This read-write switch controls whether the NRTS (Non-Real-Time Service) processor treats incoming ATM cells against the CLP1 discard threshold rather than the normal CLP0 threshold, on the forward (transmit-to-receive) leg of the circuit. Because ATM's CLP bit marks cells as eligible for discard under congestion, flipping this to 'yes' makes the switch drop tagged cells earlier and more aggressively when the NRTS queue starts backing up, which protects higher-priority traffic at the cost of the marked flow. An admin troubleshooting sporadic frame loss on a VBR-NRT PVC might set cktNrtsCLP1 to yes(2) to confirm CLP-tagged traffic is being shed first, rather than untagged cells, during a burst that pushes queue depth above threshold.