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Distinguished Guru
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Message 41 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

So your current connection speed is 62.327Mbps.

Your IP profile is 60.33Mbps. This is as expected at 96.79% of connection speed.
Note that I think this implies G.INP is not active on your downstream connection as 96.69% seems to be used in that situation.

Your downstream noise margin was around the normal target of 6dB at connection time.
It might differ a bit each time you look at the current stats due to constant noise fluctuations.

Your stats are showing a maximum possible connection speed of around 62.5Mbps. Again it will vary with noise fluctuations.
So your connection speed is very close to it.

Everything matches up as expected. You don't seem to be on a restrictive connection speed band and seem to have the normal target noise margin of 6dB.

The big question is why is your line now only capable of up to around 62.5Mbps?
Possibly crosstalk. I've read that in some cases the power output may be reduced to try and minimise crosstalk? Lower power on your line would mean a lower max speed I guess. Without previous stats to compare against it's difficult to say what has changed.
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Contributor
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Message 42 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

Thanks for all your help guys. It is a shame I don't have longer logs to look at. I will keep the thread updated while I'm testing with the main test socket and without powerline adapters. I guess that could take a month though to get a good look at as I'm leaving the powerline adapters on for now and just using the test socket.

 

Umpire, I did read somewhere that if the noise margin was high on my line at some point then the DLM can drop the connection speed which would then lower the noise margin back to around 6db to keep it all stable. I guess that's the same as what you are already suggesting though with crosstalk.

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Distinguished Guru
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Message 43 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

The noise margin and connection speed are inversely linked. If the DLM decides that your line requires a higher sync time noise margin then it would have to connect at a slower speed. That's assuming the performance of the line hasn't altered by much.

So a lower sync time noise margin equals a higher connection speed, but on Infinity VDSL2 the target sync time noise margin won't normally be set below the default of 6dB. A margin of zero would give the fastest possible speed but the connection might only last 5 mins with any slight noise fluctuation killing it. 🙂
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Distinguished Guru
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Message 44 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

It's always a trade-off between raw speed and reliability (errors) / stability (disconnections).

The people in white coats have determined that a margin of 6dB is a sensible compromise for a line with no major performance issues.
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Contributor
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Message 45 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

Just an update, did some moving around today and decided I no longer need the powerline adapters, so they have all been removed. I reset the homehub and will start the test from now and see if anything changes.

 

 

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Contributor
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Message 46 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

So I did the DSL check thing again. 

 

So when I did it on the 9/2/16 it said this:

 

1.png

 

When I did it today, it says this:

 

2.png

 

 

So this second one is more accurate considering my max download speed is 60mb if I was on the impacted line. 

 

But what happened within 10 days that they changed the data this much? Or do you think it just takes them months to update their data?

 

Also what can cause a line to go from normal to impacted in the space of 6 months?

 

Thanks

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Distinguished Sage
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Message 47 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

I think there has been a lot of line testing done by Openreach in the past few weeks at lots of people have seen their estimates change. It may well be that they have some new equipment installed in the exchanges or new software in the cabinet that allows them to test and get more accurate results.
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Contributor
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Message 48 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

ok thanks. Can you get speeds of 80meg on an impacted line? Because I was getting that at one point for a few months. I just don't know if it took this long for the DLSM to lower my speed or if my line has changed from being clean to impacted due to something BT has done.

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Distinguished Sage
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Message 49 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

As I'm sure has been mentioned, it could well be crosstalk due to a high number of users now taking up the FTTC services. I guess you could get 80meg on an impacted line if you were very close to the cabinet. At my parents old address, their maximum connection rate reported by the router was some 130meg as they were about 80m from the cabinet. So I guess on that line, even with lots of crosstalk, it would probably still connect at 80meg.
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Contributor
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Message 50 of 53

Re: BT dropping minimum guaranteed speed half way through contract.

It must be crosstalk then I guess. 😞 that sucks as there is nothing I can do about that. Thanks for your help

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