Coyote Point Systems E350GX, Installation And Administration Manual

Page: 103 / 344

Managing System Time and NTP
Equalizer Installation and Administration Guide 103
Managing System Time and NTP
Through Equalizer’s Administrative Interface, you can:
• set the time zone
• set the system date and time
• set up to three Network Time Protocol (NTP) servers, and enable or disable synchronization with these
servers
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 Administrative Interface. 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.
We do NOT recommend changing the default minpoll and maxpoll delays in the NTP configuration file, in order to
ensure an accurate system clock. NTP packets are very small and should not cause any problems with Equalizer or
network operation, except as described in the following section.
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.