Clock Synchronization
Clock sync spans four accuracy tiers with real numbers. NTPv4 (RFC 5905, 2010; maintained by IETF + the volunteer NTP Pool Project, 4,000+ servers) hits ~1ms on a LAN, 10-100ms over WAN -- fine for logs, not trading. IEEE 1588-2019 PTP (v2.1) needs hardware-timestamping NICs and boundary/transparent clocks to reach 20-100ns; EU MiFID II RTS 25 mandates 100us-1ms clock accuracy for high-frequency trading, pushing exchanges onto PTP grandmasters ($2k-$50k). GPS-disciplined oscillators deliver 20-100ns to UTC via 1PPS; CERN's White Rabbit (PTP + SyncE) hits sub-nanosecond, picosecond-class precision, now spanning Nordic fiber links (2026). Sensor-network protocols RBS, TPSN and FTSP trade GPS/PTP hardware for radio-only sync, landing at 1-20us single-hop, degrading toward milliseconds over multi-hop trees. Current version/status: PTP: IEEE 1588-2019 (v2.1); NTP: NTPv4 / RFC 5905 (2010). License: Open standards (IEEE 1588, IETF RFC 5905); implementations open-source (linuxptp GPLv2, chrony GPLv2, NTPsec BSD-style). Pricing: Protocols themselves are free; GPS-disciplined oscillator hardware runs roughly $50-$5,000 and PTP grandmaster clocks $2,000-$50,000+ depending on precision class. Maintained by IEEE 1588 Working Group (PTP); IETF + volunteer NTP Pool Project (NTP); US Space Force (GPS constellation, 31 operational satellites).
Pick PTP with hardware-timestamping switches when you need sub-microsecond: trading floors under MiFID II RTS 25, 5G fronthaul, and IEC 61850 power-grid protection all require it, and software-only NTP cannot get there. For server logs, cron jobs, and cert validation, plain NTP/chrony is the right call -- deploying PTP grandmasters for a CRUD app is theater. GPS wins for outdoor, isolated nodes with no fiber run back to a grandmaster. Honest weakness: PTP's nanosecond claims only hold with PTP-aware NICs and switches end-to-end -- run it over ordinary Ethernet gear and it degrades toward NTP-grade jitter. The hardware buys the accuracy, not the protocol. Known weakness: PTP's headline nanosecond accuracy only holds with PTP-aware hardware-timestamping NICs and switches end-to-end -- over ordinary switches it degrades toward NTP-grade millisecond jitter, a limitation timing vendors like FSMLabs and Calnex document openly.