A couple of questions about adsl2+

Hi

Connected to aaisp on Tuesday, line synched at:

Modulation: G.992.5 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 888 / 17,387
Output Power (Up/Down) [dBm]: 12.0 / 0.0
Line Attenuation (Up/Down) [dB]: 10.5 / 23.0
SN Margin (Up/Down) [dB]: 15.5 / 6.0

Interleaving was on at that point...

Today, the line dropped and now I see:

adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 1227 Kbps, Downstream rate = 20300 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): 3.4 6.3
Attn(dB): 24.0 10.4
Pwr(dBm): 0.0 12.7
Max(Kbps): 23936 1224
Rate (Kbps): 20300 1227
G.dmt framing
K: 153(0) 57
R: 16 4
S: 1 4
D: 96 4
ADSL2 framing
MSGc: 61 10
B: 152 56
M: 1 4
T: 4 3
R: 16 4
S: 0.2407 5.9108
L: 5615 314
D: 96 4
Counters
SF: 390008 370078
SFErr: 15 0
RS: 104522274 4252942
RSCorr: 381656 0
RSUnCorr: 430 0

HEC: 15 0
OCD: 1 0
LCD: 0 0
Total Cells: 301260171 1111693
Data Cells: 18665980 9567
Drop Cells: 0
Bit Errors: 0 0

ES: 6 0
SES: 0 0
UAS: 40 0
AS: 6293

INP: 1.09 0.20
PER: 16.13 17.73
delay: 5.77 5.91
OR: 33.22 7.21

Bitswap: 23 0

Total time = 1 hours 45 min 57 sec
SF = 390008
CRC = 15
LOS = 0
LOF = 0
ES = 6
Latest 1 day time = 1 hours 45 min 57 sec
SF = 390008
CRC = 15
LOS = 0
LOF = 0
ES = 6
Latest 15 minutes time = 57 sec
SF = 3544
CRC = 0
LOS = 0
LOF = 0
ES = 0
Previous 15 minutes time = 15 min 0 sec
SF = 55769
CRC = 0
LOS = 0
LOF = 0
ES = 0
Previous 1 day time = 0 sec
SF = 0
CRC = 0
LOS = 0
LOF = 0
ES = 0
15 minutes interval [-30 min to -15 min] time = 15 min 0 sec
SF = 55769
CRC = 1
LOS = 0
LOF = 0
ES = 1
15 minutes interval [-45 min to -30 min] time = 15 min 0 sec
SF = 55768
CRC = 0
LOS = 0
LOF = 0
ES = 0
15 minutes interval [-60 min to -45 min] time = 15 min 0 sec
SF = 55831
CRC = 12
LOS = 0
LOF = 0
ES = 3
Showtime Drop Reason: 8000
Last Retrain Reason: 8000
#

As you can see the downstream snr is down at 3.4dB and interleaving has gone... I'm guessing 3.4dB isn't that stable? I'm willing to trade some speed for stability. I'm guessing at 9db it would be around 14Mbps or so? Odd it is letting the modem sync at 3.4dB as yesterday it was 6dB. I'm a little confused with all this, I know having a low snr on adsl1 isn't that great, but does the same rules apply to adsl2+ - I have also selected the "stable" profile which should drag it up to 9dB or close to it?

Edited by Brynon (Thu 14-May-09 21:51:03)

Hrm, actually plugging in my DG834G v4 and using DMT tool to tweak the snr I was able to raise the snr up to 9dB and then back 3dB and now its sitting at

adslctl: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 8000
Channel: FAST, Upstream rate = 1215 Kbps, Downstream rate = 18690 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): 6.4 6.1
Attn(dB): 24.0 10.3
Pwr(dBm): 0.0 12.9
Max(Kbps): 22080 1212
Rate (Kbps): 18690 1215
G.dmt framing
K: 155(0) 57
R: 14 4
S: 1 4
D: 96 4
ADSL2 framing
MSGc: 55 10
B: 154 56
M: 1 4
T: 4 3
R: 14 4
S: 0.2649 5.9678
L: 5103 311
D: 96 4
Counters
SF: 19610 18674
SFErr: 0 64
RS: 4785062 212698
RSCorr: 133 269
RSUnCorr: 0 0

HEC: 0 18
OCD: 0 0
LCD: 0 0
Total Cells: 13958717 1928138
Data Cells: 11505 11699
Drop Cells: 0
Bit Errors: 0 348

ES: 7 0
SES: 0 0
UAS: 106 97
AS: 317

INP: 1.05 0.20
PER: 16.16 17.90
delay: 6.35 5.96
OR: 30.19 7.14

Bitswap: 54 0

Total time = 3 hours 22 min 19 sec
SF = 742366
CRC = 16
LOS = 0
LOF = 0
ES = 7
Latest 1 day time = 3 hours 22 min 19 sec
SF = 742366
CRC = 16
LOS = 0
LOF = 0
ES = 7
Latest 15 minutes time = 7 min 19 sec
SF = 24708
CRC = 0
LOS = 0
LOF = 0
ES = 0
Previous 15 minutes time = 15 min 0 sec
SF = 52225
CRC = 0
LOS = 0
LOF = 0
ES = 0
Previous 1 day time = 0 sec
SF = 0
CRC = 0
LOS = 0
LOF = 0
ES = 0
15 minutes interval [-30 min to -15 min] time = 15 min 0 sec
SF = 55831
CRC = 0
LOS = 0
LOF = 0
ES = 0
15 minutes interval [-45 min to -30 min] time = 15 min 0 sec
SF = 55769
CRC = 0
LOS = 0
LOF = 0
ES = 0
15 minutes interval [-60 min to -45 min] time = 15 min 0 sec
SF = 55769
CRC = 1
LOS = 0
LOF = 0
ES = 1
Showtime Drop Reason: 8000
Last Retrain Reason: 8000

If I can get it to sit there then that will be cool, although I did read that DMT tool snr tweaking wasn't supposed to work on 21CN? Oh well... As long as it works...

I'm with aaisp and have been on adsl2+ since 25th march and got a down sync of about 12000 (bras rate of 11000) at first but the s/n margin was quite low, starting at 6db and it dropped down to about 2db and then the next day BT had reset my noise margin to 18db but this caused my sync to drop to about 5000 (bras rate 4000) and it's been stuck at this rate since then.

I have changed the stability option from "normal" to "more stable" but this does not seem to have changed anything. I guess I'm going to have to hold out for BT's VDSL rollout as there is a green BT street cabinet right outside my house.

If anything, the 'more stable' option will increase the noise margin. It is worth contacting support about this.

Your sync rate might be below the fault threshold rate, so defining your circuit as faulty...

It looks like Shaun might have corrected the problem - looks like I was on a "banded profile" meaning BT have capped my sync rate due to line errors. Looks like the cap has now gone and my sync is 13232 kbps / 1075 kbps. I'll just have to hope it does not get re capped!

Ah that explains why before I left entanet (last time I tried 21CN) my line sync ended up at 19dB SNR and a sync of 9Mbps...

In reply to a post by boliston:

It looks like Shaun might have corrected the problem - looks like I was on a "banded profile" meaning BT have capped my sync rate due to line errors. Looks like the cap has now gone and my sync is 13232 kbps / 1075 kbps. I'll just have to hope it does not get re capped!

I think I spoke too soon - my router has just re synced at 4544 kbps / 1107 kbps and my BRAS rate has dropped from 11000 to 4000. I think BT must have re-applied the "banded profile" which was a pity as it has worked fine at the higher 13232 kbps / 1075 kbps sync rate for the last 2 days and I got a rock steady 1.3MB/s download rate (it only took me 9 minutes to download a 700mb iso image rather than the usual 24 minutes)

Heh. Welcome to the joys of the DLM - it does that to a lot of people, it seems. Maybe give them a shout on IRC and they should be able to reset it again.

An alternative method is to toggle between ADSL1/ADSL2 which resets the line statistics. That method takes a couple of days though as each change takes 24 hours to come into effect.

Are you sure about this change from ADSL1 to ADSL2?
DLM has totally borked my line from a BRAS of 6000 down to 3000!
Even getting the SNR margin reset back to 6 only last a few hours before its back to 12.
Shaun is now sending me a new router before we get BT involved and try to fix what ever has gone wrong. I hope its the router as I dont hold any hope that BT will actually do anything to try to fix this issue.

If only A&A did LLU here!

In reply to a post by TonyHoyle:

Heh. Welcome to the joys of the DLM - it does that to a lot of people, it seems. Maybe give them a shout on IRC and they should be able to reset it again.

An alternative method is to toggle between ADSL1/ADSL2 which resets the line statistics. That method takes a couple of days though as each change takes 24 hours to come into effect.

I think I'm pretty much stuck with a 4000 bras profile as I've had my line reset back to 6db a couple of times and I get 11000 bras for a day or so then back to 4000 again and a silly 18db margin.

Actually I notice that since the last reset I've got a 16db margin rather than 18db so perhaps it might eventually go lower.

It's interesting that toggling back to adsl1 will reset line stats. I was worried that if I hit the adsl1 button that I'd be stuck with adsl1. I've tried using the other buttons for normal, stable and super stable but I'm not sure they have much effect. I'm currently on stable (option 2).