Making phone calls via the internet using VoIP is something we now tend to take for granted without necessarily thinking about what goes on beneath the surface. The underlying technology, however, is important and a basic understanding of it can help in deciding which system is right for you.

Behind every VoIP system – indeed behind every phone call – is a carrier services infrastructure (CSI). This is the backbone system that ensures that calls can reach their destination. A CSI is typically made up of many different kinds of connection. Some will be fast, high bandwidth fibre connections, others will be slower, more limited copper connections.

 There will be single channel, multi-channel, switched and dedicated circuits. You can think of it as akin to a rail network, with fast, high capacity mainlines and smaller branch lines all contributing to an integrated whole that gets you where you want to go, albeit with three changes of train and a rail replacement bus service!

 Types of CSI

 Looking at different types of carrier infrastructure is something of a journey through a history of telecommunication. The CSI goes back to the very early days of telecommunication and the public switched telephone network (PSTN). This is the traditional way of making phone calls using switched lines to reach a particular destination. It may still be the endpoint for many calls that originate on VoIP.

 Next was the evolution the digital service (DS), often in the form of a leased line, which allows a dedicated connection between two sites. After this comes the optical carrier (OC) which is a dedicated connection using an optic fibre link. Most recently there’s the rise of wireless and cellular networks that enable fast mobile connection.

 CSI and VoIP

 For specialists such as IDT offering wholesale DID origination services, a smooth running CSI is essential. This generally means a packet-switched network that combines DS, OC and wireless transports.

 Because telecoms is a dynamic environment, networks are being upgraded all the time to take advantage of the latest technology. If, as a business, you have private, dedicated links between sites then they – or a portion of them – are dedicated to your VoIP traffic all the time. Once you make calls outside your own business, then you are using the public CSI offered by telecoms service providers.

 Depending on the ultimate call destination, the data may be routed via several different carriers. This needn’t especially concern you as an end user as the routing and billing of the call is taken care of by arrangements between them. The key advantage of VoIP here is that because the call is dynamically routed via the internet, it finds the most efficient way through the CSI. This is in contrast to PSTN where the call takes a fixed route and is, therefore, going to be more costly.

For the end user, VoIP is a simple and cost-effective way of making phone calls, but there’s a lot going on beneath the surface.