Vastly increased errors on ADSL connection (Exchange-Only line, CR0-postcode)

[milhousevh]

Since Friday afternoon I've been experiencing much higher than normal errors on my 20Mbps down/1Mbps up ADSL connection, and while still usable it is causing some sites (eg.github) to respond more slowly than usual.

I've listened to the line and it sounds normal - no pops, crackles or buzzing.

See if you can spot when the errors started...

And Super Frame errors:

This seems to be the culmination of issues that have been affecting my normally very stable Exchange-Only connection over the last few weeks - since the middle of Week 48 I've been experiencing instability and higher than normal SNR/attenuation:

and slightly reduced sync:

If the stats don't improve over Christmas I'll report it to BT on the 27th as there's clearly now an underlying issue with this connection. Since the connection is still working I'm half expecting to have to "prove" to BT that there's a problem, which might be tricky unless I can show them these graphs...

[Keith_Beddoe]

What is your downstream noise margin at the moment?

[milhousevh]

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@Keith_Beddoe wrote:

What is your downstream noise margin at the moment?

---

Thanks for responding.

Not entirely sure what datum you're looking for so I'll give you a dump of the current raw stats which hopefully answers all questions. 🙂

# adslctl info --state
adslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    8000
Last initialization procedure status:   0
Max:    Upstream rate = 1236 Kbps, Downstream rate = 24696 Kbps
Bearer: 0, Upstream rate = 1151 Kbps, Downstream rate = 21987 Kbps

# adslctl info --show
adslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    8000
Last initialization procedure status:   0
Max:    Upstream rate = 1228 Kbps, Downstream rate = 24696 Kbps
Bearer: 0, Upstream rate = 1151 Kbps, Downstream rate = 21987 Kbps

Link Power State:       L0
Mode:                   ADSL2+
TPS-TC:                 ATM Mode
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        4.6             8.5
Attn(dB):        15.0            9.2
Pwr(dBm):        0.0             12.6

                        ADSL2 framing
                        Bearer 0
MSGc:           52              12
B:              254             35
M:              1               1
T:              3               4
R:              0               0
S:              0.3706          0.9931
L:              5504            290
D:              1               1

                        Counters
                        Bearer 0
SF:             44556020                767565
SFErr:          1035369         52
RS:             0               2336067
RSCorr:         0               0
RSUnCorr:       0               0

                        Bearer 0
HEC:            195269          75
OCD:            32              0
LCD:            32              0
Total Cells:    2892247753              1947140145
Data Cells:     847366374               233943375
Drop Cells:     0
Bit Errors:     0               3453

ES:             71556           93
SES:            4301            4
UAS:            444             444
AS:             718191

                        Bearer 0
INP:            0.00            0.00
INPRein:        0.00            0.00
delay:          0               0
PER:            16.12           17.87
OR:             28.77           8.05
AgR:            21930.33        1155.48

Bitswap:        734/734         7/7

# adslctl profile --show

Modulations:
        G.Dmt   Enabled
        G.lite  Enabled
        T1.413  Enabled
        ADSL2   Enabled
        AnnexL  Enabled
        ADSL2+  Enabled
        AnnexM  Disabled
Phone line pair:
        Inner pair
Capability:
        bitswap         On
        sra             Off
        trellis         On
        sesdrop         Off
        CoMinMgn        Off
        24k             On
        phyReXmt(Us/Ds) Off/On
        TpsTc           Aa
        monitorTone:    On
        Training Margin(Q4 in dB):      120

I'm not using the stock BT modem - this is a Netgear DGND4000 that I've been using for the last 2-3 years without any issues (and it's not been updated for most of that time - it's defintely not been updated within the last 2 years).

[john46]

The low down noise margin is not helping you

[Keith_Beddoe]

@john46

I wonder if this is a result of the 3dB noise margin trial again? This is the second report I have seen on this forum?

Did they not learn from 2012, or has new management come in, and not looked at the past history, and thought it might be a good idea?

[milhousevh]

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@john46 wrote:
The low down noise margin is not helping you

---

Maybe not now, but it's always been low for over 2 years, and up until 3-4 weeks ago it has never been an issue, and now on Friday there's been a mass of errors.

I guess the point is that *something* has changed between me and the exchange since Week 48, possibly some twiddling by BT on their equipment, and now these errors have appeared since Friday lunchtime.

Since the exchange is less then 200 metres from me, this low margin shouldn't be (and hasn't been) a problem until whatever fault appeared that is causing these errors.

[milhousevh]

These are my margins for the period July-Nov:

During this period I had no problems - very few errors:

So really it's a matter of restoring the connection back to this original stable and (mor or less) error-free behaviour, by "undoing" whatever BT have done (or fixing the fault, whatever that may be).

[milhousevh]

Purely as an observation, it seems the downstream SNR will reduce in response to an increase of errors:

[john46]

@Keith_Beddoe

my feeling also Keith 

[milhousevh]

If anything my down margin since Week 48 and until the errors started on Friday has actually been higher at 6dB than it has in the previous 6 months (~4.5dB, entirely stable, few if any errors). With the errors starting on Friday, the down margin has reduced to about 4.5dB, but the errors continue.

Is this the 3dB Trial you refer to? http://www.ispreview.co.uk/index.php/2016/05/bt-update-fttpod-stop-sell-removal-3db-trial-long-range...

As I mentioned I'm only 200m from my exchange, and have had 3dB connections in the past. I was with O2/Be (utterly brilliant), then Sky (awful - same line as O2/Be, yet almost unusable service with far too many upstream errors), and now BT (no service problems until Week 48, outages excluded).

It's a little difficult to categorise this problem - the connection characteristics have certainly changed for the worse during and after Week 48, and there now seems to be a second fault which is introducing these errors.

I'm hoping it will clear up by itself...