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The difference between SIP Trunking and VoIP

The difference between SIP Trunking and VoIP

Onecom, UK’s largest independent business telecoms provider , , , ,

The telecoms industry is often guilty of not breaking things down simply for the masses. With many businesses running at a fast pace with a stretch on resources, there is often little time to understand all the information and work out precisely what means what. That’s why we are trying to help make things as simple for you as possible by explaining the jargon, and telling you what is what!


Here’s what you need to know

IP – Internet Protocol

VoIP – Voice Over Internet Protocol

SIP – Session Initiation Protocol

Trunking – Grouping

That’s the acronym’s covered, but what about the detail? Fortunately, here at Onecom we see ourselves as IP trunking and SIP trunking experts, so let’s look at the differences…

What is SIP trunking? Get the jargon-free answer in our simple SIP trunking guide.


As explained above, the IP in VoIP stands for ‘Internet Protocol’ and is a term used to describe the data being transferred across the internet. When applied to describe voice data, it’s often referred to as VoIP.

Hosted VoIP solutions describe how these call sessions are bundled together from one user. It’s an industry term that makes it easier to indicate how many groups of calls you might need at any one time.

If you are interested in learning about the benefits of VoIP, Take a look at our 5 advantages of VoIP for business blog for more details on how it may help you.


SIP Trunking

SIP or ‘Session Initiation Protocol’ is a set of rules used in multimedia communications to initiate and terminate data transfer between users.

Are you interested in learning all about SIP trunking? Look at our blog ISDN to SIP, which goes into more detail on the differences between traditional ISDN lines and SIP.


SIP Trunking and VoIP

To make it simple, IP/VoIP calls are calls made over the internet, whereas SIP is the protocol used to make the calls and connect the multimedia sessions. SIP isn’t the only control protocol, there are several that do the same job, but you have to have a control protocol to be able to initiate a VoIP call. It’s the control protocol that will establish the communication between endpoints; these may be between a phone system and a handset, or between phone systems over a SIP trunk.

Hosted VoIP solutions are limited to transferring voice data over the internet, whereas a SIP trunk can transfer packets of multimedia data. This could be voice, text or video. A SIP trunk only differs from a SIP phone in that it’s expected to carry more than one VoIP stream at once. As above, SIP deals with the signalling, so multiple VoIP streams can be established over a SIP trunk simultaneously. It’s important to note that you can also have SIP where there is no VoIP.

They also operate in different mediums. A VoIP call is solely over the internet or a private internal network, however, a SIP trunk can be used to transfer data packets over any network. This includes the ISDN (physical phone network), a VPN, or the internet. The main impact of this difference is the fact that a VoIP phone requires a computer to operate its software and its connections, whilst SIP equipment operates separately.

The final point is that that a softphone and a hardphone are actually identical as far as SIP and VoIP are concerned; a physical handset will be doing exactly the same in its software with regard to the VoIP packets and SIP signalling as a softphone on a computer, there’s no difference whatsoever.

Still with us? If you need to know more and would like to speak to an expert, why not call Andy today on 01273 740731. He’ll be able to tell you exactly how SIP can help to transform your business and save you money!

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