Ross SRG-4400, User Manual

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SRG-4400 User Manual (Iss. 06) NTP Option • 13–3
Background Information
A good source of reference time is the Network Time Protocol available on most commercial
Ethernet networks. Note: No frequency or phase can be accurately inferred from the NTP system.
The SRG-4400 NTP system can be configured in two ways:
• NTP Server where the SRG-4400 acts as the device from which other NTP clients request
time.
• NTP Client where the SRG-4400 requests time from a NTP Server.
NTP Server
When configured as an NTP Server, the SRG-4400 responds to requests from “Clients” and
replies with a “time-stamp”. It is up to the Client to decide on the validity and accuracy of this
time. An NTP system may be able to resolve time in the region of hundreds of milliseconds. Do
not expect anything better!
NTP Client
As the SRG-4400 is powered, the NTP Client begins requesting time from the designated remote
NTP server. The NTP Client will keep searching for a time until it gets one.
The NTP operational parameters can be monitored in the LCD menu, and on the Dashboard
remote control program.
Default Settings
The default settings of the NTP system are as follows:
• SPG IP address 192.168.001.044
• SPG IP mask 255.255.255.000
• SPG IP Gateway 192.168.001.254
• NTP Server IP address 139.143.005.030
• Remote NTP Server IP address 139.143.005.030.
Time Locking
Time lock is achieved by reading the NTP time from the NTP Server and calculating an
appropriate time-code. NTP locks the SRG-4400 central timing system.
Keep the following mind:
• The time-code needs to be checked and updated each time the NTP Server is detected.
• However in marginal networks the “question-response” message times may be so
variable the time-code update should be suppressed until it has been valid for a number of
seconds.
• Once the time-code has been set by the NTP Client, the SRG-4400 should not need to
re-check the NTP time unless a crash lock has been forced by the phase locking
arrangement.