How to get better VOIP performance

How to make VOIP signal as carrier-class quality, reliability and security, which are unavailable to enterprises from public Internet based voice services, minimized latency, packet loss and jitter as well as overall call quality. Whare are the recommended VOIP carriers providing above quailty service.

Well buddy, from my humble experience the quality of voice in 80% depends on the following things:

1. codec used
2. internet link quality.

It is not a matter of a company, but of the route.

In order to have a good quality call you need to have an Internet link with low RTT (let say up to 250ms) and enough bandwidth (depending on the codec used). If you are going to call Europe, USA, Japan or other well developed countries, of course you will get high quality because the Internet there is only fiber and its cheap.

At the other side if calling to the Middle East and Africa... except not a so good call, because:

1. VoIP is illegal here and people who do it try to hide themselves as much as possible.

2. low RTT links (like fiber) are very rarely used, because they are either expensive or dangerous to use (the local PTT will catch you), or BOTH.
Therefore they use mostly two-way satellite Internte which increases the RTT to above 600ms.

The best carrier I have seen so far is TeleGlobe and British Telecom.
But BT does not interconnect via IP, only TDM.

hth.