GE D30 Instruction Manual page 320

PRODUCT SETUP CHAPTER 5: SETTINGS
virtually identical to the grandmaster time. If one of the network devices in the hierarchy does not fully implement PP, the
associated propagation delay and/or latency may not be compensated for, and the time received at the end-device can be
in error by more than 100 µs.
See the preceding Real Time Clock section for a description of when time values received via PTP are used to update the
relay's real time clock.
The following settings are available for configuring the relay for PTP. The PTP menu displays only when the option was
purchased.
— Power profile (IEEE Std C37.238 2011) requires that the relay only select a power profile compliant
STRICT POWER PROFILE
clock as a grandmaster, that the delivered time have worst-case error of ±1 µs, and that the peer delay mechanism be
implemented. With the strict power profile setting enabled, the relay only selects as master the clocks displaying the
IEEE_C37_238 identification codes. It uses a port only when the peer delay mechanism is operational. With the strict power
profile setting disabled, the relay uses clocks without the power profile identification when no power profile clocks are
present, and uses ports even if the peer delay mechanism is non-operational. This setting applies to all of the relay's PTP
capable ports.
— Set this setting to the domain number of the grandmaster-capable clock(s) to be synchronized to. A
PTP DOMAIN NUMBER
network can support multiple time distribution domains, each distinguished with a unique domain number. More
commonly, there is a single domain using the default domain number zero.
This setting applies to all of the relay's PTP capable ports.
— This setting selects the value of the priority field in the 802.1Q VLAN tag in request messages issued
PTP VLAN PRIORITY
by the relay's peer delay mechanism. In compliance with PP the default VLAN priority is 4, but it is recommended that it be
set to 7 in accordance with PTP. Depending on the characteristics of the device to which the relay is linked directly, VLAN
Priority can have no effect.
This setting applies to all of the relay's PTP capable ports.
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— This setting selects the value of the ID field in the 802.1Q VLAN tag in request messages issued by the relay's
PTP VLAN ID
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.
— While this port setting is selected to disabled, PTP is disabled on this port. The relay does not
PORT 1 ... 3 FUNCTION
generate or listen to PTP messages on this port.
— The time delivered by PTP is advanced by the time value in this setting prior to the time
PORT 1 ... 3 PATH DELAY ADDER
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.
— This setting corresponds to "delayAsymmetry" in PTP, which is used by the peer delay
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.
5-110 D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL