OSF DCE Application Development Guide--Core Components

Chapter 20. Time-Provider Interface
This chapter describes the Time-Provider Interface (TPI) for DCE Distributed Time
Service software. The chapter provides a brief overview of the TPI, explains how to use
external time-providers with DTS, and describes the data structures and message
protocols that make up the TPI.
Coordinated Universal Time (UTC) is widely used and is disseminated throughout the
world by various standards organizations. Several manufacturers supply devices that can
acquire UTC time values via radio, satellite, or telephone. These devices can then
provide standardized time values to computer systems. Normally, one device is
connected to a computer system; the device runs a process that interprets signals and
translates them to time values, which can either be displayed or be provided to the server
process running on the connected system.
To synchronize its system clock with UTC using an external time-provider device, a DTS
server needs a software interface to the device to periodically obtain UTC. In effect, this
interface serves as an intermediary between the DTS server and external time-provider
processes. The DTS server requires the interface to obtain UTC time values and to
determine the associated inaccuracy of each value. The interface between the DTS
server process and the time-provider process is called the Time-Provider Interface.
The remainder of this chapter describes the TPI and its attendant processes in detail. The
following section describes the control flow between the DTS server process, the TPI,
and the time-provider process.
20.1 General TPI Control Flow
When you use a time-provider with a system running DTS, the external time-provider is
implemented as an independent process that communicates with a DTS server process
through remote procedure calls (RPCs). A remote procedure call is a synchronous
request and response between a main calling program and a procedure executing in
another process. RPC applications are based on the client/server model. In this context,
the following processes act as the client and server components in the RPC-based
application:
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