Linespeed dropped to 2600kbs

[#1]

I have noticed recently that my line speed has nearly halved to 2600. I used to get 4500.
Here is the output from my Belkin router.  I have tried swapping to the older Netgear router but that will not even connect!
 
Downstream Upstream  Data rate(Kbps) 2688Kb 448Kb
  Noise Margin 16 23
  Output power(dBm) 119 193
  Attenuation(dB) 40 25
The B speed  tester shows
Download speedachieved during the test was - 1505 Kbps
For your connection, the acceptable range of speeds is 400-2000 Kbps.
Additional Information:
Your DSL Connection Rate :2688 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 2000 Kbps

Can this be explained please?

[#2]

Hi stuartwalker,
The reason your sync rate has gone down looks to be because your SNR has gone up. You'd need to first try to work out what might have/be causing that. Are you using an extension cable/socket? How is your router wired up?
Jojo

[#3]

Nothing has changed. I went through another investigation earlier this year so I'm pretty well versed in the checking routine.
I did plug directly into my BT socket (no extensions).
I have no other devices plugged in aside from one telephone
I have now plugged directly into a test socket

[#4]

What are your stats now you're in the test socket?

[#5]

Data rate(Kbps) 2688Kb 448Kb
  Noise Margin 16 23
  Output power(dBm) 119 193
  Attenuation(dB) 40 25

[#6]

I've just replaced the micro filter and things look a bit better

Downstream Upstream  Data rate(Kbps) 3808 448
  Noise Margin 16 23
  Output power(dBm) 119 195
  Attenuation(dB) 41 25

[#7]

This morning the connect  speed seems to be stable

Downstream Upstream
  Data rate(Kbps) 3808Kb 448Kb
  Noise Margin 16 23
  Output power(dBm) 119 195
  Attenuation(dB) 41 25
The BT speed test results are still showing only 1.8Mb/s 0.36Mb/s which is still disappointing.
My Netgear modem still won't connect either.
What might have cauaed the SNR to increase? Is there something that can be checked?
Mark

[#8]

One of the simplest ways for the SNR value to rise if or there to have been a problem of interference on the line, sufficiently bad for your router/modem to disconnect.
At the disconnection, the modem will then attempt to negotiate a new speed with the DSLAM at the exchange. If the noise is still present at this time, and assuming your line is still set to sync with a target of 6dB SNR, then the sync speed will be reduced. If the noise then disappears, your SNR value will rise to show this, but the modem will not resync to a higher speed.
In your case, a 10dB increase in noise on a single occasion could have caused this. But bear in mind that you could also be in the middle of an ongoing/intermittent fault, so might see more disconnections and slow speeds. Your last resync suggests that BT's DLM has actually raised your target SNR value to 15dB, because it has seen a number of problems over time.
The result of you changing filter suggests it could have been the cause of the problem, and is worth leaving. If it was the only cause, and your target has been increased to 15dB, then it should start dropping, as the DSLAM sees stability in your line. That can take a number of days, during which your line nees to stay as connected as possible, with as few errors as possible. Alternatively, Plusnet can ask for your line to go through the 10-day training process again - but they will only do this when they are convinced you have solved ALL the problems, as it is impossible to do any further fault-handling on the line once this step has been started.
Either way, the result is to wait a few days, with the router best left in the test socket, and monitor the line stats.
The download speed being low may well be explained by the fact that the IP profile value hasn't been updated, either at BT or at Plusnet. This too can take some time after your sync speed changes, so you have to check in two places:
- The BT speed tester. The results tell you what BT thinks the IP profile is
- The Plusnet DB. The "current line speed" tells you how Plusnet are managing your speed - and it should match the BT value. When the BT value changes, Plusnet's value should be updated within 12 hours.

[#9]

I've checked the speed again today. The connect speed on the router shows
Data rate(Kbps) 3808Kb 448Kb
  Noise Margin 16 23
  Output power(dBm) 119 195
  Attenuation(dB) 40 25
The BTSpeedTester shows http://www.speedtest.net/result/1292760626.png
So it would appear that the download speed is improving. I'm still peeved by the "Worse than 79% of the UK" statement
Why is the service so bad in my district? Annoyingly there is a fibre connection in the street but it stops at my neighbours house so I'm stuck with ADSL for life.
The Plusnet check says
Postcode:
Phone exchange:
OAKENGATES
Estimated line speed:
5Mb (This may vary between 4Mb and 6Mb) - Checked on 2011-03-09 15:02:39
Current line speed:
3 Mb

[#10]

HI stuartwalker,
As the line has been quite stab;e at that rate now I'm going to set the SNR to 6dB as it's currently 16dB, this should improve the rate much more. I'll let you know once it takes effect.
Jojo

[#11]

Hi stuartwalker,
That seems to have gone well. The SNR is now 7dB, the sync rate is 6208k so once the DLM reacts to the new sync rate the profile will lift to 5000k.
Jojo

[#12]

Indeed, it's looking good.
Downstream Upstream
  Data rate(Kbps) 4992Kb 448Kb
  Noise Margin 12 24
  Output power(dBm) 119 196
  Attenuation(dB) 40 25

[#13]

SNR has crept up there a bit, are you in the test socket?

[#14]

Yes, I was in the test socket. Indeed, I've been on the test socket ever since.
I've come back from holiday and things are now looking pretty sick 😞
Data rate(Kbps) 2752Kb 448Kb
  Noise Margin 20 23  
Output power(dBm) 119 194
  Attenuation(dB) 40 25

You've mentioned SNR several times. Can you explain what this is and how it is derived from the figures that I'm quoting?
Have I got a real fault here? Perhaps it's time to call BT ...

[#15]

I have noticed that the slower than --% of GB is not to be relied on,on speed test net. I have noticed that regardless of my download speed it is the upload speed that seems to be tracked. Say my download speed is 8000 and my upload speed is 370, then I get slower than 52 % of GB.  I resync and my download speed goes up to 10000 and my download speed drops to 230 then I get slower than 69 % of GB. So even though my download speed is 2000 quicker I am slower than another 17 % of GB.