Hirschmann GREYHOUND GRS1020, Справочное руководство

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Synchronizing the system time in the network
9.2 SNTP
110
UM Config GRS
Release 8.0 09/2019
9.2.1 Preparation
Perform the following steps:

To get an overview of how the time is passed on, draw a network plan with the devices
participating in SNTP.
When planning, bear in mind that the accuracy of the time depends on the delays of the SNTP
messages. To minimize delays and their variance, place an SNTP server in each network
segment. Each of these SNTP servers synchronizes its own system time as an SNTP client with
its parent SNTP server (SNTP cascade). The highest SNTP server in the SNTP cascade has
the most direct access to a reference time source.
Figure 19: Example of SNTP cascade
Note:
For precise time distribution, between SNTP servers and SNTP clients you preferably use
network components (routers and switches) that forward the SNTP packets with a low and uniform
transmission time (latency).

An SNTP client sends its requests to up to 4 configured SNTP servers. When there is no
response from the 1st SNTP server, the SNTP client sends its requests to the 2nd SNTP server.
When this request is also unsuccessful, it sends the request to the 3rd and finally the 4th SNTP
server. If none of these SNTP servers responds, the SNTP client loses its synchronization. The
SNTP client periodically sends requests to each SNTP server until a server delivers a valid time.
Note:
The device provides the option of obtaining a list of SNTP server IP addresses from a DHCP
server.

If no reference time source is available to you, then determine a device with an SNTP server as
a reference time source. Adjust its system time at regular intervals.
GPS
Switch
192.168.1.2
192.168.1.1
192.168.1.11
192.168.1.12
SNTP
server
SNTP
client
SNTP
server SNTP
client
Switch
192.168.1.3
SNTP
server SNTP
client
PLC
SNTP
client