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What is bandwidth?

We look at how bandwidth works, and why your internet connection sometimes slows to a crawl

Data in a tunnel for analytics

Bandwidth refers to the absolute maximum amount of data that can be transferred over an internet connection during a marked period of time.

It relates to the network's communications capacity that allows data to move between nodes. However, this isn't equivalent to the data transfer's speed, which takes latency into account, and instead only concerns the capacity of a line at any given time.

Modern innovations in networking have meant that the amount of bandwidth in connections used by businesses and individuals across the world has skyrocketed. To illustrate this, bandwidth was once measured in bits per second (bps), which was fairly low when the unit of measurement was first created, but it can now be recorded in millions or billions of bits per second.

Understanding bandwidth: An analogy

The easiest way to understand bandwidth and its effect on data flows is to think of water moving through a pipe. Using a connection that has low bandwidth is akin to trying to drain a lake using a hosepipe – it's possible, but it would take significantly longer than using a much larger pipe. In this sense, even if the speed of the water was to increase, the pipe can only accommodate a set volume of water.

That's not to say that bandwidth and internet speed are entirely independent. In fact, low capacity could produce a bottleneck, which will drastically reduce the performance of the network, and may even cause some applications to stop entirely.

For example, a bottleneck may force a multimedia-rich website to display only text, as the network struggles to move the larger data packets. Any tasks that require constant uploading and downloading of data packets, such as online gaming, will experience high latency on a low bandwidth connection.

How do you measure bandwidth?

Measuring bandwidth can become quite complicated with numbers followed by a series of letters that might seem a tad nonsensical at first. But bandwidth is commonly measured in millions of bits per second; those large numbers of bits are known as megabits and with bandwidth per second shown as Mbps. For broadband connections with more bandwidth, Gigabits come into play, with Gbps denoting how many Gigabits per second a connection is delivering or can deliver.

Currently, the average broadband speed in the UK is 54.2Mbps, according to Ofcom's figures, with speeds having jumped by around 20% over the past 14 months. That bandwidth capacity is a boon for people working from home on projects that require the transfer of large files or high-speed access to cloud-based services such as Microsoft Office 365, or require fast and stable connections for video conferencing.

Unfortunately, for those who like the countryside, there is still a digital divide with properties and areas left out of the reach of the government's efforts to roll out superfast broadband across the whole of the UK by 2033. A lack of access to broadband connections with a healthy bandwidth could stymie the success of businesses beyond urban areas as well as limit the services other businesses within cities can target them with.

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For businesses, it's important to assess how much bandwidth you will need to perform your daily operations. That not only involves figuring out how many employees will be accessing the network at once but also taking into account the bandwidth requirements for any applications they will be using.

Another thing to consider is the fact that the data has to flow through several connections to reach you, and your connection to your ISP might impact your bandwidth speeds.

It's also important to remember that even if you have plenty of bandwidth available, you will need to reduce the network's latency in order to improve the speed at which data packets move across the network. This is particularly important for applications and services that require high data transfer rates beyond what a normal network connection can provide.

For everyday consumers, depending on your provider, where you live, and what kind of internet service you pay for, you might have a different internet connection. Here are the possibilities:

FTTH (fibre to the home) - This is easily the fastest kind of service and can deliver up to 1Gbps, but it's not been rolled out very widely yet.

FTTC (fibre to the cabinet) - By far the most common connection in the UK, FTTC sees internet service providers (ISPs) link your home to a cabinet on the street with copper wires - much slower than the fibre-optic cables connecting the cabinet to a telephone exchange.

FTTN (fibre to the node) - A node is just further away than a cabinet (miles further, sometimes), potentially slowing your internet connection even more.

FTTP (fibre to the premises) - FTTP is getting a wider rollout around the UK, but is typically designed for office buildings, where high-speed internet is in high demand. The fibre optic cables run right up to your building, supporting higher capacity lines direct to your business infrastructure.

How can I check my internet speeds?

At times, you might need to know how fast your broadband really is. Perhaps your internet connection has been acting up, or you’re considering changing your broadband provider and want to compare package deals. Sometimes, it’s just about finding out whether the offering you paid for is really up to standard.

Whatever the reason, being able to check your internet speed is a useful skill which anyone should have. The simplest way to do so is to carry out a ping test, which examines how fast it takes for the tiniest amount of data to travel over your broadband. This is done by measuring the download, upload, and response times of your laptop, PC, or tablet.

Broadband speeds can vary based on the time of day, just like travel peak times. Before the pandemic, it was common knowledge that taking the main roads between 8am and 9am, as well as 4pm and 6pm, may result in longer journeys. Your broadband works the same way. The ‘internet rush hour’ in the UK is commonly considered to be between 7pm and 11pm, as that is when the larger part of the population is either gaming with friends or streaming the latest Netflix show. That is why, during these times, your internet speed might not be at its fastest.

However, if slow bandwidth becomes a more common occurrence, you might want to check with your broadband provider. After all, since 1 March 2019, ISPs are obliged to provide their customers with information on their estimated speeds range in writing at the start of a contract. If these aren’t regularly met, you’re allowed to leave your contract without paying any penalty costs.

Bandwidth glossary

Although bandwidth may be fairly straightforward, it's always useful to read up on the most common terms used in this field. Here's a selection of them:

Data packet: A unit of data made into a single package that travels along a network path. It's a small amount of data sent over a network and, just like a real-life package, contains a source and destination, as well as the content being transferred.

Broadband: This is wide bandwidth data transmission which transports multiple signals and traffic types. It provides high-speed internet access through multiple mediums like coaxial cable, optical fibre, radio, or twisted pair. 

ISP: This stands for internet service provider, normally referring to the company that is providing you with access to the internet.

Latency: This is the time it takes one data packet to travel from its source to its destination, or in other words, the delay between a user's action and the response from a network.

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