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Author Topic: FTTC line syncing 8mb below attainable rate and no G.INP  (Read 1163 times)

andyinflitwick

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FTTC line syncing 8mb below attainable rate and no G.INP
« on: October 06, 2017, 02:10:16 PM »

Hi All,

I recently took the plunge and cancelled my Virgin Media connection because of poor network. I decided that i'd rather go for a slower speed service that is reliable rather than an unreliable service. I had Zen's 80/20 FTTC service installed last month on a new line. There's no internal cabling and OR installed a new socket with in-built micro filter. I'm using a Draytek Vigor 2860 router.

Initially my line synced at 63Mb but after 3-4 days this dropped down to 55Mb with light interleaving applied. My SNRM is 5dB. No sign of G.INP being swiched on. The line has been stable and has been up for 89 hours so far. The last disconnect was down to me trying out the supplied Fritzbox router as suggested by Zen, but that synced at an even lower speed.

Can anyone give me any insight as to why my router won't sync at the max attainable rate? Also does anyone have any suggestion as to whether G.INP might be applied by the DLM and in what kind of timescale?

My line stats are below.

Thanks for reading and for any suggestions  :fingers: :)

   
ATU-R Information
      
      
      

      
           Type:   VDSL2
           Hardware:   Annex A
           Firmware:   05-07-04-03-00-07

           Power Mngt Mode:   DSL_G997_PMS_L0
           Line State:   SHOWTIME
           Running Mode:   17A
           Vendor ID:   b5004946 544e0000


      
      
ATU-C Information
      
      
      
          Vendor ID:   b5004244 434da48c [BDCM]


      
      
Line Statistics
           Downstream               Upstream               
Actual Rate   55006   Kbps   19999   Kbps
Attainable Rate   63450   Kbps   21996   Kbps
Path Mode   Interleave   Fast
Interleave Depth   801   1
Actual PSD   7. 9   dB   12. 5   dB
            
            
   Near End                    Far End                   
Trellis   ON   ON
Bitswap   ON   ON
ReTx   0       0   
SNR Margin   5   dB   7   dB
Attenuation   19   dB   22   dB
CRC   19   471
FECS   347600   s   2607   s
ES   2   s   418   s
SES   0   s   0   s
LOSS   0   s   0   s
UAS   31   s   966   s
HEC Errors   0   0
RS Corrections   0   0
LOS Failure   0   0
LOF Failure   0   0
LPR Failure   0   0
NCD Failure   0   0
LCD Failure   0   0
NFEC   254   85
RFEC   16   16
LYSMB   5374
      




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gt94sss2

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #1 on: October 06, 2017, 02:21:47 PM »

Can anyone give me any insight as to why my router won't sync at the max attainable rate? Also does anyone have any suggestion as to whether G.INP might be applied by the DLM and in what kind of timescale?

When you have interleaving applied, the max attainable rate quoted is often incorrect. Assuming you are on a Huawei cabinet it can take several weeks for g.inp to be applied (anything from a few days up to a few months) depending on if/when DLM thinks its needed.
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WWWombat

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #2 on: October 06, 2017, 02:44:11 PM »

As @gt94 says, max attainable goes wrong in these circumstances.

When the line switches from fastpath to interleaved+FEC (without retransmission), then the sync speed drops roughly 10%, while the attainable increases roughly 10%. Roughly - depending on the degree of FEC applied.

If the stats are to believed, then FEC is using 16 bytes out of every 254 as error-correction overhead, or about 6.3%. That is indeed quite light ... but ... I have a recollection of some past cases where statistics in that format aren't quite right, so treat that with caution.

If your line swaps back to fastpath, then I'd expect it to end up syncing inbetween the two current figures - so around 59Mbps. If retransmission was turned on, it might go slightly higher still.
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tiffy

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #3 on: October 06, 2017, 02:45:25 PM »

If you are on a Huawei DSLAM (FTTC cabinet) and have a compatable modem/router (I'am sure your Draytek is) then G.Inp (re-transmission) will be applied eventually, my application took close to 8 weeks from ADSL/VDSL migration, this has been the case for many forum members although some have been lucky and had application earlier.
There are many forum threads to this effect.
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andyinflitwick

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #4 on: February 02, 2018, 08:52:50 PM »

Hi Everyone,

I just wanted to give you an update on my current scenario as well as my frustration getting Zen Internet to help me.

I still don't have G.INP enabled on my line which is annoying, but I can live with it. My Draytek 2860 router supports G.INP and I still remain on an interleaved profile, although the depth has reduced.

My line has progressively got slower and slower. It dropped from a stable 56Mb/20Mb down to 46Mb/17Mb approximately a fortnight ago overnight due to the power tripping out. I have 1 ES in 130 hours of uptime and an SNR of 5. I've attached a copy of my line stats - I'd really appreciate some advice from you guys :)

I've spoken to Zen now three times and each time I'm fobbed off with comments about my internal wiring. This was a brand new line with a new NTE5c Mk4 socket. There is no internal wiring. After arguing about this, I'm told that there's nothing that can be done as my line is "within tolerance". Cross talk has been mentioned twice but the errors look low to me. The original hand back speed on the line checker was 40Mb.

Any idea when DLM might intervene - I'd like to get back to where I was last month at 56Mb! Should I expect more from Zen or are they really powerless?

Thanks for reading and for any tips or advice you can share!

Best regards,

Andy :'(


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ejs

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #5 on: February 02, 2018, 09:14:07 PM »

Do you know what the typical SNRM was immediately before the power cut and speed drop? If, at some time before the power cut, there had been an increase in crosstalk, then the SNRM would have decreased, and later when the modem eventually got rebooted or the VDSL2 re-connected for any other reason, you'd end up at a lower speed and back at the target SNRM.

The change in interleaving depth probably does not indicate any change in the DLM profile, it'll be proportional to the bandwidth, the INP and delay values are the important ones.

I'm not sure Zen strictly speaking couldn't do anything, but sending out Openreach would be very likely to achieve nothing besides costing you if there's no fault.
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skyeci

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #6 on: February 02, 2018, 09:29:20 PM »

prolly get shot down but as you are on huawei I would still try a broadcom modem rather than the draytek . Would the draytek allow you to have a modem in front in bridge mode. might be worth a go..

I am assuming it not a broadcom chipset etc
« Last Edit: February 02, 2018, 09:31:54 PM by skyeci »
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andyinflitwick

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #7 on: February 02, 2018, 09:32:37 PM »

Do you know what the typical SNRM was immediately before the power cut and speed drop? If, at some time before the power cut, there had been an increase in crosstalk, then the SNRM would have decreased, and later when the modem eventually got rebooted or the VDSL2 re-connected for any other reason, you'd end up at a lower speed and back at the target SNRM.

The change in interleaving depth probably does not indicate any change in the DLM profile, it'll be proportional to the bandwidth, the INP and delay values are the important ones.

I'm not sure Zen strictly speaking couldn't do anything, but sending out Openreach would be very likely to achieve nothing besides costing you if there's no fault.
Thanks ejs. The SNRM has always usually been 5dB. After a reboot, it normally syncs with an SNRM of 6db and then drops to 5dB after a couple of days.

My frustration with Zen Support is that they can't (or won't) offer an explanation or even give an idea as to when the situation might change via DLM. Yes, I understand that 46Mb is "within tolerance", but this situation (and that of others) is a joke. Openreach should offer better tools to ISPs using their products.
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andyinflitwick

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #8 on: February 02, 2018, 09:33:34 PM »

prolly get shot down but as you are on huawei I would still try a broadcom modem rather than the draytek . Would the draytek allow you to have a modem in front in bridge mode. might be worth a go..

I am assuming it not a broadcom chipset etc

Thanks skyeci. It's something that I'm considering. Draytek users a Lantiq AFAIK.
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skyeci

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #9 on: February 02, 2018, 09:35:58 PM »

I have a spare vmg8324 if you want to try something if its possible with the 2860.. going cheap  ;)
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http://www.mydslwebstats.co.uk user upload ID skyECI (using win10/dsl stats)

j0hn

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #10 on: February 03, 2018, 02:46:27 PM »

There's absolutely nothing Zen can do.
The DLM system is entirely automated. ISP's have no influence on it at all.
If your speed is within the estimates at the time of sign up there's nothing OpenReach could do about it either.
Slowly degrading sync speed is an unavoidable consequence of crosstalk/interference from neighbouring lines.

Your line will probably sync about 51-52Mb when G.INP is eventually applied.
If it remains stable then the target snrm may be reduced, giving a few Mb more.

Zen can't tell you when G.INP might be applied, nobody can unfortunately.
It's usually within a couple of weeks but there's a number of lines where it takes significantly longer. It took 11 weeks to be applied to my line. Then there's a very small percentage of lines that DLM seems to ignore and never applies G.INP.
That may be related to an issue where certain modems break DLM on every line on the DSLAM/cabinet.
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kitz

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #11 on: February 03, 2018, 08:46:03 PM »

Quote
My Draytek 2860 router supports G.INP and I still remain on an interleaved profile,

Just checking.   Out of the box it doesnt.   Draytek released updated f/w which makes it compatible with G.INP.    Have you got the updated f/w?
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kitz

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #12 on: February 03, 2018, 08:52:33 PM »

Quote
Cross talk has been mentioned twice but the errors look low to me.

Crosstalk doesn't generate errors.   Its a constant which is there all the time... and for as long as the disturber's line is connected. 

I've so far lost the best bit of 40Mbps headline rate to FeXT, but nothing I can do.   
My error rate is still exactly the same and my SNRM just as steady.  The only visible signs of crosstalk is that you may get an upwards (better) SNRM spike when they reboot their modem.    You can sometimes see it in QLN graphs too. 
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andyinflitwick

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #13 on: February 04, 2018, 09:03:19 AM »

Just checking.   Out of the box it doesnt.   Draytek released updated f/w which makes it compatible with G.INP.    Have you got the updated f/w?

Thanks Kitz - I'm running 3.8.5.3_BT with modem firmware 576D17 which supposedly both support G.INP. I've ordered a Zyxel router - I'm going to give that a try to see if running with a Broadcom chipset will help. For months I had a stable 56Mb/20Mb and I just want to get back to that  :fingers:
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kitz

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Re: FTTC line syncing 8mb below attainable rate and no G.INP
« Reply #14 on: February 04, 2018, 09:41:55 AM »

np - I dont recall the f/w versions, but thought it may be worth a mention just in case.

Good luck with the BCM modem :)
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