IAX2 Billing Systems?

I was just wondering if anyone knows how companies like voicepulse connect, nufone, simpletelecom, asterlink and voipjet do their IAX2 billing?

Do they use RADIUS? Sorry if its a very broad question, but I’ve been wondering this for awhile.


I know some of them wrote their own billing systems.
Some of them use radius, some of them use 3rd party rating engines.

Trabase, astcc and trollphone are open source rating engines, if you are looking for a commercial one, our company has one. (info at asteriskguru.com )