Kind PlusNet folk, please nudge my stuck Line Speed?

[#1]

Hi there,
I can see that's been picked up by the faults team, looks like they need speed test results - if you could run the initial test and second test at http://speedtest.btwholesale.com and add that to the ticket we'll be able to push it on further for you.

[#2]

Thanks Matt, I've just run yet another BT speedtest. (Despite last doing one just before my fault report, on 9th Jan. Do the logs/reports you can access from "BT's back end system" run off so soon?)
I have to say I found the ticket response very disappointing. I pointed to this thread in my report, and summarised the problem. But I don't get the impression that anyone has read this thread, nor done anything but run through a standard script. This is what I've received :-

Quote

Thanks for your patience during our investigation. I have run sufficient testing on your line and can see that all parameters look to be running correctly. I can see that the throughput based on your profiles is running correctly. I can also see that the synchronisation rate is normal for the length of your line. Please run a speedtest at http://speedtest.btwholesale.com/ so we can use BT's back end system to diagnose further on the back of these results. Ensure the connection is with a wired connection, you will only need your telephone number for this test. If you have any further issues on the connection. Due to the very nature of faults, we can only request that you monitor the connection for several days, in order to confirm you are satisfied this is resolved in full. Please do not hesitate to get back in touch online at http://contactus.plus.net/ or by phone on 0345 140 0200 if we can be of further assistance. Kind regards,

Throughput of 6.5Mb while I have a sync rate of 12.4Mb and an IP Profile of 10.92Mb is not "running correctly". That is the problem I reported. Of course monitoring the connection for several days is not going to confirm I am satisfied. Of course I need further assistance. Sheesh :(.
Matt, would someone at PlusNet please get to grips with this?
============================
I also see this on the ticket, in case it offers any clues to anyone else. (Indeed, aren't these partially from the last BT speedtest I did?) :-

WP Profile: Generic Speed 11600 No Time Out 
 WBC 160K - 24M Medium delay (INP 1) 6dB Downstream, 448 Low delay (INP 0) 6dB Upstream (ADSL2+)
 Our test also indicates that your line currently supports an estimated ADSL2+ broadband line speed of 7.5Mbps; typically the line speed would range between 5.5Mbps and 12Mbps
xDSL Status Test Summary
Sync Status:	Circuit In Sync
General Information
NTE Status:	 	NTE Power Status:	PowerOn	Bypass Status:	 
 
 	Upstream DSL Link Information	Downstream DSL Link Information
Loop Loss:	17.1	35.5
SNR Margin:	27.5	3.3
Errored Seconds:	0	0
HEC Errors:	0	 
Cell Count:	2862	3286
Speed:	444	12375
 
Maximum Stable Rate (KBPS):	9088	Fault Threshold Rate (KBPS):	7270
Detailed Records
Attribute:	DownStream-BE	UpStream-BE
TAP ID:	TAP-1	TAP-1
Test ID:	1357747385	1357747386
Start Date/Time:	09-01-2013 16:01:54	09-01-2013 16:02:08
Test Duration:	PT12.500S	PT9.406S
Domain Name:	plusdsl.net	plusdsl.net	 
Network Identifier:	CBUK88042749	CBUK88042749
Service Identifier:	BBEU08258341	BBEU08258341
BRAS IP Address:	10.170.162.1	10.170.162.1
VPI:	0	0
VCI:	0	0
Peering IP Address:	46.208.139.101	46.208.139.101
Infrastructure Type (C+ C++ HG/LTS):	LONS	LONS
System Name:	EUSC Performance Tester	EUSC Performance Tester
System Host:	EUSC Performance Tester	EUSC Performance Tester
Policy Type:	BestEffort	BestEffort
Policy ID:	WBC	WBC
Profile Rate:	10336	448
Test File Size:	9534902	56407
File Transfer Average Throughput/Session:	6540	250

[#3]

Quote from: mplusnetuser

Throughput of 6.5Mb while I have a sync rate of 12.4Mb and an IP Profile of 10.92Mb is not "running correctly". That is the problem I reported. Of course monitoring the connection for several days is not going to confirm I am satisfied. Of course I need further assistance. Sheesh :(. Matt, would someone at PlusNet please get to grips with this?

Well, PlusNet now say that the problem is not that my throughput is too low, but that my sync rate is too high! :-

Quote

BOT - DSL Logged Faults 9:45am, Monday 14 Jan 2013 [INTERNAL] RADIUS: Connected for 3:19:42 4 drops in last 24 hours 7 drops in last 72 hours 3 of 19 (16%) User Req Drops in last 7 days [EDIT: N.B. I'm in SNR retraining since 19/1: hence the drops] WP Profile: Generic Speed 10200 No Time Out Our test also indicates that your line currently supports an estimated ADSL2+ broadband line speed of 7.5Mbps; typically the line speed would range between 5.5Mbps and 12Mbps WBC 160K - 24M Medium delay (INP 1) 3dB Downstream, 448 Low delay (INP 0) 6dB Upstream (ADSL2+) xDSL Status Test Summary Sync Status: Circuit In Sync General Information NTE Status: NTE Power Status: PowerOn Bypass Status: Upstream DSL Link Information Downstream DSL Link Information Loop Loss: 17.0 34.5 SNR Margin: 28.0 4.3 Errored Seconds: 0 2 HEC Errors: 0 Cell Count: 4028 6042 Speed: 444 12153 Maximum Stable Rate (KBPS): 9088 Fault Threshold Rate (KBPS): 7270 Mean Time Between Retrains (Seconds): 43008 Mean Time Between Errors Upstream (Seconds): 43008 Indicative Line Quality: G Mean Time Between Errors Downstream (Seconds): 424 Test ID: 1357916483 1357916484 Start Date/Time: 11-01-2013 15:00:15 11-01-2013 15:00:30 Test Duration: PT12.406S PT9.390S User Name: Domain Name: plusdsl.net plusdsl.net Directory Number: Network Identifier: CBUK88042749 CBUK88042749 Service Identifier: BBEU08258341 BBEU08258341 BRAS IP Address: 10.170.162.1 10.170.162.1 VPI: 0 0 VCI: 0 0 Peering IP Address: 87.112.145.xxx 87.112.145.xxx Infrastructure Type (C+ C++ HG/LTS): LONS LONS System Name: EUSC Performance Tester EUSC Performance Tester System Host: EUSC Performance Tester EUSC Performance Tester Policy Type: BestEffort BestEffort Policy ID: WBC WBC Profile Rate: 10917 448 Test File Size: 9469370 57232 File Transfer Average Throughput/Session: 6590 240 Summary: The speed line profile is over the estimate for the connection the throughput is in within limits of the connection. Sending a engineer for this issue is unlikely to achieve anything due to the speed being estimate. I am going to try reset the connection to a target snr margin 6db this is to give the line a more realistic line profile. Your batch Id is 1-14584311056. ============================================================== BOT - DSL Logged Faults 9:58am, Monday 14 Jan 2013 , Thanks for your patience during our investigation. The throughput you are receiving is within limits of the connections estimated speed given to us by our suppliers for your line. The line sync speed has been falsified by a very low snr margin target at 3db this can sometimes cause the poor throughput on the connection. I have reset the connection to a target to 6db which will give you a more realistic sync and line profile speed. The reset takes 4-24 hours to go through the suppliers system, the line will then enter a 10 day training period to give you the best possible speed. I would like to apologise for any inconvenience caused by this issue. Please do not hesitate to get back in touch online at http://contactus.plus.net or by phone on 0800 432 0200 or 0345 140 0200 if we can be of further assistance.

I just don't get this :(.
The target SNR was previously reduced from 4.5 to 3 by PlusNet (at my request) in an attempt to increase throughput  I (mis?)understood that if the target SNR margin was too low, then the symptom would be more frequent disconnections, not lower throughput. What happened was that I got a slightly higher sync (+0.8Mb), and I didn't get more frequent disconnections and it did nothing to throughput. So I think this target SNR adjustment is a red herring.
Does anyone have any theories why there should be such a gap between throughput (6.5Mb) and sync/line speed (12+/10+Mb)?
Or, put another way, why my line with an attenuation of ~35, for which the ADSL2+ speed calculators suggest ...
http://www.coolwebhome.co.uk/calc/calculator.php
"Normal speed range at 35dB attenuation is 10500 Kbps to 13900 Kbps"
http://www.kitz.co.uk/adsl/max_speed_calc.php
"BT 21CN WBC & adsl2+: 11712 kbps ; IP Profile: 10330 kbps"
http://www.skyuser.co.uk/adsl2_checker.php
"We estimate your line is capable of between 10mb to 12mb broadband on an ADSL2+ service."
  ... should be limited to 6.5MB?

[#4]

If the noise margin is too low you will get errors on more packets which will mean they have to be retransmitted. There is a point at which the number of retransmissions outweighs the advantage of higher sync speed so the throughput goes down.
Personally if the sync speed is good anyway (say more than 8MB) I'd stick with a higher noise margin for a smoother experience than push my luck going for ultimate speed.

[#5]

Thanks jelv. So that begs the question of whether I am getting too many errors.
Here are a couple of router stats dumps. Both are since the target SNR was lowered. The first is before I killed the bell wire, and the second (shorter period, re retraining drops) afterwards :-

Bandwidth (Down/Up - kbit/s):  9067/444
Physical Layer Statistics:        
  Modem state:                   up
  Up time (Days hh:mm:ss):       5 days, 14:05:16
  xDSL Standard:                 ITU-T G.992.5
  xDSL Annex:                    Annex A
  Channel Mode:                        Interleaved
  Number of reset:               1
  Chipset Vendor info (G.994.1):    Local Remote
    Country code:                   B500  B500
    ID:                             BDCM  IFTN
    Specific:                       0000  71BE
  System Vendor info (showtime):  Local Remote
    Country code:                 0F00  0000
    ID:                           TMMB  ----
    Specific:                     3C61  0000
  Bearers generic info            DS         US       
    Payload rate [Kbps]:   9067    444   
    Attenuation [dB]:      35.0           17.3           
    Margins [dB]:          3.9            26.8           
    Output power [dBm]:    0.0            12.8           
    Number of bearers:           1
    Bearer 0                     DS         US       
      INP [DMT symbols]:     1.05           0.00           
      Delay [ms]:            7.98           1.13           
      Depth []:            64             0.00
      R:                   10        0       
G.997.1 Statistics (Current):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      28994   
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     2641     0       
        FEC:                     213073271 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        77636    N/A
G.997.1 Statistics (last 15 minutes):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      0       
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     2641     0       
        FEC:                     213073271 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        77636    N/A
G.997.1 Statistics (last 24 hours):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      29      
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     2641     0       
        FEC:                     213073271 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        77636    N/A

Up time (Days hh:mm:ss):       0 days, 5:58:24
xDSL Type:                     ADSL2+
Bandwidth (Down/Up - kbit/s):  12154/444
Physical Layer Statistics:        
  Modem state:                   up
  Up time (Days hh:mm:ss):       0 days, 5:58:24
  xDSL Standard:                 ITU-T G.992.5
  xDSL Annex:                    Annex A
  Channel Mode:                        Interleaved
  Number of reset:               1
  Chipset Vendor info (G.994.1):    Local Remote
    Country code:                   B500  B500
    ID:                             BDCM  IFTN
    Specific:                       0000  71BE
  System Vendor info (showtime):  Local Remote
    Country code:                 0F00  0000
    ID:                           TMMB  ----
    Specific:                     3C61  0000
  Bearers generic info            DS         US       
    Payload rate [Kbps]:   12154    444   
    Attenuation [dB]:      34.5           17.0           
    Margins [dB]:          4.4            27.4           
    Output power [dBm]:    0.0            13.0           
    Number of bearers:           1
    Bearer 0                     DS         US       
      INP [DMT symbols]:     1.09           0.00           
      Delay [ms]:            7.98           1.13           
      Depth []:            64             0.00
      R:                   14        0       
G.997.1 Statistics (Current):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      145     
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     164      0       
        FEC:                     11906284 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        8760     N/A
G.997.1 Statistics (last 15 minutes):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      0       
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     164      0       
        FEC:                     11906284 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        8760     N/A
G.997.1 Statistics (last 24 hours):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      145     
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     164      0       
        FEC:                     11906284 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        8760     N/A

I have no idea how to interpret all of that, so thanks to anyone with the smarts and kindness to take a look.
Do the errors look too high? Enough to cause throughput problems?

[#6]

You need to look at the rate of errors when the noise margin is low. If it drops this evening take a look then. Perhaps take a note of the error seconds and FEC errors, then run a speed test and look after to see the difference. Errors will mainly occur when you are running the line at full speed. Perhaps do a test now and then again tonight so you can compare best and worst.
Without changing the target, you might want to consider doing a resync when the noise margin is at it's lowest. This will give you a bit slower sync and the target noise margin which will then rise higher when there is less background noise.

[#7]

Thanks again. I just ran the BT test 3 times, within the timespan of these router stats :-

  Bearers generic info     DS         US       
    Payload rate [Kbps]:   12154          444   
    Attenuation [dB]:      34.5           17.0           
    Margins [dB]:          4.3            27.9           
    Output power [dBm]:    0.0            13.0  
G.997.1 Statistics (last 15 minutes):        
  Failures:
    Line failures                Near end
      Loss of signal (LOS):     0       
      Loss of frame (LOF):      0       
      Loss of power (LPR):     0       
  Performance monitoring:
    Line PM:             Near end
      Error second (ES):      0       
    Channel PM:         Near end Far end
      Bearer 0:
        Code Violation (CV):     219      0       
        FEC:                     11937197 0       
    ATM data path PM:             Near end Far end
      Bearer 0:
        HEC violation count (HEC):        11891    N/A

So, if I've got the right idea, with a current SNR of 4.3, under the load of 3 BT tests, my error counts have incremented by these amounts (compared to the last stats dump earlier today) :-
                              Last 15 Mins        Previous 6 Hours
                              (new stats)            (posted below)
---------------------------------------------------------------------
Error Seconds:              19                              145
CRC Errors:                    55                              164
HEC Errors:                3131                            8760
FEC Errors:              30913                    11906284

Does that first column seem problematically high for 3 speedtests? I don't know if a noise margin of 4.3 is considered low or not (it's lower than the forthcoming target of 6.0). But if I'm getting low errors (if they are?) while it's at 4.3, during the load of repeated BT speed tests, then how is it supposed to be responsible for my low download rate (of 6.37 during the 3 tests)? Maybe, if I time it right later this evening, I might see an even lower throughput and more errors, while the SNR is lower (assuming the new target of 6 hasn't kicked in by then). But what will that establish if, right now, I'm seeing low errors, yet downloads of only ~6.5Mb?
Have I got the wrong end of the stick?
As for re-syncing at a lower rate - well, I'm in retraining, so it has already fluctuated between 13587 and 11717. Yet downloads are always 6.5Mb or less. Why so?

[#8]

As a gauge I'm seeing just over 8,000 error seconds in a whisker under 7 days on a sync of 15900 with noise margin varying between 4 and 7.
My speed test results are not that far short of my IP Profile.
It would help if someone from Plusnet could confirm that they are seeing speeds on BRAS and DSLAM which are the same as you see for the IP Profile.

[#9]

I ran 3 more BT tests :-
                              Last 15 Mins
                              (new stats)
----------------------------------------------
Error Seconds:              21
CRC Errors:                    49
HEC Errors:                1958
FEC Errors:              13366
Which just appear confirm the same, or lower, error rates, while conducting 3 BT tests.

[#10]

Quote from: jelv

As a gauge I'm seeing just over 8,000 error seconds in a whisker under 7 days on a sync of 15900 with noise margin varying between 4 and 7.

If my maths is right, yours are about 2.5 times higher than mine, with no ill effect. I just don't think errors or SNR margins or "falsified" sync speeds have anything to do with this problem.

[#11]

Quote from: jelv

It would help if someone from Plusnet could confirm that they are seeing speeds on BRAS and DSLAM which are the same as you see for the IP Profile.

What does that mean, please? (For completeness, my  IP Profile is currently 10.72 Mb and PlusNet Line Speed 10.2 Mb).
Previously, Matt said this :-

Quote from: Matt

Oddly I've just run a consistency check on the line and it's come back as passed with the speeds on BRAS and DSLAM matching at 8654, so given the other discrepancies we're seeing about the only thing I can think of is an SNR reset to allow the line to retrain. Let us know if you'd like to go ahead with that mplusnetuser, and we'll set it going for you.

[#12]

That's what Plusnet are seeing recorded on the BT systems for your line speed. It's because of the post you've quoted I like them to look again.

[#13]

Quote from: mplusnetuser

Quote BOT - DSL Logged Faults 9:58am, Monday 14 Jan 2013 [...] The line sync speed has been falsified by a very low snr margin target at 3db this can sometimes cause the poor throughput on the connection. I have reset the connection to a target to 6db which will give you a more realistic sync and line profile speed. The reset takes 4-24 hours to go through the suppliers system, the line will then enter a 10 day training period to give you the best possible speed. I would like to apologise for any inconvenience caused by this issue.

More than 24 hours later, nothing seems to have happened. No re-sync; and I'm still seeing a margin of 3.7dB (not that I think it's a likely fix anyway).

Quote from: jelv

It would help if someone from Plusnet could confirm that they are seeing speeds on BRAS and DSLAM which are the same as you see for the IP Profile.

No response at all from PlusNet, either on the fault ticket, or here. I seem to have been abandoned :(.

[#14]

Hi,
You've certainly not been abandoned. I'll be picking this issue up this evening for you and get in touch to discuss the issue.