Session Initiation Protocol (SIP), is the name of telecommunications protocol used for establishing a voice communication session on a data network like over the Internet. An SIP “session” might be a regular VoIP phone call between two participants, or a multi-party conference call. The most common applications of SIP are in Internet telephony for voice and video calls, as well as instant messaging over Internet Protocol (IP) networks.

Since we now know what is SIP, let's move on to the concept of SIP Trunking. An SIP Trunk in the most simplest terms would be a digital "replacement" for the traditional analog phone line. A SIP Trunk provides a user/business the same service you get from a analog phone line without the need for a physical wired connection. A SIP Trunk is a “virtual” phone line which is provided by a SIP trunk provider, the SIP trunks utilizes your data connections like Cable Modem, DSL, Ethernet over Copper, T1 etc. to connect your phone system back to their network. SIP Trunk Lines represent the number of simultaneous calls to the public telephone network that can be made at the same time. SIP Trunk Lines are the online ‘virtual’ equivalent to lines coming in from the phone company or channels on a T1 circuit – just instead of these calls ringing on a phone connected by cables at a desk, the calls ring in on your computer or mobile phone.

Google Voice has been a great way to make and receive free calls to USA and Canada. We have also shared a trick which enables users to make free calls to 60+ countries using their Google Voice account. Now, Google has announced the ability to make voice calls to regular landlines and mobiles from Gmail via Google+ Hangout, and to sweeten the deal calls to the US and Canada are now free from all countries where Hangouts calling is available. So this means if you have any relative or friend in USA or Canada you can call them for free from anywhere in the world.

This is not all, the new “Hangouts calling” also supports conference calling to multiple phone numbers and video participants on the same call, as well as play sound effects with the Google Effect app like applause or laughter.

Free calling vouchers and discount coupons for Skype are hugely popular, and here is something any VOIP user wont like to miss - a full-month of unlimited calls across the globe on Skype for just $1 verification charge.

The limited period offer from Skype allows users to receive unlimited calling free for an entire month, so apart from free Skype to Skype calls, you can also call offline contacts on their mobiles and landlines anywhere in the world (well, most of them).

The offer requires users to verify a credit-card charge of $1 and is applicable to a fair usage policy, users can make free Calls to mobiles and landlines in these countries: Canada, Guam, HongKong S.A.R. China, Puerto Rico, Singapore, Thailand and United States and land-line calls to these countries: Argentina, Australia, Austria, Belgium, Chile, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Israel, Italy, Japan, South Korea, Luxembourg, Malaysia, Netherlands, New Zealand, Norway, Poland, Portugal, Russia (Moscow and St. Petersburg only), Slovakia, Spain, Sweden, Switzerland, Taiwan, United Kingdom and Venezuela.

Just four-days ago I posted a review of Viber for iOS citing unavailability of an Android version, the good news is the application can now soon be expected on Android platform as an official video of Viber For Android is now posted online.

I was eager to review Viber but waited for an Android version to get released, sadly Viber For Android is nowhere to seen - so here we have the review of currently available Viber For iOS.

Viber the free VOIP application for iOS (Android and Blackberry versions expected soon) allows users to call other Viber users anywhere in world for free using their 3G or Wi-Fi connection, the best part of this must-have utility is the sound quality which is simply "exceptional".

Viber uses your phones address book and is always in-sync with it, highlighting contacts that have Viber so you know you can call them for free. To get started all you need to do is, enter your phone number and the confirmation code received via SMS.

There have been many services offering free international VOIP calls and most of them rely upon ad-supported funding to get things going, most of such services have closed there doors but there are still a few left. One such service Evaphone allows users to enjoy free international PC-To-Phone calling from there website (or any other flash supporting device) to any landline or mobile phone in most parts across the globe, the service supports almost all major countries of the world including USA, UK, Canada, India, Pakistan etc. with each country having a fixed single free call duration with unlimited numbers of calls.

After successfully integrating Voice and Video Chat in Gmail Google has taken another step forward and is now offering free calls to and from Gmail itself. Integrating Google Voice into Gmail users will now be able to send and receive free calls to the U.S. and Canada with calls to other countries at very low rates right from their web-browser without installing anything (Apart from Google Voice and Video Chat Plugin).

Yesterday, I shared a tip on how to do unlimited international phone-to-phone calls from USA, UK and Brazil at local rates via free local access-number based VOIP call gateway, today I will show how to trick the gateway and call more then 60+ countries absolutely free from anywhere in world.

We have shared many services offering free VOIP calling to various countries around the world, most of these services offer free calling to many countries but often does not include India as a free destinations - now here we have a new service allowing unlimited free international calls to various destinations world-over including India at local rates from USA, UK and Brazil.

The free local access-number based VOIP service is pretty straight forward to use and all you need to do is to dial the provided local access-number and then once connected follow the IVR instructions provided by the gateway.

If your profession demands a USA phone-number or if you have relatives in USA having a local forwarding number comes pretty handy, usually you need to shell out money for having such facility as most VOIP service providers charge you for having an U.S.A. incoming phone number, but today I will be sharing not one but three services which will provide you a fully-functional USA call-in landline number for free without requiring any payment information.