Class 5 switches are the most widely used among small and midsize businesses. These softswitches offer advanced features such as blind call transfer, auto-attendant, caller ID, call forwarding, audio/video conferencing support and interactive voice response (IVR). These switches allow VoIP providers to meter minutes and automatically bill consumers. Moreover, class 5 softswitches support authorization by number, IP number and prefix or log-in credentials in the case of SIP authorization.