This attribute indicates the maximum number which has recently
occurred for the txCellMemoryUsage attribute.
On CQC-based ATM FPs, this number indicates the maximum
usage of transmit cells for all ports on this FP.
On ATM IP FPs, this number indicates the maximum usage of
transmit cells in the Passport Queue Controller (PQC) ASIC.
Queuing of ATM cells for transmit normally occurs in the ATM
Queue Manager (AQM) ASIC, which is indicated in the Lp Eng Arc
Aqm/x txCellMemoryUsage attribute. Transmit cells should only be
queued in the PQC under circumstances of extreme transient
congestion.
This value is reset to the current usage every 15 minutes and when
the card is reset.