The nf-nat-sip module interferes with VoIP calls
I have been using ekiga occasionally to call my parents back home. The default VoIP provider in ekiga did not provide a very good service initially but have improved lately. A call to a landline in Bulgaria is less than $0.04/min and the quality is acceptable. Still, the service is not as good as I wish it to be. I decided to give Gizmo a chance. I do have a Gizmo account, charged with a $0.25 sign-up bonus. I thus decided to make a call home and even though I could hear my wife very clearly (much better than with Diamondcard) she could not hear me. After some bugging with Gizmo's echo test I found the culprit. When I send a request for the user "echo" to the proxy server it sends a reply with the address of the echo test -- a different IP, same port (5060). I really have no idea what happens next, but my outgoing voice packets are obviously not sent to the echo address. The following is my speculation. Traffic going to/from port 5060 is being handled by the nf-nat-si...