Priority Queue QoS Question

[robertgandy]

Hi,

We have a priority queue setup our WAN interfaces and wehn looking at the stats we see the following from show policy-map int:

Class-map: VOICE (match-any)

945666 packets, 60522624 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: ip dscp ef (46)

945666 packets, 60522624 bytes

5 minute rate 0 bps

Queueing

Strict Priority

Output Queue: Conversation 72

Bandwidth 10 (%)

Bandwidth 194 (kbps) Burst 4850 (Bytes)

(pkts matched/bytes matched) 149037/9538368

(total drops/bytes drops) 0/0

QoS Set

dscp ef

Packets marked 945666

My question is why do we only see 149037 pkts matched in the queue but 945666 pkts matched in the policy?

Any ideas?

[Nicholas Matthews · Accepted solution]

Hi,

From the command reference:

http://www.cisco.com/en/US/docs/ios/12_2/qos/command/reference/qrfcmd10.html#wp1049822

packets and bytes

Number of packets (also shown in bytes) identified as belonging to the class of traffic being displayed.

pkts matched/bytes matched

Number of packets (also shown in bytes) matching this class that were placed in the queue. This number reflects the total number of matching packets queued at any time. Packets matching this class are queued only when congestion exists. If packets match the class but are never queued because the network was not congested, those packets are not included in this total. However, if process switching is in use, the number of packets is always incremented even if the network is not congested.

In short, packets are only queued when the hardware ring is full. When the hardware ring is full, packets are queued in the software buffer. If there is space in the hardware ring, then packets are sent out and QoS isn't necessary. What you have here is probably a low use or high speed circuit that most of the voice packets are going directly onto the wire, and the queueing mechanism isn't being used for the majority of packets.

hth,

nick

[robertgandy]

Great thanks for the information, makes sense