# IEEE 1588-2019

Protocols · `IEEE 1588-2019` · verification: source checked

IEEE 1588-2019 defines the Precision Time Protocol (PTP), a packet-based protocol for synchronizing real-time clocks in networked measurement and control systems. It allows clocks with different precision, resolution, and stability to synchronize to a grandmaster clock, with sub-microsecond accuracy and minimal network and computing resources. The standard specifies timing domains, timing topology, profiles, conformance requirements, optional security, and mappings to UDP/IP and layer-2 Ethernet.

## Specification

| Property | Value |
|---|---|
| Transports | udp, ethernet_l2 |
| Architecture | master slave |
| Encoding | binary |
| Standard body | IEEE |
| Standard ref | IEEE 1588-2019 |

## Study notes

- PTP supports multicast, unicast, or both; profiles allow customization, and default profiles allow simple systems to operate without user management.
- The standard states sub-microsecond synchronization accuracy with minimal network and local computing resources; sub-nanosecond time transfer can be achieved in a properly designed network.
- A grandmaster clock can be synchronized to an external time source if time traceable to international standards or another source is required.
- Devices can compute Coordinated Universal Time (UTC) from protocol-distributed time if the grandmaster is traceable to international standards and can access pending leap-second changes.
- The protocol defines timing domains for consistent system timing and establishes the timing topology.
- The standard defines data types, message formats, required computations, internal states, device behavior, management of protocol artifacts, conformance requirements, and optional security specifications.
- The document lists amendments including BMCA enhancements (1588a-2023), OTN mapping (1588b-2022), terminology clarification (1588c-2024), GDOI key management (1588d-2023), MIB/YANG modules (1588e-2024), alternative master/slave terminology (1588g-2022), and an option to disable Announce messages (1588h-2026).
- Backward compatibility with IEEE Std 1588-2008 and IEEE Std 1588-2019 is documented under stated conditions.
- The document names IEEE Std 802.3 Ethernet, IEC 61588-2004, OTN, GDOI, MIB, and YANG; these do not have matching ids in the provided reference list.

## Sources

1. [IEEE SA - IEEE 1588-2019](https://standards.ieee.org/ieee/1588/6825/) (accessed 2026-10-25)

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