Coyote Point Systems Equalizer GX Series, Руководство администратора

Страница: 129 / 866

Configuring NTP
Network Time Protocol, or NTP is a protocol designed to synchronize the clocks of computers over
a network. NTP on Equalizer is compatible with servers running versions 1, 2, 3, or 4 of the NTP
protocol. An RFC for NTPv4 has not been written; NTPv3 is described in RFC 1305.
On Equalizer, NTP is used primarily to time various operations, to ensure accurate timestamps on
log entries (with respect to server and client log timing), and to allow for examination of the
timing of log entries on two Equalizers in a failover configuration.
NTP on Equalizer works by polling an NTP server defined through the GUI. The time between polls
of the NTP server is controlled by the
minpoll and maxpoll NTP parameters, which default to 64
seconds (1 min 4 sec) and 1024 seconds (~17 mins), respectively. The behavior of NTP is to poll
with a frequency starting at
minpoll and then decrease polling frequency over time to maxpoll ,
as the accuracy of the local clock approaches the accuracy of the remote server clock. The time it
takes for the polling delay to increase from
minpoll to maxpoll will vary based on a number of
factors, including the accuracy of the clocks on the client and server, network latency, and other
timing factors.
NTP calculates when the local and remote system clocks are sufficiently in sync to begin
increasing the polling delay towards
maxpoll . When the accuracy of the two clocks is significantly
different, or there is significant latency, for example, the two clocks may never be in sufficient
agreement to increase the delay towards
maxpoll . In this case, Equalizer will continue to sync
approximately every 64 seconds. This behavior indicates that a different NTP server should be
chosen.
NTP packets are very small and should not cause any problems with Equalizer or network
operation, except as described in the following section on NTP and plotting.
NTP and Plotting
When you initially configure NTP, this may effectively disable plotting until NTP completes the
initial synchronization of Equalizer’s system clock with the NTP server -- which may take from
several hours to several days. This is because plotting depends on accurate timestamps in the plot
log. Since initially NTP is adjusting the time at frequent intervals, the timestamps in the plot log
may become out of sync with the system clock, and so no plot data may be returned. Once NTP is
no longer making adjustments to the system clock, plotting will function normally.
Default NTP Configuration
Equalizer is delivered with a default Network Time Protocol (NTP) configuration: the NTP daemon
(
ntpd ) is enabled by default and the NTP server is set to pool.ntp.org . However, NTP will not be
able to synchronize time with an NTP server until DNS is configured and working.
Rather than point at a single NTP server, most organizations use an NTP server pool defined by
the NTP Pool Project.
Copyright © 2014 Coyote Point Systems, A Subsidiary of Fortinet, Inc.
All Rights Reserved. 129
Equalizer Administration Guide