Cisco Nexus 3548 series - PTP Process; High Availability for PTP

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.
PTP operates only in boundary clock mode. We recommend that you deploy a Grand Master Clock (10 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.
Note
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,
clock class, accuracy, and so on
• 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
synchronization message, there is a follow-up message. The number of sync messages should be equal
to the number of follow-up messages.
• 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
be equal to the number of delay response messages.
• The slave uses these timestamps to adjust its clock to the time of its master.
High Availability for PTP
Stateful restarts are not supported for PTP
Cisco Nexus 3548 Switch NX-OS System Management Configuration Guide, Release 7.x
9
Configuring PTP
PTP Process