Messaging clients that implement a browsable address book need a way to communicate with an address data store in order to access and manipulate that data. This protocol enables communication between a messaging client and a data store.
This protocol is a protocol layer that uses the remote procedure call (RPC) protocol as a transport, with a series of interface methods as described in this document, that clients can use to communicate with a server. The server will use Lightweight Directory Access Protocol (LDAP) and NSPI to retrieve data that is returned to the client.
The following figure shows a graphical representation of a typical communication sequence between a messaging client and a server.
Figure 1: Exchange Server NSPI Protocol message sequence