Number of packets stored for this VC in the Burst Queue
between successive attempts to forward to the PLP layer.
This statistic is indicative of the transient loading of
buffering mechanism between the PLP layer and the upper
layers. The maximum value that this statistic can reach
is determined by the setting of wfX25ServiceVcMaxBufCnt.
When the value of this statistic is equal to
wfX25ServiceVcBurstQDepth, all subsequently arriving
packets are dropped.