In a VoIP telephone system implementation, a computer network and Internet connection is required by the telephone system. The telephone handsets plug in to that computer network, which may be either dedicated to the telephone system or shared between the telephone system and the data network that the computers connect to. Outward calls are made via the Internet.
VoIP offers the potential for very low call rates, that continue to decrease.
In a busy office environment, there is a high possibility of degraded call quality due to congestion of the Internet connection. It is sometimes necessary to maintain a separate Internet connection for carriage of voice calls, the cost of which reduces the financial appeal of the system. Some VoIP implementations introduce potential security vulnerabilities that must also be addressed.