INM 725B Rev 21
109
13 .4 .25 SNTP Client
The SNTP client is available on Port 4 and can be used to synchronise the annunciator with
network time.
The IP address, of the Server that will provide the time to the device, can be configured via the
configuration software.
When a valid time message is received it can take up to 30 seconds for the device to fully
synchronise all the cards in the unit.
To determine the SNTP message is valid the client checks the following fields in the SNTP data:
Server IP address –
Checks the message is sent from the configured server
Mode –
Checks the message is from a Server type
Stratum –
Checks the stratum is not 0 (kiss of death packet)
Originate Timestamp – Checks the timestamp of the request matches the originate time in the
response back from the Server.
Transmit timestamp – Checks the transmit timestamp from the server is not 0.
If the client receives an invalid response or no response it will double its poll time after every
request it sends. A comm’s error will also be shown on the device.
So if for example the poll time is set to 60 seconds in the configuration software, the first poll
will happen after 60 seconds if no valid response, the next message will be sent after 120 secs,
then 240 etc.
This will continue until the maximum poll time of 3600 seconds is reached.
Once a valid response is received this will be reset to the configured poll time.
