What is VoIP?

Voip means different things to different people, so let’s look at what voip can do for you.


Background /history

Voip is an acronym for Voice over IP – IP being the Internet protocol (gotta love nested acronyms!). The biggest significance of VoIP over traditional telephone systems is the  shift in the technical side of how the call is delivered. Traditionally telephones use circuit-switched networks meaning that a dedicated channel is created between the caller and the recipient, for the duration of the call. This limits the call capacity based on the number of circuits a system can simultaneously switch at once. In the case of your house you rely on the telephone exchange. In the case of an office phone system you probably realise that you can make more simultaneous calls ‘internally’ as those ‘externally’ – this is down to the number of connections you rent from the telephone company which connect you to the rest of the world (the PSTN or Public Switched Telephone Network).


Voip and specifically IP is, by contrast, a packet switched system. This means that information – in this case your voice – is split up into small pieces and sent over a series of links. The packets can take a variety of routes to get to their destination and these routes can dynamically change, so if problems develop the packets can go around a different way.


Voip uses

So VoIP is the delivery of voice via an IP network. The common thoughts about VoIP are:

– using computers to make free phone calls (particularly long distance) over the Internet, using software such as Skype.

– linking 2 or more sites’ telephone systems to allow free calls between company sites / branch offices

– having a ‘virtual’ phone system, reducing capital costs of a new system and allowing remote extensions

– allowing larger companies to utilise existing IT infrastructure and knowledge to extend the reach of their phone systems, over fibre-optic links and wireless / free-space optical links.


VoIP is all of these things! It has so many advantages and different implementations that it can do all of these things. Some of the highlights are;

– be a part of the corporate phone system when you’re at home, at a remote office, even at your holiday home – in fact pretty much anywhere you can get on the Internet

– because it’s all IT based, anyone with a moderate IT knowledge can make simple changes, like changing names or ring group membership

– you can reduce your costs, especially on international calls and on line rental vs. traditional multi-line delivery (Featureline or ISDN)

– you can keep your phone number whether you move next door or the other side of the world

– you can have telephone numbers in multiple regions and countries, giving your customers a local number to call wherever they are, or wherever you want to appear to be located

– you can mix ‘n’ match equipment as it is all standards based, so you have the best pick of kit that exactly suits your requirements


Here are some common VoIP deployment scenarios (click to view):

Digital System with remote IP phone Voip-DigitalVoip-Digital
Distributed handsets Voip-DistributedVoip-Distributed
Voip handsets, voip trunks (with roaming cordless) Voip-TrunksVoip-Trunks
Wireless bridge Voip-BridgeVoip-Bridge


What goes up…

So are there downsides to VoIP? Sure there are, but they aren’t all show-stoppers.

– if broadband goes down, so do your phones (using SIP trunks- this does not affect you if you stick with transitional PSTN connectivity)

– you may need additional Internet bandwidth to support the number of simultaneous calls you require, just like phone lines. VoIP quality is typically thought to be poorer than the digital clarity of ISDN. This is often due to poor provision of bandwidth or of setups designed to maximise capacity at the cost of quality. In fact, done right, VoIP quality is comparable to ISDN.

– the phones require Ethernet, which can’t run on traditional 2-wire cabling, only cat5 or better. In difficult buildings the cost to re-cable can make a full VoIP system prohibitively expensive when compared to re-using traditional cables and traditional systems

– the phones require power. This will mean either factoring in power-over-Ethernet switches or using traditional power adaptors – which is fine but just not as neat as a single cable running to the phone.

– fax is a big problem. Because of the way VoIP works and the way fax machines work, they are essentially incompatible. Whilst fax machines CAN and often do work, be prepared to make alternate arrangements