It doesn't occur in 8.3 but 8.9 i have severe jitter problems that make my voip connection almost unusable. I've been experiencing this for a few days now. My cell coverage is crap so i have a femtocell here that is routed through my astaro(on it's own interface0. since it uses ipsec to phone home setup for the firewall, qos..etc etc was easy easy. it's been working fine for a long time until now. online measurements of jitter on the wan are fine but my cell calls through the firewall are not good.
