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Audio drop outs on VOIP calls in one direction

Posted on 2015-02-08
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Last Modified: 2015-03-30
I am experiencing audio drop outs on VOIP calls (in one direction only).  The problem is intermittent and it only affects external calls.  We have 120 internal extensions and we experience no problem on internal calls. Also, external callers can always here us, but we cannot hear them for 10-30 seconds periods.  All calls connect fine, and the audio almost always comes back if the caller waits.   I have replaced the router, PBX, switches, and changed our VOIP service provider all to no avail.   I have also checked, tested, and replaced every cable that is not buried behind a wall.  Nothing has helped.

The network topology is: Draytek router connects to root swtich (Cisco SG300) and 12 switches connect to that.  PBX is a Asterisk based system managed by a small company called Intuitive Voice.  I have re-installed the PBX software, changed the hardware host, reconfigured all the network switches (enabled/disabled STP, QoS, VLAN settings) with no apparent impact on the issue.

I have conducted packet captures using wireshark at two locations on the data/VOIP path.  One at the router and another at the root switch.  The audio is perfect as it enters and leaves the router (no drops detected), but it drops when it leaves the root switch and goes to the PBX.  I have several captures available for analysis but Experts Exchange site does not allow me to upload the pcapng format.
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Question by:DarrenMcIntyre
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Expert Comment

by:Kamran Arshad
ID: 40597750
Hi,

What codec are you using? Did you try to change the codec.
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Author Comment

by:DarrenMcIntyre
ID: 40598452
I am using G.711.  What codec would you suggest I switch to?  And why?
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Expert Comment

by:Kamran Arshad
ID: 40598454
and these are SIP based clients or IaX?
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Author Comment

by:DarrenMcIntyre
ID: 40599239
SIP
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Accepted Solution

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DarrenMcIntyre earned 0 total points
ID: 40688324
I resolved this issue by manually assigning the QoS values on the VOIP traffic from the firewall.
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Author Closing Comment

by:DarrenMcIntyre
ID: 40695570
none of the other comments led to a solution
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