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[Azuse]

From August to February my line was perfectly stable on the 3db, first with the Be* box bridged then my old DG843GT (DGteam) bridged, both racked up over 3 months uptime at ~13000k/1400k. Last month the line began dropping and re syncing at a lower rate ~12000k/1400k every few days, sometimes in evening sometime in the morning (10/11am). I found it odd because it seemed the snr was halving i.e. 50-60% drop regardless of a 3 or 6db profile. Obviously I started a thread on the Be* forum but before it got anywhere BT spent a Monday morning inside the cabinet (it's onside my door ) and the drops ceased. It lasted 3 weeks. BlueEther pointed out he would consider a drop of 3db or greater on the 6db profile a fault which i guess is my question, before I go on further. How great a drop in snr could/would be considered a fault on the line? I plan on checking th 9db profile, but I suspect the snr drop will be the same.

Anyway, I had 3 weeks before the drops returned and my snr is going up and down quite a bit, 3.6 to 1.8 , so before I go bug Be*, who's first response will undoubtedly be increasing the the snr, I would much rather know if this can be fixed, or at the least influenced positively. Attenuation is 38.5, modems connected to the master socket (no extensions) via a filtered adsl nation faceplate and a short, shielded, rj11 cable.

[jeffbb]

Hi and welcome .
With your attenuation you would expect to synch at about 9568Kbps with the default target SNRM of 6 db.
quote my line was perfectly stable on the 3db
Are you tweaking your Target or have you got BE to do it ?

It is quite normal to have a fluctuating SNR margin . The SNR margin will vary according to time of day ,normally drops during evening time . Would not be concerned with 2 to 3db drop during the evening period. The level of change is on its own is not the main worry its how the change takes place .Is it gradual,sharp, or very spiky.
See SNR explanation  for further info.

It would help if you could post your line stats so that we have a complete picture of your line state.

Have you tried routerstats  . This application is a very useful long term  monitoring tool.It display SNRMargin and other stats in a graphical format to see trends in line performance .
Regards jeff

[Azuse]

At 6db I sync at 11500, 13500 at 3db, Be profile.

Yes, I've had routerstatslite and dmt quite a few times over the past month and it's gradual, at least it not instant but takes a couple hours every morning/evening (as you'd expect). It's not so much the drops as the size of the drop, it's down from 3.6 to 1.3 ~65% drop.

What got my attention though was my f8lure graphs. The first is my line as it was since connection in August to 1 month ago i.e. normal. The second is 2 weeks ago, the third yesterday and lastly this morning. Seems it's degraded to me









/usr/sbin/adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason:   0
Channel: FAST, Upstream rate = 1412 Kbps, Downstream rate = 13485 Kbps
Link Power State: L0
Mode:         ADSL2+
Channel:      Fast
Trellis:      U:ON /D:ON
Line Status:      No Defect
Training Status:   Showtime
      Down      Up
SNR (dB):   1.3      3.6
Attn(dB):   38.5      20.8
Pwr(dBm):   19.1      12.4
Max(Kbps):   16042      1412
Rate (Kbps):   13485      1412
         G.dmt framing
K:      77(0)      41
R:      12      0
S:      1      1
D:      160      1
         ADSL2 framing
MSGc:      59      16
B:      76      40
M:      1      1
T:      5      3
R:      12      0
S:      0.1971      0.9969
L:      3612      329
D:      160      1
         Counters
SF:      54187793      54243446
SFErr(CRCErr):   22641      53627
RS:      431163858      0
RSCorr:      1888337666      0
RSUnCorr:   507584      0

HEC:      12937      21754
OCD:      0      0
LCD:      0      0
Total Cells:   1831883431      1584288553
Data Cells:   1417468414      1826505855
Drop Cells:   0
Bit Errors:   0      2273846

ES:      14727      4004
SES:      21      0
UAS:      39      3
AS(Uptime):   867896

INP:      2.12      0.00
PER:      16.01      16.44
delay:      7.88      0.24
OR:      32.46      10.69

Bitswap:   173701      194
Total uptime:   868256

Total time = 1 days 1 hours 12 min 6 sec
SF  = 54210100
CRC = 22644
LOS = 0
LOF = 0
ES  = 14727
Latest 1 day time = 1 hours 12 min 6 sec
SF  = 270162
CRC = 346
LOS = 0
LOF = 0
ES  = 188
Latest 15 minutes time = 12 min 6 sec
SF  = 45402
CRC = 47
LOS = 0
LOF = 0
ES  = 26
Previous 15 minutes time = 15 min 0 sec
SF  = 56175
CRC = 60
LOS = 0
LOF = 0
ES  = 39
Previous 1 day time = 24 hours 0 sec
SF  = 5394488
CRC = 6402
LOS = 0
LOF = 0
ES  = 4678
15 minutes interval [-30 min to -15 min] time = 15 min 0 sec
SF  = 56174
CRC = 76
LOS = 0
LOF = 0
ES  = 37
15 minutes interval [-45 min to -30 min] time = 15 min 0 sec
SF  = 56237
CRC = 83
LOS = 0
LOF = 0
ES  = 43
15 minutes interval [-60 min to -45 min] time = 15 min 0 sec
SF  = 56174
CRC = 80
LOS = 0
LOF = 0
ES  = 43
Showtime Drop Reason:   0
Last Retrain Reason:   0

[HPsauce]

How great a drop in snr could/would be considered a fault on the line?

The blunt answer is that no change (small or large) would be considered a fault on the line or elsewhere.
(Mine varies by "only" about 1 or 2dB over a day but many experience much more variation.)

Hopefully you've read the background info linked to, but basically SNR has an initial TARGET and conditions (interference, attenuation etc.) at the time of sync result in an approprite connection speed.
As conditions change, so does the measured SNR. If it drops too low to maintain a connection then you resync at (normally) a lower speed.

If the variation for you is significant then you may get resyncs at a frequency you consider unacceptable. The normal action is to ensure interleaving (a form of error correction) is on and to raise the target SNRM to say 9dB or even higher (I've seen 15 or 18 on BT lines) on the (normally reasonable) assumption that an external intereference factor is to blame.

If, on higher target SNRM you still get frequent problems then the ISP can ask Openreach to investigate. Most can also run their own line tests.

(PS I'm on BE too and know how their systems work)