During a call, clicks appear from time to time. There is no problem if two users are talking. If there are more than 3 simultaneous calls on the server, then the problem starts to appear. The clicks appear at random times and are heard on both sides of the speakers. The problem manifests itself both on internal calls and on external ones.
Enable Jitter Buffer solves the problem, but I would like to find another solution.
What is Jitter buffer and what is it helping mitigate for you?
Jitter Buffer Operation and Use in Asterisk ⋆ Asterisk
If you do not wish to use it, you need to resolve the root network issues that are causing it. Besides jitter buffer there is not going to be a one size fits all approach to your resolution. You need to track down where in the network the issue is occurring and resolve that. The fact that it impacts local calls too means the issue is likely in your LAN.
I was shooting tcpdump and tried to analyze it, but I didn’t find any problems. What should I pay attention to ?
Endpoints make/model, or softphone name and version?
If you record the call, does the recording have clicks or other impairments?
If endpoints not on same LAN as PBX, please describe networking.
When the encryption was turned off, the problem was almost imperceptible. When I turn on SRTP, it appears very often.
Media encryption? Use SRTP, SSL Method tlsv1, tlsclientmethod = TLSv1.2
Transcoding? i dont no
Endpoints make/model, or softphone name and version? Yealink T48G(18.104.22.168), grandstream gxp1628 (Software Version, Boot 22.214.171.124, Core 126.96.36.199)
If you record the call, does the recording have clicks or other impairments? Yes
If endpoints not on same LAN as PBX, please describe networking. - The telephony network is located in a separate VLAN. PBX and phones are in this dedicated vlan.
This sounds as if the Asterisk threads processing RTP are being starved of sufficient CPU; more concurrent calls and the extra compute load of encrypt/decrypt makes the problem worse.
Is the PBX on a VM? If so, does it have sufficient cores and RAM? If on bare metal, is it something pretty lame (like a Raspberry Pi)? Are you running any ‘big’ project (CRM system, predictive dialer, etc.) along with Asterisk in the same image?
Regardless, I’d expect this to show up as lots of jitter on RTP packets sent by the PBX to the extensions, but you report that the tcpdump is clean.
Yealink has a feature to mirror traffic on its Internet port to the PC port. Enable it, connect a computer to the PC port and run Wireshark . See what it shows for jitter (or possibly packet loss) on the incoming RTP. Compare to what you see with the tcpdump capture on the PBX.
I guess this is a network issue. I have little experience using Wireshark, and most likely I just analyzed Tcpdump incorrectly. The PBX server is virtual, I installed many versions, and the problem was still observed. I increased the power, but the situation has not changed. 6 simultaneous calls are enough for the problem to manifest itself.
What does the system resource usage look like? I assume it is fine? Can you prioritize your traffic, although I’m not sure bandwidth is the underlying root cause. What is the topography of your network?
Very nice tip you offered the poster:
Yealink has a feature to mirror traffic on its Internet port to the PC port. Enable it, connect a computer to the PC port and run Wireshark
thank you for your comments, I will look for the problem online. If something turns out, I will write.
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