New VDSL Connection with sync, attn, and SNR rates all over the show

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scottr

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#227484 9-Jan-2018 10:28

Hi all, have a question I hope someone might be able to help out with. We had VDSL installed prior to christmas (moved house to one ~18 years old) and my sync rates seem to be all over the show. I don't know whether or not this is DLM doing it's thing as it seems a bit extreme to me.

Bit of background:
I'm about 160m walking distance to the cabinet (understand cable length could be considerably longer) however my attenuation and sync speed seem to jump all over the place.

When we moved in I cleaned up the internal wiring as best I could by removing all jackpoints except one to the office. Unfortunately I couldn't replace the cables as there's not really enough roof-space to do it myself. Removing all the jack-points bar one brought my speed from 12mb to ~30mb. I seem to get roughly the same speed in the office as I do when connected to the jack-point closest to the ETP (~4m straight cable) so I've left it in the office.

I was using a fritzbox for a couple of weeks, however it went on the 'fritz' and stopped being able to reconnect DSL for hours at a time (it was suspect before we moved so not surprised). During the time we used it and it worked it sat pretty solidly at 30/5 at ~attn of 22db and SNR of 12db, although sometimes it would reconnect at 50ish/10 for a small period of time.

Have since switched to the ISP provided NF4V which seemed to sync either at 15/5 or 28/9 without a change in attn of ~25db or snr of 12db. Unsure why it's sometimes half as none of the other stats seems to change. I'd left it at 28/9 and it was solid for a few days until the resync listed below.

Yesterday ~3:20pm DSL resync'd itself to 52/11 @ attn of 13db and an SNR of 12db and was solid through to this morning at 4:20am where it's resych'd itself at 5/1 with an attn of 6.5db and an SNR of 28db. Unsure as to what's happened here at the attn is lower than i've ever seen, but SNR is crazy high. SS of DMT as below.

Is this DLM in action, trying a bunch of different stuff to test the quality of the line, or a symptom of a super dodgy line?

Any help would be appreciated!

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#1932628 9-Jan-2018 11:03

id say a dodgy line

@hio77 is the man for diagnostics on VDSL

hio77

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#1932744 9-Jan-2018 12:38

The fact that your modem is resyncing to such a high snr would tell me it's detecting instability and trying to stabilize.

Your bin allocation against hlog doesn't look all too healthy, overall i would be looking at your internal wiring first.

Past that, LQD + Fault non ssrt if your not competent in reading the output.

Please drop the use of DMT tools, opt for DSLstat.

http://dslstats.me.uk/

It will give you a far more readable (VDSL friendly) output.

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#1932761 9-Jan-2018 12:56

DSLstats is great :)

scottr

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#1932773 9-Jan-2018 13:09

Hi all, thanks for the responses. Have rebooted the modem and it's gone back to 52/11 (copied SS from DMT for comparison). Intrigued as to why it dropped by a factor of 10 though. If it keeps doing this I'll get the internal wiring replaced although I'm not sure what could be happening that could cause such a drop.

Happy to post DSLStat details if you're interested?

Thanks.

hio77

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#1932775 9-Jan-2018 13:14

dsl stats would be far better than DMT (it's only really made for ADSL)

Your signal seems to be atteuating past the ADSL mark, i would be looking at if you don't happen to have an old ADSL2+ style splitter installed there.

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scottr

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#1932813 9-Jan-2018 13:42

Yeah it looks like the graph just stops in DMT as it's built for adsl only. Is that what you're talking about? There's no adsl filter that I've found when digging about in the etp/sockets/roof of the house. Is there a particular graph/set of graph's you're interested in from dslstats?

Couple below that correlate with the DMT graphs.

Bitloading

SNR per tone

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hio77

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#1932825 9-Jan-2018 13:45

Looks like your dslstat has defaulted to 30a.

Your line is looking very clear right now for an 8b profile.

Dodgy splitter was just a quick guess as it can often cause the symptoms your experiencing.

HLOG and QLN would be nice to see, I suspect the fault won't show itself till you resync back down low (i'd leave dslstat going and it will capture the error rates etc - which i'd also check out)

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scottr

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#1932832 9-Jan-2018 13:50

It's the default graph size when setting to VDSL2 (wasn't on VDSL2 by default). Left it as it to show not much else was going on up higher.

HLOG and QLN as attached. Will leave it running for a while and report back if anything else dodgy happens. Thanks!

hio77

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#1932833 9-Jan-2018 13:51

At this moment, that's looking reasonably clean. i honestly based on seeing that would at first punt expect a line to go 17a and peg.

Based off that, i suspect your fault may be a loose leg, high resistance join it the such. as temperature drops fault occurs then comes right.

Total pain in the ass to get resolved sometimes.

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scottr

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#1933322 10-Jan-2018 08:04

Hmm connection dropped down to 16/0.5 again last night at 4:40am this time. I manually resync'd it this morning at ~7:30am and it's back at a solid 52/11.

Looking at the modem logs I can see the connection dropped at 4:40:32am, reconnected at 4:40:50am at 52/11, it dropped again at 4:41:20am, and back up again at 4:41:43am at 16/0.5.

Something fishy's definitely going on. Any ideas where to from here?

Connection speed graph at 5:05am

Bitloading at 5:05am:

HLog at 5:05am:

QLN at 5:05am:

CRC at 5:05am

FEC at 5:05am

SES at 5:05am:

Some other interesting graphs from the same time...

SNR Margin at 5:05am:

SNR Per Tone at 5:05am:

SNR Per Band (Downstream) at 5:05am:

SNR Per Band (Upstream) at 5:05am:

After I manually resync'd this morning it looks like this (less graphs for brevity):

Connection speed graph at 7:50am:

Bitloading at 7:50am:

HLog at 7:50am:

QLN at 7:50am:

Jase2985

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#1933325 10-Jan-2018 08:12

you dont have an alarm thats trying to dial out or anything like that?

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scottr

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#1933356 10-Jan-2018 08:56

Hi, no i’ve disconnected the comms cables from that, as well as the run of cable from the jackpoint to the alarm itself. I did wonder if it’s something like that though, but there’s nothing else wired in

scottr

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#1951194 3-Feb-2018 17:51

For those interested this ended up being a dodgy connection in one of cable junction points outside of the house under the shared driveway.

Ended up with over 60 disconnections in a day when it rained a week or so back so raised a fault and the chorus tech came out and re-jumpered/seated the wires. It's been rock solid @ 52/11 mb since.

Haven't seen any SNR margin or vdsl profile changes after just over a week of uptime so assume this is likely the best i'll get. Pretty happy with it though, thanks everyone for your help.

Current connection stats below.

adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 11208 Kbps, Downstream rate = 52504 Kbps
Bearer: 0, Upstream rate = 11237 Kbps, Downstream rate = 52516 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 8b
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 12.1 5.5
Attn(dB): 13.1 0.0
Pwr(dBm): 15.1 -12.0