Figure 21: Boundary Clocks In A Network - Juniper ACX1000 Configuration Manual

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Figure 21: Boundary Clocks in a Network

BC-1
ACX Series Router
P-1 P-2 P-3 P-4
S M M S
Remote M Remote S
OC-1 OC-2
Grandmaster
BC - Boundary Clock
OC - Ordinary Clock
The first boundary clock—BC-1—has four ports. Each port is configured as follows:
BC-1 P-1 and BC-1 P-4 are boundary slave ports connected to two grandmaster
clocks—OC-1 and OC-5. The grandmasters are included as the clock sources in the
slave port configurations. From the packets received on the slave ports, BC-1 selects
the best master, synchronizes its clock, and generates PTP packets, which are sent
over the master ports—BC-1 P-2 and BC-1 P-3—to the downstream clients.
BC-1 P-2, a master port, is connected to OC-2, an ordinary remote slave. OC-2 is included
as a clock client in BC-1 P-2's master configuration, and so receives PTP packets from
BC-1 P-2.
BC-1 P-3, a master port, is connected to BC-2 P-1, a remote boundary slave port. In this
situation, the master port—BC-1 P-3—is included as a clock source in the configuration
of the boundary slave port—BC-2 P-1. In addition, the boundary slave port—BC-2 P-1—is
included as a clock client in the configuration of the master port—BC-1 P-3. With this
configuration, the boundary slave—BC-2 P1—receives PTP packets from BC-1 P3.
The second boundary clock—BC-2—has three ports. Each port is configured as follows:
BC-2 P-1 is a boundary slave port connected to the upstream master port—BC-1 P3.
As described previously, BC-2 P-1 receives PTP packets from BC-1 P3. The master
ports—BC-2 P-2 and BC-2 P-3—synchronize their time from the packets received from
BC-2 P1.
BC-2 P-2 and BC-2 P-3, boundary master ports, are connected to ordinary remote
slaves—OC-3 and OC-4. OC-3 and OC-4 are included as clock clients in the
configuration of the master ports—BC-2 P2 and BC-2 P-3. Both slaves receive PTP
packets from the master boundary port to which they are connected.
In this example, the boundary clock synchronizes its clock from the packets received on
its slave ports from the upstream master. The boundary clock then generates PTP packets,
which are sent over the master port to downstream clients. These packets are
timestamped by the boundary clock by using its own time, which is synchronized to the
selected upstream master.
Chapter 9: Configuring Timing and Synchronization
BC-2
ACX Series Router
Remote M
OC-5
Grandmaster
P-1 P-2
S M
Remote S
OC-3
M- Master P - Ports on an ACX Series router
S - Slave
P-3
M
Remote S
OC-4
235