PTP: G.8275.1 phase adjustment mitigation

Use the phase adjustment mitigation feature to protect downstream timing from GNSS-induced phase jumps in hybrid deployments. This feature prevents phase adjustments to downstream Precision Time Protocol (PTP) nodes caused by a significant phase jump of the upstream T-GM or T-BC PTP node. Use the protocols ptp phase-error-limit relative-threshold configuration statement to ignore phase adjustments that exceed the threshold, with SNMP traps and syslogs for visibility. Optionally, use protocols ptp phase-error-limit force-synce-holdover and protocols ptp phase-error-limit max-holdover-time to place PTP and SyncE in holdover and control duration. The system applies a ten-measurement-window grace period before resuming adjustments. Monitor status with show ptp phase-error-monitoring status and show ptp global-information commands. This control applies to PTP-originated adjustments.