Outgoing Calls - Audio is Delayed...

[Montauk]

Hi all.

I could really use some help.

I have linux based 3CX 16 running on a new-ish dell desktop computer (1TB SSD, 8GB RAM, i5). I am trying to use Nextiva SIP Trunking. Phones are Yealink T46G and T41P. I have gone through and added all or the 3cx recommended rules, Full NAT, and QoS to my firewall. I can see SIP and RTP being accepted by my firewall, what seems to be all "green lights" from my voice network out to the internet and back. I get occasional ICMP rejects from Nextiva. Incoming call audio seems to work flawlessly, while outgoing audio has delay issues. The delay lasts anywhere from 5-20 seconds at a time. I have been told that I can be heard during that moment of silence, but i can't hear them, ringback tones, or voicemail greetings at all. I have a feeling this could be my trunk settings, but Nextiva goes only so far with supporting pbx configs.

I have changed codecs to support Nextiva's recommendation at G.711 u-law high priority, G722 low priority. However, I noticed the "HD" icon went away during calls after I did that, so that was also kinda unfortunate.

What do you think I should do to resolve this? Any help is much appreciated.

 

[leejor]

I don't recall hearing of delays that long, before. I would make use of Wireshark for more details on what may be happening, along with confirming which Codecs are being used all the way from set to your provider. The fact that incoming calls seem to be fine, it's probably not ( but I never rule out), a network issue.

 

[Montauk]

Thanks for your reply. I can tell you that a pcap from 3cx shows that g711 is used between my trunk provider and 3cx and vice versa. However, 3cx communicates with the phones (and vice versa) exclusively via a different codec, g722. I may change codecs at the phone level for a one-codec-across-the-board test.

 

[leejor]

You might want to have a read through this thread...

https://www.3cx.com/community/threads/call-quality-transcoding.67494/

Unfortunately, the link that I posted, within,no longer seems to be available. There are a number of other posts on this topic , wanting to use HD internally, yet not have to do transcoding, and deal with any issues that may bring, on external calls.

Did you check to see what Codecs are used on incoming?

 

[Montauk]

Update on this: this is now resolved. It actually had nothing to do with the codecs I was using. Although I will speak on that in a sec. My firewall had some config issues along with SIP ALG running (although not explicitly told to run), and IPS rejecting traffic. Once the rules were corrected and SIP ALG turned off and IPS exceptions enabled, all works perfectly.

To answer your question, there is no doubt in my mind that 3cx to nextiva and back is using g711. That's what the pcap shows.

In terms of codecs, I have been told by nextiva that they support g711,g721, and g722. I am going to try enabling only g722 at 3cx box tomorrow and run another pcap to ensure that one codec is being used by everything.

Thanks!