What is broadband traffic management and traffic throttling?

istock/grinvaldsThere are now tens of millions of broadband connections in UK and demand is showing no signs of slowing down. 

That puts ISPs under a lot of pressure as they have to maintain an acceptable level of service for a huge number of business and home users spread all over the country. And if things go wrong social media now offers an instant and very public channel for complaining which can quickly have an impact on their reputation.

One of the ways in which ISPs can help manage demand and keep things flowing smoothly for everyone is traffic management, but this can lead to unexpected issues for broadband subscribers who aren’t aware of such policies and how it can impact their experience.

What is broadband throttling and how does it work?

Providers have the capability to deliberately slow down internet access, either for all communications or specific types of traffic. There are various terms for this, including throttling and traffic shaping, but all essentially fall under the umbrella of ‘traffic management’ to describe how and why an ISP controls the enormous amount of data passing through their network

As data is transferred they can slow it down or prioritise certain types of traffic. The connection still works but end users will experience throttling as a reduction in performance when tasks like video buffering take longer, web pages have a more apparent loading time and downloads and uploads work at a reduced rate.

It’s important to note that traffic management is not just reserved for fixed line home broadband, it is also utilised on mobile broadband where bandwidth can be even more limited.

Why do broadband providers use traffic shaping?

It all comes down to congestion. Although ‘broadband’ implies a very wide road the virtual highways only have so much room to carry information and an overloaded network can slow things down for everyone.

As more people have come online and internet habits changed from relatively lightweight activities like email and web browsing to the widespread use of much more demanding behaviour such as streaming video, internet telephone calls and large file downloads, networks have had to deal with a lot more data.

How much more? In 2002 fixed line internet traffic was about 356 petabytes per month. By 2012 this had increased to an incredible 31,338 petabytes. Or, to put it another way, the content of 31,338,000 1TB computer hard drives full of selfies, Tweets and cat videos being sent over the internet every month.

In order to handle this without everything grinding to a halt management may be implemented to restrict or prioritise certain types of traffic, sometimes even limiting the speed of all connections. 

The how and when of traffic shaping policy differs between providers as each has their own definition of peak time and approach to types of traffic. But very broadly speaking it will be in action during the day into late evening, and mainly affect file sharing.

This is because the likes of BitTorrent and Newsgroups can result in a small number of users consuming an extremely large share of the bandwidth. But in turn other things may be prioritised to improve performance, which is often applied to VOIP (so your Skype calls work uninterrupted) and online gaming.

So at busy peak times when everyone is using the internet at work or at home browsing their favourite sites and streaming a boxset off Netflix, ISPs will slow some traffic to ensure an acceptable service for everyone else. BitTorrent downloads could get much slower, but you’ll still be able to stream Breaking Bad in HD.

Which broadband ISPs use traffic management?

Policies vary between providers so you will need to do some research if traffic management is likely to get in the way. You should be able to find the information on each ISPs site, and most are signed up to the BSG code of conduct so the information will be clearly presented. If you're having difficulty tracking down the terms on a provider's site it may be easier to find it via a Google search.

Remember that some ISPs have a fair usage policy which includes a cap on data usage each month in addition to the traffic management. Exceeding their monthly download limit can result in your connection being throttled until the next billing period or a charge for additional data. However there are an increasing number of ISPs which offer totally unlimited broadband.

Home broadband traffic management policies

Every ISP approaches this differently, but here’s some information on how the big players handle traffic management.

Affected packages: BT TV
Peak times: n/a

BT only uses traffic management to prioritise TV services for on-demand viewing. Extra bandwidth is utilised for this so it does not impact other users.

Affected packages: Sky Connect
Peak times: 16:00 - 23:00 weekdays, all day weekends

Only Sky Connect packages have traffic management. Browsing, email, media streaming, VOIP and gaming are prioritised. At peak times peer-to-peer file sharing and newsgroups are slowed, and heavy users may find their connection reduced by 90% between 17:00 and 00:00. Sky Unlimited has no traffic management or data usage limit.

Affected packages: TalkTalk Essentials and Plus TV
Peak times: n/a

TalkTalk has almost no traffic management at any time. Like BT the exception is for those on a TV package, where TV streamed to the YouView box is prioritised over other traffic.

Affected packages: All
Peak times: 30Mb+: 16:00 - 00:00 weekdays, 11:00 - 00:00 weekends / 20Mb or below: 15:00 - 20:00 for uploads, 17:00 - 22:00 for downloads

Virgin operates varying levels of traffic management depending on your service. If you have a connection speed of 30Mb or faster it mainly affects uploading - exceeding the threshold data cap (which varies between packages) for uploads at peak times will reduce your upload speed for at least 60 minutes, or until the end of the peak period if you continue. Peer to peer file sharing and newsgroups are the only services slowed during peak hours, there is no prioritisation of other traffic.

For connections of 20Mb or lower the penalty for exceeding the threshold for either upload or download is a 75% speed reduction for the entire connection for five hours. Again, peer to peer and newsgroup traffic is slowed during peak times.

Mobile broadband traffic management policies

Peak times: 08:00 - 02:00

EE restricts peer-to-peer traffic to a maximum 50Kb at peak and 1800Kb at other times. No other type of traffic is included.

Peak times: n/a

O2 does not implement traffic management for mobile broadband.

Peak times: 15:00 - 00:00

Peer to peer slowed at peak. Streaming video is ‘optimised’ for performance, which may equate to lower quality, however Three does not provide details.

Peak times: n/a

Vodafone does not implement traffic management for mobile broadband.

My broadband is slow: am I being throttled?

It’s a possibility. First, make sure you’ve not exceeded any data usage limits for your broadband package. Use your provider’s online management tools or check your email to see if you’ve been notified. Obviously this does not apply if you’re on an unlimited package unless your ISP has a sneaky fair use cap, which is increasingly rare these days.

Next, check the ISP’s traffic management policy to find out when it is active and what kind of things are affected.

If you’re outside peak hours or not doing anything which should fall under the policy then the issue lies elsewhere so it might be a question for tech support. For more information we have guides to troubleshooting home and mobile broadband and contact details for home broadband and mobile broadband