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Hi folks, We got back off holiday recently and everything had been turned off for two weeks. Upon firing things back up I initially noticed a slight increase in Attainable rate and Line rate but the day after it had dropped to below the level it was at before we went away (The Attainable rate and Line rate are usually very close around 69500 each).
I have now tried a couple of "DRM friendly" resets leaving everything switched off either all day or overnight but I can't get the Line Rate to jump back up close to the Attainable rate as it used to be, can anyone with more talent than me take a peek at the stats below and see if there are any clues please?
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| # xdslcmd info --stats
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max: Upstream rate = 26658 Kbps, Downstream rate = 74164 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 64204 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): 6.1 15.1Attn(dB): 0.0 0.0
Pwr(dBm): 12.5 6.8 VDSL2 framing
Path 0B: 51 237
M: 1 1T: 64 45
R: 12 16S: 0.0258 0.3782
L: 19868 5373D: 1257 1
I: 64 127N: 64 254
Counters Path 0
OHF: 357541 138949OHFErr: 0 0
RS: 91377317 1956294RSCorr: 1071 0
RSUnCorr: 0 0
Path 0HEC: 0 0
OCD: 0 0LCD: 0 0
Total Cells: 73052240 0Data Cells: 308115 0
Drop Cells: 0Bit Errors: 0 0
ES: 0 0
SES: 0 0UAS: 598 598
AS: 593
Path 0INP: 3.00 0.00
PER: 1.64 4.25delay: 8.00 0.00
OR: 116.41 60.17
Bitswap: 56 3
Total time = 30 min 33 secFEC: 1071 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 598 598
LOS: 0 0LOF: 0 0
Latest 15 minutes time = 33 secFEC: 0 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
Previous 15 minutes time = 15 min 0 secFEC: 1071 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 172 172
LOS: 0 0LOF: 0 0
Latest 1 day time = 30 min 33 secFEC: 1071 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 598 598
LOS: 0 0LOF: 0 0
Previous 1 day time = 0 secFEC: 0 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
Since Link time = 9 min 51 secFEC: 1071 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0 |
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Crosstalk? And it will only get worse as more join your cab.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC
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Does that mean they managed to get the big chain and padlock off that I left around the cabinet to stop anyone else using it!!! 
I did think of that but would that be more of a gradual thing especially as I initially saw an increase in speed?
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Maybe posting xdslcmd info --pbParams data would be useful, along with both sets of stats from when the connection had higher sync speed.
It does appear that just one additional connection to the cabinet can cause a drop of 5 Mbps or more in sync speeds.
Your Interleaving depth does seem quite high, so maybe your connection does suffer from some 'interference'.
DS SNR at 6.1 dB does suggest that the connection is currently maxing out whatever is available.
We have seen a couple of cases recently where DS power seems to have been reduced (thus lower sync speeds), particularly in the D2 band, possibly as a measure to avoid your own connection causing crosstalk issues on other connections.
The pbParams before & after data may confirm that has happened (or not).
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Thanks for the quick response folks!
I wish I had the stats for the higher sync speed but sadly not, I was busy after two weeks in Italy and enjoying the higher speed 
Here is the current --pbParams data however if it helps?
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22 | # xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max: Upstream rate = 26639 Kbps, Downstream rate = 73712 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 64204 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: 26639 kbps 73712 kbps
Actual Aggregate Tx Power: 6.8 dBm 12.5 dBm============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3 Line Attenuation(dB): 4.0 20.1 29.9 N/A 10.7 25.3 38.0
Signal Attenuation(dB): 4.0 19.2 29.0 N/A 10.7 25.3 38.0 SNR Margin(dB): 15.3 14.9 15.1 N/A 6.0 5.9 5.9
TX Power(dBm): -5.5 -24.0 6.5 N/A 8.4 7.8 7.0 |
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Here's something from around 12 months ago for comparison.
I THINK it's from your own connection.
It was on fastpath back then.
Stats from 22/06/12
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Ohh...I forgot about those.
For the dumb one here (Me!), how do I tell if I am on Fastpath or Interleaved?
Here is one from just under 12 months ago which is pretty much how it has been ever since up until returning from holiday...
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| # xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 0Max: Upstream rate = 24844 Kbps, Downstream rate = 70976 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 70070 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: 24844 kbps 70976 kbps
Actual Aggregate Tx Power: 6.8 dBm 12.6 dBm============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3 Line Attenuation(dB): 4.0 20.0 29.4 N/A 10.7 25.1 37.7
Signal Attenuation(dB): 9.5 19.2 28.6 N/A 10.7 25.1 37.7 SNR Margin(dB): 15.0 14.9 15.0 N/A 6.2 6.2 6.2
TX Power(dBm): -5.3 -24.2 6.5 N/A 8.4 8.0 6.9 # |
Could this be when it happened (I always forget about this tool too)...
My Broadband Ping
Edited by D_an_W (Fri 05-Jul-13 19:51:56)
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(The Attainable rate and Line rate are usually very close around 69500 each).
DLM has added FEC/interleaving. It has requested INP protection of 3.00 and allows a maximum delay of 8ms - these are the common values that DLM uses for a first attempt.
As a result, the FEC overhead has been set at 12 bytes out of every 64, which amounts to 19% - so your sync speed ends up that much below the attainable.
Presumably crosstalk has kicked in - but it doesn't do so in a linear, gradual fashion. It is all random, depending on which pair runs close to yours in the cable(s), and which subscribers take FTTC. The documentation on vectoring suggests that a line may suffer from a subset of 5-6 major disturbers from all the lines in the cable.
Even if the crosstalk you are experiencing *does* impact your line gradually, the decision to turn on FEC/interleaving happens when the error rate hits a threshold. Once you go over the threshold, then bam! ... immediate loss of 20% of sync speed. A definite case of "the straw that broke the camel's back".
Ironically...
Once FEC/interleaving has been turned on, the attainable speed seems to increase by about the same amount as the actual speed decreases. Your line has done the same.
I have now tried a couple of "DRM friendly" resets leaving everything switched off either all day or overnight but I can't get the Line Rate to jump back up close to the Attainable rate as it used to be
Won't happen.
DLM might turn off interleaving after 2-4 weeks, if the error rate has improved, though obviously it needs to be watching how FEC stats are performing to decide whether to downgrade the intervention.
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WOW!
Thanks so much folks, I couldn't have wished for a better response!
I assume this is all out of the ISP's hands (I am not with BT) and it's not something that could be switched off or reset?
I am pretty certain it is now at the speed it was at when I first moved to 80/20 but after a while it increased to the pre-holiday level and stayed there so I will leave the connection alone now for a few weeks in the hope it settles back down.
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For the dumb one here (Me!), how do I tell if I am on Fastpath or Interleaved?
Sorry - missed this.
There are 3 separate things to look for in the "--stats" info
a) If "INP" and "delay" are non-zero, then DLM has asked for intervention.
This may happen separately for upstream and downstream.
On your line, DLM wants intervention on the downstream, but not the upstream.
b) If "D" is higher than 1, then interleaving is turned on - and this usually only happens if "delay" is non-zero - and it is this that contributes to the added latency.
On your line, you have interleaving turned on for downstream, but not upstream.
c) If "R" is non-zero, then FEC is turned on. This will be on when interleaving is turned on, and causes extra "correction" data to be sent alongside your data. This extra data is hidden from you, and is what causes a reduction in sync speed.
However, FEC might also be turned on (without interleaving) even if DLM hasn't demanded it - usually when there is a lot of spare sync speed available. The modems seem to decide this on their own, as the overhead can be handled easily.
On your line, FEC is turned on for both upstream and downstream. In the downstream case, it steals some capacity from your sync speed. In the upstream, there is enough spare capacity for it to not be noticed: the overhead is (R/N), or 16 bytes out of every 254, or about 7%.
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I assume this is all out of the ISP's hands (I am not with BT) and it's not something that could be switched off or reset?
BT seem to have a rule that if sync speed drops 25% in 14-days, it should be treated as a fault. However, they seem to be more concerned with whether you are still above your estimated speed.
So, you can get the ISP involved in those cases, in order to pass the fault on.
However, a simple case of DLM being turned on is highly unlikely to get anyone's attention. It isn't a very nice thing to have happen to you without warning, but it is fully expected, and it is getting more common now the take-up is increasing.
DLM can't be reset by the ISP, and can't ask Openreach to do it either. They *will* reset it when their own engineer requests it after fixing a fault - but even then, it doesn't often happen. On the whole, we should expect DLM to intervene for most people, and for it to remain out of our control...
... at least until vectoring is introduced - perhaps in the next 4-5 years.
I am pretty certain it is now at the speed it was at when I first moved to 80/20 but after a while it increased to the pre-holiday level and stayed there so I will leave the connection alone now for a few weeks in the hope it settles back down.
Certainly worth monitoring.
Everything I said about the DLM settings is fact, but it is supposition about the cause. We *expect* crosstalk to be causing it, but it could be a fault. If it is a fault, then you'd expect to see the effects of the fault varying and DLM varying the settings.
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So, I left my modem alone for just over a month and the speed didn't change (Up or down).
Around midnight last night I simply rebooted the modem from the GUI, initially there was no change in speed but having just checked now I can see I have returned to what it was before I originally posted (Yeah!).
Am I right in saying this is not just a coincidence?
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108 | # xdslcmd info --stats
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max: Upstream rate = 24616 Kbps, Downstream rate = 69296 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 68614 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): 6.1 15.0Attn(dB): 0.0 0.0
Pwr(dBm): 12.6 6.6 VDSL2 framing
Path 0B: 239 237
M: 1 1T: 21 45
R: 0 16S: 0.1113 0.3782
L: 17248 5373D: 1 1
I: 240 127N: 240 254
Counters Path 0
OHF: 2407823 996065OHFErr: 245 2
RS: 0 1862636RSCorr: 0 4
RSUnCorr: 0 0
Path 0HEC: 66 0
OCD: 3 0LCD: 3 0
Total Cells: 558933621 0Data Cells: 182078241 0
Drop Cells: 0Bit Errors: 0 0
ES: 58 12
SES: 7 0UAS: 39 39
AS: 4238
Path 0INP: 0.00 0.00
PER: 1.75 4.25delay: 0.00 0.00
OR: 109.51 60.17
Bitswap: 163 2
Total time = 8 hours 24 min 34 secFEC: 0 0
CRC: 245 0ES: 58 12
SES: 7 0UAS: 39 39
LOS: 7 0LOF: 6 0
Latest 15 minutes time = 9 min 34 secFEC: 0 0
CRC: 2 0ES: 2 0
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
Previous 15 minutes time = 15 min 0 secFEC: 0 0
CRC: 105 0ES: 16 1
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
Latest 1 day time = 8 hours 24 min 34 secFEC: 0 0
CRC: 245 0ES: 58 12
SES: 7 0UAS: 39 39
LOS: 7 0LOF: 6 0
Previous 1 day time = 0 secFEC: 0 0
CRC: 0 0ES: 0 0
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
Since Link time = 1 hours 10 min 37 secFEC: 0 4
CRC: 245 2ES: 50 2
SES: 0 0UAS: 0 0
LOS: 0 0LOF: 0 0
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| # xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY statusStatus: Showtime
Retrain Reason: 2Max: Upstream rate = 24628 Kbps, Downstream rate = 69296 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 68614 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: 24628 kbps 69296 kbps
Actual Aggregate Tx Power: 6.6 dBm 12.6 dBm============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3 Line Attenuation(dB): 4.0 20.2 30.0 N/A 10.7 25.4 38.3
Signal Attenuation(dB): 4.0 19.1 29.0 N/A 10.7 25.4 38.3 SNR Margin(dB): 15.1 15.0 15.0 N/A 6.1 6.1 6.1
TX Power(dBm): -4.7 -23.3 6.3 N/A 8.4 7.9 6.9 # |
My Broadband Ping
Edited by D_an_W (Sat 10-Aug-13 08:26:15)
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