## Overview - RPC and Other DCE Components

This topic discusses aspects of the internal behavior of remote procedure calls that are significant for advanced RPC programmers, including the following topics:

· Threads of execution in RPC applications

· Authenticated remote procedure calls

· Using the Name Service Interface

DCE RPC is a fully integrated part of the distributed computing environment. The communications capabilities of DCE RPC are used by clients and servers of other DCE components. In turn, RPC uses services provided by the following other DCE components: the DCE Threads Service, the DCE Security Service, and the DCE Cell Directory Service.

A thread is a single sequential flow of control with one point of execution on a single processor at any instant. Multiple threads can coexist in a single process. DCE RPC uses threads internally for its own operations. DCE RPC also provides an environment where RPC applications can use thread services.

The DCE RPC runtime provides RPC applications with a programming interface to the security service. The RPC authentication interface enables RPC clients and servers to mutually authenticate (that is, prove the identity of) each other. An authenticated remote procedure call provides client authorization information and authentication information to servers. Authorization information includes the credentials a client has and the identities a client is associated with at the time of a call. By comparing client authorization information to access control lists, a server can find out whether a client is eligible to use a requested remote procedure. Client authentication information identifies a client to a server.

To help RPC clients find RPC servers, RPC applications typically use a namespace. A namespace is a collection of information about applications, systems, and any other relevant computing resources. A namespace is maintained by a directory service such as CDS. DCE RPC provides a Name Service Interface (NSI) that is independent of any particular directory service.

NSI communicates with supported directory services for both RPC applications and the RPC control program. NSI insulates RPC applications from the intricacies of using a directory service. An RPC server uses NSI to store information about itself in a namespace, and a client uses NSI to access information about a server that meets the client's requirements for a specific RPC interface and object, among other things. The client uses this information to establish a relationship, known as a binding, with the server.

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