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Author Topic: Sync speed on new line  (Read 4305 times)

Zico

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Sync speed on new line
« on: December 11, 2017, 01:16:34 PM »

I've recently had a new phone line and 80/20 FTTC service fitted (IDnet) and I am querying the FTTC sync speed of the line.

The DSL checker prediction stats (full snippet attached):
High Low High Low
VDSL Range A (Clean) 80 59.9 20 19 53.4 Available -- -- Yes --
VDSL Range B (Impacted) 77.6 54.1 20 16 40.3 Available -- -- Yes --

A few years ago I had PlusNet FTTC and synced at ~78/20 speeds back to the same ECI cabinet using an ECI Openreach modem / PlusNet Technicolor tg582n router combo. The predicted speed ranges were a reflection of what I had before (as far as I can recall) and were what I had expected on the new service (looking at the clean range for reasons below).

On the date of the phone line install, I provided the Openreach engineer a brand new 350m roll of 0.9mm BT Dropwire 12 - CW1406 spec. https://www.btcables.com/documents/CW1406-Dropwire-12.pdf. I had purchased this for two reasons; 1) our property is served by overhead power lines on the same telegraph poles and 2) the other drop wire serving the property has a few joints in it due to tree rub damage (and also runs to the opposite side of the property with another phone and FTTC service - running ~60/20).

The new line was installed from the property back to the DP pole at the edge of the road covering approx. ~125m. From the DP back to the cabinet is another ~180m (line traced using google maps - snippet attached) making an approx. line length of ~300m rounding up. Finally the fibre port was connected a few days after (was supposed to be a simultaneous provide but original engineer turned up was from MJ Quinn's and couldn't work with the overhead power lines - this was passed on by myself to IDnet in turn to Openreach).

Anyway, onto the connection stats. Full connection stats from DSLstats attached, snippet below:

adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    1
Last initialization procedure status:   0
Max:    Upstream rate = 11726 Kbps, Downstream rate = 56972 Kbps
Bearer: 0, Upstream rate = 12093 Kbps, Downstream rate = 56169 Kbps

Link Power State:       L0
Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17a
TPS-TC:                 PTM Mode(0x0)
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        5.9             6.1
Attn(dB):        13.3            0.0
Pwr(dBm):        1.2             1.2

As you can see, I'm synced at the bottom end of the Impacted range for Download and below that for the Upload speed. This has surprised me based on the new spec drop wire cable and my historical connection through PlusNet (and even comparing my upload to the other FTTC service on the other drop wire syncing at 20 compared to my 12).

I'm not sure what to think as it shouldn't be a fault (at least on the line from the DP to the house), might be crosstalk with the other FTTC service (though again not on the last ~125m drop wire span) or even crosstalk back at the ECI cabinet with more connections over the last few years.
**Edit**
Re-uploaded DSLstats as file was empty, woops :)
« Last Edit: December 11, 2017, 04:36:40 PM by Zico »
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Ixel

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Re: Sync speed on new line
« Reply #1 on: December 11, 2017, 02:16:22 PM »

Maybe it's just me but for your line attenuation I feel that the speed is lower than expected for sure. Based on your power levels I'd assume you're on a line card running version b206. Some ECI line cards have been known to run version d086 (like my first line is on b206, my second line is on d086) which for some gives improved speeds and for some others terrible speeds. My second line is significantly better than that first, I also had four SFI engineers working on the second line of which three of them did some pair swaps to find me the best pair along the route (and some lift and shifts). My attenuation is 16 dB downstream (450 meters approx to cabinet) and I'm getting an attainable rate of around 82/24 currently, but this line is connected to a line card running version d086 and is on an extremely good pair so isn't a really fair comparison I guess.

EDIT: Forgot to mention I'm running a DrayTek Vigor 2860Vac which has reed solomon coding 'R' on the downstream even on fastpath. This reduces the attainable rate. On a HG612 I think I recall getting something like 90/24.
« Last Edit: December 11, 2017, 02:26:22 PM by Ixel »
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Zico

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Re: Sync speed on new line
« Reply #2 on: December 11, 2017, 04:25:26 PM »

I'm using a Billion 8800NL R2 (was lazy and got it supplied from IDnet) and here are the stats confirming the DSLAM/MSAN:

Stats recorded 11 Dec 2017 16:23:36

DSLAM/MSAN type:           IFTN:0xb206 / v0xb206

Modem/router firmware:     AnnexA version - A2pvI042j1.d26q_rc1a
DSL mode:                  VDSL2 Profile 17a
Status:                    Showtime
Uptime:                    6 days 3 hours 15 min 20 sec
Resyncs:                   0 (since 11 Dec 2017 10:59:33)
         
            Downstream   Upstream
Line attenuation (dB):     13.3      0.0
Signal attenuation (dB):   Not monitored      
Connection speed (kbps):   56169      12093
SNR margin (dB):           6.0      6.0
Power (dBm):               1.2      1.2
Interleave depth:          1      1
INP:                       0      0
G.INP:                     Not enabled      Not enabled
Vectoring status:          5 (VECT_UNCONFIGURED)      

RSCorr/RS (%):             N/A      0.0002
RSUnCorr/RS (%):           N/A      0.0000
ES/hour:                   0.18      2.96

**Edit**
If it's the ECI line card firmware as the issue, how hard would it be to request this to be swapped to a d086 port if there is one available?
« Last Edit: December 11, 2017, 04:29:38 PM by Zico »
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Dray

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Re: Sync speed on new line
« Reply #3 on: December 11, 2017, 04:35:45 PM »

I wonder if by supplying the drop wire, you have compromised the ability to call on Openreach?
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Ixel

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Re: Sync speed on new line
« Reply #4 on: December 11, 2017, 04:36:25 PM »

I'm using a Billion 8800NL R2 (was lazy and got it supplied from IDnet) and here are the stats confirming the DSLAM/MSAN:

Stats recorded 11 Dec 2017 16:23:36

DSLAM/MSAN type:           IFTN:0xb206 / v0xb206

Modem/router firmware:     AnnexA version - A2pvI042j1.d26q_rc1a
DSL mode:                  VDSL2 Profile 17a
Status:                    Showtime
Uptime:                    6 days 3 hours 15 min 20 sec
Resyncs:                   0 (since 11 Dec 2017 10:59:33)
         
            Downstream   Upstream
Line attenuation (dB):     13.3      0.0
Signal attenuation (dB):   Not monitored      
Connection speed (kbps):   56169      12093
SNR margin (dB):           6.0      6.0
Power (dBm):               1.2      1.2
Interleave depth:          1      1
INP:                       0      0
G.INP:                     Not enabled      Not enabled
Vectoring status:          5 (VECT_UNCONFIGURED)      

RSCorr/RS (%):             N/A      0.0002
RSUnCorr/RS (%):           N/A      0.0000
ES/hour:                   0.18      2.96

**Edit**
If it's the ECI line card firmware as the issue, how hard would it be to request this to be swapped to a d086 port if there is one available?

I see. Pretty sure that Billion is good but best to wait to see what other forum members here say. While I highly doubt your problems are related to the line card version, it was merely an observation I had that for me d086 seems to perform better than b206. I believe b206 is far more common than d086 for some reason. There's no way to get this changed I'm afraid. More likely something else is causing you to have a lower than expected speed, heavy crosstalk, an underlying fault, well.. quite a few other possibilities I imagine. I'm sure someone else on here can be a bit more insightful than me :).
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Zico

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Re: Sync speed on new line
« Reply #5 on: December 11, 2017, 04:39:46 PM »

I wonder if by supplying the drop wire, you have compromised the ability to call on Openreach?

I don't think that should cause an issue. If it was going to be an issue then I would have imagined the Openreach engineer would have simply said no to putting it up in the first place. It's proper BT cable (stamped on the drum BT Cables as the original supplier) just purchased through a networking reseller Blue Helix - http://www.bluehelix.co.uk/Product.aspx?id=1724.
« Last Edit: December 11, 2017, 05:58:43 PM by Zico »
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WWWombat

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Re: Sync speed on new line
« Reply #6 on: December 12, 2017, 12:44:16 PM »

With that attenuation, speeds do indeed look a bit low. The next step is to figure why:
- Is it DLM stealing bandwidth?
- Is it high error behaviour?
- Is it high crosstalk, from other subscribers (from a "quiet line" graph)?
- Is it a bad copper line (from a Hlog graph)?
- In the absence of these issues, then power can be a question mark.

The stats as given in the text file look fine. There's no intervention from DLM (but, of course, there's no G.INP either).

The stats for "Previous 1 day" and "since Link time" show low levels of CRC and ES. There's no problem there.

The remaining issues really need a graph of the "quiet line" behaviour and the "Hlog" measurement of the line. They can be acquired from software that reads the stats from the modem.

That leaves power. Getting values of 1.2dBm for both up and down is, on the face of it, strange. But it is hard to debug; the only other indication of power comes from the output to the "--pbParams" option.

Note that while you are synced under the bottom of the clean range, you haven't fallen into the "handback" range yet. Remember that 20% of lines end up below the bottom of the range, and that 10% below the handback range. The latter is the threshold to get an engineer out.
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Zico

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Re: Sync speed on new line
« Reply #7 on: December 12, 2017, 07:59:15 PM »

I've just dumped a copy of all graphs from a few minutes ago.

Is QLN the 'quiet line' graph that you refer to (not used DSLstats before so not overly familiar with the importance of some of the tabs).
« Last Edit: December 12, 2017, 09:18:33 PM by Zico »
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burakkucat

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Re: Sync speed on new line
« Reply #8 on: December 12, 2017, 08:49:55 PM »

A G.993.2 (VDSL2) based circuit, as currently used in the UK, has 4096 sub-carriers numbered from 0 to 4095.

Unfortunately, for the QLN (quiet line noise) and Hlog plots, you haven't adjusted the scale of the X-axis so we are only seeing the first 800 (or so) sub-carriers.  :(
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Zico

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Re: Sync speed on new line
« Reply #9 on: December 12, 2017, 08:51:57 PM »

Yes, just realised that the graphs are wider. Will re-scale and re-upload :D

Right, hopefully this will be better. QLN and Hlog only.
« Last Edit: December 12, 2017, 09:01:35 PM by Zico »
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WWWombat

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Re: Sync speed on new line
« Reply #10 on: December 13, 2017, 10:33:27 AM »

Quick answer for now, explanation later...

Hlog shows a few signs of a bridge tap, but it doesn't look to be having much impact on the line.

QLN shows that your line is seeing a lot of "noise", which in reality is other VDSL2 subscribers. This is probably the main reason for the low downstream.

There isn't likely to be a lot you can do.

I'll post more explanation later. In the meantime, can you post the graphs for the SNR-per-tone and Bits-per-tone?
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jaydub

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Re: Sync speed on new line
« Reply #11 on: December 13, 2017, 10:55:26 AM »

I'll post more explanation later. In the meantime, can you post the graphs for the SNR-per-tone and Bits-per-tone?

I'll be interested with these explanations.  I'm also with IDNet as it happens, and my QLN is quite noisy as well and my HLOG has a slightly more interesting shape to it than I remember.  Don't want to pollute Zico's thread so will look and learn from what you post for him.
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burakkucat

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Re: Sync speed on new line
« Reply #12 on: December 13, 2017, 06:12:20 PM »

Quick answer for now, explanation later...

Hlog shows a few signs of a bridge tap, but it doesn't look to be having much impact on the line.

QLN shows that your line is seeing a lot of "noise", which in reality is other VDSL2 subscribers. This is probably the main reason for the low downstream.

Assuming the two textual files attached to Reply #7 are the data files for the most recent Hlog and QLN plots . . .

The circuit electrical length equivalent (cele) is -23.7 dB per sub-carrier. (The more positive the value of cele the better.)

The average noise floor (anf) is -112 dBm/Hz per sub-carrier. (We would typically expect a "good" circuit to have an anf value of -140 dBm/Hz per sub-carrier or lower (i.e. more negative).)
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Zico

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Re: Sync speed on new line
« Reply #13 on: December 13, 2017, 07:59:41 PM »

Quick answer for now, explanation later...

Hlog shows a few signs of a bridge tap, but it doesn't look to be having much impact on the line.

QLN shows that your line is seeing a lot of "noise", which in reality is other VDSL2 subscribers. This is probably the main reason for the low downstream.

There isn't likely to be a lot you can do.

I'll post more explanation later. In the meantime, can you post the graphs for the SNR-per-tone and Bits-per-tone?

SNR-per-tone attached. Not sure if you mean Bit Loading or Bitswap so will attach both.

I'll be interested with these explanations.  I'm also with IDNet as it happens, and my QLN is quite noisy as well and my HLOG has a slightly more interesting shape to it than I remember.  Don't want to pollute Zico's thread so will look and learn from what you post for him.

Hi Jaydub. You're welcome to join in on the thread. If the admin prefer otherwise then I'm sure that you will be advised accordingly.

Assuming the two textual files attached to Reply #7 are the data files for the most recent Hlog and QLN plots . . .

The circuit electrical length equivalent (cele) is -23.7 dB per sub-carrier. (The more positive the value of cele the better.)

The average noise floor (anf) is -112 dBm/Hz per sub-carrier. (We would typically expect a "good" circuit to have an anf value of -140 dBm/Hz per sub-carrier or lower (i.e. more negative).)

The text files in post #7 are for the graphs posted last night.
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Zico

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Re: Sync speed on new line
« Reply #14 on: December 13, 2017, 08:01:34 PM »

Text files for BitLoading and SNR and graph of Bitswap per min.
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