Unravelling broadband speeds: The role of contention ratio

What is contention ratio

A lot of things can affect how fast your broadband is - like the wiring in your home, what kind of router you have, or what’s available in your area - and one of those things is 'contention ratio'. But what is it?

A lot of things can affect how fast your broadband is - like the wiring in your home, what kind of router you have, or what’s available in your area - and one of those things is 'contention ratio'.

What exactly is contention ratio?

Well, to put it simply, 'contention ratio' refers to how many users are sharing the data capacity on a provider's line. It's a way of understanding how traffic on your broadband line can impact your internet experience. If your contention ratio is 20:1, for instance, that means twenty households are using one line.

Traditionally, standard contention ratios used to be around 50:1 for home broadband, and 20:1 for business broadband - but BT says these figures are no longer accurate. The landscape of broadband technology is constantly evolving, and so are the benchmarks for what is considered normal or acceptable in terms of sharing bandwidth.

How does contention ratio affect my broadband?

It's quite intuitive when you think about it: when your contention ratio is high - meaning a lot of people are connected to the same line as you - it can potentially drag down your broadband speeds. This is because you are all vying for a piece of the bandwidth pie.

Imagine you're on a 100Mbps line. On a good day, you can easily get average speeds of around 35Mbps or 63Mbps. However, if your contention ratio is 50:1, with 50 people connected to it, and you're all using it at once, you'll only get speeds of about 2Mbps.

That means that if you're in an area with a high contention ratio, you'll probably get slower speeds in the evening when more people are online. This is similar to rush hour traffic - the more cars on the road, the slower everyone moves.

A road traffic analogy

Think of it like a road. A small road can easily handle 20 cars cruising up and down it at various points throughout the day, but if all 20 cars try and pull out onto the same section of the road at once, they won't be able to go very fast and might cause a jam.

To manage this, some providers used to use web traffic management, which is akin to creating a fast lane for specific cars. By prioritising data for certain online tasks, like video streaming, they ensure that you'll get a stable connection on your line regardless of your contention ratio.

The silver lining: fibre optic broadband

However - here's the good news! Your line speed only tends to be seriously affected by a poor contention ratio if you're subscribed to standard ADSL broadband. Fibre optic broadband, on the other hand, has a far higher capacity - so more people can share a line at once without getting a major dip in speeds.

Can I find out the contention ratio in my area?

Contention ratio isn't something providers tend to advertise these days. It's become somewhat of an archaic term, as the technology and infrastructure have improved to the point where it generally does not affect households as it used to. Providers like BT now consider it on a national scale rather than locally.

When you sign up for a broadband package, though, your provider will give you an idea of the download and upload speeds you can expect - which is partly calculated using contention ratio. This gives you a more direct understanding of what your internet experience will be like, rather than focusing on the technical details.

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