nx.os.and.cisco.nexus.switching.2nd.edition.1587143046

PTP is based on IEEE 1588 and is becoming an emerging technology in applications where
submicrosecond accuracy is needed. Commonly found in financial networks and research
and scientific networks, PTP is more common than ever. PTP has some significant
differences from a protocol like NTP beyond clock accuracy. PTP networks are typically
smaller in diameter with fewer nodes per domain. With NTP it’s not uncommon to have
hundreds of devices across the world using the same clock source. NTP scales well, and the
extra distance and latency don’t have significant impact on accuracy. PTP, on the other hand,
usually spans a handful of network devices and has a much smaller diameter. Distance and
latency significantly impact the accuracy of the clock, so PTP is deployed in smaller
pockets. Typically, a GPS or cellular device takes a role called grandmaster and is the top
of the PTP domain’s hierarchy.
PTP networks have multiple types of clocks including ordinary, boundary, and transparent
clocks, each with its own set of function and capabilities. NX-OS devices operate in
boundary clock mode where each port can decide which state it is in regarding
synchronization.
Configuring PTP is a multistep process where the feature is enabled and the PTP domain
and clocks are specified. Example 7-56 illustrates enabling PTP, and setting the domain and
clocks.
Example 7-56. PTP Enablement, Domain Configuration, and PTP Source Configuration
Click here to view code image
N7K-1-Agg1# config
Enter configuration commands, one per line. End with
CNTL/Z.
N7K-1-Agg1(config)# feature ptp
N7K-1-Agg1(config)# ptp domain 100
N7K-1-Agg1(config)# ptp source 10.89.64.1
N7K-1-Agg1(config)# end
N7K-1-Agg1# show ptp clock
PTP Device Type: Boundary clock
Clock Identity : 00:26:98:ff:fe:0f:d9:c2
Clock Domain: 100
Number of PTP ports: 0
Priority1 : 255
Priority2 : 255
Clock Quality:
Class : 248
Accuracy : 254
Offset (log variance) : 65535
Offset From Master : 0
Mean Path Delay : 0
Steps removed : 0