Precision Time Protocol (PTP)

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Precision Time Protocol (PTP) provides clock synchronization to network devices to a higher degree of accuracy than NTP.

• NTP is not accurate enough for the most timing critical application requirements
  • e.g., networks supporting industrial processes, 5G cellular data, medical devices, market trading and financial services, or broadcasting
• capable of nanosecond precision
• is also a general replacement for NTP
• defined in IEEE 1588 standard
• can use layer 2 messaging plus hardware clocks in compatible network adapters and switches
  • to ensure greater levels of accuracy than NTP
• uses mechanisms to measure and account for delay
• supported clock types:
  • Grandmaster clock
    • the authoritative time source within a PTP domain
  • Boundary clock
    • one with interfaces in multiple PTP segments
  • Ordinary clock
    • one with a single PTP interface
  • Transparent clock
    • can measure path delay and adjust P2P messages
• when two clocks are connected,
  • one interface has a timeTransmitter role
  • the other has a timeReceiver role
• grandmaster clock’s interfaces are always timeTransmitter
• boundary clock has
  • timeReceiver role on its interface with the grandmaster
  • timeTransmitter role on other interfaces
• ordinary clock interfaces are usually timeReceiver

Info

PTP can also be deployed as a layer 3 protocol over IP

• but will not work as accurately as a layer 2 implementation with PTP-compatible hardware-timestamping adapters and switches