Why is a "degraded" line not a faulty line?

[#1]

Hi,
As Chris has said, I'll be investigating this issue for you and will be back in touch shortly. I'm sorry for the problems that you're experiencing with your connection, I'll do everything I can to get this put right.

[#2]

Chris is working to a plan that involves switching me back from ADSL1 to ADSL2 and then setting the snrm to 6dB
The first stage completed at about 5am today when the connection changed to ADSL2:

ADSL Status
Parameters
DSP Firmware Version 		A2pB025f.d22k
DMT Status			No Defect
Operational Mode		ADSL2
Upstream			883
Downstream			2190
SNR Margin(Upstream)		6.3
SNR Margin(Downstream)		15.6
Line Attenuation(Upstream)	33.3
Line Attenuation(Downstream)	51.5

I advised to next expect the snrm change around the middle of today and then the result would be reviewed tomorrow.

[#3]

The SNRm change from 15dB to 6dB was actioned late this afternoon, manually I think.
These are the resulting  router stats

ADSL Status
Parameters
DSP Firmware Version 		A2pB025f.d22k
DMT Status			No Defect
Operational Mode		ADSL2
Upstream			907
Downstream			3543
SNR Margin(Upstream)		6.0
SNR Margin(Downstream)		8.8
Line Attenuation(Upstream)	33.3
Line Attenuation(Downstream)	52.0

This has "caused a few errors" so Plusnet are requesting an engineer visit.

[#4]

Engineer visit has been confirmed for morning on 27/11/12.
The 3543kbps conneciton speed lasted less than a now and has dropped back a little to:

ADSL Status
Parameters
DSP Firmware Version	 	A2pB025f.d22k
DMT Status			No Defect
Operational Mode		ADSL2
Upstream			927
Downstream			3264
SNR Margin(Upstream)		6.5
SNR Margin(Downstream)		9.1
Line Attenuation(Upstream)	33.3
Line Attenuation(Downstream)	53.0

[#5]

This is now all in hand. We'll apply Interleaving to try and correct the errors shown on your line. I look forward to the engineers visit on Tuesday.
As we discussed, I'll do as much as I can to ensure we get the best out of your line.
Let me know if there is anything further I can do to help

[#6]

Well John, certainly no better is it? I can't say I'm surprised as your line now has 4dB more attenuation. Do these blokes from Openreach actually know what they are doing?
As suppose the Bits/Tone graph looks as abysmal as some of the most recent?
I think it could be suggested that you should be put on another pair as well as sorting out the drop wire. It seems the pair you were on, was better as it had 4db less attenuation!

[#7]

Here is the current Telnet Stats:

Noise Margin:     9.0   dB
Connection Rate:  3264  Kbps
Line Attenuation: 53.0  dB
Power:            0.0   dBm
Max Rate:         4376  Kbps
 
SuperFrames:      3122076
SF (CRC) Errors:  2460426
Reed Solomon:     0
RS Corrected:     0
RS Un-Corrected:  0
HEC:              2429335
Errored Seconds:  53762
Severe ES:        53758
Interleave Depth: 1
Bitswaps:         197

And some graphs showing
[list type=decimal]

Bits/Tone

thinkbroadband pings

Noise Margin

Sync Speed

[#8]

Well the Bits/Tone clearly show how badly degraded the frequency response is, and is now worse than it was before. I have no doubt it's been made worse by the pair swap (the extra 4dB attenuation) and the ONLY other common factors not touched are the Tie Pair and DP to Drop-Wire and the Drop-wire itself, and the latter and the Tie Pair should be the first step, then put you back on the pair you were on (unless it's testing faulty).
The TBB ping graphs starts showing lost packets from the changes in ADSL mode and SNR Margin, consistent with the very high error rate showing in the stats. Noise margin graph at least shows there isn't any large variations in noise, but then perhaps I wouldn't expect too much with the frequency response being so poor.  Sync speed - well, speaks for itself.

[#9]

Things were a bit sluggish this morning, so I ran a BT Speedtester at 9:15. The download speed was 0.59Mbps.
I waited until this afternoon and tried again - download speed was 0.82Mbps.
At about 3pm I did a controlled disconnect and powerdown and restart (new sync speed = 3539) and then ran BT speedtester again - download speed was again 0.82Mbps.
So, it looks like I'm stuck with it until next Tuesday

[#10]

What does the portal say for your current line speed?

[#11]

Quote

Current line speed:     3.1 Mb

I was advised that it was manually adjusted yesterday to 3.1Mb, shortly after my SNRm was moved down and the sync speed raised.
However, if I guess where you where you're coming from, I can recall reading about situations where the profile reported on the portal is not necessarily the true profile being applied at Plusnet.

[#12]

That's not a normal situation, it's more like BT's profiling isn't what the Speedtester is reporting, whichever, oh dear 

[#13]

There was a brief disconnection of my line at about 9:50 yesterday morning.
The result was the snrm increased from about 9dB to about 12dB and the speed decreased from 3539kbps to 3239kbps
[code=current modem status]ADSL Status
Parameters
DSP Firmware Version A2pB025f.d22k
DMT Status No Defect
Operational Mode ADSL2
Upstream 920
Downstream 3239
SNR Margin(Upstream) 5.6
SNR Margin(Downstream) 11.3
Line Attenuation(Upstream) 33.3
Line Attenuation(Downstream) 52.0[/code]
Download speed improved and BT Speedtester confirms that download speed = 2.78 Mbps and profile = 2.86 Mbps.

[#14]

Well, let's hope you get an experienced engineer tomorrow who understands a bit more of the issues involved, and actually does something about them - replacing the remaining damaged untwisted pair drop-wire, checking that you aren't on a 'split' pair anywhere, particularly the section of drop-wire that was replaced in January, swapping your pair to the exchange back to the pair you were on if it's not faulty assuming there isn't a better pair available, as the pair you have been put on is worse.
After that, if no significant improvement consider a Tie-pair mod.
If you haven't read this http://community.plus.net/forum/index.php/topic,109057.msg936931.html#msg936931 here is the perfect example of the devastating effect that non-twisted split pair wiring can have on performance, and what can happen when you have a disinterested arrogant & ignorant engineer and how a proper experienced engineer can resolve things.

[#15]

OK, engineer visit no. 2 is completed.
The engineer left after just less than 4 hours. He carried out lots of tests and made notes to pass on to Plusnet.
The main change he tried was his one authorised change of a D side pair.
However, his tests were still showing CRC errors well above the recommended threshold, so he doesn't reckon that he has yet traced the cause of the problem.
The error count from the pole back towards the cabinet was still so high that he wanted to spend his time investigating that direction rather than changing the drop wire, but he did renew the socket faceplate.
As he was getting a 5Mbps signal at the cabinet, he thinks that the most likely cause is between the cabinet and the pole and he was suspecting a REIN issue. he said it wa snow up to my ISP to review the test data and notes, but he suspected that they may next ask for a REIN engineer.
These are the current Router Stats:

ADSL Status
Parameters
DSP Firmware Version 		A2pB025f.d22k
DMT Status			No Defect
Operational Mode		ADSL2
Upstream			883
Downstream			2930
SNR Margin(Upstream)		5.7
SNR Margin(Downstream)		12.1
Line Attenuation(Upstream)	33.3
Line Attenuation(Downstream)	53.0

As the router stats available via telnet seem more relevant to the way the engineer was testing, here are those figures (1h 58m since router connect):

DOWNSTREAM (Rx)
Noise Margin:     12.3  dB
Connection Rate:  2930  Kbps
Line Attenuation: 53.0  dB
Power:            0.0   dBm
Max Rate:         4092  Kbps
 
SuperFrames:      414477
SF (CRC) Errors:  777
Reed Solomon:     13470530
RS Corrected:     5069987
RS Un-Corrected:  3277
HEC:              608
Errored Seconds:  158306
Severe ES:        153301
Interleave Depth: 16
Bitswaps:         9
UPSTREAM (Tx)
Noise Margin:     6.1   dB
Connection Rate:  883   Kbps
Line Attenuation: 33.3  dB
Power:            12.9  dBm
Max Rate:         888   Kbps
 
SuperFrames:      373380
SF (CRC) Errors:  0
Reed Solomon:     2418252
RS Corrected:     92
RS Un-Corrected:  0
HEC:              0
Errored Seconds:  198
Severe ES:        0
Interleave Depth: 8
Bitswaps:         39
TOTALS
Total Uptimes (From SF counts):
 WAN:   0 days, 01:58:44
 LAN:   0 days, 00:00:00

and I've attached the current Noise margin, downstream speed and Bits/Tone graphs.