Dynabrade Dynabug 57810, Руководство пользователя

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CHAPTER 1
Time Management Overview
• NTP Overview on page 3
• Understanding NTP Time Servers on page 5
NTP Overview
Network Time Protocol (NTP) is a widely used protocol used to synchronize the clocks
of routers and other hardware devices on the Internet. Primary NTP servers are
synchronized to a reference clock directly traceable to Coordinated Universal Time (UTC).
Reference clocks include GPS receivers and telephone modem services, NTP accuracy
expectations depend on the environment application requirements, however, NTP can
generally maintain time to within tens of milliseconds over the public internet.
NTP is defined in the RFC 5905: Network Time Protocol Version 4: Protocol and Algorithms
Specification
Junos devices can be configured to act as an NTP client, a secondary NTP server, or a
primary NTP server. These variations are as follows:
• Primary NTP Server—Primary NTP servers are synchronized to a reference clock that
is directly traceable to UTC. These servers then re-distribute this time data downstream
to other Secondary NTP servers or NTP clients.
• Secondary NTP Server—Secondary NTP servers are synchronized to a primary or
secondary NTP server. These servers then re-distribute this data downstream to other
Secondary NTP servers or NTP clients.
3 Copyright © 2014, Juniper Networks, Inc.