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Irby
(knowledge is power) Fri 20-May-16 10:39:09

Line rate vs actual net data rate

[link to this post]

Hi all,

Comments / advice please on the below. On day one of my install I had an attainable data rate of 71mbps, but after the install I was moving furniture around and had to unplug the router, on turning back on again I lost about 10mbps of attainable data rate.

Over the last few days, the attainable data rate has started to creep back up gain but the line rate is staying around 53mbps. Those with more experience with VDSL than me (most of you), what is likely to happen next and I suppose I should not turn off the router or unplug it!?

Thanks,

Text

============================================================================
    VDSL Training Status:   Showtime                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a            Traffic Type:   PTM Mode
             Link Uptime:   1 day: 3 hours: 13 minutes============================================================================
       VDSL Port Details       Upstream         Downstream               Line Rate:     17.655 Mbps       53.258 Mbps
    Actual Net Data Rate:     17.624 Mbps       53.168 Mbps          Trellis Coding:         ON                ON
              SNR Margin:        6.7 dB            8.3 dB            Actual Delay:          0 ms             12 ms
          Transmit Power:        7.6 dBm          13.0 dBm           Receive Power:       -7.4 dBm         -11.5 dBm
              Actual INP:        0.0 symbols       4.0 symbols       Total Attenuation:       15.1 dB           24.5 dB
Attainable Net Data Rate:     17.609 Mbps       68.393 Mbps============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.0    33.0    49.0     N/A    14.6    38.2    58.2   
Signal Attenuation(dB):  8.0    32.3    47.9     N/A    21.6    37.7    57.4           SNR Margin(dB):  6.8     6.8     6.7     N/A     8.2     8.3     8.4   
   Transmit Power(dBm):  0.5   -11.0     6.6     N/A    10.0     7.8     5.9   ============================================================================

MHC
(sensei) Fri 20-May-16 11:50:15

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

First questions: Has your cabinet been recently enabled? And where you one of te first? If so, it could well be due to cross talk from other installs.

How far from teh cabinet - line length are you?

When you moved everything around, did you move any power supplies or put te modem behind a TV or put the TV right next to te master socket?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

M H C

taurus excreta cerebrum vincit

RobertoS
(elder) Fri 20-May-16 12:05:50

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

It wasn't a good idea to have moved the router during the first two days, but that's history. (The ten day thing is a myth, but on FTTC up to the end of the day after installation/first connection is a bit sensitive).

As the downstream noise margin is well above 8dB now then I would do a single reboot of the router. During the day - but not once it gets to late afternoon.

_{^{Kindness isn't going to cure the world of all its awfulness but it's a good place to begin. Daisy Ridley.}}
My broadband basic info/help site - www.robertos.me.uk. Domains, site and mail hosting - Tsohost.
Connection - AAISP Home::1 80/20. Sync 59240/14753kbps @ 600m. - BQM

MrSaffron
(staff) Fri 20-May-16 12:17:57

Re: Line rate vs actual net data rate

[re: RobertoS] [link to this post]

It has to remembered that xDSL modems will not drop the line to resync to a higher speed even if the data says its possible, they rely on something external doing this, i.e. usually a human.

So as suggested a single reboot will let modem renegotiate things and may give back the speed.

Andrew Ferguson, [email protected]
www.thinkbroadband.com
See if your ADSL stats are any good | UK broadband availability checker | Speed test for PC, tablets and mobiles

The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.

Irby
(knowledge is power) Fri 20-May-16 13:21:46

Re: Line rate vs actual net data rate

[re: MrSaffron] [link to this post]

Rebooted as suggested and now it's a bit worse. I think I'll just leave it alone tongue

In answer to other questions:

Yes cabinet only recently enabled
Approx 10 customers live on the cabinet before me
When I say moved stuff around, it was really only unplugging the router to allow some stuff to be moved.
300m approx from cabinet

Text

============================================================================
    VDSL Training Status:   Showtime                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 0 hour: 8 minutes============================================================================
       VDSL Port Details       Upstream         Downstream               Line Rate:     17.442 Mbps       52.262 Mbps
    Actual Net Data Rate:     17.413 Mbps       52.173 Mbps          Trellis Coding:         ON                ON
              SNR Margin:        6.5 dB            8.2 dB            Actual Delay:          0 ms             13 ms
          Transmit Power:        7.6 dBm          13.0 dBm           Receive Power:       -7.5 dBm         -11.7 dBm
              Actual INP:        0.0 symbols       4.0 symbols       Total Attenuation:       15.2 dB           24.7 dB
Attainable Net Data Rate:     17.364 Mbps       65.890 Mbps============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.1    33.2    49.4     N/A    14.7    38.5    58.7   
Signal Attenuation(dB):  8.1    32.5    48.6     N/A    21.7    38.0    58.8           SNR Margin(dB):  6.5     6.5     6.5     N/A     8.1     8.2     8.3   
   Transmit Power(dBm):  0.5   -10.8     6.6     N/A     9.9     8.1     5.8   ============================================================================

trolleybus
(experienced) Fri 20-May-16 13:46:25

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

All interesting stuff and I can indeed get the same kind of information for my connection. With these statistic responses I would like to know for each shown what is good, ugly and ideal. Anyone out there that can de-mystify this information? Perhaps there is a URL somewhere on this matter that I cam immerse myself in?

Andrue
(eat-sleep-adslguide) Fri 20-May-16 13:57:15

Re: Line rate vs actual net data rate

[re: MrSaffron] [link to this post]

In reply to a post by MrSaffron:
It has to remembered that xDSL modems will not drop the line to resync to a higher speed even if the data says its possible, they rely on something external doing this, i.e. usually a human.

DLM can force a resync to a higher speed as well, can't it?

I always assumed that if you leave an FTTC modem alone it will generally end up at the 'right' speed anyway.

---
Andrue Cope
Brackley, UK

ping78
(newbie) Fri 20-May-16 14:00:51

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

Hi Irby,

No notice that your downstream attenuation is 24.5 and can manage a line rate of 53Mbps.

I went live last friday and am connected to the same cabinet as you, have a downstream attenuation of 26 dB and can only manage a line rate of 34Mbps and cannot be more than 500 Meters away from the cabinet following the cable route.

Plusnet have performed all of the checks, confirmed the line is stable but below speed estimates and sent an Openreach engineer to check the line. All Ok there - In fact the JSDU tester the engineer used could sync any higher than 28Mb even after a profile reset.

What VDSL modem are you using? - I have the Draytek Vigor 130 which I have been pretty impressed with so far but cannot work out why my line refuse to sync at a higher rate given the similar dB Attenuation you have.

deleted
(deleted) Fri 20-May-16 14:03:24

Re: Line rate vs actual net data rate

[re: Andrue] [link to this post]

In reply to a post by Andrue:
In reply to a post by MrSaffron:
It has to remembered that xDSL modems will not drop the line to resync to a higher speed even if the data says its possible, they rely on something external doing this, i.e. usually a human.
DLM can force a resync to a higher speed as well, can't it?

Yes of course it can.

RobertoS
(elder) Fri 20-May-16 14:04:34

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

That's strange, as the noise margin hasn't reverted to 6dB. The FTTC DLM doesn't adjust noise margins in order to control things the way the ADSLx ones do. I could have understood it if the Line Rate had stayed roughly the same, but not a fall.

Re your 300m from the cabinet, either your cabling distance is much greater or it's got a lot of aluminium in it. I'm almost exactly 600 cable-metres from the cabinet with an attenuation of 19.8dB and a higher sync than you. Plus band status:-

VDSL Band Status        U0     U1    U2     U3      U4     D1      D2      D3

Line Attenuation(dB):   5.3    30.0  45.5   N/A     N/A    14.6    37.3    58.3
Signal Attenuation(dB): 5.3    29.0  44.2   N/A     N/A    19.3    37.1    58.4
SNR Margin(dB):         6.0    6.0   6.0    N/A     N/A    5.8     5.8     5.8
TX Power(dBm):          0.6   -12.7  6.3    N/A     N/A    11.2    8.1     5.4

Irby
(knowledge is power) Fri 20-May-16 14:08:06

Re: Line rate vs actual net data rate

[re: ping78] [link to this post]

I'm using a Zyxel VMG1312-B10D as supplied by Zen.

RobertoS
(elder) Fri 20-May-16 14:08:21

Re: Line rate vs actual net data rate

[re: Andrue] [link to this post]

In reply to a post by Andrue:
In reply to a post by MrSaffron:
It has to remembered that xDSL modems will not drop the line to resync to a higher speed even if the data says its possible, they rely on something external doing this, i.e. usually a human.
DLM can force a resync to a higher speed as well, can't it?

Yes.

I always assumed that if you leave an FTTC modem alone it will generally end up at the 'right' speed anyway.

No. Only if DLM chooses to act one way or the another, which it doesn't necessarily do just for the sake of a difference we might find desirable but isn't really important. Like a couple of Mbps gain when we have 60Mbps already smile

Irby
(knowledge is power) Fri 20-May-16 15:41:37

Re: Line rate vs actual net data rate

[re: RobertoS] [link to this post]

FWIW, I'm delighted with the speed I can have, this is just the novelty stage when I'm wanting to optimise and get the best out of what I can get.

A few meg here or there won't really matter, right now I can stream a few HD channels downstairs while downloading big files and working. But if I was missing something easy to fix, then I'd obviously want to do it.

Irby
(knowledge is power) Sun 22-May-16 09:28:13

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

Actual speed now matching attainable, apparently. So the speed will it seems creep up again.

Text

============================================================================
    VDSL Training Status:   Showtime                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a            Traffic Type:   PTM Mode
             Link Uptime:   0 day: 2 hours: 4 minutes============================================================================
       VDSL Port Details       Upstream         Downstream               Line Rate:     18.186 Mbps       63.261 Mbps
    Actual Net Data Rate:     18.155 Mbps       63.262 Mbps          Trellis Coding:         ON                ON
              SNR Margin:        6.1 dB            6.0 dB            Actual Delay:          0 ms              0 ms
          Transmit Power:        7.6 dBm          13.1 dBm           Receive Power:       -7.3 dBm         123.3 dBm
              Actual INP:        0.0 symbols      52.0 symbols       Total Attenuation:       15.0 dB          4294967186.4294967294 dB
Attainable Net Data Rate:     18.076 Mbps       63.436 Mbps============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.0    32.8    48.6     N/A    14.5    37.9    57.8   
Signal Attenuation(dB):  8.0    32.4    48.0     N/A    21.6    37.8   -116.9           SNR Margin(dB):  5.7     6.1     6.1     N/A     5.9     5.9     6.1   
   Transmit Power(dBm):  0.6   -10.7     6.6     N/A    10.0     7.8     6.4   ============================================================================

RobertoS
(elder) Sun 22-May-16 10:42:20

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

Interleaving has been turned off. DLM resync's the line when it does that. Actual rises, attainable falls. We don't know why attainable falls, but it's normal. And vice versa.

deleted
(deleted) Sun 22-May-16 10:49:19

Re: Line rate vs actual net data rate

[re: Irby] [link to this post]

@Irby

In the variety of stats you have given us, look at the progression of two values in particular - neither of which is the speed.

Check downstream "actual delay" and "Actual INP".

Original install: unknown
Fri 10:39: delay=12ms, INP=4 symbols
Fri 13:21: delay=13ms, INP=4 symbols
Sun 09:28: delay=0ms, INP=52 symbols

In the first two readings, you are on an interleaved profile - and both the delay (of 12ms) and INP (of 4 symbols) are higher than standard DLM intervention used to be.

If, when you were originally installed, you were on a free profile, it would be easy to understand a loss of 10Mbps (edit: of /actual/ line speed) being down to DLM intervention. Do you have any data from the initial installation, rather than just /after/ the loss of attainable speed? And what happened to /actual/ speed over that time?

NB: Once DLM has intervened to turn on old-style FEC+interleaving, you lose some of your /actual/ sync speed, but modems then seem to report a higher /attainable/ speed. The difference is accounted for by the extra parity data being transmitted to provide error correction ... but the lesson to be learnt is that the attainable can never be fully attained when DLM relents. Quoting the /actual/ speed helps more.

In a case like this, where DLM appears to have intervened, and intervened quite heavily, the statistics that you need to monitor are the ones with all the error information - the FEC count, the CRC count, the ES count, the retransmission counter, the retransmission failure counter, and the LEFTRS counter.

Whatever has happened with the error counters, however, DLM has now decided to remove the heavy FEC+interleaving and turn on G.INP on your line (the latest INP value of 40+ seems to signify this). This has returned 10Mbps of actual speed.

The activation of G.INP after 48 hours is a fairly standard step for DLM these days.

In reply to a post by Irby:
I'm using a Zyxel VMG1312-B10D as supplied by Zen.

If you want to monitor the line statistics, I believe this modem is supported by DSLstats:
http://forum.kitz.co.uk/index.php/board,46.0.html

That would also allow the stats to be uploaded to MyDslWebStats.

Edited by deleted (Sun 22-May-16 11:04:03)

Irby
(knowledge is power) Sun 22-May-16 13:07:29

Re: Line rate vs actual net data rate

[re: deleted] [link to this post]

Thanks for the detailed reply, really anything over 50mbps is just gravy smile

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