When you’re researching broadband, you will often see the term latency mentioned. But what is latency and how does it impact broadband performance?
Latency is the measure of the time a network packet takes to travel from your device to its destination. A low latency number means the network is running well and your connection to another computer is fast. Higher latency means there is a delay somewhere in that link.
Latency manifests as a small delay in whatever you’re doing. It could be a pause while a webpage loads, a small delay in moving your mouse to your online character moving in a game, or a stutter or delay in movie or music playback.
Latency doesn’t take into account the processing time at the destination server or the time your program takes to display the results. It is just the time taken to make the journey.
In the best-case scenario, packets move at the speed of light. When networks are congested or suffering downtime, traffic slows and latency increases.
Generally speaking, latency is a measure of how fast and/or efficient an ISP is in managing traffic, though high latency can also be an inherent behaviour of the type of connection. Higher latency networks mean your browsing experience could be slower or suffer more interruptions than a lower latency network.
Latency is also often referred to as lag, especially among gamers.
How is latency measured?
Latency is usually measured in milliseconds (ms). A millisecond is a thousandth of a second, which doesn’t seem long but in networking terms, it’s a lifetime! We can test latency by seeing how long it takes data to travel from one point to another and back again, giving us a latency measurement, or "ping rate".
How to find out my broadband latency
You can test your own broadband latency from your computer if you want to. It’s a simple test that can give you an idea of where any network slowdown is occurring. We use a ping command to perform a basic latency test.
To test broadband latency in Windows 10:
- Type ‘CMD’ into your Windows Search box and select Command Prompt.
- Type ‘ping www.google.com’ and press Enter.
To test broadband latency in Apple MacOS:
- Open Applications and Utilities.
- Select the Network Utility and open the Ping tab.
- Select www.google.com and select Ping to launch the test.
You can, of course, use any website but Google is configured specifically to respond to ping tests.
Look at the time in the readings for the latency. Round trip delays of 10-20ms for superfast broadband are normal, with ADSL broadband usually coming in under 40ms, and mobile broadband typically measuring around 60ms.
This kind of ping speed will let you do anything you could want with your broadband. But get into three figures and - depending on what you're doing - the latency may start to be a problem.
What causes high network latency?
There are a few causes of high broadband latency. The connection itself being too busy, suffering downtime or issues or a poor quality physical connection. The wider internet can also suffer traffic problems but is more insulated against physical downtime and failures.
Not all latency is down to the network but you can soon tell by performing a ping test to several different websites. A consistently slow ping time indicates a problem with your ISP or their gateway. One or two slow ping times could mean a problem further into the network.
Speed vs latency vs bandwidth: what’s the difference?
Speed measures the rate at which traffic moves within a network.
Bandwidth is the measure of how much traffic a broadband connection can cope with at once.
Latency measures the round trip, the time it takes to send data and receive a response; the higher the number, the more delay you experience.
These terms all describe different aspects of the performance of a broadband connection, and it's important to understand how they relate to each other because fast broadband does not always mean low latency. A good example is satellite broadband. A typical domestic satellite connection can have a download speed of 30Mb, which is reasonably fast, but due to the delay between dish and satellite it also suffers from very high latency, well into hundreds of milliseconds. This means that while you can download a file quite rapidly, satellite is not well suited to things like online gaming or remote desktop access which rely on rapid communication with a remote server
Latency and gaming
While broadband latency can impact all online activities, it is gaming which suffers most because high latency can directly interfere with gameplay. Online gamers need low latency, or lag, connections to avoid being put at a disadvantage.
If you play twitch games, those that require quick reactions like shooters, any latency you experience delays the action on your controller and your character’s reaction in the game. The higher the latency, the slower the game reacts. If you have 300ms latency on your broadband but other players have 20ms, they are going to be able to see and react to you in the game before you even see what’s going on.
If you shoot at them while on a high latency connection, by the time your game traffic hits the server, the player could have moved out of the way and be shooting you. With obvious consequences!
Which broadband providers have the fastest latency?
There is very little difference in latency between providers, which is good news because it means it is not something you have to worry about too much when choosing a new package.
Ofcom's broadband performance report notes that for ADSL broadband, EE and Plusnet had the lowest latency, measuring around 20ms average during a 24 hour period. But the slowest performers (KCOM and TalkTalk) only measured around 30ms, which is a tiny difference that you would never notice in practice.
It's a similar story for fibre broadband with speeds of 30Mb+. EE, Plusnet, Sky and BT recorded an average of around 12ms. Virgin Media had the slowest at around 20ms, which is still plenty quick and not going to put you at a disadvantage or noticeably impact your experience.
How to reduce latency
There are a few practical things you can try to minimise latency on your broadband connection:
- Perform a ping test so you know how much lag you’re dealing with.
- Reboot your computer to make sure it is working properly.
- Reboot your router or modem to refresh it and make sure it has a good connection.
- Minimise the number of users online at any one time.
- Switch from Wi-Fi to a wired network connection.
- Shut down any applications that use bandwidth.
- Perform a broadband speed test to identify any issues with your connection.
- When playing online games, choose a server close to your location.
Many causes of latency are out of your control. If you are suffering from it on your broadband and have tried everything here, contact your ISP for more information. They should be able to run a line test or be able to inform you of any outages or known issues causing the delay. Sometimes lag can be caused by the server you're trying to access, in which case there is nothing you or the ISP can do.