Issue Description
The customer was experiencing bad sound quality with his eSpace 7950 IP phones mostly when holding conferences with external parties.
Handling Process
1. I checked the IP phone version.
Found out that the IP phones version was not up to date.
I suggested to the customer to upgrade the IP phones to the latest software version.
2. I checked the environment/topology where the calls were made.
The customer was making conferences with external parties. This meant long duration calls and a lot of bandwidth used.
3. I checked the codec negotiated by phones by asking a wireshark trace.
I analyzed the wireshark trace and found out that the customer was using G.722 codec, which takes a lot of bandwidth compared to G.729 for example. I suggested to the customer to change the settings on the IP phones from G.722 to G.729A/B. You cand find this setting on the IP phone web manangement page in the Advanced - > Media - > Voice Codec Priority tab.
4. I checked if customer had any QoS policies implemented.
I noticed in the wireshark trace that customer sent back, that there were no COS or DSCP tagged packets.
I checked the qos configuration on the IP PBX with these commands:
[%eSpace U1980(config)]#show qos mode
Vlan function: disable
==== Command executed success ! ====
[%eSpace U1980(config)]#show qos rule
QoS Rule
Ruleid Rulename Protocoltype Beginport Endport Vlanid Vlanpriortity Rfctype Rfcpriority
------ -------- ------------ --------- ------- ------ ------------- ------- -----------
0 --- OTHER --- --- 0 0 --- ---
Rfcservertype
-------------
---
==== Command executed success ! ====
There was no QoS configuration.
5. After the customer updated the IP phones software version and changed the codec to G.729A/B, the sound quality was back to normal.
Root Cause
1. I checked the IP phone version.
2. I checked the environment/topology where the calls were made.
3. I checked the codec negotiated by phones by asking a wireshark trace.
4. I checked if customer had any QoS policies implemented.
Suggestions
Always check the bandwidth requirenments for your needs and also take QoS implementation into consideration.