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Newbie
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Message 1 of 4

Speed slow down again

Dear all,

 

New to this forum and looking for some advice.   Since end of April my speed has dropped to the same speed as last year after a period of improved speed for nearly 6 months after the last incident when this happened. Things improved after I had a chat with a friendly Openreach engineer who had been working on the pole next door to my house.  

 

Given I have a low speed already the difference between 2.4Mb and 1.8Mb can be quite noticeable and latency has also increased noticeably

 

current stats 

 

Downstream Upstream
Line Coding(Trellis): On On
SNR Margin (0.1 dB): 133 170
Attenuation (0.1 dB): 580 315
Output Power (0.1 dBm): 174 123
Attainable Rate (Kbps): 3,024 980

 

This has changed from when speed was better am I assume probably as a result of works impacting the aluminium/copper when a neighbour had some repairs as the timing is related 

 

Am some 4.5Km from exchange so don't expect great figures but this has made things like my suresignal to fail to operate properly 

 

I am connected to the master socket and the stats I am using to check speeds are based upon my SamKnows box 

 

My resumption is I have to live with this slowdown and if I call BT nothing will be changed due to the guaranteed minimum quoted of 1.5Mb when I signed up and this is within tolerance 

 

Any thoughts welcome

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Distinguished Sage
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Message 2 of 4

Re: Speed slow down again

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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Newbie
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Message 3 of 4

Re: Speed slow down again

Understand entirely about not re-booting and the relationship with stablity ,  from reading more widely what I am able to see is SNR margin (0.1dB)  does appear to have increased from a best of 49 earlier this year to current 131, which I suspect is the culprit and its been gently climbing over the past 2 weeks or so from 115.  

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Distinguished Sage
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Message 4 of 4

Re: Speed slow down again

The noise margin will drop automatically given time the stable connection is the essential part
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