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Author Topic: SNR Margin going up and down constantly  (Read 1470 times)

kitz

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Re: SNR Margin going up and down constantly
« Reply #15 on: August 22, 2018, 11:59:36 AM »

Quote
I am roughly 400 - 500m from the cabinet

You may be correct that it is ambitious...  but if that is a brand new cab and not many on it yet, then at a stretch its possible until crosstalk gets a hold.  To give an indication when I first went live my max attain was ~40 Mbps more than it is now.


Quote
Previous 15 minutes time = 15 min 0 sec
FEC:            605760          3
CRC:            9408            0
ES:             484             0
SES:            183             0

Latest 1 day time = 12 hours 57 sec
FEC:            79253419                11
CRC:            398463          3
ES:             23034           3
SES:            8962            0

I'm afraid that is not good at all :'(
You are getting a heck of a lot of Errored Seconds (ES).   DLM allows ~2880 per day before it will take action.
Combination of the SNRM oscillations and the amount of error suggests that there is some sort of noise ingress on that line.   I'm afraid I can't identify anything else from the graphs though.

I think you should get your ISP involved.  Send them a copy of your SNRM graph, Zen are astute enough to know that is not a normal graph and also how many Errors you are getting.  I'd also send a copy of the results from the BR checker as it strengthens your case. 

Good luck and please do let us know how you get on.
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bobmoss

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Re: SNR Margin going up and down constantly
« Reply #16 on: August 22, 2018, 02:23:26 PM »

OK, I think I may have a faulty modem??

After I posted my last stats I noticed that when running a ping to bbc.co.uk I was getting packet drops every 5 or 6 pings (which I guess would be consistent with all the errors).

So I decided to swap the modem out with my original Vigor 130. It's only been an hour but I've not had any packet drops and my speed test speeds have gone up.

I've been checking every few minutes and the modem is constantly reporting a SNR of 4. It's not moved at all. My only concern is that it always a whole number so is it rounding? And is it reporting the actual SNR or the desired/target SNR?

Anyway, I've posted my stats below. To my eye they look so much better with not a lot of errors?



> vdsl status
  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
   Running Mode            :      17A       State                : SHOWTIME
   DS Actual Rate          : 50855000 bps   US Actual Rate       : 10866000 bps
   DS Attainable Rate      : 51535532 bps   US Attainable Rate   : 10848000 bps
   DS Path Mode            :        Fast    US Path Mode         :        Fast
   DS Interleave Depth     :        1       US Interleave Depth  :        1
   NE Current Attenuation  :       22 dB    Cur SNR Margin       :        4  dB
   DS actual PSD           :     6. 6 dB    US actual PSD        :    13. 0  dB
   NE CRC Count            :        0       FE CRC Count         :      116
   NE ES Count             :        0       FE  ES Count         :      107
   Xdsl Reset Times        :        0       Xdsl Link  Times     :        1
   ITU Version[0]          : b5004946       ITU Version[1]       : 544e0000
   VDSL Firmware Version   : 05-07-06-0D-01-07   [with Vectoring support]
   Power Management Mode   : DSL_G997_PMS_L0
   Test Mode               : DISABLE
  -------------------------------- ATU-C Info ---------------------------------
   Far Current Attenuation :       34 dB    Far SNR Margin       :        5  dB
   CO ITU Version[0]       : b5004244       CO ITU Version[1]    : 434da48c
   DSLAM CHIPSET VENDOR    : < BDCM >

> vdsl status more
  ---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
                  Near End        Far End    Note
 Trellis      :      1               1
 Bitswap      :      1               1
 ReTxEnable   :      0               1
 VirtualNoise :      0               0
 20BitSupport :      0               0
 LatencyPath  :      0               0
 LOS          :      0               0
 LOF          :      0               0
 LPR          :      0               0
 LOM          :      0               0
 SosSuccess   :      0               0
 NCD          :      0               0
 LCD          :      0               0
 FECS         :      0             174 (seconds)
 ES           :      0             107 (seconds)
 SES          :      0               0 (seconds)
 LOSS         :      0               0 (seconds)
 UAS          :     28            1598 (seconds)
 HECError     :      0               0
 CRC          :      0             116
 RsCorrection :      0               0
 INP          :      0             215 (symbols)
 InterleaveDelay :      0              14 (1/100 ms)
 NFEC         :    254              32
 RFEC         :     16              16
 LSYMB        :   2918              16
 INTLVBLOCK   :    127              32
 AELEM        :      0            ----

>



> vdsl status counts
 [ Counters: Showtime ]
                  Near End        Far End    Note
 ElapsedTime  :   5544            5544 (seconds)
 CRC          :      0             116
 FEC          :      0             174
 HEC          :      0               0
 CRC_P        :      0               0
 CRCP_P       :      0               0
 CVP_P        :      0               0
 NCD          :      0               0
 LCD          :      0               0
 ES           :      0             107
 SES          :      0               0
 LOSS         :      0               0
 UAS          :      0               0
 LOFS         :      0               0

 [ Counters: 15Min ]
                  Near End        Far End    Note
 ElapsedTime  :    146             146 (seconds)
 CRC          :      0               0
 FEC          :      0               0
 HEC          :      0               0
 CRC_P        :      0               0
 CRCP_P       :      0               0
 CVP_P        :      0               0
 NCD          :      0               0
 LCD          :      0               0
 ES           :      0               0
 SES          :      0               0
 LOSS         :      0               0
 UAS          :      0               0
 LOFS         :      0               0

 [ Counters: 1DAY ]
                  Near End        Far End    Note
 ElapsedTime  :   6446            6446 (seconds)
 CRC          :      0             116
 FEC          :      0             174
 HEC          :      0               0
 CRC_P        :      0               0
 CRCP_P       :      0               0
 CVP_P        :      0               0
 NCD          :      0               0
 LCD          :      0               0
 ES           :      0             107
 SES          :      0               0
 LOSS         :      0               0
 UAS          :      0               0
 LOFS         :      0               0
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kitz

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Re: SNR Margin going up and down constantly
« Reply #17 on: August 22, 2018, 05:08:27 PM »

That sync is also much better 50.8Mb compared to 46Mbps.

I note that you have 107 ES since up time of 6446 (1hr 47:25), yet none in the past 15min bin... so without doubt it has stopped. 

Quote
I think I may have a faulty modem??

It's looking possible.   However I have just had another thought. You havent had any power surges or power cuts have you?

I'm actually kicking myself now that I didn't suggest earlier to power down the modem and let it rest a while.
We have seen many modems which will flap after a power surge and start racking up lots of errors.  It doesnt clear until you completely power down the modem.

If it was a power surge, then that would also explain why we couldn't see anything in QLN and hlog as those are taken during initialisation.
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bobmoss

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Re: SNR Margin going up and down constantly
« Reply #18 on: August 22, 2018, 05:19:02 PM »


It's looking possible.   However I have just had another thought. You havent had any power surges or power cuts have you?


Now, funny you should mention that, we had a power cut last night at about 10.30pm. So that could account for all the errors this morning. But it wouldn't account for the SNR going up and down like crazy the two days before.

I've just ordered a 2nd hand HG612, so as soon as that arrives I'll plug that it and get it logging again and we can see if we get similar SNR issues.

I've just found the "Average error rates per day" text file that DSL stats produces. Here it is:

22 Aug 2018
CRC errors per hour: 32785 Down, 0.20 Up
FEC errors per hour: 7095723 Down, 0.71 Up
HEC errors per hour: 0 Down, 0 Up
ES per hour: 1913 Down, 0.20 Up
SES per hour: 746 Down, 0 Up
Total ES in the day: 18732 Down, 2 Up

21 Aug 2018
CRC errors per hour: 1511 Down, 0.72 Up
FEC errors per hour: 403075 Down, 1.22 Up
HEC errors per hour: 0 Down, 0 Up
ES per hour: 82.2 Down, 0.63 Up
SES per hour: 32.4 Down, 0 Up
Total ES in the day: 1949 Down, 16 Up

20 Aug 2018
CRC errors per hour: 0 Down, 1.05 Up
FEC errors per hour: 130038 Down, 2.59 Up
HEC errors per hour: 0 Down, 0 Up
ES per hour: 0 Down, 0.91 Up
SES per hour: 0 Down, 0 Up
Total ES in the day: 0 Down, 15 Up

[Moderator edited to fix a typo. (s/HG621/HG612)]
« Last Edit: August 22, 2018, 06:27:41 PM by burakkucat »
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kitz

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Re: SNR Margin going up and down constantly
« Reply #19 on: August 22, 2018, 05:51:18 PM »

Quote
we had a power cut last night at about 10.30pm. So that could account for all the errors this morning.

From the previous stats, it does look like it.

Quote
But it wouldn't account for the SNR going up and down like crazy the two days before.

It's possible if you had a surge a few days previously, yes it can cause the SNRM to flap which doesn't clear until the modem has had a full power down. 
There's several times where we have seen it (even on my own line) which is why I'm kicking myself that I didn't recall earlier.
B*cat will back me up that it does occasionally occur and recommended action is to give the port time to rest.

Its perhaps also worth looking at the SNRM per Band for the downstream to see if there is any of the subtone bands more affected than the others.

I may have suggested a fresh reboot if I'd seen it was evenly spread across all 3 bands, but that's easy for me to say now with the benefit of hindsight.

---
At some point in the future it may be worth just giving the Zyxel another test run before permanently ditching it in the bin, just to make sure it wasn't a power issue.   
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burakkucat

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Re: SNR Margin going up and down constantly
« Reply #20 on: August 22, 2018, 06:26:03 PM »

B*cat will back me up that it does occasionally occur and recommended action is to give the port time to rest.

Yes, I agree . . . whilst also pondering why I did not think of it. :paperbag:
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Weaver

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Re: SNR Margin going up and down constantly
« Reply #21 on: August 22, 2018, 09:50:05 PM »

And a rather belated filte oirbh bhuamsa since I am also in Skye, in Heasta. Welcome to the forum.  ;D
« Last Edit: August 22, 2018, 10:08:49 PM by Weaver »
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bobmoss

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Re: SNR Margin going up and down constantly
« Reply #22 on: August 29, 2018, 02:00:57 PM »

And a rather belated filte oirbh bhuamsa since I am also in Skye, in Heasta. Welcome to the forum.  ;D

Thank you! We only moved up here in March and are loving it! And also finding that everyone is so friendly and welcoming.
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bobmoss

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Re: SNR Margin going up and down constantly
« Reply #23 on: August 29, 2018, 02:14:18 PM »

So an update on this issue as it may be useful for other people.

I put the Vigor modem back in and my connection has been rock solid. The SNR slowly went down from 6 to 3 over a few days and my connection speed has slowly gone up to 51917000bps. So I assume this is the DSLAM putting me on a 3dB profile.

Today I received my HG612, so after installing the unlocked firmware, configuring (in PPPOE bridge mode) and installing it I can now run DSL stats again. Looking at my graphs below, the SNR is now holding at 3.4dB, the QLN looks much better than before (less spikes) and even the Bitloading looks better (using a few extra tones at the end).

So either my other modem was faulty or the power outage caused an issue - either way the HG612 is giving me slightly better stats so I think I'll be sticking with it for the moment. I'll keep an eye on the errors level but at the moment it all looks OK.

One interesting thing, as I thought, the Draytek only reports whole numbers for SNR, so I still don't know if that's actual SNR or a target SNR.

Thanks for your help everyone!.

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j0hn

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Re: SNR Margin going up and down constantly
« Reply #24 on: August 29, 2018, 05:05:40 PM »

It would be worth trying the Zyxel again at some point.
If you see the same again then the modem is duff.

As Kitz mentioned it could have been that the DSLAM port just needed a time out.

I've seen similar on Kitz line but the oscillating SNRM seemed much more uniform on her line. I believe the consensus at the time was it was an ECI DSLAM thing and I didn't spot the relevance.

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kitz

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Re: SNR Margin going up and down constantly
« Reply #25 on: August 30, 2018, 08:46:37 PM »

It would be worth trying the Zyxel again at some point.
If you see the same again then the modem is duff.
As Kitz mentioned it could have been that the DSLAM port just needed a time out.

Agreed.  I wouldn't write it off just yet.

Quote
I've seen similar on Kitz line but the oscillating SNRM seemed much more uniform on her line. I believe the consensus at the time was it was an ECI DSLAM thing and I didn't spot the relevance.

I don't think its specific to ECI's.    I've been seeing these sort of issues after power outages since the days of Maxdsl and when I was using a BTVoyager 2100 something.   I'm pretty certain if you search back far enough I reported it occurring when I was having work done on the house and the electrician just switched off power at the mains rather than me doing a power down first.  After coming back up it would have a hissy with SNRM jumping all over the place and a lower than normal sync.   Back then it was harder to spot as there wasn't any such thing as  DSLstats, but I was one of the few who recorded using custom scripts and MRTG which was a PITA to set up. :/
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