IP Profile Massively Dropped - Reset?

Assuming this should go in the generic fibre forum as it's more of an OpenReach FTTC DLM issue than related to my specific ISP? [Mods please move it if you want]

ISP: BT Retail
Package Details: Unlimited BT Infinity 2.
Estimated speed given when signing: 51.5Mb/s.


So I've had BT Infinity a while and have now got used to it. Speedtest result when the connection first went live was about 55Mb/s download and 17MB/s upload. The IP Profile was 57.1Mb/s download and 20Mb/s upload.

After a few weeks speedtest results went down to 52Mb/s, and from looking the IP Profile had gone down to 53.89Mb/s download. So that's pretty much spot on the 51.5Mb/s estimate and I'm not complaining, that's fast enough for me! The upload speedtest and IP Profile both stayed the same.
It then stayed perfectly stable at this speed and up until now I've been perfectly happy - loving that FTTC is finally available on my exchange (I thought we were never going to get it!).

This week (Thursday 3rd October at 1PM) for some reason the connection dropped and then came back online with a new IP address. Don't know why it dropped suddenly when it never normally does and is perfectly stable, but for whatever reason it did (there was an OpenReach van next door if that's any coincidence?).

Since this drop, the pings and upload speed are fine. But... the download speed has taken a nosedive. Speedtest results are now 35Mb/s.
Doing the BT Wholesale test I can see that this is because my IP Profile has been knocked right down. The IP Profile now since Thursday is 36.7Mbps, down from 53.89Mb/s before (but the upstream profile is still 20 Mbps).

So obviously I'm not a happy chappy that one loss of sync on a previously perfectly stable connection has reduced by IP Profile by over 17Mb/s!

So the question is... what can I do to get the speed back? I guess the IP Profile has to be reset somehow?

If a burst of noise was enough to drop the connection and was still present during renegotiation then you might have a false low sync speed. In which case a resync another day to see if you can resync better

The open reach dlm also looks at error rates as well as dropped connections

my hunch is its crosstalk caused by the installation next door and DLM hasnt done anything if thats the situation you are probably stuck with the new speed.

If you lucky it was just temporary noise as mrsaffron suggested meaning if you manually reboot the modem you will get your speed back.

I doubt is DLM as that typically doesnt kick in during the day.

Thanks both.

This will actually be the first time that the modem has been restarted since I got FTTC installed (it's on a UPS so stayed on even when the power cut out!).

Edited by Westyfield2 (Sat 05-Oct-13 15:57:37)

So I got lucky whilst out in the garden earlier. Parked up was an OpenReach van, who had just been in next door sorting out a problem.

Spoke to him and he offered to do me a DLM reset . He said that if it didn't bring the speeds back up to what they were pre-thursday, then I should call up to report the fault.

Looking at the BQM, at 2:30PM (just after speaking with him) my modem lost sync, and now the routers got a new IP address. So in effect as-well as whatever it was he did in the OpenReach system to reset the DLM, the modem has done a resync (and I can maintain my record of never having unplugged it!)

Doing a speedtest now an hour and a half later I'm getting 39.3Mb/s. And on the Wholesale test the IP Profile is for 40.7Mb/s.

So the good news is that the IP Profile is now +4MB/s on what it was this morning (thanks to the DLM reset and resync), but at 40.7Mb/s that's still 13meg less than what it was pre-thursday (53.89Mb/s) .

Suggestions on what I do next?

Edited by Westyfield2 (Sat 05-Oct-13 16:37:05)

In reply to a post by Westyfield2:

So I got lucky whilst out in the garden earlier. Parked up was an OpenReach van, who had just been in next door sorting out a problem.

Spoke to him and he offered to do me a DLM reset . He said that if it didn't bring the speeds back up to what they were pre-thursday, then I should call up to report the fault.

Looking at the BQM, at 2:30PM (just after speaking with him) my modem lost sync, and now the routers got a new IP address. So in effect as-well as whatever it was he did in the OpenReach system to reset the DLM, the modem has done a resync (and I can maintain my record of never having unplugged it!)

Doing a speedtest now an hour and a half later I'm getting 39.3Mb/s. And on the Wholesale test the IP Profile is for 40.7Mb/s.

So the good news is that the IP Profile is now +4MB/s on what it was this morning (thanks to the DLM reset and resync), but at 40.7Mb/s that's still 13meg less than what it was pre-thursday (53.89Mb/s) .

Suggestions on what I do next?

You can't do anything. The speed loss is simply as your neighbour is now also using VDSL2, which causes crosstalk to occur.

When another neighbour gets VDSL, you'll see your speeds drop even further.

If your DLM had been reset, I would have thought the BT Wholesale test would show your IP Profile at maximum 80Mbps not 40.7Mbps. Sounds like only your linecard was reset and you could have done that yourself with a reboot IMO.

no the BTw profile page shows the IP profile, not the DLM profile.

So my plan now is to leave it for a couple of weeks and see what happens before reporting the fault.

Assuming this is crosstalk and not some other noise issue, I was the first on this cabinet (and it's the first cabinet on the exchange) so I was expecting speeds to dip slightly after a while when more customers signed up and crosstalk kicked in.

But surely this can't be right? It lost 25% of speed in one hit!

Crosstalk is dependent on various factors, including the geometry of the cable. If another user takes up FTTC whose pair is in close proximity within the cable to yours, the extra noise from crosstalk between your pair and his can cause a substantial drop in your speed.

In other words, speed drops due to crosstalk are not necessarily a gradual process as the number of subscribers climbs. You can have lots of people subscribe with little effect on you, then one further connection is enabled and the performance of your connection drops significantly.


If this is crosstalk, it's not a fault, just an unfortunate consequence of trying to squeeze the maximum performance out of a twisted pair of wires. Ultimately, vectoring will give the cabinet DSLAM a degree of flexibility to look for a solution to cancel out near end crosstalk, which is responsible for the majority of these issues. At the moment, vectoring is only in the trial stage and it may be some time before it is deployed.

A DLM reset on FTTC will only reset it to mirror whatever the sync is upon resetting.

In reply to a post by Westyfield2:

So my plan now is to leave it for a couple of weeks and see what happens before reporting the fault.

Assuming this is crosstalk and not some other noise issue, I was the first on this cabinet (and it's the first cabinet on the exchange) so I was expecting speeds to dip slightly after a while when more customers signed up and crosstalk kicked in.

But surely this can't be right? It lost 25% of speed in one hit!

it happens.

I had 2 large hits.

from 110 down to 90. then from 90 down to 73. Just unlucky where your cable is positioned in the bundle and the neighbour who got activated was on a disturber pair.

There is a chance there is a fault somewhere that has made the crosstalk amplified, or a fault has started as a result of the installation, a while back robertos posted once he seen a engineer at a cabinet and that engineer only had to slightly touch pairs to cause disruption to service so pairs can be very fragile. But I think openreach wont look for a fault if you above the estimated speed.

The fact you were early on the cabinet means you were more likely to see such a large drop as you started of in a single pair environment. If you were installed later you would start off on the lower speed and be happy I guess.

I have had FTTC for about 18 months. During that time my max attainable has fallen from 102 to 82Mbps. The most recent fall was last week at about 4am. I suspect that the problem was increased noise due to local storms. My modem log is showing that INP has increased from 0 to 3 on the down side of my line (interleaving kicking in?). When this has happened before, I have just sat back and waited for the system to do its thing. As many have noticed this can take weeks rather than days. All that said, I am fortunate that I still have speeds above 80/20 so there has been no change in my profile. I can well appreciate that for those who live some distance from their FTTC cabinet, this process can be extremely frustrating.

So I've now left it for 4 weeks� things haven't improved.


Just to recap, I'm now (for the last four weeks) getting a speed of 39Mb/s - compared with the original speed of 54Mb/s. That's a loss of 28% according to my maths. For reference, the provided estimate when signing up (and still on wholesale checker) is 51.5Mb/s.

I'd like to get this investigated, even if it turns out to be "Crosstalk, sorry nothing we can do about it" I'd like that confirmed to know it's not some other line fault or noise problem that could be solved!

Remembering that coincidentally next door had an OpenReach van round on the day my drop happened four weeks ago, I asked them... they confirmed they had various phone & internet problems but didn't know if their internet was Fibre/FTTC/Infinity (I got the feeling we're the geeky house and not them!)

Soo� what's my best bet on how to get BT Retail interested and pass it through to OpenReach?

I know the feeling. 62 down to 46 here. The ISP are fantastic with helping out but ultimately the bit of wire is BTW and they (and even forum users) will likely just shrug and pass it off as crosstalk.

Looking forward to this vectoring thing as it'll hopefully blow that excuse out of the water