Ptp Process - Cisco Nexus 3548 Configuration Manual

Configuring PTP
Transparent clock
PTP operates only in boundary clock mode. We recommend that you deploy a Grand Master Clock (10
Note
MHz) upstream. The servers contain clocks that require synchronization and are 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:
• Examines the contents of all received announce messages (issued by ports in the master state)
• Compares the data sets of the foreign master (in the announce message) and the local clock for priority,
• Determines its own state as either master or slave
After the master-slave hierarchy has been established, the clocks are synchronized as follows:
• The master sends a synchronization message to the slave and notes the time it was sent.
• The slave receives the synchronization message and notes the time that it was received. For every
• The slave sends a delay-request message to the master and notes the time it was sent.
• The master receives the delay-request message and notes the time it was received.
• The master sends a delay-response message to the slave. The number of delay request messages should
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.
clock class, accuracy, and so on
synchronization message, there is a follow-up message. The number of sync messages should be equal
to the number of follow-up messages.
be equal to the number of delay response messages.
Cisco Nexus 3548 Switch NX-OS System Management Configuration Guide, Release 6.x
PTP Process
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