As a small trader, I must be able to communicate with my trading partners who are often in other countries. We...
use IP telephony to keep costs down. Can you suggest how I can have high quality VoIP calls that will exceed PSTN call quality?
That may be an issue because you cannot control the flow of traffic on the Internet. You also don't have control of the circuits. Since some countries are a bit behind on their Internet infrastructures and offerings for endusers, this can be particularly dicey. Some countries also mandate latency for VoIP systems with the thought that if they are as good as PSTN they should be taxed as one.
The only way to really guarantee quality is to control the circuits and all providers in between. If you are calling a particular country, you can put a VoIP gateway there. You can also look into some of the newer outsourced circuits from the international providers. The advantage there is that they maintain QoS understanding on all circuits. But bear in mind, even though we can make digital communications scream these days, there is still going to be some additional overhead for the conversion to digital data.