# PTP

## 1. Function Overview

PTP (Precision Time Protocol) is a protocol for synchronizing the time of multiple devices in measurement and control systems with high accuracy on the nanosecond timescale.
Time is synchronized by sending and receiving PTP messages between a time transmitter clock, which distributes the reference time within the network, and a time receiver clock, which synchronizes with the distributed time.
If a PTP-incompatible switch is used to relay the time transmitter clock and time receiver clock, the forwarded PTP message will arrive at each device with a delay equal to the time it took the switch to forward the message (relay delay time).
In order to synchronize time with high precision, this relay delay time cannot be ignored.

- In relaying with a PTP-incompatible switch

In relaying with a PTP-compatible switch, the relay delay time of the switch is added to the PTP message to be forwarded by the switch. Therefore, the receiving device can correct the time including the relay delay time of the switch.

- In relaying with a PTP-compatible switch

This product supports PTPv2 (IEEE1588-2008).
The transparent clock of this product can only be used in configurations that employ the 1-step or 2-step end-to-end mechanism. The clock does not work in configurations that employ peer-to-peer mechanisms.

## 2. Definition of Terms Used

Time transmitter clock (timeTransmitter Clock)

A PTP-compatible device that distributes the reference time with which PTP-compatible devices on the communication path are synchronized.

Time receiver clock (timeReceiver Clock)

A PTP-compatible device that synchronizes with the time distributed by a time transmitter clock.

Transparent clock (Transparent Clock)

A device that measures the time taken for a PTP message to pass through the device and reflects that information in the PTP message before relaying it.

End-to-end mechanism

A mechanism for measuring the transmission delay time between a time transmitter clock and a time receiver clock. Relay devices such as switches add only the relay delay time to the PTP message as a correction value.

1-step

A method of acquiring time information when sending a PTP message and notifying of the time information with the same message.

## 3. Function Details

This product supports the following functions.

- Setting the operation mode

- Setting the PTP message transport protocol

### 3.1. Setting the operation mode

The operation mode cannot be changed because only the end-to-end transparent clock (1-step) is currently supported.
If the function is expanded in the future, the operation mode will be set by using the ptp mode command.

### 3.2. Setting the PTP message transport protocol

PTP messages can be forwarded using a variety of frame formats.
To relay PTP messages with a switch, the switch must use the same frame format as the time transmitter clock and time receiver clock.
This product supports IPv4 UDP, IPv6 UDP, and L2 Ether frames.
You can set the transport protocol with the ptp transport protocol command.

## 4. Related Commands

Related commands are indicated below.
For details on the commands, refer to the Command Reference.

Operations | Operating commands
--- | ---
Set the PTP for a system | ptp
Set the PTP for an interface | ptp
Set the operation mode | ptp mode
Set the transport protocol for PTP messages | ptp transport protocol
Show the PTP setting status | show ptp
Show PTP information for an interface | show ptp interface

## 5. Examples of Command Execution

### 5.1. Setting the end-to-end transparent clock

IPv4 UDP is used as the transport protocol for PTP messages.
Enable the PTP function on the interface to which the time transmitter clock and time receiver clock are connected.
The PTP function of the interface connected to the PTP-incompatible device should be kept disabled.

1. Set the transport protocol for PTP messages to IPv4 UDP.

       Yamaha(config)#ptp transport protocol ipv4-udp

2. Enable the PTP function for the system.

       Yamaha(config)#ptp enable

3. Enable the PTP function for the interface.

       Yamaha(config)#interface port1.1
       Yamaha(config-if)#ptp enable (1)
       Yamaha(config-if)#exit
       Yamaha(config)#interface port1.7
       Yamaha(config-if)#ptp enable (2)
       Yamaha(config-if)#exit
       Yamaha(config)#interface port1.8
       Yamaha(config-if)#ptp enable (3)
       Yamaha(config-if)#exit

   1 | Enable the PTP function for port1.1
   2 | Enable the PTP function for port1.7
   3 | Enable the PTP function for port1.8

4. Check the PTP settings.

       Yamaha#show ptp
         PTP State                 : Enabled
         PTP Mode                  : Transparent Clock
         Delay Mechanism           : End to End
         Step Mode                 : One-step
         Transport Protocol        : UDP (IPv4)

5. Check the PTP settings for the interface.

       Yamaha#show ptp interface
       Interface  PTP
       -------------------
       port1.1    Enable
       port1.2    Disable
       port1.3    Disable
       port1.4    Disable
       port1.5    Disable
       port1.6    Disable
       port1.7    Enable
       port1.8    Enable

## 6. Points of Caution

- This function only supports communication speeds of 1G, 10G, 25G, and 100Gbps.

- This function cannot be used in conjunction with the stack function.

- PTPv2 messages are always flooded even if IGMP/MLD snooping is enabled.

- PTPv1 messages are transmissive.

- This function is not supported in conjunction with link aggregation.

## 7. Related Documentation

- PTP

  - IEEE1588-2008

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