Networking · Protocols
NTP
Network Time Protocol synchronises clocks across an estate, which is a prerequisite for authentication, logging and forensics.
FoundationalUpdated 2026-09-01
Overview
NTP builds a hierarchy of strata from reference clocks outward and corrects for network delay statistically. Windows domains distribute time from the PDC emulator down the domain hierarchy by default.
Clock skew has outsized consequences: Kerberos rejects tickets beyond a five minute default skew, TLS certificates appear invalid, and correlating logs across systems becomes guesswork.
Security considerations
- Use authenticated or at least tightly restricted internal time sources and monitor for drift.
- Do not leave NTP servers open to the internet, they have been abused for amplification attacks.