirectoryService`. To use the directory service component, the user needs to authenticate himself/herself by calling the `DirectoryService.declareIdentity` method. Upon authentication successful, the user can lookup his/her user information (e.g. extension number, access level, custom message, etc.), manipulate his/her locations information (e.g. default and customized location), change his/her password, lookup all registered users in the ITX network, and reach them by their extension number or userID.

Administrator using the directory service is provided with a management interface to add or remove a user from the ITX network.

Currently the directory service uses BIND as its database, if it is desired to use another database, the programmer should inherit the DSComm class and override the included methods.