Summary
The Precision Time Protocol (PTP), developed by the Institute of Electrical and Electronics Engineers (IEEE), is a protocol used to synchronize clocks across a local area network. It is essential in industries and applications where precise timing is critical, such as telecommunications, finance, and industrial automation. PTP typically ensures time accuracy in the sub-microsecond range, but nanosecond-level accuracy is also achievable when hardware requirements are met. MikroTik’s implementation of PTP supports IEEE 1588-2008 (PTPv2) and includes hardware timestamping capabilities that ensure synchronization within the nanosecond range. For additional details on MikroTik’s PTP features, please refer to the list below.
Supported Features:
- Two-step Ordinary Clock and Boundary Clock.
- Hardware timestamping, ensuring clock syncronization in nanosecond(ns) range.
- IPv4 and Layer 2 (L2) multicast transport modes.
- End-to-End (E2E) and Peer-to-Peer (P2P) delay mechanisms.
- Profile Support for:
- 802.1AS: Audio Video Bridging (AVB) and Time-Sensitive Networking (TSN).
- AES67: High-performance audio-over-IP interoperability.
- G.8275.1: Frequency and phase synchronization in PTP-aware networks.
- SMPTE: Audio/video synchronization in professional broadcast environments
Mikrotik PTP support is hardware-dependent, please refer to the list of supported devices.
General Properties
Sub-menu: /system ptp
| Property | Description |
|---|---|
| port | Sub-menu used for adding, removing, or viewing assigned ports. |
| status | Sub-menu that shows PTP ports, their state, and delay on slave ports. |
| comment (string; Default: ) | Short description of the PTP profile. |
| name (string; Default: ) | Name of the PTP profile. |
| domain (integer [0..255]; Default: auto) | Identifier used to separate different PTP instances. |
| delay-mode (auto | e2e | p2p; Default: auto) |
|
priority1 (integer [0..255]; auto; Default: auto) | Parameter which takes part in the election of a grandmaster clock. |
priority2 (integer [0..255]; auto; Default: auto) | Parameter which takes part in the election of a backup grandmaster clock. |
| profile (802.1as; aes67; g8275.1; smpte; default; Default: default) | Each profile comes with its own predefined auto values for PTP operating parameters and options:
|
| transport (auto; ipv4; l2-forwardable; l2-non-forwardable; Default: auto) | Transport protocol to be used:
|
Configuration
Configuring Precision Time Protocol (PTP) on MikroTik devices is a straightforward process. The primary steps involve creating a PTP profile and assigning the relevant ports to this profile for PTP operation.
Create a PTP Profile
To create a PTP profile, use the following command. In this example, we use the 802.1as profile, but you can select from other available profiles as needed:
/system ptp add name=ptp1 profile=802.1as
To verify that the profile has been created successfully, execute:
/system ptp print
The output will display the created profile with its current settings:
Flags: I - inactive, X - disabled 0 name="ptp1" priority1=auto priority2=auto delay-mode=auto transport=auto profile=802.1as domain=auto
By default, parameters for each profile are configured to "auto," which automatically selects the appropriate values based on the profile chosen. Before making manual adjustments, verify that the settings conform to relevant standards (e.g., ITU-T G.8275.1, IEEE 802.1as, SMPTE, AES67).
Assign Ports to the PTP Profile
As the final step, assign the ports that will participate in PTP. For example, lets include ether1 (connected to the grandmaster clock) and ether2 (connected to an ordinary clock/slave):
/system ptp port add interface=ether1 ptp=ptp1 /system ptp port add interface=ether2 ptp=ptp1
Monitoring
To monitor the status and performance of the PTP profile, use the following command:
/system ptp monitor 0
The output will provide detailed information about the profile's operational status:
name: ptp1 clock-id: 64:D1:54:FF:FE:EB:AD:C7 priority1: 246 priority2: 248 i-am-gm: no gm-clock-id: 64:D1:54:FF:FE:EB:AE:C3 gm-priority1: 100 gm-priority2: 248 master-clock-id: 64:D1:54:FF:FE:EB:AE:C3 slave-port: ether1 freq-drift: 2690 ppb offset: 3 ns hw-offset: -889419842 ns slave-port-delay: 306 ns
This information includes critical details such as the clock IDs, priority values, and timing offsets, which are essential for monitoring the accuracy and synchronization of your PTP setup.
Monitor Properties
| Property | Description |
|---|---|
| clock-id: | Local clock identifier, used to uniquely identify the clock within the PTP network. |
| priority1: | The priority parameter used in the election of the grandmaster clock. A lower value indicates higher priority. |
| priority2: | The priority parameter used in the election of the backup grandmaster clock. A lower value indicates higher priority. |
| i-am-gm: yes | no | Indicates if the device is a grandmaster clock (yes) or not (no). |
| gm-clock-id: | Identifier of the grandmaster clock. This is the clock providing the primary time source. |
| gm-priority1: | The priority1 value of the grandmaster clock as seen from the slave device. |
| gm-priority2: | The priority2 value of the grandmaster clock as seen from the slave device. |
| master-clock-id: | Identifier of the master clock in the PTP communication path. This may be a grandmaster clock or a boundary clock, depending on the network topology. |
| slave-port: | The port on the device that is connected to the master or grandmaster clock. |
| freq-drift: | The frequency drift between the master and slave clocks, measured in parts per billion (ppb). This indicates how much the slave clock's frequency deviates from the master clock's frequency. |
| offset: | The time difference between the master and slave clocks, measured in nanoseconds (ns). This reflects the synchronization accuracy. |
| hw-offset: | Offset difference from the hardware clock. |
| slave-port-delay: | The time delay for packets traveling between two devices, measured in nanoseconds (ns). This delay can be influenced by the quality of cables and transceivers used in the network. |
Supported Devices
Important: Devices not listed in this section do not support Precision Time Protocol.
- CRS326-24G-2S+: Supported only on Gigabit Ethernet ports.
- CRS328-24P-4S+: Supported only on Gigabit Ethernet ports.
- CRS317-1G-16S+: Supported on all ports.
- CRS326-24S+2Q+: Supported on SFP+ and QSFP+ interfaces.
- CRS312-4C+8XG: Supported on all ports.
- CRS318-16P-2S+: Supported only on Gigabit Ethernet ports.
PTP Support Added in RouterOS Version 7.16 and Later:
- CCR2116-12G-4S+: Supported on all ports.
- CCR2216-1G-12XS-2XQ: Supported on all ports.
- CRS518-16XS-2XQ: Supported on all ports.
- CRS504-4XQ: Supported on all ports.
- CRS510-8XS-2XQ: Supported on all ports.
- CRS520-4XS-16XQ: Supported on all ports.
PTP Support Added in RouterOS Version 7.17 and Later:
- CRS320-8P-8B-4S+RM: Supported only on Gigabit Ethernet ports.