The directory service of Microsoft Exchange Server supports the Lightweight Directory Access Protocol (LDAP) over TCP/IP connections. This means that the objects and attributes in the Microsoft Exchange Server directory are exposed to all applications that communicate through the LDAP protocol.
LDAP is an on-the-wire protocol used to perform directory operations such as read, search, add, and remove. The operations supported by LDAP have a close relationship to those specified by the CCITT X.500 Directory Access Protocol (DAP) but without the overhead of the session and presentation OSI layers.
With LDAP, all operations and parameters are carried directly over TCP or any other transport. LDAP and DAP are not interoperable; in other words, an LDAP client cannot be connected to a DAP server or vice versa without an agent that performs conversion between LDAP and DAP operations.
LDAP as implemented by Microsoft Exchange Server supports paged results. This means that, if a request from an LDAP client would produce results too large for the client to handle (such as the address book of an entire organization), it can choose to receive the results in pages of smaller chunks (say, 100 entries each), one at a time. When the client finishes processing one page, it responds to the server, which then delivers the next page to the client.
LDAP as implemented by Microsoft Exchange Server supports referrals. With this mechanism, the DLL that provides LDAP support (WLDAP32.DLL) can be configured to automatically search for a given entry in a directory other than the one to which the request was originally sent. It can find this alternative directory through an IP address or a DNS name.