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Standard User gab81
(newbie) Tue 23-Jul-13 11:54:08
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FTTC Link speed, strange behaviour


[link to this post]
 
hi there guys,

I'd like to hear your opinion on my FTTC line stats, just to give you a bit of background...

Had the service installed on Jun 12th, started perfect, i have the 40/10 w/ Sky, 39996/9996 sync, ping 12ms, happy. Then on sunday 16th connection went down for like 10 mins and when it came back DLM kicked in and lowered the speed to 27400 / 9996.

....long story short, i had a BT engineer check the line on the following wed, said everything is OK, he checked the sync with his tool and it shown 35000 and during these past weeks connection improved, speed changed a bit, I have restarted it maybe just once (so it was up for 28 days which i thought was the logging period as the BT guy said b4 they reset stats...) first ping changed, then download speed a bit, then upload, then right now it seems to be stuck on the following 35000 / 9996 and 13ms ping which is actually good and very stable, solid.

However, i'd like to understand why i am not getting the 39996 i had before, some people said sometimes DLM recovers in UP TO 6 weeks, but is that a myth or is really like that?

Interestingly, i am 150mts walking distance from the nearest BT fibre cabinet, no strange plugs or extensions and the BT engineer also told me "you should get good speed indeed", and i often walk past it just behind the corner smile

BTW i removed QoS as someone suggested here and had a nice boost in the upload, nice trick!!!! Is there any drawback by doing so?

here are my stats:

# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 10908 Kbps, Downstream rate = 46704 Kbps
Path: 0, Upstream rate = 9995 Kbps, Downstream rate = 35000 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): 8.5 6.4
Attn(dB): 0.0 0.0
Pwr(dBm): 12.0 -6.6
VDSL2 framing
Path 0
B: 239 235
M: 1 1
T: 64 7
R: 0 16
S: 0.2182 0.7508
L: 8799 2717
D: 1 1
I: 240 255
N: 240 255
Counters
Path 0
OHF: 1474773 437016
OHFErr: 40 17
RS: 0 1756802
RSCorr: 0 80
RSUnCorr: 0 0

Path 0
HEC: 9 0
OCD: 0 0
LCD: 0 0
Total Cells: 347593607 0
Data Cells: 4759952 0
Drop Cells: 0
Bit Errors: 0 0

ES: 28 16
SES: 0 0
UAS: 215 215
AS: 5169

Path 0
INP: 0.00 0.00
PER: 3.49 11.82
delay: 0.00 0.00
OR: 59.57 152.21

Bitswap: 4 1

Total time = 1 hours 30 min 44 sec
FEC: 0 0
CRC: 40 0
ES: 28 16
SES: 0 0
UAS: 215 215
LOS: 0 0
LOF: 0 0
Latest 15 minutes time = 44 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 0 0
CRC: 4 0
ES: 2 3
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Latest 1 day time = 1 hours 30 min 44 sec
FEC: 0 0
CRC: 40 0
ES: 28 16
SES: 0 0
UAS: 215 215
LOS: 0 0
LOF: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Since Link time = 1 hours 26 min 7 sec
FEC: 0 80
CRC: 40 17
ES: 28 16
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
#

# xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 10924 Kbps, Downstream rate = 46704 Kbps
Path: 0, Upstream rate = 9995 Kbps, Downstream rate = 35000 Kbps

Discovery Phase (Initial) Band Plan
US: (0,95) (880,1195) (1984,2771)
DS: (32,859) (1216,1959) (2792,4083)
Medley Phase (Final) Band Plan
US: (0,95) (880,1195) (1984,2771)
DS: (32,859) (1216,1959) (2792,4083)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 10924 kbps 46704 kbps
Actual Aggregate Tx Power: - 6.6 dBm 12.0 dBm
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 0.1 7.3 10.5 N/A 4.5 10.3 18.4
Signal Attenuation(dB): 0.1 7.3 10.4 N/A 4.5 10.3 18.4
SNR Margin(dB): 6.8 6.9 6.1 N/A 8.6 8.5 8.4
TX Power(dBm): -11.3 -128.0 -8.4 N/A 9.9 7.4 0.8

when i look at the MAX speed the line supports, it doesn't look great since im so close to the cabinet, what is your diagnosis? bad cables?

thanks a lot guys!
Gabrio
Administrator MrSaffron
(staff) Tue 23-Jul-13 12:12:45
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Re: FTTC Link speed, strange behaviour


[re: gab81] [link to this post]
 
The DLM system is slow to give speed back as all the DLM profiles try to give a stable speed, rather than something that is fast but breaks a lot.

Any neighbours with fibre to see how they compare on similar distances? If they are good consider turning off the mains circuits in the home until you have the minimum running and see if connection speed improves after a restart.

Andrew Ferguson, andrew@thinkbroadband.com
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 gab81
(newbie) Tue 23-Jul-13 12:57:16
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Re: FTTC Link speed, strange behaviour


[re: MrSaffron] [link to this post]
 
In reply to a post by MrSaffron:
The DLM system is slow to give speed back as all the DLM profiles try to give a stable speed, rather than something that is fast but breaks a lot.

Any neighbours with fibre to see how they compare on similar distances? If they are good consider turning off the mains circuits in the home until you have the minimum running and see if connection speed improves after a restart.


That is an interesting point. I dont know any other neighbours connected to fibre. I was wondering if anyone can help me interpret the values to understand. Or is simply the DLM gnome inside the cabinet playing with us smile


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Standard User ryant704
(member) Tue 23-Jul-13 13:25:59
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Re: FTTC Link speed, strange behaviour


[re: gab81] [link to this post]
 
The connection itself looks fine, personally this looks like 'banding' to me.

If you actually are 150m away from the cabinet I would expect you to get sync of around 60Mbps but the stats say otherwise. Is this walking distance? Do you know how the cables are routed in your area? In some areas it can be very hard to diagnose how it's routed back to the PCP.

Your stats seem fine, though I do have one question. Your stats indicate that it was a manual restart from your modem as the Retrain Reason is 0. Is this the one time you restarted it or from the engineer visit?

Your attenuation for all 3 Download bands are actually good and I would expect you will be able to achieve over the 40Mbps mark.
Standard User gab81
(newbie) Tue 23-Jul-13 13:32:39
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Re: FTTC Link speed, strange behaviour


[re: ryant704] [link to this post]
 
In reply to a post by ryant704:
The connection itself looks fine, personally this looks like 'banding' to me.

If you actually are 150m away from the cabinet I would expect you to get sync of around 60Mbps but the stats say otherwise. Is this walking distance? Do you know how the cables are routed in your area? In some areas it can be very hard to diagnose how it's routed back to the PCP.

Your stats seem fine, though I do have one question. Your stats indicate that it was a manual restart from your modem as the Retrain Reason is 0. Is this the one time you restarted it or from the engineer visit?

Your attenuation for all 3 Download bands are actually good and I would expect you will be able to achieve over the 40Mbps mark.


Cheers for the insider detail...let's see:

- about 150 mtrs is walking distance, checked on google maps too, true, i dont know the actual cabling underground
- yeah i guess you are seeing that restart since i had restarted the BTO modem this morning
- since the last engineer visit on june 19 (he went to the cabinet, he did "something", DSL light and phone went down like 5 minutes), i have restarted it just a few days ago (so it stayed up like 4 weeks), i just did a "reset" with the button to see if things would change but no

thanks!
Gab
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