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Time Quality Monitor

The Time Quality Monitor (TQM) evaluates whether the system clock meets the accuracy requirements for issuing RFC 3161 timestamp tokens. The platform provides the active Time Quality Configurations to TQM, which evaluates the configured NTP sources and reports an OK or DEGRADED result to the platform.

The platform uses the result to determine whether a Signing Profile associated with a Time Quality Configuration can issue timestamp tokens. To define the evaluation requirements, see Time Quality Configuration.

NTP evaluation​

TQM runs an independent check cycle for each Time Quality Configuration active in the platform. Within each cycle it evaluates the NTP servers defined in that configuration in four steps:

  1. Server reachability — TQM contacts every NTP server in parallel. Any server that does not respond or reports that its own clock is unsynchronized is excluded from further evaluation.

  2. Minimum server count — If too few servers remain after exclusion, the result is DEGRADED. The required minimum is set in the Time Quality Configuration.

  3. Clock drift — TQM computes the median offset of the reachable servers against the local clock. If it exceeds the configured limit, the result is DEGRADED.

  4. Leap second consistency — If the reachable servers disagree about an upcoming leap second, the result is DEGRADED.

All four checks must pass for the result to be OK. The first failure determines the reason reported to the platform.

Diagram

How the result affects timestamping​

The platform applies the latest time quality result to each Signing Profile associated with the evaluated Time Quality Configuration:

  • When the result is OK, timestamp issuance proceeds normally.
  • When the result is DEGRADED, the profile does not issue timestamp tokens.
  • When no Time Quality Configuration is associated with the profile, time quality enforcement is not applied.