Lenovo ThinkSystem NE2552E, Application Manual

Page: 235 / 574

© Copyright Lenovo 2018 Chapter 13: Precision Time Protocol
235
Chapter 13. Precision Time Protocol
As defined in the IEEE 1588 ‐ 2008 standard, Precision Time Protocol (PTP) is a
precision clock synchronization protocol for networked measurement and control
systems. PTP provides system ‐ wide synchronization accuracy and precision in the
sub ‐ microsecond range with minimal network and local clock computing
resources. The synchronization is achieved through the exchange of messages:
General messages that carry data but need not be time stamped; Event messages
that are time stamped and are critical for clock synchronization accuracy.
A PTP network consists of PTP ‐ enabled devices such as switches or routers. These
devices consist of the following types of clocks:
 Master clock: In a PTP domain, the clock with the most precise time is
considered the master clock. A best master clock algorithm determines the
highest quality clock in a network.
 Ordinary clock: An ordinary clock synchronizes its time with the Master clock.
The ordinary clock has a bidirectional communication with the master clock. By
receiving synchronization/delay response and sending delay request packets,
the ordinary clock adjusts its time with the master clock.
 Boundary clock: A boundary clock connects to multiple networks. It
synchronizes with the attached master clock and in turn acts as a master clock to
all attached ordinary clocks. Boundary clocks help to reduce the effect of jitter in
Ethernet ‐ based networks.
 Transparent clock: A transparent clock listens for PTP packets and adjusts the
correction field in the PTP event packets as they pass the PTP device.
Lenovo ThinkSystem NE2552E Flex Switch supports the configuration of ordinary
clock and transparent clock. It cannot be a master clock as the switch does not
participate in the master clock selection process.
Note:
Lenovo ENOS does not support IPv6 for PTP.
By default, PTP version 2 is installed on the switch but is globally disabled. Use the
following command to globally enable PTP:
PTP is configured on switch ports. In case of LAG ports, the PTP configuration
must be the same on all ports participating in the same LAG. The switch uses only
one port from a LAG (typically the one used by a multicast protocol) to forward
PTP packets.
By default, PTP is enabled on all the switch ports. To disable PTP on a port, use the
following commands:
Note:
PTP cannot be enabled on management ports.
NE2552E(config)# ptp {ordinary|transparent} enable
NE2552E(config)# interface port
<port>
NE2552E(config-if)# no ptp