GE B30 UR Series Instruction Manual page 172

5.2 PRODUCT SETUP
Time messages issued by the grandmaster are delayed as they pass through the network both due to the finite speed of
the signal in the interconnecting fiber or wire, and due to processing delays in the Ethernet switches. Each clock and switch
implementing PP measures the propagation delay to each of its PP neighbors, and compensates for these delays in the
time received. Each network device implementing PP measures the processing delay it introduces in each time message
and compensates for this delay in the time it transmits. As a result, the time delivered to end-devices such as the UR are
virtually identical to the grandmaster time. Should one of the network devices in the hierarchy not fully implement PP, the
associated propagation delay and/or latency may not be compensated for, and the time received at the end-device could be
in error by more than 100 µs.
See the Settings > Product Setup > Real Time Clock section of this manual 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.
STRICT POWER PROFILE
• Power profile (IEEE Std C37.238 2011) requires that the relay only select as a grandmaster power profile compliant
clocks, 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 will only select as master clocks displaying the IEEE_C37_238
identification codes. It will use a port only when the peer delay mechanism is operational. With the strict power profile
setting disabled, the relay will use clocks without the power profile identification when no power profile clocks are pres-
ent, and will use ports even if the peer delay mechanism is non-operational.
• This setting applies to all of the relay's PTP capable ports.
PTP DOMAIN NUMBER
• This setting should be set to the domain number of the grandmaster-capable clock(s) to be synchronized to. A network
may support multiple time distribution domains, each distinguished with a unique domain number. More commonly,
5
there is a single domain using the default domain number zero.
• This setting applies to all of the relay's PTP capable ports.
PTP VLAN PRIORITY
• This setting selects the value of the priority field in the 802.1Q VLAN tag in request messages issued by the relay's
peer delay mechanism. In compliance with PP the default VLAN priority is 4, but it is recommended that in accordance
with PTP it be set to 7.
• Depending on the characteristics of the device to which the relay is directly linked, VLAN Priority may have no effect.
• This setting applies to all of the relay's PTP capable ports.
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 may be left at its default value.
• Depending on the characteristics of the device to which the relay is directly linked, VLAN ID may 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, this setting should be 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 will be later than the time indicated in the mes-
sage. This setting can be used to approximately compensate for this delay. However, as the relay is not aware of net-
work switching that dynamically changes the amount of uncompensated delay, there is no setting that will always
5-50 B30 Bus Differential System
5 SETTINGS
GE Multilin