GE Reason RT430 Technical Manual page 88

GPS Grandmaster Clock
The algorithm establishes an order of searching for the attributes and from the results, determines which will
be used as time source.

Boundary Clock: According to IEEE1588 standard, a boundary clock has multiple PTP ports in a
domain and maintains the timescale used in the domain. It may serve as the source of time, i.e., be
a master clock, and may synchronize to another clock, i.e., be a slave clock.

Ordinary Clock: According to IEEE1588 standard, an ordinary clock has a single PTP port in a
domain and maintains the timescale used in the domain. It may serve as a source of time, i.e., be a
master clock, or may synchronize do another clock, i.e., be a slave clock.

Transparent Clock: According to IEEE1588,a transparent clock is a device that measures the time
take from a PTP event message to transit the device and provides this information to clocks
receiving this PTP event message.

End-to-end Transparent Clock: According to IEEE1588 standard, it is a transparente clock that
supports the use of the end-to-endy delay measurement mechanism between slave clocks and
master clock.

Peer-to-peer Transparent Clock: According to IEEE1588 standard, it is a transparent clock that, in
addition to providing PTP event transit time information, also provides corrections for the propagation
delay of the link connected to the port receiving the PTP event message.

One-step Clock: According to IEEE1588 standard, it is a clock that provides time information using
a single event message.

Two-step Clock: According to IEEE1588 standard, it is a clock that provides time information using
the combination of an event message and subsequent general message.

Accuracy: According to IEEE1588 standard, the mean of the time or frequency error between the
clock under test and a perfect reference clock, over na ensemble of measurements. Stability is a
measure of how the mean varies with respect to variables such as time, temperature, and so on. The
precision is a measure of the deviation of the error from the mean.

Profile: According to IEEE1588 standard, profile is a set of all allowed PTP features applicable to a
device.

Timeout: According to IEEE1588 standard, timeout is the time in which a device waits to receive
synchronization messages. In case the message is not received within this time interval, the clock
that sends messages is considered out of operation and the BMC algorithm is ran, and chooses a
second master clock.
Hierarchical Topology
IEEE1588 defines a hierarquical topology composed of different types of clocks that send and receive
synchronization messages.
In hierarquical topology, a boundary clock is elected the grandmaster clock that sends PTP messages for the
entire network, which are also connected ordinary and boundary clocks. The boundary clocks connected to
the network are used as intermediate synchronism source for ordinary clock. The selection of the source
clock is performed by each receiver device, using the BMC algorithm.
Multicast e Unicast Networks
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