Sudden sync speed drop

[cdavman]

Hi, wondering if somebody with more knowledge than me can help me understand the following situation.

I've been a BT broadband customer for 3.5 years on the Fibre 1 package, but with the boosted speeds due to my line being able to handle it.  My contracted speeds during this time have therefore been:

Down: 64 - 73 Mbps
Up: 17-18 Mbps
Guaranteed Minimum: 59Mbps

Throughout the 3.5 years the sync speed shown at my router has been around 80 down/ 20 up, and speed tests on wired connections has always been at the top-end of my estimates above - perfect.  Connection and speed has always been rock solid... until now.

My contract with BT is due to end at the end of the month so in the last few weeks I've been comparing a lot of offers.  For my own reference I took a screen grab of my router stats on the 5th January, and this confirmed my sync speeds:

However, on the 8th January my speeds suddenly dropped, to a sync speed of around 50Mbps down, and I observed an increase in line attenuation.  I also noticed that doing quotes from ANY broadband providers (including BT themselves) shows they'll now only offer me a maximum of around 40-50Mbps, with a guarantee down at 38-40Mbps (depending on provider).  The reason for this is that my line stats on the BT wholesale page have also updated in line with what my router stats are showing.  Below is a screen grab of the router stats as they are today:

I reported the fault via BTs online fault reporting system on Saturday 8th, and an engineer visit was arranged for Monday 10th.  The engineer did something at the cabinet - I never had direct communication with him, so I've no idea what he did, but my connection disappeared completely for around 30 minutes, then returned and I received a text saying the fault was fixed.

It wasn't - as the router is still showing the slower sync speeds as confirmed in the screenshot above.  I've now got BT to reopen the fault, and have been told that it'll be investigated again "some time in the next few days"...

The problem I've got is my contract ends at the end of this month - and my out of contract price is due to shoot up at that point, so I'm keen to lock in a cheaper deal (with BT or an alternative if necessary).  However, as the BT wholesale checker now reports this lower faulty speed, any quote I get with a new provider, or even a renewal with BT, only states my line is capable of this new lower (fault induced) speed.  If I sign a new contract, then I suspect my chances of ever getting it fixed diminishes, as I'll simply be told "your speed meets our guarantee", but the guarantees have been lowered in line with the fault.  Catch 22.

My question is - what is the likely cause of this sudden drop in sync speed?  Is it likely to be fixable, or am I going to end up stuck at this speed forever more?  Any suggestions as to what it might be?

[imjolly]

You had a drop in connection recently was that a manual reset or hub dropping connection?

Try quiet line test by dialling 17070 option 2 should be silent and best done with corded phone

[Gary_C]

What is notable is that your noise margin on the upload has worsened and the download noise margin has only remained the same by lowering the speed showing the problem is affecting both. The significant increase in attenuation is possibly the cause, reducing signal power therefore increasing decreasing signal to noise and thus noise margin.

This is significant because it means the problem wasn't transient but is still there suggesting that the connection has degraded, possibly water somewhere. I suppose you might have sustained some damage in the recent storm, does the line go overhead somewhere ?

Thing is, you actually have a better line than I used to have, just one thats not as excellent as it was and you probably wont be able to hear any noise.
Your going to have to demand BT meet their min guarantee before you move because I bet if you move they will just use the current speed to set your minimum as you suspect.

[cdavman]

Thanks for your responses.

@imjolly the drop in connection shown in the second screenshot was due to the Openreach engineer disconnecting us for around 30 minutes. Sadly I'm not sure of the state from just after the drop in speed.

@Gary_C you've confirmed my concerns that there is a risk that they will simply state that my line is still "good enough". As it stands the fault ticket is showing an estimated fix date of tomorrow, so we shall see if another engineer comes out. If not I'll keep chasing.

[cdavman]

Thought I'd provide an update on the status of this.  After several phone calls back and forth with the BT support desk and some cryptic notes from Openreach, the BT support desk attempted to remotely reboot my router (thinking this was in some way the problem - it was not).  This caused the following state, where the upload rate also started dropping!

An Openreach engineer took a look this morning and phoned me and informed there was a "dodgy crimp" at the cabinet.  In the process of him working on it, I was diving into the router every time it reconnected to capture the stats.  During his work it suddenly returned to the speeds I've been seeing for that last 3.5 years (Wahoo!)...

However, when I checked again while he was on the phone telling me the job was complete, the stats for my download speed had dropped a bit:

However, I notice that my line attenuation is back to what it was originally, and the noise margin is higher than it was before.  The engineer suggested this may be DLM kicking in, and it should return to the higher level in the coming days??  He said he couldn't request a DLM reset though as he was the wrong type of engineer?

Obviously very happy to see the fault was found, however surprised to see the speed go up and then drop back a bit so quickly, despite the apparent noise margin values.  Can I expect that to improve again?

[imjolly]

now your line problem has been fixed and attenuation back to previously your speeds are back to normal  you now need to maintain connection and DLM will start G.INP which should drop your noise margin bringing speed up to previous level.  could take 7/10 days

[cdavman]

Many thanks for this - I'll keep an eye on it.  I'm not one for switching my router off - so fingers crossed.

On a related note - do you know how long the BT Wholesale availability checker site takes to update the observed line stats?

It's last observed speed for my line was taken on the date my fault hit - so as a consequence all providers (including BT themselves) are now quoting me a much lower minimum speed guarantee, which I'd like to try and avoid as it should now be capable of more (as it was previously).

Curiously I noticed the cabinets' VDSL Range B (Impacted) row on the wholesale checker has updated to show slightly lower bottom end speeds in the last few days too - suggesting to me, it may not have just been my line affected, as the stats for the whole cab have been dragged down a bit.

[cdavman · Accepted solution]

Just thought I'd post a final update on this:

As mentioned in an earlier post, after the engineers visit the line attenuation was restored to its pre-fault state, but with a download speed of 65.25 Mbps.

2 days later the connection went up to 75.80 Mbps.

2 days after that (yesterday) the connection went right back up to 80 Mbps.  So everything is now back as it was before the fault.

Looks like DLM has done it's thing.

In both of the above cases the BT wholesale availability checker page updated with the latest observed speed 1 day after each increment - so as of this morning, is now reporting the latest data for my line.

[NeilO]

@cdavman That's a great result, I'm glad it's sorted and thanks for keeping the thread updated.

Thanks

Neil

[Paul608085]

@cdavman 

I'm late to this thread, but glad you have got it sorted.

In case the DLM had taken longer to restore to the full speed, (I have been told that this can take up to 4 weeks), and for the BT Wholesale checker to get updated and your current BT contract then expired, I assume that you could have just done nothing, rolled on to BT's standard pricing until the Wholesale checker has been updated, and then look to either re-contract with BT of move supplier with a line running at its maximum speed, (and maximum guaranteed speed) ?

AFAIK, there is no necessity to re-contract when your current deal expires - it just means that you will likely be paying a higher price for a few weeks, (the "price to pay" as it were)?

Perhaps someone else can confirm this is correct please?