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Obtaining a Free SIP VoIP Account – How Does It Work?

Updated on February 14, 2012

SIP Addresses are like Email

Using a free SIP account, it's possible to make phone calls at extremely cheap rates to PSTN phones and for free to SIP VoIP connected devices. This might seem like magic to those who don't know how it works and how the Internet has revolutionized voice calling throughout the globe. In this article, we take a quick overview of the SIP architecture by comparing it to that used by e-mail and by explaining why it is possible to make VoIP calls so cheaply or even for free.

SIP VoIP systems are based on a completely different paradigm compared to that used by the PSTN system. To start with, you receive an address which is very much like the e-mail IDs issued to you by your service provider. It consists of two parts – a username, and a domain name. So the structure will be something like If you are using a free SIP service, the company name part of the SIP address will be the name of the provider who is giving you VoIP service in the first place to. Just like if you have a free e-mail account with Gmail, every e-mail ID you create with them will end with "". If however you choose to go the premium route, you will most likely be able to replace the second half of your SIP address with your own company name. This provides the possibility of giving each and every employee in your business the same SIP address as their e-mail ID. You can imagine how convenient this will be to those who need to connect to them using VoIP.

VoIP Telephone Numbers
VoIP Telephone Numbers

Using Telephone Numbers for VoIP calling

Once you understand the basic architecture of the SIP address and how similar it is to e-mail, the rest is simple. To start with, imagine that another SIP VoIP user wishes to connect to you. Just like you, they will have their own SIP service provider like they will also have their own e-mail service provider. When they dial your SIP address, their provider makes a direct connection to yours. This is where the model deviates from the e-mail architecture which we have seen so far. Since VoIP is a real-time protocol, there's no way to "store" another person's calls on your SIP providers servers. Instead, they're routed immediately to your system which has its own "SIP client" on it. Of course, if you're not there any voicemail which the other person leaves will be stored with your provider just like an e-mail. So far, we haven't dropped down to the PSTN network yet and all communication has taken place entirely over the Internet. This is because the two parties are both using SIP VoIP. The equation changes slightly when one of them is on the PSTN line. This time, we need to integrate our VoIP network with the PSTN one. Predictably, this incurs some charges as well.

Your SIP provider will make the necessary connections to the PSTN system and will pass along any costs to you. Even then, the bulk of the transmission occurs over the Internet making even these calls cheaper than usual. International calls will see the most drastic savings since intercountry traffic will be routed through the Internet. One final adjustment has to be made to deal with PSTN integration – and that is the use of telephone numbers instead of SIP addresses. Telephone numbers are unfortunately still widely in use and will continue to be so as long as the traditional PSTN system is in use. This is probably the greatest paradigm shift we have to get people used to. The usage of telephone numbers is so deeply ingrained it us that it's difficult to think of making calls without them. But sooner or later we have to be weaned off them if we are to progress.


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