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ADSL Stats, fibre perfomance predictions?

helidan
Grafter
Posts: 25
Registered: 30-07-2009

ADSL Stats, fibre perfomance predictions?

Is there any way to use your current ADSL stats to predict what level of performance you could expect after upgrading to fibre?
Thanks guys!
6 REPLIES
Plusnet Help Team
Plusnet Help Team
Posts: 5,637
Thanks: 533
Fixes: 205
Registered: 01-01-2012

Re: ADSL Stats, fibre perfomance predictions?

Hi there.
The checker does give a good indication most of the time what speeds you should expect however there can be various different factors that can affect it such as distance from the cabinet to your property or any aluminium.
Our checker shows you should get speeds within the range of 60 to 70 mbps.
If this post resolved your issue please click the 'This fixed my problem' button
 Matthew Wheeler
 Plusnet Help Team
helidan
Grafter
Posts: 25
Registered: 30-07-2009

Re: ADSL Stats, fibre perfomance predictions?

Thanks for the prompt reply.  My fibre is due to be installed next Thursday but I was wondering what sort of performance I could expect.  My ADSL is usually quite solid at 10-11meg with no disconnects or anything like that.  The phone line is also very clear.
Community Gaffer
Community Gaffer
Posts: 17,665
Thanks: 658
Fixes: 162
Registered: 05-04-2007

Re: ADSL Stats, fibre perfomance predictions?

You can't really use your ADSL performance as an indicator, that's because Fibre goes to the local cabinet, so the line length and therefore quality and performance may not be the same as ADSL.
If this post resolved your issue please click the 'This fixed my problem' button
 Chris Parr
 Plusnet Staff
Community Veteran
Posts: 1,412
Thanks: 4
Registered: 29-01-2009

Re: ADSL Stats, fibre perfomance predictions?

Quote from: helidan
My fibre is due to be installed next Thursday but I was wondering what sort of performance I could expect.  My ADSL is usually quite solid at 10-11meg with no disconnects or anything like that.  The phone line is also very clear.

A solid line with no disconnects suggests you should start with a similar quality, but there are no guarantees. On my first FTTC installation, the ADSL line was truly solid with almost no errors (less than 10 an hour). However, the FTTC connection started up with around 4% packet loss until DLM intervened a couple of days later.
There are a few things you should expect, over time, related to your speeds. I sound pessimistic here, but setting expectations fairly is the best way to go...

  • The BTW estimation is not normally massively wrong, but it can be - it is still only an estimate.
  • Whatever sync speed you get on day 1 is likely to be the fastest it will go. There is no 10-day training period where speeds go up and down.
    (Note that Plusnet can be slow getting your new fibre-based speed profile running, so you get left on your old download speed, like this guy)

  • BT run DLM on every line, monitoring for issues that prevent stability (such as resyncs and bit errors) - and intervening if it sees any issues.

  • DLM will monitor for the first two days; if the error rate is too high on day 2, it will intervene on day 3 - even if the errors are otherwise invisible to you

  • DLM will then monitor forever, and may intervene at any time the error rate hits their threshold. A single intervention is enough to fix things for most people, but it causes a drop in sync speed of around 10% and an increase in latency of 10ms.

  • If the error rate reduces a long way below the level that triggered DLM, it can choose to de-intervene. But this can take days or even weeks.

  • FTTC's biggest drawback is that every line suffers from crosstalk (ie interference from other FTTC lines), which naturally increases as other subscribers are added to the cabinet.

  • Crosstalk is noise, and the effect of any noise on your line is to reduce the sync speed.

  • The effect of crosstalk on your line is accumulative, yet random. You might see small reductions in speed over months, or a large hit in one day; either kind of impact is to be expected.

  • This crosstalk also increases the error rate (in the same accumulative, but random way). This means that it might trigger a DLM intervention, which will also cause a step change in speeds & latency.

  • BTW/BTO know and expect the effects of both crosstalk and DLM intervention, so will not normally attend for faults where the only indication is a small drop in speed. They will attend if there is an indication of a fault on the line, but otherwise will only pay attention if your speed drops off the bottom of the expected speed range, or if it drops by 25% or more in one week.


If you approach FTTC believing that, once you achieve speed X, you should always expect X, then you are only in for disappointment.
If you approach FTTC expecting speeds to drift downwards - especially if you are one of the first subscribers onto a newly-installed cabinet - then you will do fine. I still find it sad to know that my line, at one time, proudly displayed an attainable speed of 90Mbps, but that isn't possible now.
There is a technical solution to help overcome the effects of crosstalk, known as vectoring, so all is not lost. However, it'll be a good while before it gets rolled out. In the meantime, we just have to live with it...
So ... how can you help yourself?
Two key things:
- When the engineer installs things, you will probably be most interested in discovering the speed. What you should spend more time being interested in is making sure that the speed is achieved with few errors.
- Once installed, you want to do things to show the capability in the first few days, so that you have evidence of that capability long before anything goes wrong. This includes screenshots of at least:
- The BTW estimation - http://www.dslchecker.bt.com/
- Speed test results from, say, http://www.speedtest.net/
- Speed test results from, say, http://www.thinkbroadband.com/speedtest.html (or, without flash, http://labs.thinkbroadband.com/speedtest/ )
- Speed test results (including the IP profile) from the BTW tester, after asking for extra diagnostics - http://speedtest.btwholesale.com/
- If you have a static IP, you can set up long term monitoring of the line using TBB's ping monitor - http://www.thinkbroadband.com/ping
(there are many similar graphs available at http://community.plus.net/ping-graphs/ )
After my house move, we should finally get our fibre connection on Friday. I'll be doing all these and more...
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.
helidan
Grafter
Posts: 25
Registered: 30-07-2009

Re: ADSL Stats, fibre perfomance predictions?

Great post WWWombat!!  Nice amount of info there.  I'll post back here after the engineer has visited next Thursday with the initial performance results of my fibre.  I have read a few bit and pieces on vectoring, anyone know when it might start to be rolled out?
Community Veteran
Posts: 1,412
Thanks: 4
Registered: 29-01-2009

Re: ADSL Stats, fibre perfomance predictions?

I wish we knew.
As the second trial appears to be ongoing (and *might* have leaked to a few more cabinets), I don't think we can expect a rollout to start until at least the middle of next year.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.