GE L30 Instruction Manual

Also see for L30: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

CHAPTER 5: SETTINGS PRODUCT SETUPL30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-1115Time messages issued by the grandmaster are delayed as they pass through the network both due to the finite speed ofthe signal in the interconnecting fiber or wire, and due to processing delays in the Ethernet switches. Each clock and switchimplementing PP measures the propagation delay to each of its PP neighbors, and compensates for these delays in thetime received. Each network device implementing PP measures the processing delay it introduces in each time messageand compensates for this delay in the time it transmits. As a result, the time delivered to end-devices such as the UR arevirtually identical to the grandmaster time. If one of the network devices in the hierarchy does not fully implement PP, theassociated propagation delay and/or latency may not be compensated for, and the time received at the end-device can bein 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 therelay’s real time clock.The following settings are available for configuring the relay for PTP. The PTP menu displays only when the option waspurchased.STRICT POWER PROFILE — Power profile (IEEE Std C37.238 2011) requires that the relay only select a power profile compliantclock as a grandmaster, that the delivered time have worst-case error of ±1 μs, and that the peer delay mechanism beimplemented. With the strict power profile setting enabled, the relay only selects as master the clocks displaying theIEEE_C37_238 identification codes. It uses a port only when the peer delay mechanism is operational. With the strict powerprofile setting disabled, the relay uses clocks without the power profile identification when no power profile clocks arepresent, and uses ports even if the peer delay mechanism is non-operational. This setting applies to all of the relay’s PTPcapable ports.PTP DOMAIN NUMBER — Set this setting to the domain number of the grandmaster-capable clock(s) to be synchronized to. Anetwork can support multiple time distribution domains, each distinguished with a unique domain number. Morecommonly, 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 issuedby the relay’s peer delay mechanism. In compliance with PP the default VLAN priority is 4, but it is recommended that it beset to 7 in accordance with PTP. Depending on the characteristics of the device to which the relay is linked directly, VLANPriority can 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’speer delay mechanism. It is provided in compliance with PP. As these messages have a destination address that indicatesthey are not to be bridged, their VLAN ID serves no function, and so can be left at its default value. Depending on thecharacteristics of the device to which the relay is linked directly, VLAN ID can have no effect. This setting applies to all ofthe 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 notgenerate 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 timebeing used to synchronize the relay’s real time clock. This is to compensate to the extent practical for time delivery delaysnot compensated for in the network. In a fully compliant PP network, the peer delay and the processing delay mechanismscompensate 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 alldelays are compensated, so the time of message arrival at the relay is later than the time indicated in the message. Thissetting can be used to approximately compensate for this delay. However, as the relay is not aware of network switchingthat dynamically changes the amount of uncompensated delay, there is no setting that always and completely correctsfor uncompensated delay. A setting can be chosen that reduces the worst-case error to half of the range betweenminimum 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 delaymechanism to compensate for any difference in the propagation delay between the two directions of a link. Except inunusual cases, the two fibers are of essentially identical length and composition, so make this setting zero.