This read-write integer defines the maximum egress queue depth in bytes, beyond which the card begins outright dropping cells rather than merely marking or throttling them, and it must be configured greater than both egressQDEThresh and egressQECNThresh on the same card; it is not supported on FRSM12. An administrator uses it as the hard ceiling on egress buffering, ensuring the two softer thresholds (discard-eligible and flow-control) always trigger before cells are actually lost. For example, if egressQDEThresh is set to 40000 bytes and egressQECNThresh to 50000 bytes, egressQDepth must be set above both, such as 60000 bytes, so DE-marking and flow control act as early warnings before hard drops occur.