About Ptp; Ptp Device Types - Cisco Nexus 7000 Series Configuration Manual

About PTP

About PTP
PTP is a time synchronization protocol for nodes distributed across a network. Its hardware timestamp feature
provides greater accuracy than other time synchronization protocols such as the Network Time Protocol (NTP).
Beginning with Cisco NX-OS Release 7.3(0)D1(1), PTP also implements IEEE 802.1AS to support Audio
Video Bridging (AVB) on Nexus 7700 platform for F3 line cards. For details on AVB configuration, see
"Cisco Nexus 7000 Audio Video Bridging Configuration Guide".
A PTP system can consist of a combination of PTP and non-PTP devices. PTP devices include ordinary clocks,
boundary clocks, and transparent clocks. Non-PTP devices include ordinary network switches, routers, and
other infrastructure devices.
PTP is a distributed protocol that specifies how real-time PTP clocks in the system synchronize with each
other. These clocks are organized into a master-slave synchronization hierarchy with the grandmaster clock,
which is the clock at the top of the hierarchy, determining the reference time for the entire system.
Synchronization is achieved by exchanging PTP timing messages, with the members using the timing
information to adjust their clocks to the time of their master in the hierarchy. PTP operates within a logical
scope called a PTP domain.

PTP Device Types

The following clocks are common PTP devices:
Ordinary clock
Boundary clock
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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.
Configuring PTP