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What is SIP? And how is it different from VoIP?

Published in Voice over IP

What is SIP and how does it differ from VoIP?

The world of telecommunications is full of acronyms. GSM, WiFi, VoIP, ISDN or ADSL are just a few. They are widely used, but not everyone knows what they stand for.

As we have explained in previous articles, VoIP stands for Voice over Internet Protocol. It is a technology that converts voice from the phone into digital packets so that it can be transported over the Internet.

SIP is part of this voice technology.

SIP or SIP trunk

SIP is short for Session Initiation Protocol. As with VoIP, 'protocol' stands for a set of defined rules that the structure of an established session (between SIP devices) must follow.

Freely translated, SIP can be said to be the rules that determine how a call is established over the Internet, how packets are created and sent, and how that call is terminated.

This Internet protocol, SIP, is part of how a PBX communicates with devices and how it establishes and maintains connections.

The SIP trunk is the link between the PBX and the public telephone network. SIP trunks are digital telephone lines to which a company's telephone numbers are attached.

If you choose to run your communications over VoIP, you can do so with a PBX in the cloud, or with a PBX at your own site or data centre connected to the telephony network via a SIP trunk.

What is the difference with VoIP?

VoIP is actually a collective name for technologies that allow you to communicate with another user over the Internet. SIP is one of the technologies used for this purpose. The majority of VoIP applications are based on SIP.

Often, the two terms are used interchangeably and one provider will want to sell you a SIP phone, while another will talk about a VoIP device.

Frequently asked questions:

SIP stands for Session Initiation Protocol. It is a protocol used in telephony to set up a telephone call (session). This happens when two devices, such as two telephones, want to connect. Or when two users call each other using softphones such as Skype or Apple FaceTime.

A SIP device is a phone that connects to an online PBX via the Internet. Another term for a SIP device is a VoIP device. A SIP device can also be a softphone or intercom that is connected to SIP and talks to another SIP device.

SIP registration means that a SIP device has registered with an online PBX. Registration completes the SIP registration process.

A SIP address is an IP address at which a SIP device can be reached via a data connection. This means that any SIP device can be reached.

A SIP trunk is a digital voice connection between a (local) SIP PBX and a telephony provider connected to the public telephone network. In order for a PBX to provide telephone lines to the telephone network, a SIP trunk with a certain capacity of telephone lines is required. This capacity determines how many simultaneous phone calls can be made. A SIP trunk is the new modern type of ISDN phone line.

The SIP protocol is one of many protocols and competing technologies that exist within VoIP telephony to establish digital phone calls.

If you want a business phone number and want to receive calls, we can forward calls directly to to your current mobile phone or other devices. You will not need any (new) SIP devices or SIP trunk.

If your current phone system is connected via traditional telephony, you can sometimes still buy a SIP extension to make your phone system ready for new SIP telephony. It is often cheaper and easier to subscribe to a new online phone system and get rid of the old equipment.

Let us know how much traffic you have to which international countries and we may be able to help you get a good SIP trunk to those destinations so you can make cheaper SIP calls.

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