Technical data

Conﬁguring and Managing NTP

The Network Time Protocol (NTP) synchronizes time and coordinates time

distribution throughout a TCP/IP network. NTP provides accurate and

dependable timekeeping for hosts on TCP/IP networks. TCP/IP Services NTP

software is an implementation of the NTP Version 3 speciﬁcation and maintains

compatibility with NTP versions 1 and 2.

NTP provides synchronization traceable to clocks of high absolute accuracy and

avoids synchronization to clocks keeping incorrect time.

Time synchronization is important in client/server computing. For example,

systems that share common databases require coordinated transaction processing

and timestamping of instrumental data.

This chapter reviews key concepts and describes:

• How to start up and shut down NTP (Section 12.2)

• How to conﬁgure the NTP host (Section 12.3)

• How to conﬁgure the host as a backup time server (Section 12.4)

• How to adjust time zone offsets (Section 12.5)

• NTP event logging (Section 12.6)

• How to conﬁgure NTP authentication (Section 12.7)

• How to use NTP utilities (Section 12.8)

• How to solve NTP problems (Section 12.9)

12.1 Key Concepts

Synchronized timekeeping means that hosts with accurate system timestamps

send time quotes to each other. Hosts running NTP may be either time servers or

clients although they are often both servers and clients.

NTP does not attempt to synchronize clocks to each other. Rather, each server

attempts to synchronize to Universal Coordinated Time (UTC) using the best

available source and best available transmission paths to that source. NTP

expects that the time being distributed from the root of the synchronization

subnet will be derived from some external source of UTC (for example, a radio

clock).

If your network is isolated and you cannot access other NTP servers on the

internet, you can designate one of your nodes as the reference clock to which all

other hosts will synchronize.

Conﬁguring and Managing NTP 12–1