Synchronizing the system time in the
18
7.4
Interaction of PTP and SNTP
Basic - L3P
Release
4.0
11/07
7.4 Interaction of PTP and SNTP
According to PTP and SNTP, both protocols can exist in parallel in the same
network. However, since both protocols effect the system time of the device,
situations may occur in which the two protocols compete with each other.
Note: Configure the devices so that each device only receives the time from
one source. If the Switch gets the time via PTP, you enter the "External serv-
er address" 0.0.0.0 in the SNTP client configuration and do not accept SNTP
broadcasts. If the Switch gets the time via SNTP, make sure that the "best"
clock is connected to the SNTP server. Then both protocols will get the time
from the same server. The example (see fig. 33) shows such an application.
Figure 33: Example of the coexistence of PTP and SNTP
Application example:
The requirements with regard to the accuracy of the time in the network
are quite high, but the terminal devices only support SNTP (see fig. 33).
GPS
NTP-
Server
SNTP Client
SNTP Server
PTP
SNTP Server
PTP
SNTP Server
PTP
SNTP-Client
SNTP-Client
PLC
PTP
SNTP
SNTP
SNTP
PTP
149.218.112.1 149.218.112.2 149.218.112.3
149.218.112.0
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