GE b30, Instruction Manual, Page: 320 / 632

5-112 B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
PRODUCT SETUP CHAPTER 5: SETTINGS
5
PTP VLAN ID
— This setting selects the value of the ID field in the 802.1Q VLAN tag in request messages issued by the relay’s
peer delay mechanism. It is provided in compliance with PP. As these messages have a destination address that indicates
they are not to be bridged, their VLAN ID serves no function, and so can be left at its default value. Depending on the
characteristics of the device to which the relay is linked directly, VLAN ID can have no effect. This setting applies to all of
the relay’s PTP capable ports.
PORT 1 ... 3 FUNCTION
— While this port setting is selected to disabled, PTP is disabled on this port. The relay does not
generate or listen to PTP messages on this port.
PORT 1 ... 3 PATH DELAY ADDER
— The time delivered by PTP is advanced by the time value in this setting prior to the time
being used to synchronize the relay’s real time clock. This is to compensate to the extent practical for time delivery delays
not compensated for in the network. In a fully compliant PP network, the peer delay and the processing delay mechanisms
compensate for all the delays between the grandmaster and the relay. In such networks, make this setting zero.
In networks containing one or more switches and/or clocks that do not implement both of these mechanisms, not all
delays are compensated, so the time of message arrival at the relay is later than the time indicated in the message. This
setting can be used to approximately compensate for this delay. However, as the relay is not aware of network switching
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
— This setting corresponds to “delayAsymmetry” in PTP, which is used by the peer delay
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.
5.3.7.3 SNTP protocol
SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  SNTP PROTOCOL
The B30 supports the Simple Network Time Protocol specified in RFC-2030. With SNTP, the B30 can obtain clock time over
an Ethernet network. The B30 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
SNTP FUNCTION
setting enables or disables the SNTP feature on the B30.
To use SNTP in unicast mode, set
SNTP SERVER IP ADDR
to the SNTP/NTP server IP address. Once this address is set and
SNTP
FUNCTION
is “Enabled,” the B30 attempts to obtain time values from the SNTP/NTP server. Since many time values are
obtained and averaged, it generally takes three to four minutes until the B30 clock is closely synchronized with the SNTP/
NTP server. It takes up to two minutes for the B30 to signal an SNTP self-test error if the server is offline.
To use SNTP in broadcast mode, set the
SNTP SERVER IP ADDR
setting to “0.0.0.0” and
SNTP FUNCTION
to “Enabled.” The B30
then listens to SNTP messages sent to the “all ones” broadcast address for the subnet. The B30 waits up to 18 minutes
(>1024 seconds) without receiving an SNTP broadcast message before signaling an SNTP self-test error.
The
SNTP UDP PORT NUMBER
is 123 for normal SNTP operation. The change takes effect when the B30 is restarted.
After enabling and waiting for the synchronization, verify that there is no SNTP Failure message in the Event Records.
 SNTP PROTOCOL


SNTP FUNCTION:
Disabled
Range: Enabled, Disabled

SNTP SERVER IP ADDR:
0.0.0.0
Range: standard IP address format

SNTP UDP PORT
NUMBER: 123
Range: 1 to 65535 in steps of 1