What is VOIP?

Voice over IP (VOIP)

Voice over Internet Protocol (VoIP), the process of converting voice into digital data packets and transmitting them over the Internet, is a readily available technology that consumers and businesses can employ to save millions of dollars. Applying this technology to make phone calls, known as Internet telephony, is simple, cost-effective and requires only a PC, telephony software and a communications device, such as a VoIP Phone, microphone or headset.

IP hard phones that resemble traditional desktop phones are available, and can be used with standard telephone headsets. A softphone, on the other hand, has the features of a traditional desktop phone but is PC-based digital telephony software, allowing users to make calls directly through their computers using the softphone and a headset. Softphones typically cost about 50 percent less than comparable-function IP telephones.

The benefits of VoIP Phone are many, with cost savings at the top of the list. Internet telephony enables companies to send and receive calls over existing data, or digital lines rather than conventional telephone lines. In doing so, companies take advantage of current infrastructure and incur costs only for a local ISP connection, reducing or altogether eliminating long distance telephony charges and realizing significant savings as a result.

Businesses can also save money by simply employing softphone software in conjunction with a communications headset, saving on the expense of desktop telephone units. If a company is laying wires for a new facility, an Internet telephony set-up provides even greater cost savings because it requires just two (voice/data and electrical) rather than three (voice, data and electrical) sets of cables. VoIP also delivers impressive sound quality.

In fact, technological advances have improved audio quality so much that Internet telephony can rival that of a landline, and it frequently provides a better connection than one available with a mobile phone.

Voice quality, processing speed, memory capacity and other factors that enhance Internet telephony have dramatically improved in the past few years, positioning it for widespread, rapid adoption in a number of markets. In fact, Avaya, a manufacturer of softphones, estimates that worldwide, LAN-based Internet telephony will grow at a compound annual growth rate of 75% through 2007.

VOIP's advantages over traditional telephony include:

- lower costs per call, especially for long-distance calls
- lower infrastructure costs: once IP infrastructure is installed, no or little additional telephony infrastructure is needed.
- new advanced features.

Note that Voice over IP traffic does not necessarily have to travel over the public Internet: it may also be deployed on private IP networks.

The protocols used to carry the signal over the IP network are commonly referred to as Voice over IP, or VoIP protocols.

VoIP protocols

In the overwhelming majority of implementations, the RTP protocol is used to transmit VoIP traffic ("media").

For signaling, there are several alternative protocols:

- SIP, the IETF Session Initiation Protocol, a newcomer gaining popularity
- H.323, an older protocol still used by many legacy applications
- Skinny Client Control Protocol, proprietary protocol from Cisco
- Megaco (a.k.a. H.248) and MGCP, both media gateway control protocols
- MiNET, proprietary protocol from Mitel
- IAX, the Inter-Asterisk eXchange protocol used by the Asterisk open source PBX server and associated client software.