This attribute indicates the maximum number which has recently
occurred for the txFrameMemoryUsage attribute.
On CQC-based ATM FPs, this number indicates the maximum
usage of transmit frames for all ports on this FP.
On ATM IP FPs, this number indicates the maximum usage of
transmit frames in the Passport Queue Controller (PQC) ASIC.
Queuing of frames for transmit only occurs in the PQC.
This value is reset to the current usage every 15 minutes and when
the card is reset.