 How Set? defaultDS.domainNumber Configurable 0-255 Operator configuration defaultDS.clockQuality.clockClass Dynamic 0-255 Announce from current master defaultDS.twoStepFlag Static Property of clock implementation currentDS.stepsRemoved Dynamic 0-255 Announce from current master parentDS.grandmasterPriority1 Dynamic 0-255 Announce from current master portDS.portIdentity Static Clock ID and port number portDS.portState Dynamic Clock processing and BMCA portDS.logAnnounceInterval Configurable -3 to 4 Operator configuration/profile timePropertiesDS.currentUtcOffset Dynamic Announce from current master timePropertiesDS.leap61 Dynamic Announce from current master Transparent clocks can also maintain transparent clock datasets: one Default dataset (section 8.3.2) for the clock and a Port dataset for each port (section 8.3.3). These two datasets are known as trans- parentClockDefaultDS and transparentClockPortDS respectively. Note that these datasets are optional (section 8.3.1). 7.3.1 Virtual PTP Ports A virtual PTP port on a PTP clock is a connection to an external phase/time input reference (such as a GNSS receiver), but to the clock, it looks like a PTP slave port. This allows the external interface to participate in the BMCA and can be selected as a source of time/phase. This feature is not in- cluded in the IEEE 1588-2008 standard but is covered in Annex B of ITU-T G.8275, "Inclusion of an external phase/time interface on a PTP clock." This feature allows a lot of flexibility when deploying a mixed solution of PTP combined with GNSS receivers. Figure 7-5 shows a basic outline of a virtual port in an example topology. Grand- Boundary master clock Ordinary Ordinary slave slave Time/phase flow M = Master port S = Slave port PTP message flows V = Virtual port Figure 7-5 Example of a Virtual Port in a Timing Distribution Network When this feature is used in a boundary clock, it allows the BMCA to select the local time reference as a primary source of time/phase but still have the possibility to select another port (syn