This read-write parameter enables or disables periodic delay measurement packets on this PVC to sample round-trip latency across the Frame Relay service. Network engineers enable this feature when both ends of the PVC have TSUIQ devices to passively measure latency and detect performance degradation; it should be disabled for PVCs terminating on other equipment. For example, when enabled, the device periodically injects a small probe packet and measures the time until the remote TSUIQ echoes it back, allowing ongoing latency monitoring without affecting user traffic.