This attribute counts the number of ack stacking timer expiries.
It is used as an indicator of the acknowledgment behavior across the
subnet when ack stacking is in effect. If it expires often, usually this
means end users will experience longer delay.
The ack stacking timer specifies how long the Vc will wait before
finally sending the subnet acknowledgment. if this attribute is set to
a value of 0, then the Vc will automatically return acknowledgment
packets without delay. If this attribute is set to a value other than
zero, then the Vc will wait for this amount of time in an attempt to
piggyback the acknowledgment packet on another credit or data
packet. If the Vc cannot piggyback the acknowledgment packet
within this time, then the packet is returned without piggybacking.