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SIP Calling

by OnSIP

Learn how a SIP call works.

Free Calls over the Internet

The majority of the population is so used to paying usage fees for their telephone services that phone calls made using SIP protocol may be an eye-opening concept.

But if you think about it, Voice over IP calls are not all that different from text-based chat sessions. Both forms of communication are simply packets of data sent from one IP address to another. If it’s all the same to your network, then how come IM sessions are always free and telephone calls are not?

The Key Difference between Old Telephone Systems and Voice over IP

Telephone calls, IM sessions, and video chats can all be broken down into two parts:

  1. The signaling step, which refers to the initiation and termination of the communication session.
  2. The media stream, which refers to the actual data being passed from one end to the other.

Traditional telephone system infrastructure meant that the telephone carriers handled both the signaling and the media stream (which costs significantly more to send). Since they handled the entirety of the communication session, a service charge was required, usually in the form of a pay-per-minute fee. If your call had to go through two carriers, then it was probably even more expensive.

With the emergence of Internet-based services like business VoIP providers came the separation of the signaling process and the media stream. Now, different parties can focus on different parts of the communication session, allowing companies to develop better services with a lower price tag to their customers.

Anatomy of a SIP Call

Let’s look at how a SIP call works for an OnSIP customer. After the number has been dialed, OnSIP handles the signaling step by sending a small packet of data to both parties to initiate the call. The cost of this data packet is so negligible that it is free to OnSIP users. If the call is to another SIP address, then the digitized voice data (the media stream) will be sent through the Internet providers of the callers on each end. Since they are already paying for their Internet service, there is no need to charge either of them for that call. In other words, this type of call should cost the people on each end absolutely nothing.

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Free SIP calls with OnSIP

Whether you’re making a call to a SIP address or receiving one, it’s always free with OnSIP. If you’re dialing a number with a SIP address associated with it, OnSIP will automatically recognize it and handle the call, meaning that it will also be free. Calls within your OnSIP network of users, which are inherently SIP calls, can be handled on your own LAN, meaning that they do not go through the Internet. These calls will also cost you nothing. And what's more, OnSIP customers can use our free mobile app and desktop app to make these calls directly from their computer, laptop, or smartphone.

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