Information Technology Reference
In-Depth Information
Bandwidth 128 (kbps) Burst 3200 (Bytes)
(pkts matched/bytes matched) 14231/3903582
(total drops/bytes drops) 1253/391292
This output allows you to see the success or failure of the QoS policy applied to the out-
bound direction of Serial 3/1. Notice the QoS policy is named VoicePriority. It grants
strict priority to the first 128 kbps of voice traffic. Notice the number of packets dropped
(1253). This indicates a problem; this is roughly 8 percent of your voice packets. On an ac-
tual network, this could call degradation issues of active calls.
The drops are most likely caused by one of two things: a congested WAN link or voice
traffic exceeding the provisioned amount. A congested WAN link simply means that there
is not enough bandwidth to send the calls in the time required, so the packets are
dropped. The latter issue seems almost identical to the first. That is, if you have too many
voice calls, won't you congest the WAN and not be able to get all the packets through? Al-
though this may be true, the more likely cause is the Strict Priority queuing configuration.
Strict Priority ensures that the VoIP traffic gets the first and fastest 128 kbps available.
However, once the voice traffic tries to exceed this amount, the router begins dropping
the traffic (even if there is bandwidth available on the WAN link). This ensures that you
know exactly how much voice traffic is going over your WAN connections. The data traf-
fic won't have to fight for the scraps of bandwidth left over.
Note:
All these troubleshooting guidelines also apply to phones registering with CUCM.
