PTP - Offset and Delay times

Precision Time Protocol (PTP) is a protocol used to synchronize clocks in computer networks. PTP synchronizes clocks by exchanging a couple of timestamped messages and storing the time these messages are sent and received. A slave clock calculates its delay and offset and updates its clock accordingly.

  • Delay: In PTP, delay refers to the time it takes for a message to travel from one device to another over the network. This delay can be influenced by various factors, including the physical distance between devices, the speed of the network, and the amount of traffic on the network. Accurately measuring this delay is critical for precise time synchronization.
    • Path Delay Measurement: PTP uses a mechanism to measure the path delay between two devices (often referred to as the master and slave clocks). This involves sending and receiving timestamped packets to calculate the round-trip time. The protocol assumes that the path delay is symmetrical, meaning the delay from master to slave is the same as from slave to master. This assumption allows the protocol to estimate the one-way delay.
  • Offset: Offset in PTP refers to the difference in time between a device's clock (e.g., a slave clock) and a reference clock (e.g., a master clock). The goal of PTP is to minimize this offset to ensure all devices in the network have synchronized clocks.
    • Offset Correction: Once the delay is measured, PTP calculates the clock offset. This involves comparing the timestamps of the master and slave clocks, taking into consideration the measured delay. The slave clock then adjusts its time based on this offset to align with the master clock's time.

In a PTP-enabled network, these processes of measuring delay and calculating offset occur continuously to maintain precise synchronization, compensating for any changes in network conditions or clock drift. This makes PTP highly effective for applications requiring high precision in time synchronization, such as in telecommunications, industrial automation, and financial trading systems.