Directory System Agent

A Directory System Agent (DSA) is the element of a X.500 directory service that provides User Agents with access to a portion of the directory (usually the portion associated with a single Organizational Unit). X.500 is an international standard developed by the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU-T). The model and function of a directory system agent are specified in ITU-T Recommendation X.501.