ADSL Troubleshooting

Following on from my post below, if you are experiencing problems with your ADSL internet connectivity such as frequent packet loss or regularly being disconnected from the internet altogether there are a couple of things to check first before escalating the issue with your ISP/BT. Even if you are still unable to resolve the issue yourself you will at least be able to rule out the most common issues, saving yourself some time and pointing your ISP/BT in the right direction.

  • Check, and if possible, replace your micro-filters. A maximum of four microfilters can be used on a BT phone line. This corresponds to the recommended maximum number of items of telephony equipment you can plug into a standard voice line – known as the maximum Ringing Equivalent Number (REN).
  • Try unplugging all non ADSL equipment from the line including fax machines, Sky TV, alarms etc.
  • Try plugging your ADSL modem directly into the master socket via the filter with all other devices still unplugged.

Having checked the above first and if you are still continuing to experience problems the next things to check are: the line attenuation and signal to noise ratio. There is an excellent forum sticky post here which I have copied into a pdf document here which explains the basics of line attenuation and noise. Although its written for sky broadbands’ LLU service in the UK the principles should apply to all ADSL services.

Listed below are a few of the main tests BT offer should you find you need to escalate your issue with your ISP:

Tests normal telephony (voice) end to end connectivity. Checks if there is current from another telephone line leaking on to your pair or if there is current leaking from your pair. You will also get an accurate line distance (attenuation) measurement from this test. Should the test come back all OK that’s not to say there isn’t something else affecting your DSL service, this test is designed mainly for voice connections, however any conditions shown here will typically have an effect on your DSL service.

The name says it all really. This test will check your line attenuation again as well as noise and SNR (signal to noise ratio.) If possible BT will shorten your line to reduce the noise and SNR.

SFI is the Special Faults Investigation engineers – the SAS (Super Army Soldiers) of broadband. They pretty much check everything; wiring and broadband as well as activity beyond the NTE, including the router. I have just recently had a really good experience following an SFI test from BT where a previously undetected issue after 2x end-to-end tests and a line degradation task failed. The problem was diagnosed within an hour which turned out to be a line issue after all. The problem was resolved within a few days after a couple of trips backwards and forwards between the local exchange and our offices. I have heard however that the call out fee is not cheap and they will only spend 2hours on the issue so may well not find an intermittent fault. – If a fault is not found you will be charged which could be something to consider.

Again the name says it all really. Sometimes BT will offer you a cease and re provide if you are experiencing on going issues. I’m not sure if this is something you can request or whether there are costs involved for this but it is worth mentioning. Also worth mentioning is that if this is something you do pursue it might be worth requesting that the re provisioned line is implemented over a different line pair.

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