This read-write integer sets the egress queue depth, in bytes, at which the card begins flow control on outbound traffic, ranging up to 0x1fffff bytes on FRSM-VHS cards but limited to 0xffff bytes on other cards, and it is not supported on FRSM12. An administrator uses it to trigger back-pressure on egress traffic before the queue reaches the hard drop threshold defined by egressQDepth. For example, on a non-FRSM-VHS card an engineer configuring egressQECNThresh near its 65535-byte ceiling would allow the egress queue to grow substantially before flow control engages.