Network Related Issues; Packet Loss - Cisco TelePresence C20 Troubleshooting Manual

Network related issues

if you are experiencing bad video quality in calls with symptoms such as pixilation, smearing or pulsing
of the image, the most likely cause for this is packet loss in the network.

Packet loss

You can check the packet loss information from the web interface, on the Touch panel if one is connected
to your system, or on the System Information screen using a remote control.
Packet loss statistics – Touch panel
if you have a Touch panel connected, tap the
you will see the call status shown below. Here you can see the current packet loss statistics as well as
the total packet loss statistic (average packet loss percentage over the whole call).
Packet loss statistics – remote control
press the Home button on the remote control to open the on-screen menu. Navigate to
Settings -> System Information to open the System Information screen. You can find the packet loss
information under the Video heading.
Packet loss statistics - web interface
To check the packet loss on the current call log in to the web interface. On the top navigation panel
click Call Control -> Call Control and then under Participants select the
details visible. Now you can see the packet loss for the transmit and receive video and audio streams.
As you can see below there is a constant 5% packet loss on both the transmit and receive streams
which needs to be investigated. This is the loss percentage calculated over the entire call time frame.
D15029.01 Troubleshooting Guide TC6.0, April 2013.
Settings icon on the screen. Then tap Call Status
symbol to expand the
On the web interface you can only see loss averaged for the duration of the call, meaning loss could
have spiked higher during the call.
and
Packet loss – more information
Even a small amount of loss, for example 0.5%, can have noticeable effects on the image quality.
if you are calling another system running TC software directly (a point to point call), a technology called
Clearpath will be used. This helps to mask the effects of packet loss and is enabled by default. When
calling systems that do not support Clearpath, call quality will appear worse if there is packet loss, than
a call to another TC based system with the same percentage loss. When Clearpath is not used the
system will try and hide the loss when displaying the image (decoder concealment) and will down speed
the bandwidth of the call. This results in the resolution being decreased thus lowering the amount of
data being transmitted and thus hopefully reducing the packet loss. See "Appendix A - Other sources
of information" on page 31 for information on the Clearpath whitepaper.
packet loss can be caused by many issues and after making some basic checks on the endpoint you
should start to investigate your network to see where the loss is occurring and take steps to eliminate
this loss.
Network Port speed
it is worth checking the duplex/speed settings of the network port on the system and network switch
to ensure they are set to the same settings. We recommend that both the network interface on the
system and the interface port of the network switch both be set to auto. For example if one is set at a
fixed rate 100/full and the other to auto, the port speed and duplex negotiation can fail and produce
mismatched settings. To check the status of the port on the codec go to
and click on Network 1 and look under the
that the speed matches that in the network switch.
To check the configuration of the network port look under
then click on Network 1 and look under
if both the network switch and the system are set to auto and the port speed and duplex settings do
not match, set both to manual values (e.g. 100/full), restart and retest.
8
Troubleshooting Guide TC6.0
Configuration -> System Status
Ethernet section. Ensure the system is using full duplex and
Configuration -> System Configuration
General Settings.
Copyright © 2013 Cisco Systems, Inc. All rights reserved.
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