Description: 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.