PTP (Precision Time Protocol)
Precision Time Protocol (PTP), standardised as IEEE 1588, distributes a common reference time across packet networks so that distributed nodes share a clock with sub-microsecond to nanosecond accuracy — far beyond what NTP typically achieves over IP. PTP operates in a master–slave hierarchy: a Grandmaster Clock (GM) holds traceability to GNSS (GPS, Galileo, etc.) or a Primary Reference Time Clock (PRTC); Boundary Clocks (BC) terminate and regenerate timing on hops; Transparent Clocks (TC) correct residence time in switches without terminating the protocol. Messages (Sync, Follow_Up, Delay_Req/Resp, optional Announce) implement a delay request–response mechanism to estimate path asymmetry and offset each Ordinary Clock (OC) slave relative to the grandmaster.