In most cases, a broadband internet connection is a requirement for using VoIP telephone service. A broadband connection simply ensures that there is enough bandwidth to handle the disassembly and re-assembly of voice transmissions. It is possible to take advantage of internet telephony with a dial-up connection, but call quality usually suffers--and there can also be issues concerning dropped calls.
The wide availability and decreasing costs of high-speed internet connections have played significant roles in the rapid growth of the VoIP industry. This growth has led to better equipment, better service offerings, better technical support, and increased customer satisfaction. VoIP telephony is reaching the point where it can compete with the traditional telcos in terms of reliability.
VoIP's increasingly reliable and broad service offerings mean that business users with elaborate phone systems can switch to VoIP telephony with fewer hassles and greater confidence. This is also true for residential users who want to switch to a completely internet-based telephone system. Before leaving the traditional telcos completely behind, however, some issues should be addressed.
VoIP services are connected to the power grid (rather than drawing power from the telephone lines), so you should invest in an uninterruptible power supply (UPS) to maintain telephone service in case of blackouts. Also, VoIP phone calls are incompatible with the 911 system, so you should have a cell phone or some other way of reaching authorities in case of emergency. The 911 issue is well known in the industry, however, so some companies have provided their own means for routing VoIP calls to the correct emergency response centers.