Ptp Device Types - Cisco Nexus 5000 Series Configuration Manual

PTP Device Types

PTP Device Types
The following clocks are common PTP devices:
Ordinary clock
Boundary clock
Transparent clock
PTP operates only in boundary clock mode. Cisco recommends deployment of a Grand Master Clock
Note
(GMC) upstream, with servers containing clocks requiring synchronization connected to the switch.
End-to-end transparent clock and peer-to-peer transparent clock modes are not supported.
PTP Process
The PTP process consists of two phases: establishing the master-slave hierarchy and synchronizing the clocks.
Within a PTP domain, each port of an ordinary or boundary clock follows this process to determine its state:
Cisco Nexus 5000 Series NX-OS System Management Configuration Guide, Release 5.2(1)N1(1)
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Communicates with the network based on a single physical port, similar to an end host. An ordinary
clock can function as a grandmaster clock.
Typically has several physical ports, with each port behaving like a port of an ordinary clock. However,
each port shares the local clock, and the clock data sets are common to all ports. Each port decides its
individual state, either master (synchronizing other ports connected to it) or slave (synchronizing to a
downstream port), based on the best clock available to it through all of the other ports on the boundary
clock. Messages related to synchronization and establishing the master-slave hierarchy terminate in the
protocol engine of a boundary clock and are not forwarded.
Forwards all PTP messages like an ordinary switch or router but measures the residence time of a packet
in the switch (the time that the packet takes to traverse the transparent clock) and in some cases the link
delay of the ingress port for the packet. The ports have no state because the transparent clock does not
need to synchronize to the grandmaster clock.
There are two kinds of transparent clocks:
End-to-end transparent clock
Measures the residence time of a PTP message and accumulates the times in the correction field
of the PTP message or an associated follow-up message.
Peer-to-peer transparent clock
Measures the residence time of a PTP message and computes the link delay between each port
and a similarly equipped port on another node that shares the link. For a packet, this incoming
link delay is added to the residence time in the correction field of the PTP message or an associated
follow-up message.
Configuring PTP