Phone Behavior During Times Of Network Congestion; Where To Find Additional Information - Cisco 8800 Series Manual

Phone Behavior During Times of Network Congestion

Metric Change
Conceal Ratio is near or at zero, but the voice quality
is poor.
MOS LQK scores decrease significantly
MOS LQK scores increase significantly
Note Voice quality metrics do not account for noise or distortion, only frame loss.
Phone Behavior During Times of Network Congestion
Anything that degrades network performance can affect Cisco IP Phone audio and video quality, and in some
cases, can cause a call to drop. Sources of network degradation can include, but are not limited to, the following
activities:
• Administrative tasks, such as an internal port scan or security scan
• Attacks that occur on your network, such as a Denial of Service attack
To reduce or eliminate any adverse effects to the phones, schedule administrative network tasks during a time
when the phones are not being used or exclude the phones from testing.

Where to Find Additional Information

If you have additional questions about troubleshooting your phone, see the Cisco IP Phone 6800, 7800, and
8800 Series Multiplatform Phones Troubleshooting FAQ in the the following Cisco website:
Cisco IP Phone 8800 Series Multiplatform Phone Administration Guide for Release 11.3(1) and Later
426
Condition
• Noise or distortion in the audio channel such as
echo or audio levels.
• Tandem calls that undergo multiple
encode/decode such as calls to a cellular network
or calling card network.
• Acoustic problems coming from a speakerphone,
handsfree cellular phone or wireless headset.
Check packet transmit (TxCnt) and packet receive
(RxCnt) counters to verify that voice packets are
flowing.
Network impairment from packet loss or high jitter
levels:
• Average MOS LQK decreases may indicate
widespread and uniform impairment.
• Individual MOS LQK decreases may indicate
bursty impairment.
Cross-check the conceal ratio and conceal seconds
for evidence of packet loss and jitter.
• Check to see if the phone is using a different
codec than expected (RxType and TxType).
• Check to see if the MOS LQK version changed
after a firmware upgrade.
Troubleshooting