ASA QOS - priority LLQ statistics

robetrem · ‎03-18-2009

I have activated: priority queueing on specific interfaces, create simple class-map (classifying voice and signaling) and finally applying a policy-map calling those class-map and indicating priority handling for them.

Problem is the command 'sh priority statistic' don't show the real count of packets under LLQ (very few packets)!

Question is: does those counter increment only when congestion really happen (TX-RING full) ?

vikram_anumukonda · ‎03-18-2009

"After marking, the next step is another classification process based on packet markings. At this point, packets might be discarded by a policer (for example, if they exceed an SLA) or a congestion-avoidance mechanism (for example, early dropping because buffers reached the maximum limit). Packets that are not discarded are subject to congestion management (queuing) to prioritize and protect various traffic types when congestion happens to the transmission link. Finally, these packets are scheduled for transmission on the egress link"

so, QOS kicks in only when there is congestion.

HTH

vikram

robetrem · ‎03-18-2009

Yes - for me also it is clear that QOS will kick in only when congestion happens.

My question was really related to the ASA product and more specific oriented against the "show priority statistic" command and results.

I see a lot of traffic statistics under BE and very a few under LLQ number paquets. Those numbers seem to be wrong ! Was then asking myself if LLQ number get count only when congestion happen ?? OR should reflect the match number paquets ?

vikram_anumukonda · ‎03-18-2009

your assumption is correct

"To ensure priority forwarding of traffic at the interface, the security appliance looks at the flag for priority queue and sends the packet for immediate transmission unless the transmit ring is congested. In that case, traffic is queued to the high-priority queue. As soon as the transmit ring has room available, the security appliance services the high-priority queue and transmits the packet"

the packets will be queued to low-priority queue only if the transmit-ring is congested ( and " show priority-queue statistics " reflects the packets queued to the low-priority queue )

what about the statistics from " show service-policy " ?

HTH

vikram

vikram_anumukonda · ‎03-19-2009

I mis-typed the high-priority/low-latency queue as low-priority queue :(

the packets will be queued to high-priority/low-latency queue only if the transmit-ring is congested ( and " show priority-queue statistics " reflects the packets queued to the high-priority/low- latency queue )