What is contention ratio? - broadbandchoices explains

ByKim Staples
Ethernet cables plugged in

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?

Well, to put it simply, 'contention ratio' refers to how many users are sharing the data capacity on a provider's line. To put it even simpler, it's a count of how many households are using the same main broadband line as you.

If your contention ratio is 20:1, for instance, that means twenty households are using one line.

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 completely accurate.

How does contention ratio affect my broadband?

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.

If the line you have access to is a 100Mb one, for example, you can easily get speeds of up to 38Mb or 76Mb on a good day. But 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 2Mb.

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.

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

This is why some providers practise web traffic management. 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. It's like opening a fast lane for the cars that really, really need to get somewhere.

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?

Not really, no. Contention ratio isn't something providers tend to advertise these days. Most households aren't affected by it in quite the way they used to be a few years ago, and providers - like BT - often think of it on a national scale rather than a local one.

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.

 

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