Remote peers audio quality issue

I have a asterisk server in Turkey(150Mbit/s symmetrical BW) and some agents in Egypt (50 Mbit/s symmetrical BW). Two office is connected via IPsec (Fortigate Fw in Turkey , Pfsense in Egypt.) Meanwhile we are communicating VoIP provider via private network.

The connection between offices is about 10Mbit/s over ipsec. The agents in Egypt is able to make outbound and inbound call. When they are on phone sometimes their voice is breaking. I tried to enable jitter but I could not be successful.

Im missing the question…

Now I will assume that you are requesting some help in how to pinpoint the cause of the quality issues.

I would first make some tcpdumps to be able to analyze the rtp packets and go on from there…

Jus to be sure I would try to make some calls without using the vpn, my experience is that the vpn improves quality, but you never know.