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Author Topic: Close to cab (100m) but unusually slow?  (Read 9517 times)

boxhead

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Close to cab (100m) but unusually slow?
« on: June 01, 2012, 12:01:26 AM »

I had a FTTC install last week on a brand new master socket.

I am aout 100m from the wiring cabinet and the DSLAM (are they still called that?) is right next to it.  The engineer found a fault with the port I was supposed to get - it tested slow at the cab - and arranged for a move.  He waited there for 30 minutes and came back.  I wandered down to see what was taking so long - that's why I know what happened.

Anyway, given that I am 100m from the cab I figured I should be getting excellent sync speed.

Speedtests indicate about ~50Mbps down and ~12Mbps up, both from BT and speedtest.   The estimated speed at provisioning time was 68.1Mbps which is more realistic.

I've tried a number of routers and a direct connection - no difference.

I finally unlocked the modem and can see the following.  Not sure where to look, but I'm sure there's still a fault somewhere, or does this look about right?


# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   0
Max:   Upstream rate = 17383 Kbps, Downstream rate = 62092 Kbps
Path:   0, Upstream rate = 17804 Kbps, Downstream rate = 53233 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3959)
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      17383 kbps         62092 kbps
Actual Aggregate Tx Power:        6.6 dBm          13.3 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):    3.1    19.6    32.1     N/A    9.4    25.6    37.8   
Signal Attenuation(dB):    8.1    18.5    31.3     N/A    9.4    25.6    37.8   
        SNR Margin(dB):    6.0    6.1    6.0     N/A    6.1    6.1    6.2   
         TX Power(dBm):   -5.1   -23.9    6.4     N/A    10.4    7.9    6.9   


# xdslcmd info --show   
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   0
Max:   Upstream rate = 17350 Kbps, Downstream rate = 62532 Kbps
Path:   0, Upstream rate = 17804 Kbps, Downstream rate = 53233 Kbps

Link Power State:   L0
Mode:         VDSL2 Annex B
VDSL2 Profile:      Profile 17a
TPS-TC:         PTM Mode
Trellis:      U:ON /D:ON
Line Status:      No Defect
Training Status:   Showtime
      Down      Up
SNR (dB):    6.3       6.0
Attn(dB):    0.0       0.0
Pwr(dBm):    13.5       6.6
         VDSL2 framing
         Path 0
B:      63      237
M:      1      1
T:      64      64
R:      16      16
S:      0.0382      0.4253
L:      16733      4778
D:      843      1
I:      80      127
N:      80      254
         Counters
         Path 0
OHF:      1931849      523623
OHFErr:      11      88
RS:      370963447      3426904
RSCorr:      68466      13816
RSUnCorr:   1109      0

         Path 0
HEC:      366      0
OCD:      0      0
LCD:      0      0
Total Cells:   364324571      0
Data Cells:   2897380      0
Drop Cells:   0
Bit Errors:   0      0

ES:      1      54
SES:      0      3
UAS:      18      18
AS:      3563

         Path 0
INP:      3.00      0.00
PER:      1.83      6.80
delay:      8.00      0.00
OR:      104.58      34.09

Bitswap:   1604      1128


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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #1 on: June 01, 2012, 06:51:53 AM »

Hi boxhead & welcome to the Kitz forum.

These are the stats from a 400m connection.
You will see that attenuation levels are only slightly worse than yours, which suggests that your attenuation levels are too high for only 100m line length:-

Code: [Select]
# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 24809 Kbps, Downstream rate = 73424 Kbps
Path: 0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
Medley Phase (Final) Band Plan
US: (0,95) (868,1207) (1972,2783)
DS: (32,859) (1216,1963) (2792,3939)
       VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      24809 kbps         73424 kbps
Actual Aggregate Tx Power:        6.9 dBm          13.1 dBm
============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB): 3.6 20.9 30.7   N/A 10.8 26.4 39.8
Signal Attenuation(dB): 10.6 20.1 29.7   N/A 10.8 26.4 39.8
        SNR Margin(dB): 23.4 22.0 22.2   N/A 15.8 15.9 15.8
         TX Power(dBm): -4.4 -26.6 6.6   N/A 9.8 8.2 6.7

Also, your SNRM levels ar around the target level of 6 dB.
This is telling us that currently your connection is performing at around maximum capability. i.e. there is no spare margin to cope with any noise.

Over 100m, I would have expected really high SNRM levels, perhaps in the high 20s if on a capped 40Mb service & higher than 15dB on the 80Mb service.

You mentioned the engineer found a slow port fault.
Did he actually confirm that had been resolved on completion of his work?

Did he also confirm the line length, attenuation, Max rate, SNRM etc. as reported directly via his JDSU or Exfo tester?

I also see that Interleaving, Impulse Noise Protection & delay are switched on, which does suggest noise interference issues.

If you are a Windows user, you could try the HG612 Graphing Scripts, obtainable via this link for us to have a look at:-

http://forum.kitz.co.uk/index.php/topic,10552.0.html

They would give us a graphical view of your current line conditions and/or how it performs over a period of time.

Examples for my "up to" 1000m length connection are attached.
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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #2 on: June 01, 2012, 06:54:19 AM »

Also 31 days of Ongoing stats for my connection are attached, showing the before & after a recent engineer's repair visit.
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Black Sheep

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Re: Close to cab (100m) but unusually slow?
« Reply #3 on: June 01, 2012, 07:35:32 AM »

Very quick 'heads up', boxhead. If the engineer found a faulty port, it takes an average of 50-60 mins to have a 'Lift & Shift' implemented.
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boxhead

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Re: Close to cab (100m) but unusually slow?
« Reply #4 on: June 01, 2012, 10:04:59 AM »

Very quick 'heads up', boxhead. If the engineer found a faulty port, it takes an average of 50-60 mins to have a 'Lift & Shift' implemented.

I was expecting good things, so didn't really probe the engineer about the stats on his tester - doh!

The ISP looked up the install notes and he confirmed the notes said "performed a lift and shift".  It's odd that the slow speeds he quoted on the original port are about what I am getting.  But no one would say they moved it and really didn't? Would they?  Or are they expecting someone to fix the port instead?

Anyway, I'll set up the graphing and see what I get.

Thanks guys.  Wish I'd read a bit more about this stuff before the install.

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boxhead

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Re: Close to cab (100m) but unusually slow?
« Reply #5 on: June 02, 2012, 05:44:10 PM »

Some stats if anyone cares to take a look.  I was fillding with cables between 9am-12pm. Other than that, this is what I've got over the past day or so.

The logging is very useful!  Oddly, when I recevied my first phonecall on the new line at approx 21:30, it appears the connection dropped?

Also, I did notice some crackling.  I did a quiet line test a few times and there's definitely a muffled crackling noise which seems to build up and then fade out.  Sadly, the line tests fine.

I'm going to try and use the phone a bit to quantify the line noise and them hopefully get someone out to look at it.  I don't use the landline often but having noise on the line isn't acceptable when I do.

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burakkucat

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Re: Close to cab (100m) but unusually slow?
« Reply #6 on: June 02, 2012, 07:00:43 PM »

Quote
The logging is very useful!  Oddly, when I recevied my first phonecall on the new line at approx 21:30, it appears the connection dropped?

That is indicative of a HR fault on the D-side cable.  :(

Quote
I'm going to try and use the phone a bit to quantify the line noise and them hopefully get someone out to look at it.  I don't use the landline often but having noise on the line isn't acceptable when I do.

Noise on the line ist verboten by the telephony standard of service.  :no:  Have the (suspected) HR fault fixed -- by reporting the crackling to your telephone service provider (do not make any mention of the broadband service) -- and your broadband sync (& thus throughput) speed should then improve.  :)
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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #7 on: June 02, 2012, 07:03:19 PM »

You could try looking at the modem's GUI while making/receiving phone calls.

Especially look at SNR margin (dB).
It should not really change much when using the phone.
If it changes by more than 0.4dB, it would point to a definite problem.

I had that recently & running my connection via a dangly filter was fine. (filtered faceplate removed from the master socket & dangly filter plugged into the test socket).

This proved the issue was a faulty filtered faceplate (SSFP).
When the engineer visited, he firstly replaced the SSFP which sorted out the disconnections when the phone was used issue.

He also carried out some other external work & my connection is now stable again.

Your Hlog graph looks a bit "dodgy" at the top left.
That seems to have affected the bit-loading at the same tones.

Also your QLN doesn't look great, averaging somewhere around -120dB.
Even my long & problematic connection has always shown QLN to be a lot closer to -140dB (i.e. quieter than yours).

Your SNR graph looks quite jagged, indicating noise issues again.

I have attached an example montage from a 400m connection.

The attainable rate is higher & the graphs are smoother.

If you would like to plot your graphs in the same format (mainly for QLN), that will also be a smaller filesize that can be directly attached in this forum let me know.
I could post a replacement GRAPH6.BAT for you.


EDIT:

For only 100m distance from the cabinet, your SNRM levels should be much, much higher than the 6dB or less as shown in your stats/graphs.

For such a short distance, I would have expected an attainable rate of higher than 100Mb (as seen for many other short connections).

« Last Edit: June 02, 2012, 07:12:10 PM by Bald_Eagle1 »
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boxhead

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Re: Close to cab (100m) but unusually slow?
« Reply #8 on: June 08, 2012, 12:10:04 PM »

Quote
Your SNR graph looks quite jagged, indicating noise issues again.

Quote
For such a short distance, I would have expected an attainable rate of higher than 100Mb (as seen for many other short connections).

Spot on Bald Eagle.   After a 3 hour engineer's visit this morning to fix intermittent crackling I could hear during calls, I see expected sync - 100Mbps / 30Mbps.

Now to wait for DLM to do it's thing...???  Because the actual speed is LOWER than before.

See attached.
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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #9 on: June 08, 2012, 12:29:30 PM »

That looks a lot better, all round.

Is that you sat with the engineer in the photo, telling him what to do?  :lol:

Did he mention that he would be requesting a DLM reset/recalc following his repair work? He should have done.

 
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boxhead

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Re: Close to cab (100m) but unusually slow?
« Reply #10 on: June 08, 2012, 12:59:16 PM »

Quote
Is that you sat with the engineer in the photo, telling him what to do?

That's his mate who came to help.  I did offer coffee, looked so cosy.

Quote
Did he mention that he would be requesting a DLM reset/recalc following his repair work? He should have done.

Given it was booked as a voice fault, doubt it.  I'll see what the ISP says when they update the voice fault. Or I'll give them a nudge tomorrow.

It's annoying when you know something's not right, can prove it but no one listens coz "it's in tolerance".  Near enough ain't good enough.

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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #11 on: June 08, 2012, 01:17:30 PM »

At least you now have before & after stats/graphs as PROOF ;)
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burakkucat

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Re: Close to cab (100m) but unusually slow?
« Reply #12 on: June 08, 2012, 06:07:05 PM »

A definite result. :thumbs:

We will look forward to a new data set, once the DLM has been forced into submission.  :-X
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Bald_Eagle1

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Re: Close to cab (100m) but unusually slow?
« Reply #13 on: June 11, 2012, 08:28:11 PM »

@ boxhead,

Any news regarding a DLM reset/recalc yet?
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boxhead

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Re: Close to cab (100m) but unusually slow?
« Reply #14 on: June 11, 2012, 08:52:20 PM »

I had a change at around 6am today.
DS: 48998 -> 59999 (max. ~102000)
US: 16999 -> 20000 (max. ~31000)

SNRM dropped at the same time. Not sure I like that part, but attainable sill maxed out.

I'll post full stats when it stabilises.

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