Microsoft Exchange Server services communicate with each other as client and server processes by using remote procedure calls (RPCs). An RPC is a routine that transfers functions and data between client and server processes; it is an industry standard protocol for client/server communication. With RPC, clients and servers can communicate with one another efficiently on almost any type of network. When the client and the server run on the same computer, RPCs are mapped to local procedure calls, which are much faster than RPCs.