What is VOIP ?

Definition:

VoIP (Voice over Internet Protocol) is simply the transmission of voice traffic over IP-based networks.

Introduction:

VoIP services convert your voice into a digital signal that travels over the Internet. If you are calling a regular phone number, the signal is converted to a regular telephone signal before it reaches the destination. Three methods VOIP calls: PC to PC, PC to fixed-network lines, and telephone calls via IP-based internal networks. Some people use VOIP in addition to their traditional phone service, since VOIP service providers usually offer lower rates than traditional phone companies, but sometimes doesn't offer 911 service, phone directory listings, 411 service, or other common phone services. While many VoIP providers offer these services, consistent industry-wide means of offering these are still developing.

So! How VOIP Works?

As said, the interesting thing about VoIP is that there is not just one way to place a call. There are three ways one use VOIP service to make a phone call is.

• ATA
The simplest and most common way is through the use of a device called an ATA (analog telephone adaptor). The ATA allows you to connect a standard phone to your computer or your Internet connection for use with VoIP. The ATA is an analog-to-digital converter. It takes the analog signal from your traditional phone and converts it into digital data for transmission over the Internet. Providers like Vonage and AT&T CallVantage are bundling ATAs free with their service. You simply crack the ATA out of the box, plug the cable from your phone that would normally go in the wall socket into the ATA, and you're ready to make VoIP calls. Some ATAs may ship with additional software that is loaded onto the host computer to configure it; but in any case, it's a very straightforward setup.

• IP Phones -- These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ-11 phone connectors, IP phones have an RJ-45 Ethernet connector. IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call. Wi-Fi phones allow subscribing callers to make VoIP calls from any Wi-Fi hot spot.

• Computer-to-computer -- This is certainly the easiest way to use VoIP. You don't even have to pay for long-distance calls. There are several companies offering free or very low-cost software that you can use for this type of VoIP. All you need is the software, a microphone,speakers, a sound card and an Internet connection, preferably a fast one like you would get through a cable or DSL modem. Except for your normal monthly ISP fee, there is usually no charge for computer-to-computer calls, no matter the distance.

Advantages: 

·         Low cost: VOIP services in the United States allow you to call anywhere in    North America at no extra charge.

·         Portability: you can take your phone converter and phone number and use them wherever you travel in the world, just as long as you have access to a high-speed Internet connection.

·         Features:  Call forwarding, call waiting, voicemail, caller ID and three-way calling are some of the many services included with VOIP telephone service at no extra charge.

·         Video-conferencing: User can enjoy the benefit of simultaneously Voice plus video call used for video conferencing.

Disadvantages:

·         Limited Emergency Calls: Traditional phone equipment can trace your location. Emergency calls are diverted to the nearest call center where the operator can see your location in case you can't talk. However, because a voice-over-IP call is essentially a transfer of data between two IP addresses, not physical addresses, with VOIP there is currently no way to determine where your VOIP phone call is originating from.

·         Sound Quality And Reliability: VOIP QoS(Quality of service) depends many factors say for example your broadband connection, your hardware, the service provided by your provider (ISP), the destination of your call etc.

·         Security: The most prominent security issues over VoIP are identity and service theft, viruses and malware, denial of service, spamming, call tampering and phishing attacks.

VOIP Protocol Stack:

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