L04
NTP and why clocks affect authentication
Cram this first — memory hook
123: one-two-three, synchronize me. Lower stratum = fewer timing steps from the reference.
Exam trap
A lower stratum number alone does not prove a trustworthy or more accurate source.
The slide facts
Network Time Protocol synchronizes devices, uses User Datagram Protocol 123, and supports troubleshooting, security and scheduled work. The hierarchy shows reference clocks at stratum 0 and connected time servers at stratum 1.
If you have time — extra
Network Time Protocol () helps devices agree on time. Without consistent clocks, a log may appear to record a response before its request, certificates may appear not yet valid or expired, and time-sensitive authentication can fail. exchanges timestamps and estimates clock offset while accounting for network delay; it is more sophisticated than blindly copying the time printed in one arriving packet. A stratum describes distance in the timing hierarchy, not a guaranteed accuracy score. A stratum 0 reference may be an atomic clock or Global Positioning System () receiver; a stratum 1 server uses a reference directly. normally uses User Datagram Protocol () port 123. Reliable authorized sources and multiple peers can improve resilience.
Walkthrough
A client exchanges time information with configured servers, estimates its difference from reference time, and adjusts its clock under the implementation's clock-discipline rules. Logs from multiple systems can then be correlated meaningfully.