the voip is voice transmission using the Internet bandwidth and as such has direct interference by it not being possible to have a quality internet bad for so long and needed to have a minimum of 200k broadband and is not performing any type of upload or donwload that will directly affect the quality of converça.

According to wikipedia Operation

The procedure consists in digitizing voice into data packets to flow to the IP network and convert it into voice again at your destination. Follow a step by step use case of a connection. The user removes the IP phone of the hook, at which time a beep to signal the application router "phone off the hook." The application part emits a dial tone. The user enters the destination number, whose digits are accumulated and stored by the application session. Gateways comparing the accumulated digits programmed with the numbers, when there is a coincidence it maps the IP address up to the destination gateway. The application session session protocol runs over IP, to establish a transmission and reception for each direction over the IP network. If the connection is performed by a PBX, the gateway switches the analog signal to digital PBX, indicating the connection status. If the destination number to take the call, an RTP stream is established between the gateway on UDP source and destination, making conversation possible. When either end of the call disconnect, the session ends.