This sets the CBR queue depth at which the card starts discarding all CLP-1, discard-eligible, cells to protect the higher-priority CLP-0 cells sharing that queue, continuing until the queue drains back below this threshold. This is the direct mechanism behind selective cell-loss-priority discard on latency-critical CBR traffic; tuning this threshold controls exactly how much queue buildup the card tolerates before it starts sacrificing discard-eligible cells to protect the CBR queue's guaranteed cells, which matters because CBR is typically used for voice or circuit emulation where the CLP-0 cells need protecting most. For example, an admin lowers cardClp0CbrThreshold on a voice-carrying CBR queue to start shedding discard-eligible cells earlier, keeping the guaranteed voice cells better protected during brief congestion spikes.