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Standard User smouty
(learned) Thu 07-Mar-13 11:19:14
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Interpreting line stats


[link to this post]
 
Since having Infinity 2 installed I've 'lost' around 10mbit of sync speed.
I know I'm lucky to get 70mbit+ but as I'm <25m from the cab I'm wondering what the issue could be.
I've got the following graphs from RS-UX and appreciate any pointers.

http://farm9.staticflickr.com/8524/8535335580_b2363c...

http://farm9.staticflickr.com/8243/8534227405_7b84e4...

http://farm9.staticflickr.com/8508/8536518186_342c37...

http://farm9.staticflickr.com/8381/8536518234_520685...
Standard User BatBoy
(legend) Thu 07-Mar-13 11:40:16
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
Did you know that first graph is scrollable horizontally? Also, it's more recognisable if you untick Expanded View.

What about Bitswaps per min?


__________________________________________________________________________The back pedalling starts here__________________
Standard User smouty
(learned) Thu 07-Mar-13 11:54:21
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Re: Interpreting line stats


[re: BatBoy] [link to this post]
 
Thanks. I did assume that after looking at the 2nd graph so I'll uncheck that option next time.
I saw the option for bitswaps which I'll enable and try again.


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Administrator MrSaffron
(staff) Thu 07-Mar-13 12:18:31
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
Cross talk as the cable bundles get fully populated

http://www.thinkbroadband.com/guide/fibre-broadband.... and scroll down the page a bit and the table there is often accussed of been wrong, but its line length speed estimate takes into account cross talk as well as distance.

Andrew Ferguson, [email protected]
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Standard User Andrue
(knowledge is power) Thu 07-Mar-13 13:00:02
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
I lost about 4Mb/s when interleaving was enabled after an engineer visit.

---
Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User smouty
(learned) Tue 19-Mar-13 08:51:29
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
I've been looking a bit further and the SNR seems to be stable.
My cabinet is <50m away so I'm a bit surprised that my DS SNR is down to 5.7db.

Graphs on Dropbox - http://db.tt/T6xoo39k

Edited by smouty (Tue 19-Mar-13 08:53:57)

Standard User eckiedoo
(member) Tue 19-Mar-13 09:37:25
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
"My cabinet" is about 25 yards away, literally just across the road; but the phone wire length is about 125 yards (or possibly longer), going first east from the cabinet and coming across the road (somewhere) to a small Jointing Box, by a near-neighbour's house, before returning west-ward to my front door.

It was a GPO/BT Phones lad who pointed this out to me back about 1990, when sorting out noise interfering with my Dial-Up access to work.

He had already re-made the joints in the very obvious cabinet - but this had not cured the problem.

Looking at the 1967-Installation records he had with him, showed this little Jointing Box, which being at footpath level, was more exposed to rain etc.

Re-making its joints cured the problem.
Standard User RobertoS
(sensei) Tue 19-Mar-13 09:43:30
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
In reply to a post by smouty:
I've been looking a bit further and the SNR seems to be stable.
My cabinet is <50m away so I'm a bit surprised that my DS SNR is down to 5.7db.
SNRM on FTTC is not treated the same way as on ADSLx. In particular it is not, so far as we know, used to improve stability. It looks as though it is always set at 6dB at sync time.

Stability is achieved through various depths of interleaving if Fast Path proves unreliable, and speed banding if even that doesn't sort things out.

My broadband basic info/help site - www.robertos.me.uk | Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. - BQM

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.

Edited by RobertoS (Tue 19-Mar-13 09:44:25)

Standard User Andrue
(knowledge is power) Tue 19-Mar-13 11:44:19
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Re: Interpreting line stats


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
Stability is achieved through various depths of interleaving if Fast Path proves unreliable, and speed banding if even that doesn't sort things out.
One thing intrigues me. Prior to this month my modem was showing an attainable rate of ~73Mb/s and that's more or less where I connected. Then an SFI engineer visited and I got lumbered with interleaving of 1041 and attainable rate went up to 78Mb/s. After 14 days the interleaving was dropped back down to 1 which as far as I know puts me back where I was before the engineer visited but my attainable rate is now ~71Mb/s.

Is it just a coincidence? I have noticed that my throughput is about where it was back when I connected at ~73Mb/s even though I'm now connected at ~71MB/s so in practical terms I am back where I was before the visit.

---
Andrue Cope
Brackley, UK

Just because he could. RIP.
Standard User smouty
(learned) Tue 19-Mar-13 15:08:53
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Re: Interpreting line stats


[re: RobertoS] [link to this post]
 
My understanding is that 6db is the minimum. If you can hit 80mbit with a higher SNR then you will. I looked for other peoples SNR graphs and this appears to be the case.
Standard User Bald_Eagle1
(committed) Tue 19-Mar-13 18:56:57
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
In reply to a post by smouty:
My understanding is that 6db is the minimum. If you can hit 80mbit with a higher SNR then you will. I looked for other peoples SNR graphs and this appears to be the case.


From my own observations of many other users' connections, I'd agree with/confirm that.

Here's an example from a very, very short D-side length from the cabinet (SNRM at almost 31dB on a capped 40Mb/10Mb service).

I had to increase the y-axis scale of my initial graphing scripts to allow for just such a connection smile:-

Text
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=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2011.12.29 13:28:59 =~=~=~=~=~=~=~=~=~=~=~=
xdslcmd info --pbParamsxdslcmd: ADSL driver and PHY status
Status: ShowtimeRetrain Reason: 0
Max:    Upstream rate = 40574 Kbps, Downstream rate = 127540 KbpsPath:   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 PlanUS: (0,95) (868,1207) (1972,2783) 
DS: (32,859) (1216,1963) (2792,3939)        VDSL Port Details       Upstream        Downstream
Attainable Net Data Rate:      40574 kbps        127540 kbpsActual Aggregate Tx Power:    -   8.6 dBm          13.3 dBm
============================================================================  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  2.2     7.8     10.0     N/A    4.4     9.2     13.8   Signal Attenuation(dB):  0.0      N/A    7.6      N/A    4.4     9.2     13.8   
        SNR Margin(dB):  30.6     N/A    30.2     N/A    30.7    30.5    31.1            TX Power(dBm): -25.1   -128.0  -10.2     N/A    10.5    7.7     6.2    
  
 # xdslcmd info --linediag
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max:    Upstream rate = 40363 Kbps, Downstream rate = 127540 Kbps
Path:   0, Upstream rate = 10000 Kbps, Downstream rate = 39998 Kbps 
                Down            UpSNRM(dB):        30.8            30.2
LATN(dB):        0.0             0.0SATN(dB):        0.0             0.0
TxPwr(dBm):      13.3           -8.6ATTNDR(Kbps):   127540          40363

Edited by Bald_Eagle1 (Tue 19-Mar-13 18:58:57)

Standard User smouty
(learned) Wed 20-Mar-13 07:52:31
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Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
So, If my cab is a fairly short distance away and my SNR is <= 6db then I should assume either my atten is high or crosstalk is having an effect.
Is there any way to get around the HG612 bug to measure the attenuation?
Are there other ways to get a loop length without a TDR?
Standard User Bald_Eagle1
(committed) Wed 20-Mar-13 08:05:28
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
In reply to a post by smouty:
So, If my cab is a fairly short distance away and my SNR is <= 6db then I should assume either my atten is high or crosstalk is having an effect.

Yes, that's about the gist of it




Is there any way to get around the HG612 bug to measure the attenuation?


It's already displayed (per US/DS band) via the xdslcmd info --pbParams example as shown above:-

Text
1
2
Line Attenuation(dB):    2.2     7.8     10.0     N/A    4.4     9.2     13.8   
Signal Attenuation(dB):  0.0      N/A    7.6      N/A    4.4     9.2     13.8




Are there other ways to get a loop length without a TDR?

Not that we are aware of.
Attempts have been made to calculate it from attenuation over frequency Hlog data, but results were too inaccurate to be classed as reliable.

Edited by Bald_Eagle1 (Wed 20-Mar-13 08:07:29)

Standard User smouty
(learned) Wed 20-Mar-13 17:39:02
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Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
Here are my pbParams

Text
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xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max:    Upstream rate = 30793 Kbps, Downstream rate = 70252 Kbps
Path:   0, Upstream rate = 20000 Kbps, Downstream rate = 70711 Kbps 
Discovery Phase (Initial) Band PlanUS: (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        DownstreamAttainable Net Data Rate:      30793 kbps         70252 kbps
Actual Aggregate Tx Power:    -   5.9 dBm          12.4 dBm============================================================================
  VDSL Band Status        U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  2.0     9.5     13.5     N/A    5.6     11.8    17.6   
Signal Attenuation(dB):  2.0     8.6     12.2     N/A    5.6     11.8    17.6           SNR Margin(dB):  15.3    15.2    15.2     N/A    5.8     5.8     5.8    
         TX Power(dBm): -20.3   -34.0   -6.2      N/A    8.0     7.7     7.1
Standard User Bald_Eagle1
(experienced) Wed 20-Mar-13 17:58:14
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
That looks pretty good, but what distance do you estimate you are from the cabinet (allowing for any detours, up & down poles etc.)?
Standard User smouty
(learned) Wed 20-Mar-13 18:39:06
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Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
I would say no more than 50m.

Edit - I've just measured it on a map and 50m is about right given the probable route.

Edited by smouty (Wed 20-Mar-13 18:51:03)

Standard User RobertoS
(sensei) Wed 20-Mar-13 18:56:28
Print Post

Re: Interpreting line stats


[re: smouty] [link to this post]
 
That's close.

The distance required is from the FTTC cabinet to the PCP plus from the PCP to your modem.

My broadband basic info/help site - www.robertos.me.uk | Domains,website and mail hosting - Tsohost.
Connection - Plusnet UnLim Fibre (FTTC). Sync ~ 54.2/15.2Mbps @ 600m. - BQM

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Allergy information: This post was manufactured in an environment where nuts are present. It may include traces of understatement, litotes and humour.
Standard User Bald_Eagle1
(experienced) Wed 20-Mar-13 19:41:24
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
In reply to a post by smouty:
I would say no more than 50m.


Hmm.

I would have expected a higher attainable rate & sync speed for such a short distance (at least the full 80Mb & more), with a higher SNRM level.

Have numerous disconnections caused Interleaving to be applied at quite a high depth?

xdslcmd info --stats would confirm that, along with various error counts etc.

If you are a Windows user, have you tried the new logging/graphing programs downloadable from here yet?:-

HG612 Modem Stats 1.0
Standard User smouty
(learned) Wed 20-Mar-13 19:56:58
Print Post

Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
I'm not sure on interleaving but think it is 1.

Text
1
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xdslcmd info --stats
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max:    Upstream rate = 30769 Kbps, Downstream rate = 70252 Kbps
Path:   0, Upstream rate = 20000 Kbps, Downstream rate = 70711 Kbps 
Link Power State:       L0Mode:                   VDSL2 Annex B
VDSL2 Profile:          Profile 17aTPS-TC:                 PTM Mode
Trellis:                U:ON /D:ONLine Status:            No Defect
Training Status:        Showtime                Down            Up
SNR (dB):        5.8             15.2Attn(dB):        0.0             0.0
Pwr(dBm):        12.4           -5.9                        VDSL2 framing
                        Path 0B:              239             237
M:              1               1T:              21              45
R:              0               16S:              0.1080          0.3782
L:              17775           5373D:              1               1
I:              240             127N:              240             254
                        Counters                        Path 0
OHF:            164223390               2832611OHFErr:         1281            191
RS:             0               2883194RSCorr:         0               1329
RSUnCorr:       0               0 
                        Path 0HEC:            5244            0
OCD:            0               0LCD:            0               0
Total Cells:    3763578860              0Data Cells:     139746331               0
Drop Cells:     0Bit Errors:     0               0
 ES:             549             136
SES:            0               0UAS:            17              17
AS:             280486 
                        Path 0INP:            0.00            0.00
PER:            1.70            4.25delay:          0.00            0.00
OR:             112.85          60.17 
Bitswap:        12530           2987


I'll try that logging tool. Cheers smile

Edited by smouty (Wed 20-Mar-13 19:58:40)

Standard User Bald_Eagle1
(experienced) Wed 20-Mar-13 20:28:08
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
In reply to a post by smouty:
I'm not sure on interleaving but think it is 1.


It is indeed still OFF (fastpath)

You seem to be averaging around 170 errored seconds per day, which is a shade high.
Other error counts seem quite low though.

Do you know if you have aluminium cabling in your D-side connection?

I'm not sure what attenuation levels to expect for such a short distance, but the example I cited is also around 50m or less from the cabinet.

Are you 100% sure you are actually connected to the closest cabinet?
Occasionally users are connected to a cabinet further away, due to actual cable routing.
Standard User smouty
(learned) Wed 20-Mar-13 20:54:51
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Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
Pretty much 100%
I did get the full 80mbit to start with and there isn't another cab within 500m or so.
I don't know about the cable type though.

Edited by smouty (Wed 20-Mar-13 21:25:13)

Standard User WWWombat
(fountain of knowledge) Thu 21-Mar-13 19:49:58
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
Sorry - I'd normally do more analysis than this, but I have almost no time right now...

What I can say, from looking at the graphs on the original Dropbox page, is that you appear to have very high QLN values - especially at the higher frequencies.

QLN= Quiet Line Noise
QLN is measured before synchronising, and the graph will not change until there is a new sync.

I understand that a QLN of "-140" represents really good silence. Values of between -120 and -140 seem to be pretty reasonable (and are what I get). I suspect that values around -100 are not very good.

On my line, I get values starting at -130, dropping to -140 at tone 350, suddenly rising to -120 and then gradually dropping to -135 at tone 3900.

In your case, it suggests that the modem has measured "high noise" throughout the spectrum (above tone 500). This means the SNR values will be correspondingly lower, and thus that the number of bits that can be carried on each tone are lower.

Your SNR graph is 40dB in higher D1, 30-35dB in D2, and 25dB in D3. Mine runs at 45-50dB in higher D1, 38-42dB in D2, and 25-30dB in D3. I'm getting better signal levels throughout.

The good news is that, because you are so close to the cabinet, the modem can use all of the tones.

You broadly seem to get 6-8 bits per tone over the full spectrum. I get 14 bits around tone 500, dropping to 4 bits at tone 3900.

Your line is 50 metres (ish), while mine is 400 metres. To back up the fact that my line is a lot longer, the three attenuation figures are: D1=11.4dB, D2=27.4dB, D3=41.7dB.

So, it is all down to noise. Presumably the noise is crosstalk.

Again... sorry. I won't have chance to add more to the conversation.

Edit: Added SNR and length comparisons.

Edited by WWWombat (Fri 22-Mar-13 01:15:09)

Standard User smouty
(learned) Fri 22-Mar-13 06:32:14
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Re: Interpreting line stats


[re: WWWombat] [link to this post]
 
Many thanks to all.
It has been a really interesting experience learning about this so far and I'll do a QLT.
Standard User Bald_Eagle1
(experienced) Fri 22-Mar-13 06:57:40
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
A Hlog graph would show an overview of the line characteristics i.e. demonstrating if a bridged tap or some other defect was potentially dragging speeds down.

These sort of defects can knock quite a few Mb off sync speeds, possibly causing (S)ignal to (N)oise (R)atio to be reduced
Standard User smouty
(learned) Fri 22-Mar-13 09:39:14
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Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
Thanks again BaldEagle.

The Hlog is pretty flat. Is that good or bad?

http://db.tt/6x9yW0g8
Standard User smouty
(learned) Fri 22-Mar-13 10:13:43
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Re: Interpreting line stats


[re: smouty] [link to this post]
 
I've just setup the logging program.
Results are output to Dropbox for anyone interested - http://db.tt/BtX4TiAG
Standard User Bald_Eagle1
(experienced) Fri 22-Mar-13 12:58:55
Print Post

Re: Interpreting line stats


[re: smouty] [link to this post]
 
There's a slight 'wobble' between tones 350 & 500, which could explain the gap in your bitloading graph, unusually as these lower frequencies usually tend to display the highest bitloading.

Also, as mentioned by WWWombat (I hadn't spotted it earlier), your QLN graph does indeed display quite high 'noise' levels.
-140dB tends to be a quieter & more 'normal' level.
Do you hear any hissing, humming or crackling at all when running the telephone quiet line test?



OT, but for my own curiosity, are you running the new HG612 Modem Stats programs through native Windows, or through Wine or some other program on a Linux box?
Standard User smouty
(regular) Fri 22-Mar-13 14:49:12
Print Post

Re: Interpreting line stats


[re: Bald_Eagle1] [link to this post]
 
I hear a faint background hiss during a QLT but when reported to BT this morning their test comes back OK.

I'm running the HG612 tool natively in Win7 on a laptop at the moment.
A linux service would be my ideal choice though as I have a 24/7 box running.
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