Voice Over IP

What is VoIP and why should you care?
The Internet protocol (IP) was originally designed for sending data packets. VoIP involves sending spoken conversations, in real time, over an IP network. A regular phone line transmits voice as analogue signals, but to be sent over the Internet (or a TCP/IP-based private network), an extra step is added. Sound is converted to analogue signals, then digitised (converted from analogue to digital) and then transmitted over the network. At the receiving end, the conversion process is done in reverse.

VoIP is part of a larger technology category, IP telephony, which encompasses transmission of FAX, video, and any other form of data traditionally transmitted over the public switched telephone network (PSTN). The idea of IP telephony is itself part of a larger trend toward convergence of computer, telephone, television, security monitoring, lighting automation, and related technologies.

Advantages of VoIP over public telephone service
PSTN has worked fine for transmitting voice for many decades -- so if it's not broken, why fix it? The compelling factor behind VoIP is a practical one: cost. Long distance charges can cost businesses hundreds or thousands of pounds per month. If the business has a fixed cost (unlimited access connection to the Internet) calls transmitted over that connection can be effectively free. Some VoIP services do charge a monthly fee, but it is typically far less than Telco charges for long distance.

Disadvantages of VoIP
Given the cost advantage, why haven't all businesses rushed to abandon the public telephone network? Why aren't all long distance calls being made over IP? As with any business decision, there are tradeoffs. Some of the disadvantages of using Internet technology for all of your voice calls include:

• Initial setup cost: Although there are low cost and even no-cost ways to transmit voice over IP, an enterprise level company serious about VoIP will have to invest heavily in one or more VoIP devices (such as one of Cisco's voice gateways).
• Quality issues: Although it is getting better all the time, the quality of most VoIP services and products can't yet match that of PSTN. There are inherent challenges in sending a voice stream over a packet network.
• Incompatibility issues: Some services require that both the caller and the called party be subscribers to their service, and some software programs require that both parties have the same software installed. However, there are other services/programs that allow you to call anyone, including calling from your computer to a regular telephone, or even calling from phone to phone with packets routed over IP in between.