Black Box ASTCKEY - Manual (Page 9)

Chapter 1: Introduction
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1.3. Auto-Sync Time Clock Installation & Operation Guide
The Auto-Sync Time Clock Installation & Operation Guide was designed to assist
you in the daily operation of your clock and to provide a comprehensive
understanding of the Auto-Sync Time Clock. This Guide can be found on the Auto-
Sync Utility CD that came with your clock.
1.4. Time Servers General Information
A time server is a server computer that reads the actual time from a reference
clock and distributes this information to its clients using a computer network. The
time server may be a local network time server or an Internet time server.
The most important and widely-used protocol for distributing and synchronizing
time is the Network Time Protocol (NTP), though other less-popular or outdated
time protocols continue to be used.
The time reference used by a time server could be another time server on the
network or the Internet, a connected radio clock or an atomic clock. The most
common true time source is a GPS or GPS master clock. Time servers are
sometimes multi-purpose network servers, dedicated network servers, or dedicated
devices. All a dedicated time server does is provide accurate time.
An existing network server (e.g. a file server) can become a time server with
additional software. The NTP homepage provides a free and widely-used reference
implementation of the NTP server and client for many popular operating systems.
The other choice is a dedicated time server device.
The term "stratum" is used to label the closeness to a central or high quality time
server. The stratum indicates the place of a particular time server in a hierarchy of
servers. The scale is 0 to 16 where 0 is the most accurate and likely a highly
specialized physical hardware device. Some time clients will reject a time update
from a server whose stratum is too high, and most will prefer lower strata time
sources to higher ones. This can be a pitfall for administrators setting up an in-
house time server with no true time source.