Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[mlmclaren]

So for some reason my VDSL connection is currently hanging on with a 2db downstream SNR, Yesterday it was a healthly 6.4db...

Yesterday's Stats:
lcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   0
Last initialization procedure status:   0
Max:   Upstream rate = 24114 Kbps, Downstream rate = 78100 Kbps
Bearer:   0, Upstream rate = 19999 Kbps, Downstream rate = 78564 Kbps
Bearer:   1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3959)
Medley Phase (Final) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3959)
     VDSL Port Details        Upstream        Downstream
Attainable Net Data Rate:       24114 kbps          78100 kbps
Actual Aggregate Tx Power:          7.1 dBm           13.4 dBm
====================================================================================
  VDSL Band Status   U0   U1   U2   U3   U4   D1   D2   D3
  Line Attenuation(dB):   4.6   22.1   33.1   N/A   N/A   11.7   28.6   43.7
Signal Attenuation(dB):   4.6   21.1   32.3   N/A   N/A   13.2   28.4   43.7
        SNR Margin(dB):   16.1   15.7   15.5   N/A   N/A   6.3   6.2   6.3
         TX Power(dBm):   -2.5   -21.5   6.6   N/A   N/A   10.2   7.9   7.0


Today's Stats:
xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   0
Last initialization procedure status:   0
Max:   Upstream rate = 22253 Kbps, Downstream rate = 63720 Kbps
Bearer:   0, Upstream rate = 19999 Kbps, Downstream rate = 78564 Kbps
Bearer:   1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3959)
Medley Phase (Final) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3959)
     VDSL Port Details        Upstream        Downstream
Attainable Net Data Rate:       22253 kbps          63720 kbps
Actual Aggregate Tx Power:          7.1 dBm           13.4 dBm
====================================================================================
  VDSL Band Status   U0   U1   U2   U3   U4   D1   D2   D3
  Line Attenuation(dB):   4.6   22.1   33.1   N/A   N/A   11.7   28.6   43.7
Signal Attenuation(dB):   4.6   21.2   32.1   N/A   N/A   13.2   28.4   43.7
        SNR Margin(dB):   13.3   12.5   12.5   N/A   N/A   2.4   2.4   2.4
         TX Power(dBm):   -2.5   -21.5   6.6   N/A   N/A   10.2   7.9   7.0
#

What the hell has gone wrong???

In the beguinning, (January 2016) I had an attainble of 116Mb/s down... that got chipped away as my neighbours moved into the other 23 flats in our newly built 24 apartment building...

I understand crosstalk taking a bit of bandwidth but 15Mb/s in one go is a bit much...

Worst part is if this don't fix itself overnight, I'm gonna have to approach BT about it.... that should be fun.... specially the look on my face when I'm trying to hold back the rage that follows "well you line is operating in range (80 - 35Mb/s) " or the one I've had a few times from a couple of providers about my usage being above 100GB so it must be fine....

I may be running of into a forest at some point soon, technology really starting to **** me off..

[NewtronStar]

Thanks for the rant we all have crosstalk issues you need to reboot your modem and get the Snrm back to 6dB and with a loss of sync most people are not blessed like Roseway running at 2dB with zero errored seconds and loads of crosstalk.

No two lines are the same take it from me 

[kitz]

Are you on MDWS?   I'd like to see if the SNRm was a sudden one hit loss.   It would also be useful to see if you get any variance.

15Mbps does seem rather a lot in one hit    

[mlmclaren]

It's not crosstalk, my DSLstats shows it just going back to normall for a few minutes then back again... somthing is interfering really bad...

[mlmclaren]

Are you on MDWS?   I'd like to see if the SNRm was a sudden one hit loss.   It would also be useful to see if you get any variance.

15Mbps does seem rather a lot in one hit    

Sorry Kitz, Yes I am, 'mlmclaren' started using yesterday

[kitz]

What's MDWS ?

Sorry, I thought you knew     It stands for My DSL Web Stats
DSLstats can automatically upload to MDWS, so we can look at your graphed stats to try see what is going on.

https://www.mydslwebstats.co.uk/

my DSLstats shows it just going back to normall for a few minutes then back again

Can you attach a copy of your SNRm graph so we can have a look please.

[kitz]

oops.. posts crossed.   I'll go have a look

[NewtronStar]

He does not have any previous data on MDWS   

[kitz]

I was sat scratching my head because I could only see limited data... and nothing for SNRm

Then as I was sat puzzling I got a notification.
"G.INP is now enabled for mlmclaren".

So I dont think its been uploading. 

---

Going to need to do it the old fashioned way and ask for the graphs to be attached please. 

[mlmclaren]

I was sat scratching my head because I could only see limited data... and nothing for SNRm

Then as I was sat puzzling I got a notification.
"G.INP is now enabled for mlmclaren".

So I dont think its been uploading. 

---

Going to need to do it the old fashioned way and ask for the graphs to be attached please. 

OK One moment...

[mlmclaren]

Here you go... sorry I can't provide much on MDWS, I only started messing with it yesterday and don't have any computers running 24/7... though working on sorting something soon!

[Chrysalis]

Sadly the most likely cause is crosstalk, and yes disturbers can be turning their modems on and off, second most likely cause is someone has a device in the area that is interfering, but external interference is less common on short cable lengths, more of a problem for those 4km adsl lines.

[mlmclaren]

Sadly the most likely cause is crosstalk, and yes disturbers can be turning their modems on and off, second most likely cause is someone has a device in the area that is interfering, but external interference is less common on short cable lengths, more of a problem for those 4km adsl lines.

Yeah I've already dealt with crosstalk chipping way my connection from 116Mb/s to 78Mb/s but too lose an additional 15Mb/s in a matter of hours isn't right, I'll be down at 5Mb by the end of the year in that case.

[kitz]

I see that overnight there has been a resync.    Probably best as a line running at 2.5dB SNRm is likely to incur more errors than one running at 6dB.

So it looks like your disturber has taken just over 13Mbps    

10Mbps due to a single cross-talker is something that isnt too unusual.  Unfortunately if it is crosstalk, then there isnt anything much you can do about it and its why so many of us wish that BT could pull their finger out when it comes to vectoring.  As Chrys says, on short lines crosstalk is far more of an issue than external RFI/EMI.   

Last year I looked at stats that people had been posting and came to the conclusion that 20Mbps loss from crosstalk was not a too far out average.  As expected, it was the  shorter lines lost the most.  Unfortunately your line appears to be one of those on the high side
You can usually spot crosstalk quite easily if monitoring full time, because SNRM will go up when they turn their modem off and go back down again when they reconnect.

The SNRm variance of up to 0.5dB is quite normal, most lines will see some sort of small jitter from time to time.
 
I attach below my SNRm for the past two days,  here you can see an example on the left where one of my cross-talkers rebooted their router.  You can also see that soon after I had a period of 0.5dB jitter... and again near the dot.   

[mlmclaren]

Kitz, I understand what your saying but losing 50+Mb/s due to crosstalk is surely not right, I have a feeling that somebody has messed up the DP in building, based on them leaving it unlocked the other day, probably not a bright minded engineer...

Depending on what BT say... if I ever get through... I might go and take a look at it myself...