NTP (Network Time Protocol)
ntp
A networking protocol for clock synchronization between computer systems over packet-switched networks.
PTP (Precision Time Protocol)
ptp
Definition
PTP (Precision Time Protocol) is a network time synchronization protocol standardized as IEEE 1588. Where NTP provides millisecond-level accuracy, PTP leverages hardware timestamping to achieve microsecond or even sub-nanosecond synchronization. It is designed for LAN environments, and its precision depends heavily on hardware support in network switches and network interface cards.
Architecture
PTP uses a hierarchical structure headed by a Grandmaster Clock (GMC), which is typically connected to a GPS receiver or atomic clock. The GMC distributes precise time to all devices on the network. The Best Master Clock Algorithm (BMCA) automatically selects the most accurate clock among multiple GMC candidates.
Use Cases
PTP is deployed in financial exchanges (the EU's MiFID II regulation mandates microsecond-precision timestamps), 5G base station synchronization, broadcast audio/video alignment, power grid phase synchronization, and industrial control systems. In cloud environments, AWS Amazon Time Sync Service supports PTP, enabling EC2 instances to achieve microsecond-level time synchronization.
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Related Terms
Stratum
stratum
Stratum is the designation for each level in NTP's hierarchical model, ranging from Stratum 0 (atomic clocks and GPS receivers) to Stratum 15, indicating distance from the reference time source.
Atomic Clock
atomic clock
An atomic clock measures time by using the quantum-mechanical transition frequency of atoms as its reference, achieving accuracies on the order of one second in hundreds of millions of years and forming the backbone of modern timekeeping.
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