Tips for getting the best broadband speed

A number of people have asked how to get the best speed from their current broadband connection and this page tries to provide that information with the minimum of "tech speak"............(Please note, this page is still under construction).

Assuming you are using a normal exchange telephone line for your broadband service, irrespective of whoever is your ISP (Internet Service Provider)......................

1. Avoid switching off your router once it is set up, and if does go off because of a power cut or similar, check the speed when it comes back on.

2. There are two speeds that it is worth making sure they are at maximum for your router: the synchronisation speed with the exchange and the data download speed.

3. The synchronisation speed will always be 20% to 30% higher than your download speed. This is because the synchronisation speed is measured including all the bits that are passed between the router and the exchange in order for the two to talk to each other. The download speed is a measure of the speed that data reaches your computer once all the overhead bits that synchronise the router with the exchange are removed. The download speed determines how fast a file of data gets to your computer. Not all routers have a facility for reading synchronisation speed. Please look at your routers set up screens for more information on measuring synchronisation speed.

4. Download speed is best measured using the BT Wholesale Speed Test website. Simply follow the instructions on screen.

5. As well as measuring download speed, speedtest websites (and there are many) give you your upload speed, which is typically 15% of your download speed and your "ping latency". This is the time in millliseconds that it takes for one bit of data to get from your computer to the internet server you are connected to and back again. 

6. Synchronisation speed is dynamically set by your exchange and will vary depending how far you are from the exchange and the signal to noise ratio for your line. Your speed will be slower the further away you are because the signal strength decrease with distance and the noise level increases with distance. If the wire connecting you to the exchange is more than 4km long then your speed will be very slow (<2Mbps). NB This is not the "as the crow flies" distance from the exchange, because BT cables sometimes take very circuitous routes which can double the "as the crow flies" distance to the exchange. For more information on this see

7. Your download speed is managed by an algorithm (or programme) in the exchange equipment which adjusts the synchronisation speed in response to data errors on your line and any breaks in the connection (which is why you should always leave your router switched on if possible). Some routers allow you to read the errors/disconnections on your line and they are called FEC, CRC, HEC errors, loss of signal, loss of link and error seconds. Errors and signal loss can be corrected by the algorithm in the exchange but most often error seconds (the number of seconds for which errors occur), will cause the algorithm to reduce the synchronisation speed and hence the download speed. 

8. When the exchange equipment reduces your speed because of errors over a period of time (this can be over many hours or days), it reduces your synchronisation speed gradually in a series of steps until the algorithm stops detecting errors and the error seconds count is zero or close to zero. Between each step down in speed it will wait, sometimes for many hours before making another reduction in speed, particularly when the error seconds reading is approaching zero. In this way it optimises the speed for the least number of error seconds. Reaching this optimum speed after a disconnect or when the router has been turned off can take between 3 to 6 days. NB The number of error seconds will always be lower the slower the speed.

9. Sometimes, particularly in rural areas when your telephone line is carried on overhead poles and you are 2 or more kilometres from the exchange, noise on the line can cause the algorithm in the exchange equipment to set your synchronisation speed (and hence download speed) much lower than you typically receive. Lightning storms or fluctuations on the mains power supply to your house or the exchange will make this happen. If that is the case, turn your router off for approx 5 minutes then turn it on again and wait for it to reconnect itself to the exchange (The lights on the router will tell you when this has happened). This will effectively reset the exchange algorithm and set your synchronisation speed high. Your download speed will probably not be improved at this time but if you then leave the router running for 3 to 6 days and the noise (e.g. thunderstorm) does not re-occur, you should find that your download speed then increases over a few days whilst the synchronisation speed reduces until the download speed is approx 75% of your synchronisation speed. You will then be getting the best speed that you can get at the distance you are from the exchange. Be careful though, don't do this re-booting of the router too often - only when you find your speed has dropped lower than you expect and avoid rebooting the router more than (say) 3 times in any one day.

10. One other tip: If you are on a noisy line, your ISP can add "interleaving" to your line. This is additional error correction specifically designed for noisy lines and it prevents the algorithm in the exchange equipment from detecting too many errors and so keeps your speed higher. There is one downside to this: Interleaving increases the "ping latency" on the line and whilst this is not a problem for email and most websites it can make response times slower when you are using an interactive website or online games. It can be worth seeing if this helps keep your download speed high and you can always request your ISP to remove it if it seems to reduce response times.

11. Finally if you use the BT Wholesale speed tester (link above) and you get slow speeds, there is a second page where you can run a further test on your line. The test is different for ADSL (copper wire broadband) and FTTC (fibre to the cabinet broadband) from the test for FTTP (fibre to the premises) broadband. This second test takes a few seconds to run. This test will shows you what BT calls the "maximum achievable speed for your line". This may be the maximum speed you can get at the time the test is run but don't assume you can't get a faster speed than this test shows because it can still be possible to get a better speed if you follow the steps described in tip No. 9 above. Good luck with your copper wire connection until we all get fibre optic broadband connections and have speeds around 50Mbps.