7210 SAS-M, T, R6, R12, Mxp, Sx, S Basic System
Configuration Guide
System Management
Edition: 01 3HE 16132 AAAB TQZZA 295
6.5.8.6 PTP Ordinary Slave Clock for Frequency
Traditionally, only clock frequency is required to ensure smooth transmission in a
synchronous network. The PTP ordinary clock with slave capability on the 7210 SAS
provides another option to reference a Stratum-1 traceable clock across a packet
switched network. The recovered clock can be referenced by the internal SSU and
distributed to all slots and ports.
Figure 30 shows a PTP ordinary slave clock network configuration.
Figure 30 Slave Clock
6.5.9 PTP Boundary Clock for Frequency and Time
Although IEEE 1588v2 can function across a packet network that is not PTP-aware,
performance may be unsatisfactory and unpredictable. PDV across the packet
network varies with the number of hops, link speeds, utilization rates, and the
inherent behavior of routers. By using routers with boundary clock functionality in the
path between the grandmaster clock and the slave clock, one long path over many
hops is split into multiple shorter segments, allowing better PDV control and
improved slave performance. This allows PTP to function as a valid timing option in
more network deployments and allows for better scalability and increased
robustness in certain topologies, such as rings.
Boundary clocks can simultaneously function as a PTP slave of an upstream
grandmaster (ordinary clock) or boundary clock, and as a PTP master of downstream
slaves (ordinary clock) and boundary clocks. The time scale recovered in the slave
side of the boundary clock is used by the master side of the boundary clock. This
allows time distribution across the boundary clock.
Figure 31 shows routers with boundary clock functionality in the path between
grandmaster clock and the slave clock.
Packet
Network
1588v2
Grand
Master
PTP Slave
1588v2
Grand
Master
OSSG737
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