UPDATE MECHANISM of WFQ COUNTERS

(from Clarence Filsfils)
CBWFQ counters ("Packets Matched 2543") are only updated when CBWFQ is "active", that is when the VC is "congested". The Per-VC Qing architecture is like this

   -------+      1:1      --------+
          |  <--------->          |
   -------+               --------+

   VIP-SRAM               Per-VC TxQ (PA-A3 driver)

For any VC managed by the PA-A3, a per-VC txQ is dedicated by the PA-A3's driver. These per-VC TxQ have a maximum depth. When this is reached, the VC is said to be "congested". At this point, the Pa-A3's driver will refuse to read any new packets delivered by the VIP-SRAM, hence causing the packets to be delayed in the VIP SRAM's CBWFQ system dedicated to this VC. Thus, _NO_ drop (you can check this via sh atm vc via the 'OutPktDrops: 0' counter) should occur by design between the VIP per-VC CBWFQ and the PA per-VC TxQ.

[end]