If your line is not purely fibre always keep your router / modem connected to the Internet and synced, this is because if you repeatedly disconnect and reconnect it, it will make the DLM (dynamic line management) in the exchange think that your line is unstable, it will then cap your line lowering the speeds lower and lower and it will take a minimum of 14 days to start returning your speed once your line is stable, in the green zone (more about the green zone further down the page) and kept connected synced. This applies to the UK, but this could also apply to other countries as well.

Replace your router / modem if you have an ISP provided one and if it is disconnecting and reconnecting your Internet sync often, a third party router / modem is best because they also let you access advanced line diagnostics and they let you change advanced settings. Also, It is best to choose an integrated router and modem, as it stops the need for an extra cable that could lose you speed because of radio frequency interference noise which causes errors and because of more attenuation / insertion loss (signal loss) due to an extra cable. Additionally, different router / modems can have different CPU's in them, so if your line is not purely fibre it is best to match your router / modem's CPU to the CPU in your local Internet cabinet for the best compatibility, if they are matched and are Broadcom CPUs you get the fastest modem speeds can be whilst still being the most stable and the most reliable. Finally, even if your local Internet cabinet doesn't contain a Broadcom CPU, if your line is not purely fibre and if you have a router / modem which contains a Broadcom CPU, the Broadcom CPU will still provide the fastest modem speeds can be whilst still being the most stable and the most reliable.

Buy a multi-band radio or if you already have one use it to scan all the frequencies on shortwave and medium wave to check if you have any devices that emit radio frequency interference noise that could interfere with your Internet signals it will be heard as a noise on the multi-band radio, if you do detect anything then eliminate the source of it to decrease errors that are caused by it.

If your line is not purely fibre and If you do have to disconnect your line always use the session disconnect button in the GUI (graphical user interface), as this will also let the DLM in the exchange know you have terminated the connection on purpose and it will then take no action on your line because of this. Also, if your line gets disconnected by accident either way always keep it disconnected preferably for at least 30 minutes, this is because the DLM in the exchange monitors your line in batches of 15 minutes, so if you let it stay disconnected for more than 30 minutes it discards all the batches instead of taking action on your line, as it understands that you have terminated the connection on purpose and it takes no action on your line because of this. This applies to the UK, but this could also apply to other countries as well.

If your line is not purely fibre and If you have powerline adapters HomePlugs make sure they are set to low interference mode, this is because powerline adapters HomePlugs run on the same radio frequencies as Internet signals, so they will interfere and cause errors in your line if they are not in low interference mode. If you want powerline adapters HomePlugs, to get the best speeds from them get Gigabit HomePlug AV2 versions which offer the fastest most stable speeds of any powerline adapters HomePlugs, but your results will depend on your house's wiring quality. WiFi mesh devices may promise high connection speeds, but depending on how far each node is from each other say through walls and floors will determine the actual speed they deliver. To get the best speeds from WiFi mesh devices always buy tri-band versions, as these versions usually will have a dedicated 5GHz radio for connecting each node to each other, so it will not slow down the other radios that are actually providing a connection to your devices.

Buy or make your own twisted pair Internet cable, as these cables reject radio frequency interference noise, but don't get shielded, as these will act as an antenna picking up and emitting interference if you do not ground them. This is what to look for in a pre-made cable or what to look for when you make your own. You can make your own by buying a CAT 5e or CAT 6 twisted pair Gigabit Ethernet cable, CAT 6 reduces crosstalk radio frequency interference noise more by separating the twisted pairs and CAT 6 twists the twisted pairs tighter. Make sure the cable is 100% pure copper, which has better conductivity, as it can be CCA (copper-clad aluminium), but don't get this because as it's just copper coated aluminium it will increase attenuation / insertion loss (signal loss). Also, if you are not making an RJ45 to RJ45 cable for a purely fibre line then the cable can only be stranded, a stranded cable is more flexible, but it will increase attenuation / insertion loss (signal loss), so get a thicker cable and make it shorter to compensate. This is because a solid cable is less flexible and it can not be crimped into RJ11 or RJ12 connector plugs reliably, as it only has two prongs to bite down into the internal wire which is ok for stranded, but for solid it will be an unreliable connection, it would need three prongs with the middle being thicker to peirce the sides of the internal wire instead holding it in place and with solid you shouldn't bend the cable or the internal cables too much or they can break which will reduce the speed. But if you could have used solid it would have had even lower attenuation / insertion loss (signal loss). Make sure the cable is either 23 or 24 AWG, as these are thicker to lower attenuation / insertion loss (signal loss). Additionally, by buying the correct size RJ45 plugs for either CAT 5e or CAT 6 and if you are not making an RJ45 to RJ45 cable for a purely fibre line, by buying RJ11 plugs for CAT 5e or RJ12 plugs for CAT 6 as well. Make sure the connector pins in the plugs are gold plated, 50 microns thick gold plating if possible. Then by buying a cable crimper that has RJ45, RJ11 and RJ12 slots for the plugs, the cable crimper will crimp your cable once you have wired it up in the connector plugs to the correct pins that your Internet uses. Remember to make the cable as short as possible without causing too sharp of a bend, this is to make the attenuation / insertion loss (signal loss) as low as possible, remember to push the cable into the connector plug as far as it can go, so the sheath is fully in and the internal wires are fully in, remember to use the twisted pairs with the tightest twist rate (number of twists) and remember to only untwist the twisted pairs to a maximum length of 1/2 an inch or 1.27cm, when you are wiring them up, this is so the minimum amount of radio frequency interference noise is let in. Finally, if you are not making an RJ45 to RJ45 cable for a purely fibre line, I have provided links to two videos on YouTube showing you how to make the Internet cable using either a CAT 5e or a CAT 6 twisted pair Gigabit Ethernet cable.

Get Openreach to fit the new NTE5C master socket and the new Openreach MK4 filtered face plate, as these offer the best connection with the best line filtering. This applies to the UK, but other countries will have their own new master sockets and new filtered face plates.

Get Openreach to check your line to make sure there are no faults or radio frequency REIN interference (Repetitive Electrical Impulse Noise), but you can check for it yourself like I told you to do with your multi-band Radio. This applies to the UK, but other countries will have their own engineers to check your line.

If your line is not purely fibre make sure that your overhead wire from your telephone pole is not an older grey coloured one, as these are not twisted pair wires and because of this they will let radio frequency interference noise into your line. This applies to the UK, but other countries if you have overhead wires from telephone poles make sure they are using twisted pair wires to reject it from going into your line.

If your line is not purely fibre check your line for noise using Openreach's free line test facilities by dialling 17070 and choosing option 2, to run a quiet line test, then listen for any noises on your line, a hiss / static sound can be normal if it's consistent. This applies to the UK, but other countries might have their own line test facilities phone number.

Make sure that your Internet cables and your Ethernet cables are not touching any other cables or are near any power outlets, this is to prevent radio frequency interference noise from entering the cables and this makes sure that no errors in your line are caused by it.

Make sure if you are not using a cable that you unplug it, because if you keep a cable plugged in that is only connected at one end it will act as an antenna picking up radio frequency interference noise and emitting it. This can cause errors in your line.

Buy ferrite beads / ferrite chokes or if you already have them clip them to your power cables, as they reduce radio frequency interference noise coming from and going into your power cables. This radio frequency interference noise can cause errors in your line, always put one near the end of the power cable near the source of it and if both ends of the power cable are near the sources of it then put one near each end of the power cable.

Fit surge and spike protectors to your devices in your property, as this will limit radio frequency interference noise coming from your devices entering your house wiring or from going into your devices, this will help powerline adapters run at full speed through your house wiring and it will also protect your devices from damaging surges and spikes.

If you want to make sure that your router / modem will not get turned off even with a power cut, then you will need to buy a UPS (uninterruptible power supply), the UPS will instantaneously or near instantaneously take over powering your devices in the event of a power cut, so your devices will not turn off and you will not lose sync of your Internet connection. They also provide surge and spike protection, radio frequency interference noise filtering to limit it coming from your devices entering your house wiring or from going into your devices, voltage trimming and adding to keep voltage stable and some are even able to provide the purest power a battery can provide called pure sine wave.

If your router / modem allows Telnet or SSH access, enable it and monitor your line using dslstats via Telnet or directly via Telnet or SSH by running for an example xdslctl --stats. Your router / modem might need a slightly different command to show the results, but when you see the results by running the right command it will show you all your line statistics which will allow you to understand your line fully, as for an example how many errors you are getting, what your lines SNR values are and what your lines attenuation / insertion loss (signal loss) values are.

If your line is not fully fibre once you know how many errors your line is getting that will allow you to keep your line in the green zone of the DLM in the exchange, which will allow it to increase your lines speed by lowering SNR (signal-to-noise ratio), as the lower it is the faster your speed is, but it will only do this if your line is stable enough to not produce more errors because of this. The DLM in the exchange if your line is stable enough will remove interleaving which will increase your speed and will also enable G.INP which will give you back the speed that was lost when interleaving was enabled, it will do this by reducing errors and increasing your speed. This applies to the UK, but this could also apply to other countries as well.

ES errors and some other values like SNR are the only ones the DLM in the exchange cares about, not CRC errors and not FEC errors, as FEC errors are just errors that have already been corrected, so find your ES errors value then find your sync uptime, change your sync uptime into seconds by entering into a calculator, first add the days, then times that by 24, then add the hours, then times that by 60, then add the minutes, then times that by 60 and now you have the seconds of how long your line has been synced. The goal is to keep the total uptime error seconds value (which is your total uptime in seconds once divided by your ES errors value) above 300 for fibre/copper lines and above 250 for only copper lines. If it is then your line is in the green zone and your speed will be set to the maximum your line can support, as long as you keep it connected synced. This applies to the UK, but this could also apply to other countries as well.