ADSL2+ Download Speed Collapsed

[#1]

Good morning

The download speed on our Plusnet broadband connection has dropped dramatically, from a consistent 15-18Mbps to around 200kbps.  So it has gone from being very satisfactory to hardly usable.  Two things that seem quite odd:

1.  The upload speed seems unaffected.  We can still sometimes achieve over 1Mbps.

2.  The neighbouring property, which shares a cable (approx. 700m) from the main BT line on the nearest road, still has the consistent 15-18Mpbs.

Unfortunately, I can’t say exactly when the problem started, as the place was unoccupied for a while due to a combination of the pandemic and building work.  But I do know that it has been like this for at least a couple of weeks.

This is an ADSL2+ line.  BT’s broadband availability checker shows an expected downstream range of 7.5-17.5 Mbps.

We have the white 2704n modem.  On the xDSL statistics page it shows:

Current rates: 288kbps / 446 kbps (downstream / upstream)

Attainable rates: 11564kbps / 1099kbps

SNR margins: 42.1 / 26.6

Attenuation: 26.5 / 14.1

Output power: 15.8 / 12.1

(The neighbouring property, which is currently at around 17Mbps download, has SNR margins of 3.1 / 6.4.)

If it would help, I can post a screenshot of the whole statistics page and can obviously let you know the ‘phone number if you can tell me how to do that privately.

Any advice or suggestions as to anything I might try would be greatly appreciated.

Thanks ….

Andrew

[#2]

Hello Andrew,

A warm welcome to the forums.

The information you have posted is very helpful and points direct to the issue - the SNRM is wildly high suggesting that the equipment in the exchange is managing your line aggressively to maintain stability, at the expense of speed.  Both downstream and upstream speeds are banded.

As indicated by the max speed figures, both DS and US could be better, so the first steps need to check the line for the usual suspects.

Broadband is not going to work well if the "phone" line is not working properly.

Please perform a quiet line test - dial 17070 select option 2 using a corded phone plugged into the test socket behind the face plate of the master socket. It should be silent. A noisy phone line (or no dial tone) will have a marked adverse impact on the performance of broadband.

If the line is noisy or there is no dial tone, then a PHONE LINE fault needs to be raised with your phone provider. If this is PlusNet, you can report a fault on line using the button below.  From the Q&A list, choose the one which matches the problem, 'open' the 'section' and click the trouble-shooter link.  NB: If you receive a failure message (rather than a log-in prompt) then log-in to the user portal in a different browser tab and attempt to use the trouble-shooter again.

• Phone Faults

Is the router plugged directly into the master socket only via the supplied router cable and filter?

Are there any telephone extensions, wired from either behind or out of the face plate?

There is little point at this juncture plugging direct into the test socket, for given that the line appears to be banded, your speed will not improve without staff intervention to remove the banding, which will not be done until all potential causes for the cause of this have been eliminated.

[#3]

Thank you for the very quick reply!

I can tell you without doing the quiet line test that there is a certain amount of noise on the line -- but there always has been, and there also is next door where the download speed is still fine.  So I'm pretty confident that, in this regard, nothing has changed.  That is to say, we were getting 15-18Mbps perfectly fine, from the moment the exchange had the 21CN upgrade early last year, with that level of noise on the line.

Now, I can quite appreciate that the normal reaction would be: there's noise on the line that needs to be fixed first.  But, as I say, it was working fine (and still is at the neighbouring property).  One thing I should explain is that we are somewhere quite remote in the Highlands.  The line from the exchange runs down the road along the glen for about half a mile, with the 700m spur to these two properties running up from the road.  The level of noise on the line is no different from how it was when our line was installed about eight years ago.

Please don't think I'm trying to be awkward.  I greatly appreciate your help.  I guess all I'm trying to explain is the noise on the line may be something we have to live with -- and did not stop the broadband working fine before.  So, ideally, I'd simply like to get the SNR margin adjusted, at least as an experiment, to see if that gets us back to how it was previously.  It was perfectly stable, even with this amount of noise on the line.  Is there anything I can do via the router to force a lower SNR margin?  (I seem to recall that it used to be possible to do that with certain Billion routers.)

I'm happy to try the trouble-shooter link, if you think that might still help.  Do I need to do that while connected to the internet via the line in question, or can I do it next door (where the broadband speed is fine), and simply enter the correct 'phone number?

In answer to your other question: the router is not plugged into the master socket (but it never has been).  So far as I know, it's the supplied cable and probably the supplied filter (but could easily enough try a different one, if you think that might help; we have several).  I can try it in the master socket temporarily, but can't leave the router permanently at the master socket.  Let me know if that is worth trying.

I hope that makes all sense and doesn't seem unreasonable.

Thanks again .... Andrew

[#4]

Hi Andrew,

The location sounds idyllic!  Though sounding remote, your line stats and description suggest that you are not far from the exchange - certainly closer than I was in not so rural North Cheshire.

The issue to be considered here is what caused the DLM to band the line?  Un-banding it might well lift the speed ... for a short while, but there is the risk that it will return.  The router is "on the line" all of the time.  When you pick up the handset you only hear the noise present at the time you pick it up.  Some sources of noise can be mitigated simply by picking up the telephone handset ... for a short time.  Therefore I would recommend that you run the phone fault test (see below).

This can be run from any internet connection - just log into your account in the user portal.  Similarly the broadband speed fault trouble shooter can be run from a different line.

The fact that your neighbour's line is OK and yours is not does rather point to an issue with your circuit or possibly internal wiring.  Though you do not believe anything has changed, a bad joint anywhere on the circuit can deteriorate causing the problems you describe.  It has been known for oxidation on the contacts of the BT socket faceplate to cause intermittent issues.

There is every possibility that Plusnet support will request you work though the troubleshooting steps ... so it would be helpful if you could do them sooner rather than later.

[#5]

Thanks again for replying so quickly!  (And, yes, it is indeed idyllic here, apart from the midges ....)

And, yes, we're not actually too far fro the exchange.  Approx. one mile as the cable runs (half a mile or so along the road and then c.700m up from the road).  The 700m is shared and then another 20-30m cable for the line in question.

What you say makes complete sense.  I agree, it does look like a problem specifically with the circuit for this line, although that could presumably still be anywhere between the router and the exchange, not necessarily just the final 20-30m cable run or within the property?

In any event, I will try the troubleshooting steps shortly and will report back.

Andrew

[#6]

So, I have run the line test (from the "Phone Troubleshotter") several times.  Every time, I get either "The result of your line check is unclear" or, less frequently, "Oops, something seems to have gone wrong".  I also tried moving the router to the master socket, which didn't change anything.

Is there anything else I could try?  Alternatively, is there any way to try reducing the SNR margin, to check whether the sort of speeds we used to get are still achievable (with reasonable stability)?  I also wondered if there is any way to force it to "retrain" (if that's the right word)?

Thanks .... Andrew

[#7]

Hi Andrew,

It would be worth checking your account's tickets - see the link below.  There are some instances where the phone line checker reports a failure, but none the less still raises a fault report.

There is nothing you can do to force lowering the SNRM (at least with the Plusnet Router) and even if you could, there is a fair chance that you would still not see an increase in usable speed due to the over heads of data retransmission.  Plusnet might approach this with a SNRM reset, but I would not expect that to offer anything more than a temporary reprieve!

As things stand, with the line being banded, if the issue were to be your internal wiring, moving the router to the master socket will not deliver any improvement before Plusnet agree to remove the line banding.

[#8]

Okay, thanks.

Have checked the tickets.  Apart from a billing notification, there's only one that says "Bandwidth usage has been reset" from about three weeks ago.  Nothing that looks interesting or indicating a known fault.

Is there anything else you can suggest I might try, or do I now need to call Plusnet to report the problem (or to ask them to try removing the banding)?  If so, what's the best number to use?

[#9]

Hi Andrew,

A phone call - standard support number will kick things off, though personally I would run the BB fault reporter (see below) and wait a staffer picking up this topic.

You have done all you can do for now...

• Done the QLT - there is some noise but not atypical
• Done the phone fault trouble shooter which is inconclusive
• Tried the master socket which delivers no improvement (which I feel un the circumstances is to be expected)

Plusnet now need to run with this...

• Their manual phone line tests might find a POTS fault
• The broadband trouble shooter might find a line fault not picked up by the phone line tests
• You are not going to see a change in speeds until the banding is lifted and that might not be done prior to locating and fixing the issue which caused then to become banded

[#10 · Accepted solution]

Hi Andrew, sorry for the issues with your connection and welcome to our community forums.

Can you drop me a PM by going Here with your account username so I can take a closer look?