PTP

1 second, is 1000 ms.

1 millisecond: Network latency is measured in ms, or 1 thousandth of a second 0.001.

1 microsecond

1 μs (a millionth) of a second. 0.000 001. 1000 μs is 1 ms.

1 nanosecond

1 ns (a billionth) of a second. 0.000 000 001. 1000 ns is 1 μs.

NTP

An older time standard. Can sync time between 10 to 1 ms.

PTP

Modern time standard. Can sync time between 10 to 1 ns.

PTPv1

Defined in IEEE 1588-2002

PTPv2

Defined in IEEE 1588-2008, not backwards compatible.

PTPv2.1

Defined in IEEE 1588-2019, is backward compatible.

1588 Clock

A clock in the PTP time domain. Clocks have ports.

Terminating Clock

A clock with one port.

Ordinary Clock

A clock in a terminating device.

Boundary Clock

A clock in a transmitting device, like an Ethernet switch. Connects PTP domains.

Transparent Clock

Forwards PTP messages but updates the correction fields for residence time.

Grandmaster

All clocks sync to this one clock.

Master

All clocks in a subdomain sync to the master. The master sync’s to the grand master.

Time Terms

• Epoch: The start of time.
• Offset: The estimated time between a master clock sending time, and a slave clock receiving it.

Uses

• Robotics, synchronizing movements.
• Mobile Phone networks, telemetry, billing, logging
• Financial Networks, trade settling fairness.
• Power Networks, to sync to the 60hz grid.
• Science network, seismic data

Process

After PTP has time from something like a GPS device, it can pass that time along, so long as the devices in the path can mark and read the timestamps

General Messages

• Announce: Used to determine which Grand Master is selected Best Master

• Follow_Up: Used to convey a captured timestamp of a transmitted SYNC message

• Delay_Response: Used to measure delay between IEEE 1588 devices

• Pdelay_Response_Follow_Up: Used between IEEE 1588 devices to measure the delay on an incoming link

• Management: Used between management devices and clocks

• Signaling: Used by clocks to deliver how messages are sent

Event Messages

• Sync: Used to convey time

• Delay_Request: Used to measure delay from downstream devices

• Pdelay_Request: Used to initiate and measure delay

• Pdelay_Response: Used to respond and measure delay