Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[outoftownie]

Hi all,

I can't seem to get more than a few days out of my FTTC before downstream SNR drops sufficiently that there's a resync - see attached for a graph over the past week and a bit. This seems to have been going on for at least a couple of months, possibly longer (my logging is not the most reliable).

SNR starts at around 5db but then drops over a period of anything from 2 to 5 days to below 2db before a resync brings it back up and the cycle starts again.

Downstream vectoring and G.INP seems to normally be on, upstream vectoring sometimes.

Any idea what is going on here, and how I can make it stop?!

Modem is a HG612.

Thanks!

[burakkucat]

Any idea what is going on here, and how I can make it stop?!

Modem is a HG612.

For both parts of your question, it is difficult to give an answer.

If I was experiencing the problem, I would try testing with a different device in place of the HG612. Considering the age, both physical and technological, of the Huawei HG612 modem it would be a worthwhile test.

[Subsequent edit to insert the indefinite article that "got away".]

[re0]

Your SNR seems a bit drunk, I'd say. I think it's time for it to go home.

... I would try testing with a different device in place of the HG612 ...

^^^ This. Do you have any other VDSL2 modems? Preferably, something you can log the stats with.

[outoftownie]

Thanks folks - I'll get hold of a Zyxel modem and report back...

[siofjofj]

Agreed about trying a different modem.

Something else you may wish to consider in the meantime is that I had a similar phenomenon visible in my SNRM as a result of a high resistance fault (see attached graphs, perhaps yours looks similar if zoomed in with a higher sample rate). When it was in the gradual decay state (as opposed to the times when the SNRM was oscillating quickly), picking up the phone would result in a noticeable jump in SNRM and usually also a resync. Does picking up or ringing your telephone cause anything to change? Any noise on the line if you do a quiet line test on 17070 option 2 (or 02087599036 if 17070 has no such option).

[outoftownie]

Thanks for the suggestion, I don't own a phone though... 

I called the line number and while its ringing that doesn't seem to make any difference to SNRM... Ii'll try another modem!

[outoftownie]

I got hold of a Zyxel 8324-B10A, flashed it to the latest official firmware, and hmm, it's not gone well...

HG612 would sync at between 25-30Mbps down with 5dB slowly falling to 2-3dB over a few days before resyncing. Upstream between 2.5 and 3Mbps at a solid 5-6dB.

The Zyxel initially synced at around 25 down and 2.5 up with similar SNRMs to before, but within a couple of hours had resynced itself at 14Mbps down with 10dB SNRM, and 2.5Mbps up at 6.8dB. I basically lost all of D2 band.

Having left it a day or so like that, we had a brief power cut, and it's now syncing at 12.6Mbps/12dB down!

So I now have boatloads of dBs but a significant lack of Mbps 

The connection has now been stable just over 2 days, with downstream never falling below 10.5dB.

Will DLM eventually improve this? At the moment the line is well below the handback threshold (16Mbps)...

I am also going to wire it in the UPS, but don't want to touch it for now...

[siofjofj]

Can you confirm the output of the xdslctl info --vectoring command please? The A2pv6F039v DSL firmware in the latest Zyxel firmware is known to have some problems that result in the sync speed halving on lines with vectoring enabled.

Trying other Zyxel firmwares which have different DSL firmware within them can help, see this thread https://forum.kitz.co.uk/index.php/topic,22306.0.html.

TLDR: Some people with vectoring have solved this issue by using the newer A2pv6F039x6 firmware (a custom build available here https://github.com/johnson442/custom-zyxel-firmware/releases) and others have had success with the older A2pv6F039o1 (which is in the official Zyxel V1.00(AAKL.13)C0 build).

Before going ahead and flashing something, you might want to wait until someone more experienced with vectoring on VDSL comments as I only have ADSL so I'm not the most knowledgeable on this subject.

[re0]

Just a thought, perhaps the DLM had just taken action from the line's previous few days? Not necessarily because of the Zyxel.

[outoftownie]

Thanks for the super-quick responses. Firmware is 1.00(AAKL.28)C0 - so yes I could have duff firmware.

Vectoring is indeed on:

Code: [Select]

Stats recorded 18 Nov 2020 12:57:09

DSLAM type / SW version: BDCM:0xa4a1 (164.161) / v0xa4a1
Modem/router firmware:  AnnexA version - A2pv6F039v.d26a
DSL mode:                VDSL2 Profile 17a
Status:                  Showtime
Uptime:                  2 days 4 hours 32 min 52 sec
Resyncs:                1 (since 16 Nov 2020 07:52:06)

Downstream Upstream
Line attenuation (dB):  27.6 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 12626 2366
SNR margin (dB):        11.8 6.4
Power (dBm):            10.0 7.2
Interleave depth:        2 1
INP:                    50.00 0
G.INP:                  Enabled Not enabled
Vectoring status:        1 (VECT_FULL)

RSCorr/RS (%):          0.0332 0.0672
RSUnCorr/RS (%):        0.0000 0.0000
ES/hour:                0 10.6
I'm going to read the other thread which sounds like a carbon copy of mine - replacing a failing HG612 with a Zyxel...

[outoftownie]

...but also:

Number: 01xxxxxxxxx
The current Downstream IP profile rate is: 10.96
The current Upstream IP profile rate is: 10

(according to the Kitz calculator that profile results in a sync of 11335, and I'm at 12626?)

Hm, Firmware or DLM, Firmware or DLM? Could be both!

[re0]

I imagine the Kitz calculator is doing the calculation on the basis of low ReTX, in which case it would be using ~96.7-96.8% as the basis depending on whether G.INP or not - 10.96 / 0.968 = approx 11.3223 without G.INP. G.INP adds a small overhead, so the figure of 11335 Kbps sync if would be correct in the case of low ReTX.

However, I believe you may have high ReTX. In this case there is a larger overhead. It is no longer ~3.2-3.3%, but rather 8-9%. So doing 10.96 / 0.91 gives 12.04 Mbps, so it is closer to what you expect.

ReTX meaning retransmission, just to clarify. There's information about it on the page you were at - which I presume was this. And you could go here too for more information regarding retransmission.

As for the firmware, I cannot comment since I've never dealt with these devices. Hopefully someone else should be able to assist with that.

[tiffy]

From the stats provided I would say the DS G.Inp re-tx was high profile based on the generally applicable observation, DS INP 50 or greater = re-tx high, 49 or less = re-tx low.

Of course, checking the state of bearer 0 INPRein will positively confirm:
1.00 = re-tx high profile
0.00 = re-tx low profile

As to any possible side effects on particular modems due to vectoring being active, absolutely no idea, vectoring has very rarely been provisioned on the Huawei FTTC cabinets and never on the ECI cab's, further deployment is very, very unlikely now with the extensive FTTP rollout.

[outoftownie]

I've applied Johnson's firmware to the Zyxel (leaving the modem off for 30 mins so as not to anger the DLM gods) and things have improved somewhat - syncing at 21037 downstream but still with what seems a very high downstream SNRM of 10.8dB:

Code: [Select]

Stats recorded 18 Nov 2020 18:08:09

DSLAM type / SW version: BDCM:0xa4a1 (164.161) / v0xa4a1
Modem/router firmware:  AnnexA version - A2pv6F039x6.d26a
DSL mode:                VDSL2 Profile 17a
Status:                  Showtime
Uptime:                  0 hour 22 min 15 sec
Resyncs:                2 (since 16 Nov 2020 07:52:06)

Downstream Upstream
Line attenuation (dB):  30.0 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 21037 2570
SNR margin (dB):        10.6 6.5
Power (dBm):            11.5 7.3
Interleave depth:        4 1
INP:                    48.00 0
G.INP:                  Enabled Not enabled
Vectoring status:        1 (VECT_FULL)

RSCorr/RS (%):          2.3729 0.0005
RSUnCorr/RS (%):        0.0000 0.0000
ES/hour:                0 10.3


xdslctl info --stats
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 2570 Kbps, Downstream rate = 29068 Kbps
Bearer: 0, Upstream rate = 2570 Kbps, Downstream rate = 21037 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State:       L0
Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17a
TPS-TC:                 PTM Mode(0x0)
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        10.8            6.5
Attn(dB):        30.0            0.0
Pwr(dBm):        11.5            7.3

                        VDSL2 framing
                        Bearer 0
MSGc:           -6              58
B:              227             78
M:              1               1
T:              0               27
R:              12              12
S:              0.0000          0.9774
L:              5570            753
D:              4               1
I:              240             92
N:              240             92
Q:              4               0
V:              0               0
RxQueue:                48              0
TxQueue:                12              0
G.INP Framing:          18              0
G.INP lookback:         12              0
RRC bits:               0               24
                        Bearer 1
MSGc:           90              -6
B:              0               0
M:              2               0
T:              2               0
R:              16              0
S:              10.6667         0.0000
L:              24              0
D:              1               0
I:              32              0
N:              32              0
Q:              0               0
V:              0               0
RxQueue:                0               0
TxQueue:                0               0
G.INP Framing:          0               0
G.INP lookback:         0               0
RRC bits:               0               0

                        Counters
                        Bearer 0
OHF:            0               91982
OHFErr:         0               3
RS:             14021088                670183
RSCorr:         339872          5
RSUnCorr:       0               0
                        Bearer 1
OHF:            75579           0
OHFErr:         0               0
RS:             453105          0
RSCorr:         0               0
RSUnCorr:       0               0

                        Retransmit Counters
rtx_tx:         77095017                0
rtx_c:          19              0
rtx_uc:         0               0

                        G.INP Counters
LEFTRS:         0               0
minEFTR:        21044           0
errFreeBits:    389300          0

                        Bearer 0
HEC:            0               0
OCD:            0               0
LCD:            0               0
Total Cells:    49113943                0
Data Cells:     1145132         0
Drop Cells:     0
Bit Errors:     0               0

                        Bearer 1
HEC:            0               0
OCD:            0               0
LCD:            0               0
Total Cells:    0               0
Data Cells:     0               0
Drop Cells:     0
Bit Errors:     0               0

ES:             0               3
SES:            0               0
UAS:            120             120
AS:             1215

                        Bearer 0
INP:            48.00           0.00
INPRein:        1.00            0.00
delay:          0               0
PER:            0.00            13.24
OR:             0.01            38.65
AgR:            21083.64        2608.93

                        Bearer 1
INP:            2.50            0.00
INPRein:        2.50            0.00
delay:          0               0
PER:            16.06           0.01
OR:             47.81           0.01
AgR:            47.81   0.01

Bitswap:        600/656         3/3

Total time = 22 min 15 sec
FEC:            339872          5
CRC:            0               3
ES:             0               3
SES:            0               0
UAS:            120             120
LOS:            0               0
LOF:            0               0
LOM:            0               0
Latest 15 minutes time = 7 min 15 sec
FEC:            142435          3
CRC:            0               2
ES:             0               2
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
LOM:            0               0
Previous 15 minutes time = 15 min 0 sec
FEC:            197437          2
CRC:            0               1
ES:             0               1
SES:            0               0
UAS:            120             120
LOS:            0               0
LOF:            0               0
LOM:            0               0
Latest 1 day time = 22 min 15 sec
FEC:            339872          5
CRC:            0               3
ES:             0               3
SES:            0               0
UAS:            120             120
LOS:            0               0
LOF:            0               0
LOM:            0               0
Previous 1 day time = 0 sec
FEC:            0               0
CRC:            0               0
ES:             0               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
LOM:            0               0
Since Link time = 20 min 13 sec
FEC:            339872          5
CRC:            0               3
ES:             0               3
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
LOM:            0               0
NTR: mipsCntAtNtr=0 ncoCntAtNtr=0
I've got D2 back which explains the speed boost. ReTX is still high based on INPRein. Vectoring is still on downstream (yes I'm on a Huawei cabinet).

I'm encouraged by the line "Max Downstream rate = 28068kbps"!

I think I'm going to leave it at that for now, and see what DLM does over the next few days. Will report back.

Thanks all for your help so far!

[outoftownie]

Hello folks, hope you're all surviving life on Plague Island...

As a recap: I replaced a failing HG612 with a Zyxel, and was getting some very low sync rates, but with very high downstream SNR Margin (12dB or more).

I've waited a few weeks for DLM to do its thing with my line, and each time there's a resync the downstream rate is improving - we're now at:

Code: [Select]

Stats recorded 22 Dec 2020 12:22:13

DSLAM type / SW version: BDCM:0xa4a1 (164.161) / v0xa4a1
Modem/router firmware:  AnnexA version - A2pv6F039x6.d26a
DSL mode:                VDSL2 Profile 17a
Status:                  Showtime
Uptime:                  19 hours 43 min 35 sec
Resyncs:                0 (since 22 Dec 2020 12:21:08)

Downstream Upstream
Line attenuation (dB):  29.7 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 23194 3337
SNR margin (dB):        10.6 5.9
Power (dBm):            11.7 7.2
Interleave depth:        4 4
INP:                    51.00 40.00
G.INP:                  Enabled Enabled
Vectoring status:        1 (VECT_FULL)

RSCorr/RS (%):          0.0069 0.6023
RSUnCorr/RS (%):        0.0000 0.0000
ES/hour:                0 0
(for comparison this is slightly slower downstream than I used to get with my HG612, but higher upstream). I still have double digit downstream SNRM though...

We had the power off yesterday for a while for some electrical work - I powered off the router beforehand and turned it on manually when the supply was stable again, and watched the line resync - see the attached image - downstream syncs at 3.4dB SNRM initially but then rises over a couple of minutes to 10dB.

Does anyone know what that is all about then?! I've never seen such behaviour before...