Voice over IP

Voice over Internet Protocol (VoIP) is a new way of communicating. It requires the use of the internet and the technology that allows information to travel between users. Before I delve into how VoIP works it is important to understand how the plain old telephone system (POTS) works.

When you make a telephone call your voice travels in its analog form from your telephone to a telephone company switch. At the switch it is determined if your call is passed to another switch or if it can be routed to its destination. Using the POTS system your phone call travels the same path along physical wires based upon where the phone call will terminate.

VoIP requires an individual to have broadband Internet access. The most common of which is either through the use of a cable modem or DSL (direct subscriber line). Data travels the Internet in packets. In order for your voice to travel the Internet, it must be converted from analog to digital. Once your voice has been converted to digital packets it can be transferred via the Internet. But before your voice can enter the Internet and travel to its destination some information has to be added to it so that it meets IP (Internet Protocol) standards.

It mentioned earlier that data travels in packets, that is your voice is broken up into several different packets that must reach your destination and be reassembled in the right order and converted from its digital form back to an analog form so that the recipient can hear your voice. So each packet of data, which contains a portion of your phone call, has a minimum of 160 bits added to it so it can reach its destination. (White, Curtis, 2002) In addition to the IP protocol it also requires the use of real-time protocol (RTP). “It provides timing information that allows the receiver to reconstruct the original timing of the transmitted material in a way that identifies the content being sent, provides security, and notifies the overriding application of lost data.” (Gilmer, 2004) RTP is usually used in conjunction with unreliable datagram protocol (UDP). UDP allows for information such as voice and video to be sent without waiting for acknowledgement of it being received. “It is useful in cases where one sender wants to send the same information to multiple receivers and is not too worried if some pieces get lost along the way.” (Gilmer, 2004) VoIP requires the use of these three protocols in order to function. For this reason broadband access is needed. The fastest modem dial up connection using POTS can only achieve 53Kbps (kilobits per second) whereas cable modems and DSL can achieve speeds of 10 – 100 Mbps (megabits per second). The higher speed is needed in order for an actual conversation to take place over the Internet without significant delay.

VoIP telephone is relatively new and as such can have some potential drawbacks. First it requires access to the Internet so if the power goes out so does the phone service and therefore contingencies should be made. “sound quality and reliability are still not up to the level of traditional telephone service.” (Trope & Royalty, 2004)