Huge delay with conference calls


I am experiencing huge lag on conference call between software sip clients. I created conference which is used when we play games online (6 users connected). I am experiencing around 15 seconds delay (even if I don’t play).

I also have SIP provider and make phone calls overseas every day. This is without any problem with absolutely clear phone calls.

My ADSL2+ line sync is 10000/1000. I think that I should not have a bandwidth problems.

I run asterisknow version with FreePBX (1.7.1) on Xen (Debian Stable) in HVM mode.

Do you have any advise which can help me to resolve this problem?