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Author Topic: BT Option 1 Slow Speed  (Read 16479 times)

UncleUB

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BT Option 1 Slow Speed
« on: July 12, 2007, 09:04:27 AM »

Hi,I had a line fault about 3 weeks ago,before the engineer came my IP profile was 250k,upstream 448kbps,downstream 960 kbps.After he fixed the line fault my IP profile was 1000k,448kbps upstream and 1856 kbps downstream.Over the next couple of weeks my IP profile and upstream have remained the same but my downstream had gone down to as low as 1344kbps.however at the beginning of the week my IP profile has dropped to 500k,my upstream is still 448kbps but my downstream is now 968kbps.The engineer visited me yesterday and said my line was ok,as was my router(BT voyager 220v).he telephoned someone in the UK where the machine that sets the speeds is,he was told yes my line is set at 500k but he would lift this to 2mb.This has not happened.My computer is 3 months old ,I scan every week for spyware etc,no problem there.Can anyone tell me whats wrong.I am told I am 4000 metres from the exchange.I live in Sheffield,only about 2 miles from where the flooding was.Can this be a problem.Also BT say mine line can only support 2MB.
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roseway

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Re: BT Option 1 Slow Speed
« Reply #1 on: July 12, 2007, 10:06:40 AM »

Hi UncleUB and welcome.

First, you have an ADSL Max connection, so the engineer can't 'lift this to 2 Mbps'. It's a rate-adaptive service which automatically adjusts its speed to line conditions. By the same token, the statement that your line can only support 2 Mbps has no real meaning with a Max connection.

There are numerous possible reasons why your connection speed varies so much, e.g.:-

- an intermittent line fault
- serious local interference
- problems with your own telephone extension wiring
- poor quality or defective filters

There's a lot of helpful information about improving your own installation at http://www.kitz.co.uk/adsl/lowSNR.htm, and it's certainly worth swapping filters if you have some alternatives available.

If you can give us your router stats (in particular, downstream attenuation and noise margin) it would help us to give more advice.
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  Eric

UncleUB

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Re: BT Option 1 Slow Speed
« Reply #2 on: July 12, 2007, 10:47:03 AM »

thanks for your quick reply Roseway,i,m new to broadband but i think these figures are what you want
Downstream
Line rate 896kbps
noise margin 13.9dB
line attenuation 63.0dB
output power 16.6dBm

Upstream
line rate 448kbps
noise margin 11.0dB
line attenuation 31.5dB
output power 12.0dBm

I have changed the microfilter( BT sent me 2)My internal wiring is brand new,which was installed by BT in April.I have only the one phone line,no extensions,sky boxes,fax machines etc.I hope this helps
« Last Edit: September 19, 2007, 10:39:56 AM by UncleUB »
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kitz

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Re: BT Option 1 Slow Speed
« Reply #3 on: July 12, 2007, 11:35:31 AM »

Hi and welcome

63dB indicates a long line.  The 4000m could be "straight line" rather than length of the actual phone line.

You can check the "crow flies distance" from here.  Put in your phone no and post code - then once the results come up click the locality button.
http://www.samknows.com/broadband/checker2.php

>> IP profile was 1000k,448kbps upstream and 1856 kbps downstream

That sounds about right

>> my upstream is still 448kbps but my downstream is now 968kbps.

There appears to have been some sort of deterioration on the line  :(

Re flooding - It is a possibility water on underground cables can cause problems.


>> he was told yes my line is set at 500k but he would lift this to 2mb.

If your line is syncing at 968 kbps then the line will indeed be set at 500k - its the way the dynamic system works.  Even if he did manage to get someone to reset the bRAS profile, then as soon as your next sync occurred at below 1152 kbps, then the DLM system would automatically switch you back to 500k.

The fact that your router has never synced above 2272 kbps on MAX even temporarily (and the 63db atten) would indicate that your line isn't capable of a fixed 2Mb service.  Your line could probably cope with a fixed 1Mb connection - where at least you would get the full 1Mb rather than messing with bRAS and IP profiles.
Its certainly an option to consider.

Alternatively at the end of this month some new IP profiles are going to be introduced which may help you.
The new profiles 750Kbps and 1250Kbps may be the ones that interest you.

If you can fine tune your line and stay there then you may pick up one of the higher profiles.

Currently your SNR Margin stands at 13.9 dB - which gives you a bit of leeway.  Its worth giving your router a reboot NOW whilst there is a good margin on the line and see if you can attain a higher sync speed.
Immediately after you have re-synced, can you make a note again of your line stats again..  I'd like to see the SNR Margin straight after a reboot to try see what Target SNR has been set on your line. 
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UncleUB

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Re: BT Option 1 Slow Speed
« Reply #4 on: July 12, 2007, 05:42:37 PM »

Thanks for the info,I rebooted the router which showed the following
line rate 1600 down/448 up
noise margin 13.9/11.0 up
So the only thing which changed was the downstream from 896kbps to 1600kbps.Is it possible to get downstream 1600kbps when my IP profile is only 500k.
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roseway

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Re: BT Option 1 Slow Speed
« Reply #5 on: July 12, 2007, 06:48:50 PM »

Your router will always sync at the best speed it can for the target noise margin. It looks as though your target noise margin is either 12 or 15 dB, which means that the DLM process has increased it from the default 6 dB because the connection hasn't been stable. The IP profile is derived from the sync speed, so if you continue to sync at 1600 kbps for three days your IP profile should go up to 1000 after that period, and your download speed will increase accordingly.

But there's no guarantee that this will happen with a long line like yours unfortunately. :(
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  Eric

kitz

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Re: BT Option 1 Slow Speed
« Reply #6 on: July 12, 2007, 08:58:08 PM »

Yep - what roseway says.

As I suspected it does look like your target SNR has been increased to possibly 12dB* which is affecting the maximum sync speed, but your line must need this in order to be stable.

If I were you I would now keep the router connected for as long as you can and dont reboot it..  your now syncing at a higher rate of 1600 which you need to keep there and stable for a minimum of 3-4 days.

If you can achieve this - then your IP profile should automatically increase to 1000 kb

>> Is it possible to get downstream 1600kbps when my IP profile is only 500k.

Yes/no - depends what you mean by downstream.
If you mean throughput speeds then no
if you mean sync speeds, as you have just seen, its why I wanted you to reboot the router asap during the day to take advantage of any spare SNR Margin, to try connect at a higher rate.

The value of the SNR Margin in your case is what is keeping your IP profile lower.  You will probably find that in the evenings your SNR Margin is lower than during the day.  If you resync when your router is showing a lower SNR then your sync speed wont be as high.

As soon as you sync at the lower speeds then that puts your IP profile back down to the 500 region.
The trick is trying to avoid a resync when SNR Margin is at its lowest.

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tired

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Re: BT Option 1 Slow Speed
« Reply #7 on: July 15, 2007, 01:20:50 AM »

Hi,

Its also worth looking at a different hub, not too sure what one you have a present, on a long line the 2 wire or netgear routers perform very well, up to 500kbs difference on mine, couple that with a top filter and cable you may hit that magic 2016sync speed to get you the new 1750 profile at the end of the month.

cheers,
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UncleUB

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Re: BT Option 1 Slow Speed
« Reply #8 on: July 15, 2007, 08:49:36 AM »

Hi,Iam using the router BT supplied which is the BT voyager 220v adsl voice router,and they also supplied me with 2 filters.I have read with great interest about having a stuck bRAS and the problems getting the BT Indian tech support to acknowledge this.I have had all those scripted replies from them which makes you want to slash your wrists!!.Are there any good ISP,s out there which have UK technical support,and will understand about a stuck bRAS and actually help you sort it out.
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roseway

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Re: BT Option 1 Slow Speed
« Reply #9 on: July 15, 2007, 09:51:50 AM »

Zen fulfil those criteria, but they are quite a bit more expensive.
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  Eric

UncleUB

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Re: BT Option 1 Slow Speed
« Reply #10 on: July 15, 2007, 11:04:15 AM »

Hi Roseway,I,ve a lot of good press about Zen,are they that good? Are there any more ISP,s with UK call centres?
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UncleUB

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Re: BT Option 1 Slow Speed
« Reply #11 on: July 15, 2007, 11:16:08 AM »

Hi again,just done speedtester after 3 days since re boot.Ip profile gone up from 500k to 1000k . :)upstream 448kbps/downstream 1600kbps.I suppose since my line attenuation is 63.0db this is not too bad.The only thing is the test concludes that the actual IP achieved during the test is 0kbps (zero).This has happened to every bt speedtester I have done?
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roseway

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Re: BT Option 1 Slow Speed
« Reply #12 on: July 15, 2007, 12:42:27 PM »

I guess that result is just a bug in the tester. I presume that in practice you always get better than 0 kbps. :)

Regarding ISPs, yes, Zen is that good. I've seen good reports about Newnet as well, but no personal experience.
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  Eric

UncleUB

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Re: BT Option 1 Slow Speed
« Reply #13 on: July 17, 2007, 05:21:25 PM »

Hi,Just done a bt speedtester and found my downstream speed gone from 1600kbps to 1184 kbps,IP profile is still 1000k? actual IP throughput achieved during the test was 202k(Its only ever registered 0 kbps up to now).When I checked my router it said time connected 1hr 27 mins yet I never turn it off.I re booted over five days ago so what causes my router to do this.Also Line margin gone from 14.3 to 15.3 downstream.Is that better or worse?
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kitz

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Re: BT Option 1 Slow Speed
« Reply #14 on: July 17, 2007, 07:12:02 PM »

hmmm  not looking too good.

it looks like to me that your router has had to reconnect due to poor signal.  Therefore its had to try and sync at a lower speed to compensate.

Im wondering if your low speeds could be due to getting lots of crc/hec errors.   These occur when the signal strength falls and your router has to re-request packets, which can and does cause some pretty poor speeds whilst this is going on.

Does your router record HEC/CRC Errors / Errored Seconds?

>> Line margin gone from 14.3 to 15.3 downstream

With maxdsl its impossible to say when you just look at the one statistic - we need to view the overall stats to be able to form a more accurate diagnostic.

The theory is that the higher the SNR Margin the better the line...  but you also have to take into account the sync speed.

So for example if your stats are
SNR Margin 15.3dB but you are syncing at 1184 kbps.
My stats are
SNR Margin 12.5 dB but Im syncing at 8128 kbps.

At first glance you may perhaps (wrongly) think that yours is the better line because its got a higher SNR Margin. 
However the 2nd set of stats are actually better...  because the higher the sync speed the more SNR Margin is required.

Hope that makes sense - if not theres a more in depth info :- An explanation of SNR and SNR Margin.

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