GE L90 Instruction Manual page 283

CHAPTER 5: SETTINGS
that dynamically changes the amount of uncompensated delay, there is no setting that always and completely corrects
for uncompensated delay. A setting can be chosen that reduces the worst-case error to half of the range between
minimum and maximum uncompensated delay, if these values are known.
PORT 1 ... 3 PATH DELAY ASSYMMETRY
mechanism to compensate for any difference in the propagation delay between the two directions of a link. Except in
unusual cases, the two fibers are of essentially identical length and composition, so make this setting zero.
In unusual cases where the length of the link is different in different directions, set this setting to the number of
nanoseconds the Ethernet propagation delay to the relay is longer than the mean of path propagation delays to and from
the relay. For instance, if it is known say from the physical length of the fibers and the propagation speed in the fibers that
the delay from the relay to the Ethernet switch it is connected to is 9000 ns and that the delay from the switch to the relay
is 11000 ns, then the mean delay is 10000 ns, and the path delay asymmetry is 11000 - 10000 = +1000 ns.
5.3.6.3 SNTP protocol
SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  SNTP PROTOCOL
 SNTP PROTOCOL

The L90 supports the Simple Network Time Protocol specified in RFC-2030. With SNTP, the L90 can obtain clock time over
an Ethernet network. The L90 acts as an SNTP client to receive time values from an SNTP/NTP server, usually a dedicated
product using a GPS receiver. UR family relays support unicast, broadcast, multicast, and anycast SNTP functionality.
The setting enables or disables the SNTP feature on the L90.
SNTP FUNCTION
To use SNTP in unicast mode, set
is "Enabled," the L90 attempts to obtain time values from the SNTP/NTP server. Since many time values are
FUNCTION
obtained and averaged, it generally takes three to four minutes until the L90 clock is closely synchronized with the SNTP/
NTP server. It takes up to two minutes for the L90 to signal an SNTP self-test error if the server is offline.
To use SNTP in broadcast mode, set the
then listens to SNTP messages sent to the "all ones" broadcast address for the subnet. The L90 waits up to 18 minutes
(>1024 seconds) without receiving an SNTP broadcast message before signaling an SNTP self-test error.
The is 123 for normal SNTP operation. The change takes effect when the L90 is restarted.
SNTP UDP PORT NUMBER
Do not set more than one protocol to the same TCP/UDP port number, as this results in unreliable operation of
those protocols.
5.3.6.4 Local time
SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  LOCAL TIME
 LOCAL TIME

L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
— This setting corresponds to "delayAsymmetry" in PTP, which is used by the peer delay
SNTP FUNCTION:

Disabled
SNTP SERVER IP ADDR:

0.0.0.0
SNTP UDP PORT

NUMBER: 123
to the SNTP/NTP server IP address. Once this address is set and
SNTP SERVER IP ADDR
setting to "0.0.0.0" and
SNTP SERVER IP ADDR
LOCAL TIME OFFSET

FROM UTC: 0.0 hr
DAYLIGHT SAVINGS

TIME: Disabled
DST START MONTH:

January
DST START DAY:

Sunday
DST START DAY

INSTANCE: First
Range: Enabled, Disabled
Range: standard IP address format
Range: 1 to 65535 in steps of 1
to "Enabled." The L90
SNTP FUNCTION
Range: –24.0 to 24.0 hr in steps of 0.5
Range: Disabled, Enabled
Range: January to December (all months)
Range: Sunday to Saturday (all days of the week)
Range: First, Second, Third, Fourth, Last
PRODUCT SETUP
5
SNTP
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