Industrial Managed
Ethernet Switch – EH9711
User Manual
Page
138
of
223
They are broadly categorized into ordinary clocks and boundary clocks. The primary clock and the client clock are known as
ordinary clocks. The boundary clock can operate as either a primary clock or a client clock. The following list explains these
clocks in detail:
Primary clock—The primary clock transmits the messages to the PTP clients (also called client node or boundary
node). This allows the clients to establish their relative time distance and offset from the primary clock (which is the
reference point) for phase synchronization. Delivery mechanism to the clients is either unicast or multicast packets
over Ethernet or UDP.
Member clock—located in the PTP client (also called client node), the client clock performs clock and time
recovery operations based on the received and requested timestamps from the primary clock.
Boundary clock—The boundary clock operates as a combination of the primary and client clocks. The boundary
clock endpoint acts as a client clock to the primary clock, and also acts as the primary to all the slaves reporting to
the boundary endpoint.
PTP sends messages between the primary clock and client clock device to determine the delay measurement. Then, PTP
measures the exact message transmit and receive times and uses these times to calculate the communication path delay. PTP
then adjusts current time information contained in network data for the calculated delay, resulting in more accurate time
information.
This delay measurement principle determines path delay between devices on the network, and the local clocks are adjusted for
this delay using a series of messages sent between masters and slaves. The one-way delay time is calculated by averaging the
path delay of the transmit and receive messages. This calculation assumes a symmetrical communication path; however,
switched networks do not necessarily have symmetrical communication paths, due to the buffering process.
PTP provides a method, using transparent clocks, to measure and account for the delay in a time-interval field in network
timing packets, making the switches temporarily transparent to the master and slave nodes on the network. An end-to-end
transparent clock forwards all messages on the network in the same way that a switch does.
The PTP webpage as shown in Figure 2.113 allows the user to configure and inspect the current PTP clock settings. Table
2.101 summarizes the parameters for PTP Clock Configuration.
Figure 2.113 Webpage to Configure PTP
Figure 2.114 Webpage to Configure New PTP Clock
