Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Pages: [1] 2 3 4

Author Topic: Slow Connection Speed on DSL Max  (Read 13433 times)

matthewcl375

  • Member
  • **
  • Posts: 25
Slow Connection Speed on DSL Max
« on: March 08, 2013, 04:00:57 PM »

Hey everyone  :) This is my first post on Kitz  ;D

I have an issue with my ADSL Max connection that I can't seem to get to the bottom of: my broadband from Tesco (advertised as up to 8Mbps) had been giving a throughput of up to 7Mbps (875KBps) until 26th January. On this date we started getting disconnections every few minutes, and later found that this was a line fault causing noise on the phone line. On the 27th an engineer came out and installed a new line to the street pole across the road, fixing the noise problem.

After he had gone, we got a sync of around 4.7Mbps, this was with a Target Noise Margin of 15db due to the previous line fault. Over time this Noise Margin has gone down and we are now on a Target of 9db, getting a sync of 6.8Mbps.

The problem is this: According to the Kitz ADSL Line Checker, we are only 0.2Km from the exchange by road, and I have been told by others that this should give a sync of 8128 or 7616 (depending on the presence of interleaving) even with a 9 or 12db Target Noise Margin. This seems to show that our connection is underperforming. I have included line stats below:

DSL Type:   ITU-T G.992.1
Bandwidth (Up/Down) [kbps/kbps]:   448 / 6.880
Data Transferred (Sent/Received) [MB/MB]:   8,44 / 66,22
Output Power (Up/Down) [dBm]:   11,9 / 13,8
Line Attenuation (Up/Down) [dB]:   6,0 / 6,0
SN Margin (Up/Down) [dB]:   23,0 / 9,1

I would really appreciate any help with this. I and a few others are struggling to get to the bottom of why this line is not performing optimally  :(
Logged

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 39528
  • Penguins CAN fly
    • DSLstats
Re: Slow Connection Speed on DSL Max
« Reply #1 on: March 08, 2013, 04:36:22 PM »

Hi and welcome

Certainly, if those attenuation figures are correct, you should be connecting at the maximum speed for your service. The figures suggest that there is some constant level of interference which is causing the reduced performance.

I suggest that you install a monitoring program to see how the SNR margin varies over time. Depending on your router, you could install Routerstats (or Routerstats-Lite) (which works with most routers) or rs-ux /rs-w if you have a compatible router. If you run it preferably for 24 hours and copy the SNR margin graph here, it may help to understand what the problem is.
Logged
  Eric

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #2 on: March 08, 2013, 05:15:45 PM »

Thank you for the quick reply!

I forgot to mention I have already been running routerstats since this problem occurred, right now its showing a steady 9db to 9.1db all day and all night which is confusing to say the least...

I have also eliminated my cordless phone as a source of noise, there's nothing else in the house which I can think could cause it, we don't have any extensions plugged into the phone line, filter is plugged into test socket etc. etc.

In light of this I really don't see how noise could be causing a problem, unless its noise from neighbouring houses... Others have suggested I may be on a banded profile, a bad joint in the new line, or that there could be an issue exchange-end.

Do any of these sound likely?
« Last Edit: March 08, 2013, 05:53:54 PM by matthewcl375 »
Logged

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 39528
  • Penguins CAN fly
    • DSLstats
Re: Slow Connection Speed on DSL Max
« Reply #3 on: March 08, 2013, 06:39:48 PM »

Quote
Others have suggested I may be on a banded profile, a bad joint in the new line, or that there could be an issue exchange-end.

If you were on a banded profile, the SNR margin would be higher, so it's not that. A bad joint in the line would cause the SNR margin to jump about far more, so it's not likely to be that.

It's difficult to imagine any other explanation than a constant level of interference. This would imply something electrical which runs continuously. It could be a malfunctioning or badly designed power supply for some kind of electronic equipment, or a local factory or pumping station, or something of that nature. It could also be some malfunctioning equipment at the exchange.

Perhaps the first thing to do is to switch off everything in your house except the computer and router, and see if the SNR margin increases. If it does, then it would appear that the problem is internal, and you would need to identify the culprit by a process of elimination. If not, then the problem is external, and that will be much harder to identify.
Logged
  Eric

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #4 on: March 08, 2013, 08:04:42 PM »

@Roseway, I will certainly try that the next time I can (i.e. when no one else is in the house), another thing I am considering is plugging in my old extension wiring and then relocating the router to the upstairs phone socket, to eliminate any noise from the room the router is currently in. If that gives a higher sync/SNR Margin then that would show it is something in that room causing noise.

@Everyone What I didn't mention is that I am moving to BT Broadband over 21CN, on around the 25th March. They estimate speeds of between 16 and 19.5Mbps. Is there a good chance this will fix any issues at the exchange end of the line?
« Last Edit: March 08, 2013, 08:22:17 PM by matthewcl375 »
Logged

roseway

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 39528
  • Penguins CAN fly
    • DSLstats
Re: Slow Connection Speed on DSL Max
« Reply #5 on: March 08, 2013, 10:39:04 PM »

The upgrade to 21CN-WBC involves switching your line over to new equipment (from a DSLAM to an MSAN) so if the DSLAM is the problem then the change would fix it, but I'm not sure how likely that is.
Logged
  Eric

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #6 on: March 08, 2013, 11:33:00 PM »

So, if it's an exchange problem that could fix it, Openreach tested the new line after it was installed and it seemed good to them, so must either be noise or exchange issues...

Eliminating noise can be tricky  :-\ Think it's worth trying the router in the upstairs extension socket?
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 32223
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: Slow Connection Speed on DSL Max
« Reply #7 on: March 10, 2013, 11:08:51 AM »

Something is weird with those stats.

Output power is only 13.8 dBm.  If that line was running at its maximum, i'd expect it to be in the 18-19dBm region.
However such a short line will have the highest PSD mask which will cause some power cut back, but I would expect the router to try & give more because its not reaching any where near the full potential.   Have you got another router to try?   Because your output power is so low, this is stopping you from reaching maximum speeds.

Normally I would assume it was some sort of banded profile, but then you'd expect the SNRM to be much higher and not at a constant 9dB.

A constant 9dB SNRm from RStats would suggest there isnt an obvious noise issue. (unless it is constant noise as suggested by roseway)

Im wondering if the DLM has done something weird on that line during the period of the line fault.   As the owner of a short line myself I know the 20CN DLM does strange things on very short lines... and I often found myself with some very weird profiles that were hard to get rid of without ISP & BTw intervention.  The stuck profiles I got most often was 2Mb, but iirc I did have a couple there were around 4.5 Mb mark after occurrences such as power cuts.

If it were my line I would be requesting a full line reset from my ISP.    However if that line is due to go 21CN next week... a line reset should occur then anyhow.

« Last Edit: March 10, 2013, 11:12:39 AM by kitz »
Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #8 on: March 10, 2013, 03:15:44 PM »

Kitz, thank you for your very helpful reply  :)

The only other router I have is a BT Home Hub (version 1), and that gave output power of 11.5db up, 9.5db down, giving a lower sync of 5664Kbps  ???

I would agree with you about noise, also in the last few weeks the target SNR margin has been dropping steadily from 15db which points to there being no noise issues on the line, I also ran a quiet line test showing the same...

The only thing I can think of it being is something DLM has done, noise at the exchange end, or maybe a bad joint/fault in the new line that was installed, though from the quiet line test it sounds just like a normal line to me

I would add that before the line fault, going by the throughput I was seeing we were on a 7.15Mbps profile, which would show our line was getting the full speed, which would point to the current issue being DLM related, or maybe a fixed setting at the exchange.

Others have mentioned that the SN Margin should be a lot higher and that I don't have any 'spare SNR' to give higher speeds, does this sound right?
« Last Edit: March 10, 2013, 03:35:54 PM by matthewcl375 »
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 32223
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: Slow Connection Speed on DSL Max
« Reply #9 on: March 10, 2013, 05:24:27 PM »

I'm posting from a mobile device ATM so can't C&P or post links easily.   excuse the formatting too.

As rebards to the higher SNR..  Normally I would say yes that is the case.....  However like me I think you are suffering from one of the frequent problems that I also saw when on maxdsl that would affect my own line and only seems to affect the very shortest of lines.   The DLM seems to seems to flip its lid and do very strange things.

I've just managed to find one of my old posts to show you what I mean.  In such cases the DLM seems to set a fixed rate  SNRM..... And cuts back the power instead.

As you can see, in my case after a power outage, what it did was set the SNRM at 6db...  And reduce my output power.  I'd copy the stats if I could, but for now youll have to look at the link to see what I mean.

http://forum.kitz.co.uk/index.php/topic,1637.0.html

I'm pretty sure you are experiencing the wonderful joys of being on a maxdsl short line.
Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #10 on: March 10, 2013, 07:51:26 PM »

Had a read through your thread, there are some differences i.e. your router was reporting 8128 whilst DLM reported another value... with mine both are reporting the same sync and apparently I don't have spare SNR...

What was your output power supposed to be before it dropped?

I've got various questions going through my mind right now, like 'why would DLM reduce my output power' and 'how come the engineer didn't reset the line after he had fitted the new line from the pole'?

Sorry if I'm asking too many questions here, this thread seems to explain these kind of problems well for anyone else reading this:

http://www.skyuser.co.uk/forum/sky-dlm/47557-why-dlm-falls-short-mark.html
« Last Edit: March 10, 2013, 08:10:04 PM by matthewcl375 »
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 32223
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: Slow Connection Speed on DSL Max
« Reply #11 on: March 10, 2013, 09:35:21 PM »

Perhaps with only being able to link to the thread, you missed the stats in that particular thread which is what I was trying to show.   All the stuff that happened afterwards was whilst trying to get the original problem sorted.  I went through numerous 'stuck bRAS' problems during that period.  The router reporting 8128, and the DLM another figure, didnt occur until later on


If you look closely at the first post stats, you will see I was experiencing the low Output power which is what you are displaying now:-
These were the stats taken from my router after the power outage.

Quote
Statistics Downstream Upstream
 Line Rate 736 576
 Noise Margin 6.8 dB  6.0 dB   
 Line Attenuation 7.0 dB  7.0 dB   
 Output Power 11.9 dBm  13.1 dBm   

Someone looking at those stats without noticing the power output would think that line is syncing as fast as it possibly can because there is no spare SNRM above 6dB.
It seems that somehow the DLM was able to throttle back the power to 11.9 dBm... meaning that I didnt have any surplus SNRM at all. (default is 6dB)


For comparison, these are some stats showing what the line was usually like



Notice full sync speed, normal tx power in the region of 18dBm, and surplus SNRM over the default 6dB.


Re the sky thread, Sky uses a totally different (new) DLM system.  Im not aware that BT 20CN uses ASSIA for powercut back to control DLM. 

What is beyond doubt though is that very short lines do and always have suffered badly when it comes to stuck profiles and odd things happening with the BT 20CN DLM system.   Its the reason why I got off it asap and was glad to go LLU adsl2+ (about 2 weeks after that thread).


For some reason, something is holding back your output power, which is why your sync speed is now so low.   The fact that there is no surplus SNRM doesnt hold relevance - nor follow the 'normal' rules - in your particular case.

Your line needs a total reset.
« Last Edit: March 10, 2013, 09:40:43 PM by kitz »
Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #12 on: March 10, 2013, 11:09:35 PM »

Kitz thanks for the reply,

What I did find helpful about the Sky thread was that it shows how a reduced output power leads to a reduced amount of 'spare' SNR, which in turn leads to a sub-optimal sync, it was connecting those dots which was confusing me before  ;)

Whilst I'm not moving to an LLU ISP (I'm moving to 21CN BT Broadband) I assume that the migration of ISP will trigger a line reset? I was also thinking isn't a slight reduction of output power sometimes necessary to reduce crosstalk in densely populated areas?
« Last Edit: March 10, 2013, 11:31:20 PM by matthewcl375 »
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 32223
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: Slow Connection Speed on DSL Max
« Reply #13 on: March 11, 2013, 12:02:34 AM »

>> how a reduced output power leads to a reduced amount of 'spare' SNR, which in turn leads to a sub-optimal sync,

Yes :)

>> I'm moving to 21CN BT Broadband)

Yes hopefully it should.   Its a different DLM system so you should start afresh.

>> I was also thinking isn't a slight reduction of output power sometimes necessary to reduce crosstalk in densely populated areas?

Normally BT use PSD masks on adsl1/adsl2+ to help prevent cross-talk.   iirc theres 4 different profiles in use depending upon the length of your line.  Theres not much info out there (or at least wasnt last time I looked) on what these profiles are, but afaik the masks are applied on certain tones/frequencies...  so that when those particular tones are fully loaded, it ensures that short lines dont drown out neighbouring long length lines.* 
VDSL also use PSD masks but in a slightly different way.



*by neighbouring I dont mean as in the same are, but lines that may be on the same MSAN, or say cables bundled nearby from the exchange on the way to the cabs.

Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

matthewcl375

  • Member
  • **
  • Posts: 25
Re: Slow Connection Speed on DSL Max
« Reply #14 on: March 11, 2013, 01:29:42 AM »

Ah, that makes perfect sense, as you said I would be on the highest of those profiles...

Another difference between your problem and mine is that with mine, after the fault my target snr was put at 15db, as well as the possible (likely) reduction of output power that occurred  :-\ Also yours recovered pretty quick whereas my output power has been like that since the fault at the end of January
« Last Edit: March 11, 2013, 01:55:08 AM by matthewcl375 »
Logged
Pages: [1] 2 3 4