Why switch to use? The main advantage in using such services is that it avoids high telephone charges (mainly long distance) found in the use of traditional telephony (PSTN). The savings is that you use one and the same network to carry voice and data, while allowing to use the full capacity of an existing network – which usually is not at full capacity, which can be used without cost additional. It's very interesting the fact that calls between VoIP users are usually free, unlike VoIP calls to PSTN usually cost the user. This should be the attractive feature for businesses, and why not individuals, together generate a strong tendency for implementation of this technology, minimizing end communication costs. Must be taken into account prior to the acquisition of this technology that there are two types of PSTN service to VoIP, "direct inward dialing (DID for its acronym in English) "Access Numbers." This is important to know what limitations we get to have a future. In the first case, connects the caller directly to the VoIP user, the second case, requires that the caller enter the extension number of the VoIP user. The communication service numbers are charged as local call for those who made the call from the traditional telephony and is free to the VoIP user. The development and progress in the creation of codecs for VoIP has allowed the voice is encoded into data packets of ever smaller size, thus, communication of voice over IP technology required bandwidth increasing reduced, allowing use wireless internet that it exists, particular level, but especially at the company..