What Is SIP and How Does It Work?

What SIP means, how it works, and why use it

What to Know

  • Session Initiation Protocol is a protocol used in VoIP communications, allowing people to communicate over the internet.
  • Requirements: SIP address/account, SIP client, internet connection, telephony devices, people to talk to.

SIP (Session Initiation Protocol) is a protocol used in VoIP communications, allowing users to make voice and video calls, mostly for free.

Why Use SIP?

SIP allows people around the world to communicate using their computers and mobile devices over the internet. It is an important part of Internet Telephony and allows you to harness the benefits of VoIP (voice over IP), providing a rich communication experience.

The most interesting benefit of SIP is how it cuts down on communication costs. Calls (voice or video) between SIP users are free, worldwide. There are no boundaries and no restrictive laws or charges. Even the SIP apps and SIP addresses are obtained free.

VoIP Equipment Wireless LAN Router and Phone
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SIP as a protocol is also very powerful and efficient. Many organizations use SIP for their internal and external communication, centered around a PBX.

How SIP Works

You get a SIP address, you get a SIP client on your computer or mobile device, plus whatever else is necessary (see the list below). Then you need to configure your SIP client. You'll also want to have your SIP credentials handy.

What Is Required?

If you want to communicate through SIP, you need the following:

  • A SIP address/account. This is obtained free from providers, and you can register online. Here are links to help you get a free SIP account.
  • What is a SIP Address?
  • Providers of Free SIP Addresses
  • Registering for a SIP Address
  • A SIP client. This is a program that you install on your computer or mobile device. It contains softphone functionality and some other features and provides an interface for you to communicate. There are different types of SIP clients. Among the most common ones are the applications offered free by VoIP service providers to use with their VoIP services. Some of them support SIP, but there are also clients that are built for SIP and do not depend on any service. You can use them with any SIP account, and can even use them within a PBX environment. You can check out our list of the most popular free SIP clients on the market and how to configure a SIP client.
  • An Internet connection. You'll need sufficient bandwidth for voice and video communication. Not much is required for voice communication, especially if you are using enhanced codecs for low bandwidth consumption, but you need solid bandwidth for video communication.
  • Hearing and talking devices. A headset, earpieces, a microphone, and a webcam for video communication are all acceptable.
  • Buddies to talk to. Maybe this is the first item in the list that’s checked. You may have buddies, but they need to be using SIP too if you want the calls to be free. Share the SIP addresses just like you do phone numbers.

How About Skype and the Other VoIP Providers?

SIP is one of the pillars of VoIP. But along with SIP, there are a number of other signaling protocols used for voice and video communication on IP networks. For instance, Skype uses its own P2P architecture, as do some other service providers.

Most VoIP service providers support SIP both in their services and the VoIP client apps they offer. There are so many SIP address providers and clients that Skype is not necessary for SIP communication.

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