Understanding Broadband Speed
Since the beginning of always-on broadband services, the speed of services
has been a constant discussion topic and a central feature of broadband
advertising and marketing. The average consumer will usually see one figure,
usually prefixed with the words 'up to', but the true quality of a broadband
connection can vary significantly from this figure.
This guide will help you understand what affects your broadband speeds, how
you can test the speed of your broadband connection, and what you can do to
What is affecting my speed?
There are a number of different factors which can affect your service speed.
Some factors are dependent on the technology used to deliver your connection
whilst others affect all types of broadband connections.
In this guide, when we talk of 'ADSL', we are referring to a broadband
service delivered over your telephone line which terminates on an ADSL
modem/router. 'Cable' services refer to those provided by a cable company such
as Virgin Media. There are also other types of services (mobile broadband,
wireless services, etc.) so this guide may not cover every possibility.
Things in the home
- Wireless / Wi-Fi—If you are using a 'wireless' connection for your broadband (e.g. your
laptop connects to your broadband router using a Wi-Fi connection), the distance from the
wireless router/access point can make a difference to the speed you are getting. If you are two metres
away from your router, you will likely have a faster connection than if you are 20
meters away. You will also find that walls and ceilings/floors will affect the
signal as well, especially in some older buildings. In some circumstances, you might find that being too close to a router
(e.g. under 2 metres) and actually reduce speeds so it is worth testing in slightly different locations.
- The speed of a wireless/Wi-Fi connection will depend on the protocol
used; some older protocols (e.g. 802.11b) are much slower than the latest
(e.g. 802.11n) and if you're on a superfast broadband connection, the
wireless speed can be slower than your broadband connection speed, even if
your laptop is right next to the router. It's worth considering using an
Ethernet cable connected directly to the router when running a speed test.
- Wireless interference—Interference from different wireless networks can also reduce your
speed, particularly if they are operating on the same channel. If you have a choice of using 2.4GHz or 5GHz wireless,
it can be beneficial to use 5GHz if you can receive strong signal everywhere you need it as this band is generally less
crowded and the signal does not travel as far, so you should see less interference in this band. If you live in an urban
area, it is common to find over 20 wireless networks competing for the same wireless spectrum and it may be worth
considering using Ethernet cables if you find the wireless signal poor.
- Electrical interference—Electrical interference inside your home can affect the speed and
stability of your broadband connection. This can commonly cause your ADSL
connection to re-sync resulting in both a speed reduction at times, as well
as a brief break in service. The cause can be any electrical device (even a
neighbour's device) but common causes include boilers switching on. You can
minimise the effects of this by ensuring that you use high quality telephone
extension cabling, or disconnecting extensions altogether at the master
- Microfilters—ADSL broadband services require you to fit a 'microfilter' to every
device which attaches to a phone line (or in some cases you may have a
'faceplate filter' on the master socket which filters all extensions). This
means phones, faxes, answering machines, Sky+ boxes and anything else with a
connection to the phone line. If you forget to install a microfilter on each
extension, you are likely to have significant problems with your broadband
connection, although it may work fine at times. A faulty microfilter may exhibit
the same effects as a microfilter not being present so it can be worth disconnecting
all other devices and extensions if you are diagnosing a problem.
- Speed of your computer—Some older computers will struggle to keep up
with modern super-fast broadband connections; this may be due to the age of
the computer, or due to the amount of software installed. You may be able to
upgrade the computer or remove unused software. Consult your local IT
support service for advice.
- Other users in the household—If you share your
broadband with other users in the household, your bandwidth (the speed
available) will also be shared across all the users.
Between your home and your ISP
- Contention—Broadband networks are 'contended' networks a bit like the road
network—this means that there isn't enough capacity for every user to
use the service at full capacity, at the same time. This contention helps to
ensure prices remain low as generally speaking demand varies. However at
peak times, you may find your broadband slows down. Remember that 'peak' in
broadband terms can be in the evening, although this may vary by where you
live and who your broadband provider is. Also, it's more likely you will see
congestion during major events;
during the World Cup, there was noticeable congestion on broadband networks.
- Congestion—If there are lots of people using the Internet in your area at peak
times, it may slow your speed down. This is most likely to be visible in
small communities where the link from the telephone exchange back to the
service provider is likely to be smaller.
- Where you live—The distance from your home to the local
telephone exchange is the most common factor which affects DSL
broadband services as the signal degrades the longer it needs to travel. If
you have a
fibre-optic broadband connection, you're less affected as the distances
are shorter (from your home to the street cabinet instead of the exchange; see the
fibre broadband guide for more details)
How near you live to your local exchange will affect the speed of your
broadband. If you have fibre broadband, your speed shouldn't be as affected by line
Between your ISP and the Internet
The Internet is made up of tens of thousands of separate networks; your
provider is one of them. When you visit a website hosted on another network,
there are a number of possible paths for your traffic to take and sometimes,
some of these paths can become congested.
This type of congestion can mean that at times, some websites will appear
slow whilst others may be working just fine. It can be caused by your ISP
congesting some of their peering links to other networks, or even inside other
networks (e.g. those hosting the website you're having difficulty accessing).
This is not a reflection on your broadband speed, but something to think about
if you are experiencing problems.
Broadband ISP Peering Congestion Diagram (click to enlarge)
Traffic Management / Shaping
The term 'traffic shaping' or 'traffic management' refers to technology used
by providers to control the amount of bandwidth (i.e. speed) available to a
particular user, device, application or website. These are commonly used to
restrict high volume transfers, either by restricting bandwidth available to the
most heaviest users at peak times, or by slowing down certain types of services
such as peer-to-peer (p2p) file sharing.
Some types of traffic are less sensitive to speed variations. If you are
downloading an operating system update or sending an e-mail, then a delay of a
couple of minutes is unlikely to affect your user experience very much. However,
if you are watching a live broadcast/television stream, listening to a radio
station or having a video chat with someone, an interruption/slow-down can have
a noticeable effect. Broadband providers use traffic management technology to
sometimes prioritise these applications, to help you get a better experience
without requiring additional investment in capacity which would in turn require
them to charge more for their broadband service.
The ASA Rules
Since the beginning of April 2012, the Advertising Standards Authority has
adopted a policy which states that where a provider states a numerical speed
claim in their marketing communications (i.e. in advertising, on the website,
etc.), they should "be able to demonstrate that the speed is achievable for at
least 10% of the relevant customer base". This means that if you see an 'up to
14 meg' broadband service, you would expect at least 1 in 10 users to be able to
What is a speed test?
A broadband speed test
is a useful tool which you can use to measure the download
and upload speed of your broadband connection. It works by measuring the time it
takes to download a certain amount of information, and then carrying out the
same test in the upstream direction. The measurement is then provided to you
along with other information about the quality of your connection.
Our speed test
is used by various websites including the Gadget Show because
of its reliability, accuracy and our capability to cope with scale. Our speed
testing platform has been built from the ground up by our staff for over ten
years and uniquely, it runs on a network we control so we can monitor its
performance and ensure there are not bottlenecks caused by our end of the
connection. Many other speed tests run on shared servers on third party
networks, or even on many different networks so the results can vary depending
on which server you use. Our test servers are based on dedicated hardware with
direct 1Gbps connection to our core network.
The results you receive may vary from one test to the next as the performance
of your connection will not always be the same. Please refer to the
things affecting my broadband speed
section above for more details, and remember the speed test is between your
computer and our servers, so make sure it's not affected by anything under your
I've done the speed test, what does it mean?
A fast download speed means information will come to you quickly. This means
that for example, when you download a music album, it will finish sooner than if
you were on a slow connection. A fast upload speed means it's quicker to send
information, such as uploading photos or videos to a website.
Broadband speeds are usually measured in "Megabits per second",
"Mbps" or "Mb/s" although this is often (incorrectly strictly speaking)
referred to as 'meg' or "Mb". Sometimes you may see speeds in
"Kbps" or "Kb/s" which refers to "Kilobits per second". There are 1,000
Kbps in 1 Mbps. Typical broadband download speeds range from a few Mbps
through to 100 Mbps for a
service whilst upload speeds range from 250
Kbps (0.25 Mbps) to around 5 Mbps on the super-fast services.
Check the speed your ISP advised you'd be able to get when you signed
up. If you're not getting the speed you're paying for, then consider a
different provider, but do remember that many of the factors affecting
speed may be the same (e.g. your computer, your wireless network at
home, the quality of your phone line, etc.) You should raise your
concerns with your current broadband provider in the first instance.
Why is my download speed faster than my upload speed?
Since the start of broadband services, download speeds have generally been
several times faster than upload speeds. This is called an 'asymmetric' service
and it's also the first word in the 'ADSL' acronym. The reason is primarily that
with limited bandwidth available, the protocols used have been developed to
maximise download speeds as more content is consumed from the Internet than is
uploaded to the Internet.
There are some technologies such as ADSL2+ Annex-M
which increase the upload speeds, but at a cost of slower download speeds. Also,
broadband providers can use this imbalance to provide hosting services (which
typically use the upload segment) and share some of the cost of running a
network between different types of users.
Why is your speed test slower/faster than ... ?
There are a number of differences between our speed test and most others on
the Internet. It's worth noting that most other tests run in a similar way, so
the fact our tester gives you a different result to many others doesn't mean
there's anything wrong with our test.
Here are some of the key differences:
- Network—our speed test runs on a network we control giving us the
ability to ensure nothing on our end is causing any problems. Some providers
run more congested interlinks to the main London peering points such as
LONAP and LINX (to which we connect), in which case traffic to us might be
affected. The routes to other testers may be different, so they might not be
affected in the same way. All our tests run from dedicated servers on our
network so we can vouch for our end of the test. Some other testers may pick
from a number of servers to pick the fastest ones–We don't believe this is
a fair way to measure speed as you get the best result which may not match
your true experience when using the Internet.
- Traffic shaping—our speed test runs using a custom protocol developed
by us. Specifically, this is not using HTTP which is the protocol used for
web browsing and which is also used by most other speed tests. We have
chosen our own protocol to ensure that we can test the true speed of the
connection. Various speed tests using HTTP will give you results which are
faster than your line is capable of, often caused by security software which
intercepts the connection, breaking the speed measurement system. We let you
test over port 80/tcp which is typically used for HTTP, but the protocol is
still the same, but sometimes you may notice a difference if your provider
is simply filtering certain ports.
- Software—our speed test is available either as a
Flash version. Most other speed tests are available in Flash only. Sometimes the
speed of your computer or the version of Java/Flash can cause problems. This
is not necessarily related to the speed of your broadband connection.
- Threading—our speed test runs with a single thread which means that it
makes one connection to download and upload data. Other testers can use
multiple threads to boost speed. Our servers are more than capable of
delivering full speeds for broadband connections on a single thread. If
you're running an old version of Windows, there are some instances where
your settings may mean that a multi-threaded tester performs significantly
better, but often the cause of speed issues with single threaded tests are
related to your provider's capacity. You can run a
multi-threaded test on our download test files
- Compression—we send random data which has been
pre-compressed so that the test reflects the true speed of your connection.
Sometimes, it's possible to compress data further and therefore the apparent
speed would be faster.
- Measurement—we measure the mean average speed of the
connection by taking the amount of data transferred and dividing it by the
time. Many other testers will measure speed in intervals and show you either
the fastest measurement, or a percentile. This means in practice that you
could disconnect your broadband service during the test for a few seconds,
and then reconnect it, and still get a fast result on some other tests!
(yes, we've tried it!). We don't think this is a fair way to represent speed
without informing the user.
- IPv6—our speed test has been IPv6-compatible for many
years. If you have IPv6, you may find routing is a bit different so this can
cause a difference. You can run an
IPv6 speed test on ipv6-speedtest.net which shows you if you're using IPv4 or IPv6.
We also have an
IPv6 readiness test to check if your broadband is IPv6 enabled.
Other tools to test speed
In addition to web-based speed tests, we also provide some useful tools you
can use to monitor the speed of your broadband connection:
- Bandwidth Meter (tbbMeter)—this is a tool for Windows PCs which allows you to monitor the
bandwidth usage of all applications on your computer. It's useful to see
when your computer is downloading or uploading to/from the Internet when
you're not expecting it. It will also let you track how much data you use
each month. It can also do a multi-threaded download from our servers to
- Download Test Files —these are files fill of random data which has been pre-compressed and available
for you to download over various ports.