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Aspiring Contributor
Message 1 of 21

Broadband slowed down a couple of weeks ago

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I'm very happy to have discovered this forum, having been pulling my hair out a bit.


I've got regular broadband on a cabinet that is miles from the exchange. In the past, we've had remarkably good service -- 4.5Mbps.  A few weeks ago, it dropped to 1Mbps and it won't recover.


I had to go away for a few days and switched off all the computer stuff in the house, including the router / modem. When I got back, the speed had dropped to 1Mbps and it won't increase. Anything like Skype, Hangouts, streaming, screen sharing, etc. is now just not possible.


I've had a couple of chat sessions / calls with BT support, but their guidance (change ports on your router and your router is broken) haven't helped (I did follow both of their suggestions).


Having read some of the threads on this forum, and followed some of the links, I took various steps: configured modem to ADSL2+, and have determinedly avoided switching off the kit. I was hoping that this would allow the connection to negotiate upwards, but it's not helped and it seems to be stuck.


I also did the quiet line test. It does have a bit of a hum, but no static. It's not obtrustive, during a phone call, but is that likely to make a difference? If so, I should properly try it, as in remove face plate, try another phone, etc. etc.


Current stats from the site are:


Download speed 0.98
Upload speed 0.44
Ping 37.5


and the extended information is:


1. Best Effort Test: -provides background information.

Download Speed
0.99 Mbps

0 Mbps 1 Mbps
Max Achievable Speed

Download speedachieved during the test was - 0.99 Mbps
For your connection, the acceptable range of speeds is 0.4 Mbps-1 Mbps.
IP Profile for your line is - 1.01 Mbps


2. Upstream Test: -provides background information.

Upload Speed
0.44 Mbps

0 Mbps 0.83 Mbps

Max Achievable Speed

Upload speed achieved during the test was - 0.44Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps


I'm sure that turning the kit off -- and the power's been a bit up and down here recently -- has contributed to our problem. We've got a UPS now...


Any help or guidance you could offer would be very gratefully received. If modem stats or DSL checker info would help, I have those too.


Many thanks in anticipation,





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Distinguished Sage
Message 2 of 21

Re: Broadband slowed down a couple of weeks ago

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Why has my speed suddenly dropped?
ADSL connections (see notes about Infinity at the end), and the notes by RogerB
Changes in your connection speed are automatically managed by the exchange equipment, using a process called
Dynamic Line Management (DLM).
Its purpose it to give you the best speed possible, without introducing a lot of errors back into the BT network.
These errors impact on other users, and can slow their connection down, as your data packets have to keep being resent.
This is a continous process, but certain things can cause it to make drastic changes to your connection speed.

These can include the following:-
You could have also been recently moved from ADSL max to ADSL2+, this would mean that the line
would have to re-train again, and must be left undisturbed  for at least 10 days.
If you keep restarting or disconnecting your BT Home hub, then the exchange equipment will see this as a fault condition, and reduce your connection speed, in an attempt to stabilise your line.
You have recently had a fault on your line which has just been fixed.

Sometimes a single interruption to your line can cause this too, especially if it generates a large error burst.
The effect is that you get placed in a low banded speed profile, and you will notice that your downstream margin is high, usually over 15dB.
The lower the banded speed profile, the quicker it will recover, but it could take up to a month before the fullspeed is recovered.

If you want your speed to recover, then these are the steps you need to take.
DO NOT restart or disconnect the power to your BT Home Hub.
DO NOT disconnect your BT Home hub from your phone line.
Leave everything alone for at least 10 days, so that the exchange can record a stable connection.

During this time, the exchange may drop the connection, and re-establish a faster connection.
If you use the BT Speedtester, then do not restart the BT Home Hub, even if it tells you to.
If after 10 days your speed does not increase, then please return to your forum post.
showing  that you have 10 days of connection time, then the problem can be escalated.

You can calculate your final speed by using this website.

Maximum speed calculator
Infinity connections
A similar process is applied to the connection between the Infinity cabinet, and the Openreach modem.
You cannot view that connection information, but the same thing applies, do not restart or disconnect the Openreach modem.
The BT home hub only acts as a router, and restarting it will not affect your physical connection speed to the cabinet.
Additional information by forum member RogerB
BT broadband is line adaptive, if you have a good line, you get good broadband , BUT consider this, you only get good broadband
from the outset, if you let the exchange "train" the connection, when it is new, simply because it has to try various methods of modulation.
And once it is running at full speed and set the MSR (maximum stable rate) provided you don't keep disconnecting the router, it will stay that way.
So two important things:  ALWAYS leave the router on, 24/7 and DO NOT impede the training process which can take up to 10 days.
The reasons are vaguely the same for both scenarios:  DLM trains the connection during setup, and DLM runs the connection in a similar but different mode once it's running.
And the most common issue apart from line faults in causing poor broadband is FREQUENT RESETS and DISCONNECTIONS of the router or hub, because if you interupt line management it will demote the line profile if done to excess, with often time consuming efforts and long waits to get it back.
BT don't punish users indiscriminently by making them wait for their broadband speed to come up, but the line management is in place  to DEFEND the network against bad and corrupted data, and if the exchange sees your line being reset too often it assumes a fault,
whereby your linespeed is demoted, and often profoundly so.
Also, because the exchange can't tell the difference between you messing around resetting all the time, and a real line fault, it assumes (using logic) the worst and demotes the line profile.
If you get a real line fault and the noise margin increases, the linespeed will decrease, it's normal, again it's a defence to help give you a service  allbeit a depleted one, and at the same time stop corrupted data getting back to the exchanges.
But unfortunatlely it's at this point when people in general start to become frustrated,  and guess what?
They then start to reset the router in an attempt to "repair" the connection. And in doing so, impede the line management from promoting the linespeed again. (providing any fault is or was fixed).
And to summarise, if the connection is left to run unimpeded, no excess resetting, and left to its own devices, it actually benefits from the good line

history that the exchange has accumulated for your connection, simply because the attention span by the line management is not so profound when it does bite the dust, for whatever reason.
So regardless of the opinions of some, switching off broadband routers is NOT a good idea, not if you want consistent broadband and a good line rate.
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Aspiring Contributor
Message 3 of 21

Re: Broadband slowed down a couple of weeks ago

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Thanks john46. 


So, does it take 10 days and then just jump up?  It's been connected for nearly 7 days now and steadfastly refused to budge.

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Distinguished Sage
Message 4 of 21

Re: Broadband slowed down a couple of weeks ago

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providing your hub has been connected 24/7 then yes it should could you post the stats from your hub please
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Aspiring Contributor
Message 5 of 21

Re: Broadband slowed down a couple of weeks ago

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I wondered if it would go up gradually or sort of monitor things and then come up with its new speed in one hit after ten days.


Yes, it's been on 24/7... After reading the forums, I learned not to take any notice of the "reset your router" instruction on the BTW speed test.


Modem status as follows: 




Time : Jun 22, 2017 16:27:30
Firmware Version : EU_1.25


Cable Status : Up
ADSL Status : Connected
Connection Up Time : 145 hours, 41 minutes, 25 seconds

Downstream Line Rate (Kbps) : 1151
Upstream Line Rate (Kbps) : 579
Connection Type : PPPoA VC-Mux
Subnet Mask :
Default Gateway :
Preferred DNS Server :
Alternate DNS Server :



and stats as follows:


Product: DSL-320B Firmware Version: EU_1.25 Hardware Version: D1


Mode: ADSL2+
Type: Interleave
Line Coding: Trellis

Downstream Upstream
Rate (Kbps): 1151 579

SNR Margin (dB): 17.3 5.1
Attenuation (dB): 61.0 35.0
Output Power (dBm): 0.0 12.9

Super Frames: 32294192 30497802
Super Frames Errors: 1381 -32
RS Words: 0 0
RS Correctable Errors: 0 0
RS Uncorrectable Errors: 0 0

HEC Errors: 791 0
OCD Errors: 1 0
LCD Errors: 0 0
Total Cells: 1407537660 361553
Data Cells: 45165682 1800
Bit Errors: 0 0

Total ES: 1017 0
Total SES: 1 0
Total UAS: 33 0



Many thanks, 


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Aspiring Contributor
Message 6 of 21

Re: Broadband slowed down a couple of weeks ago

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Hi John -- do you have any thoughts on this and what I could do next?  


Many thanks, James

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Distinguished Sage
Message 7 of 21

Re: Broadband slowed down a couple of weeks ago

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I have asked a forum moderator to help you they will post their contact link here
Message 8 of 21

Re: Broadband slowed down a couple of weeks ago

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Hi @jamesbristol Sorry you are experiencing slow speeds. 


We will be happy to help you with this if you send us your details. You can contact us by clicking on my user name and selecting contact the mods.


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Aspiring Contributor
Message 9 of 21

Re: Broadband slowed down a couple of weeks ago

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Thanks John (and john46 too) -- I've sent you a PM. 

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Distinguished Sage
Message 10 of 21

Re: Broadband slowed down a couple of weeks ago

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the mods cannot help you if you send a PM you must use the contact the mods link
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