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Author Topic: Unexplained speed increase  (Read 1280 times)

andyfitter

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Unexplained speed increase
« on: June 04, 2018, 04:52:55 PM »

Hi,

Some of you may remember my ramblings about how long it was taking for G.Inp to be reinstated, as it is a pre requisite for xdB (and the increased speed that a it brings). It finally got added back a month or so ago.

My Line normally syncs between 72 and 75 Mb. If I can jump on before anybody else, after a power cut, I can often squeeze 77Mb at about 3db snrm once everybody else comes back online. My downstream snrm varies by a db or two in single steps, up and down, once or twice a day. I presume this is a single disturbing line or some other form of crosstalk causing interference being switched on and off.

About a week ago, we were having heavy storms. I looked at my connection and saw that downstream snrm was much higher than usual, around 8dB, and my attainable was huge too, around 86Mb (Normally 76 or so) - I assumed a bunch of other people had been knocked offline by the storm, so did a resync to grab the extra speed.

What has happened since is the strangest part. I'm still synced at 80Mb, still have a downstream snrm of 6, and still have an attainable of around 86Mb. If it was storm related I'd assume that my snrm would drop as the other users came back online. The only difference in my stats that I can see is that my downstream interleave has gone from 8 to 16. Would this give me all the extra bandwidth/attainable etc? I've attached telnet data from before and after the resync if anybody can explain what might be happening to me.

Thanks.

Andy.
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j0hn

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Re: Unexplained speed increase
« Reply #1 on: June 04, 2018, 04:55:50 PM »

Sounds like 1 of your crosstalkers is offline.
Could either be away on holiday or they may have ceased their service.

The change in interleaving depth is unrelated.
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Talktalk FTTP 550/75 - Speedtest - BQM

andyfitter

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Re: Unexplained speed increase
« Reply #2 on: June 04, 2018, 04:58:55 PM »

Thanks, that sounds likely. I was looking for something more complex when the simple answer are often more likely. The normal daily 1or 2 dB steps are still happening, but this recent change is much more major. Here's hoping they've gone forever :-)
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sotonsam

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Re: Unexplained speed increase
« Reply #3 on: June 04, 2018, 05:01:16 PM »

It really is crazy how just 1 connection can impact your speed so much.

But yeah, that's pretty much what's happend here! You can notice it really clearly when there's a powercut in the area, if your modem is powered by a UPS - your attainable will fly up!
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Vodafone FTTC 80/20. ECI Cab.

FTTP via Toob. 900/900.

Adam86

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Re: Unexplained speed increase
« Reply #4 on: June 04, 2018, 05:31:58 PM »

It really is crazy how just 1 connection can impact your speed so much.

I recently had two lines installed as my attainable on my original line had dropped by nearly 20mbit over the years.

Openreach had to run some new pairs in pavement side from further down the road as there were no available pairs.  They put both lines onto this new segment of cable and my original line now syncs back up at 78mbit as long as that modem syncs first.  As soon as my 2nd modem syncs up it instantly looses over 10mbit attainable sync on the first line.  The 2nd line I've only ever seen sync at around 67mbit and if both are synced at the same time they connect around that speed.

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Weaver

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Re: Unexplained speed increase
« Reply #5 on: June 04, 2018, 07:33:13 PM »

Vectoring is very badly needed with this copper that is being abused like this.
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j0hn

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Re: Unexplained speed increase
« Reply #6 on: June 04, 2018, 10:05:17 PM »

Vectoring is actually a possible reason for the speed increase. You can check with...

adsl info --Vectoring

State 5 means no vectoring. Anything else is a good sign.

I would expect vectoring to have given a higher increase in sync/attainable than what's been reported in this thread.
It would likely stop the 1-2dB jumps in SNRM (if they are indeed caused by crosstalkers).

Vectoring also more than doubles the time it takes a line to sync on VDSL2.
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Talktalk FTTP 550/75 - Speedtest - BQM

andyfitter

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Re: Unexplained speed increase
« Reply #7 on: June 04, 2018, 10:19:48 PM »

Vectoring is set at state 5, so it’s not that. I’m also in central London so it’s unlikely I’d ever get it.
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