Sntp; Sntp Settings; Sntp Modes - GE 350 Communications Manual

CHAPTER 3: ETHERNET INTERFACE

SNTP

SNTP settings

SNTP modes

SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
With SNTP, the device can obtain the clock time over an Ethernet network, acting as an
SNTP client to receive time values from an SNTP server.
SNTP Port configures the ports that the device uses, so it's necessary to configure it in all
cases.
The relay binds to the first unicast message (see below) received from any server, then
continues operating with the SNTP server in unicast mode. Any further responses from
other SNTP servers are ignored. In the unicast mode of operation the chosen time server
can go offline, in which case it takes about one minute for the device to signal an SNTP FAIL
state and switch again to anycast mode in order to try to find another time server.
Three different modes of SNTP operation are supported. These modes are unicast,
broadcast and anycast.
To use SNTP in unicast mode, the SNTP IP Address must be set to the SNTP server IP
address. Once this address is set and the function setting is "UNICAST", the device attempts
to obtain time values from the SNTP server. Since many time values are obtained and
averaged, it generally takes 10 seconds until the clock is synchronized with the SNTP
server.
It may take up to 30 seconds for the device to signal an SNTP FAIL state if the server is off-
line. In this case the main CPU generates an alarm similar to that of the IRIG-B case.
To use SNTP in broadcast mode, set the function setting to "BROADCAST". The device
listens to SNTP messages sent to "all" the broadcast addresses for the subnet.
The device waits up to eighteen minutes (>1024 seconds) to receive an SNTP broadcast
message before signaling an SNTP FAIL state.
To use SNTP in anycast mode, set the function setting to "ANYCAST". Anycast mode is
designed for use with a set of cooperating servers whose addresses are not known
beforehand by the client. The device sends a request to a multicast group address
assigned by IANA for SNTP protocol purposes. This address is 224.0.1.1 and a group of
SNTP servers listens to it. Upon receiving such a request, each server sends a unicast
response to the SNTP client.
The relay binds to the first unicast message received from any server, then it continues
operating with the SNTP server in unicast mode. Any further responses from other SNTP
servers are ignored. In the unicast mode of operation, the chosen time server can go
offline, in which case it takes about one minute for the device to signal an SNTP FAIL state
and to switch again to the anycast mode to try to find another time server.
SNTP
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