User's Manual Part 1

3: Detailed Description
APCD-LM043-8.0 (DRAFT C) 55
3.7.3 SNTP/UTC Time Clock
The Simple Network Time Protocol (SNTP)/UTC feature provides LMS4000 devices with an
accurate clock for time stamping events in the log file.
SNTP/UTC Time Clock operation is illustrated in Figure 31.
Figure 31 SNTP/GMT Time Clock
The CCU, acting as an SNTP time client, regularly resynchronizes to one of several NTP
Servers from which it obtains UTC (Universal Coordinated Time). The CCU resynchronization
and retry periods can be set by the operator. The resynchronization period is the time between
a successful CCU resynchronization and the next CCU resynchronization attempt, typically
set to one hour. The retry period is the time between an unsuccessful resynchronization
attempt and the next resynchronization attempt, typically set to 30 seconds.
The operator can configure the CCU to act as an SNTP time server to the EUMs and
broadcast time information to all EUMs after it has synchronized with the NTP server. It also
broadcasts this information whenever an EUM powers up and registers.
UTC, the international time standard, is based on a 24-hour clock. It is the current term for
what was commonly referred to as Greenwich Mean Time (GMT). SNTP, specified in
RFC1769 and RFC2030, is a simplified version of NTP, which is specified in RFC1305.
By default, the CCU SNTP client is disabled. Once SNTP is enabled, the CCU tries to
synchronize with an NTP server. The operator can configure the CCU to synchronize with
• a local router or network device, if the router or network device is configured as an
NTP time server,
• any open-access NTP server of the operator’s choosing, or
• one of the factory-default open-access NTP servers listed below:
• 132.246.168.148 time.nrc.ca stratum 2, Canada
• 140.162.8.3 ntp.cmr.gov stratum 2, US
• 136.159.2.1 ntp.cpsc.ucalgary.ca stratum 2, Canada
• 192.5.5.250 clock.isc.org stratum 1, US
CCU3000
Antenna
EUM3000
NTP Server
Internet
Time Request
Time
Time
Broadcast