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[lewisp8]

So, I've had FTTC for 2 years. However now my speed is at the lowest I've ever seen. Could someone who is good at analysing line stats possibly tell me why my 21Mb connection dropped to 15Mb in the past 3 months? I understand i have vectoring applied to the line but also from what i can see i dint see any sign of G.inp? The line length is about 1800M


Stats recorded 15 Aug 2016 14:27:04

DSLAM/MSAN type:           BDCM:0xa48c / v0xa48c
Modem/router firmware:     AnnexA version - A2pv6C038m.d24j
DSL mode:                  VDSL2 Profile 17a
Status:                    Showtime
Uptime:                    9 min 3 sec
Resyncs:                   0 (since 15 Aug 2016 14:21:02)
         
            Downstream   Upstream
Line attenuation (dB):     27.2      0.0
Signal attenuation (dB):   Not monitored      
Connection speed (kbps):   17877      3117
SNR margin (dB):           6.3      6.4
Power (dBm):               10.5      6.8
Interleave depth:          351      1
INP:                       3.00      0
G.INP:                     Not enabled      Not enabled

RSCorr/RS (%):             0.0641      0.0000
RSUnCorr/RS (%):           0.0000      0.0000
ES/hour:                   38.7      5.52




xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   2
Last initialization procedure status:   0
Max:   Upstream rate = 3134 Kbps, Downstream rate = 20512 Kbps
Bearer:   0, Upstream rate = 3117 Kbps, Downstream rate = 17877 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):    6.3       6.4
Attn(dB):    27.2       0.0
Pwr(dBm):    10.5       6.8
         VDSL2 framing
         Bearer 0
MSGc:      26      58
B:      51      95
M:      1      1
T:      62      35
R:      12      14
S:      0.0925      0.9724
L:      5536      905
D:      351      1
I:      64      110
N:      64      110
         Counters
         Bearer 0
OHF:      94500      31916
OHFErr:      2      0
RS:      23393374      2233708
RSCorr:      14990      0
RSUnCorr:   4      0

         Bearer 0
HEC:      0      0
OCD:      0      0
LCD:      0      0
Total Cells:   18684234      0
Data Cells:   12071399      0
Drop Cells:   0
Bit Errors:   0      0

ES:      14      2
SES:      12      0
UAS:      115      103
AS:      544

         Bearer 0
INP:      3.00      0.00
INPRein:   0.00      0.00
delay:      8      0
PER:      5.75      17.08
OR:      44.47      29.97
AgR:      17921.99   3146.97

Bitswap:   391/391      13/13

Total time = 22 min 37 sec
FEC:      39666      71
CRC:      2241      2
ES:      14      2
SES:      12      0
UAS:      115      103
LOS:      0      0
LOF:      13      0
LOM:      10      0
Latest 15 minutes time = 7 min 37 sec
FEC:      12827      0
CRC:      2      0
ES:      1      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Previous 15 minutes time = 15 min 0 sec
FEC:      26839      71
CRC:      2239      2
ES:      13      2
SES:      12      0
UAS:      115      103
LOS:      0      0
LOF:      13      0
LOM:      10      0
Latest 1 day time = 22 min 37 sec
FEC:      39666      71
CRC:      2241      2
ES:      14      2
SES:      12      0
UAS:      115      103
LOS:      0      0
LOF:      13      0
LOM:      10      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
LOM:      0      0
Since Link time = 9 min 3 sec
FEC:      14990      0
CRC:      2      0
ES:      1      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
#



xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   2
Last initialization procedure status:   0
Max:   Upstream rate = 3134 Kbps, Downstream rate = 20512 Kbps
Bearer:   0, Upstream rate = 3117 Kbps, Downstream rate = 17877 Kbps

Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3959)
Medley Phase (Final) Band Plan
US: (7,32) (871,1156)
DS: (33,859)
     VDSL Port Details        Upstream        Downstream
Attainable Net Data Rate:        3134 kbps          20512 kbps
Actual Aggregate Tx Power:          6.8 dBm           10.5 dBm
====================================================================================
  VDSL Band Status   U0   U1   U2   U3   U4   D1   D2   D3
  Line Attenuation(dB):   12.7   61.5   N/A   N/A   N/A   24.4   75.0   N/A
Signal Attenuation(dB):   12.7   60.4   N/A   N/A   N/A   39.2   N/A   N/A
        SNR Margin(dB):   6.3   6.4   N/A   N/A   N/A   6.3   N/A   N/A
         TX Power(dBm):   0.7   5.5   N/A   N/A   N/A   10.5   N/A   N/A
#

[ktz392837]

Retrain reason 2 means negative margin, no bearer 1 means no Ginp, I would say vectoring is likely not enabled unless you are lucky to be on the limited trial. 

As you have had negative margin I would guess more people are being enabled on you cab and you are getting more crosstalk interference.  When this crosstalk takes your margin down so modem can't hold connection you will retrain with a 6db target therefore reducing your speed.

Until Ginp & vectoring is available  this is something we are all having to put up with.  If you are on an eci cab (like me) we may be waiting a long long long time for this.

I am sure someone with more experience will post more information and correct me where wrong.

[lewisp8]

Excuse the vectoring, i meant to say Interleaving    My cab is a Huawei 288 so hopefully some luck will come

[j0hn]

sounds like crosstalk reducing speeds. have you ever had g.inp?  unless you've had a recent dlm reset I wouldn't expect g.inp to randomly turn on after 2 years. vectoring is even less likely unfortunately, as that's what you need to mitigate the crosstalk.

[WWWombat]

With only limited statistics, I can only surmise, but...

Your line has had interleaving+FEC activated (INP=3, delay=8) downstream. This is likely to be because of a high error rate seen by the DSLAM (or you've had a recent DLM reset), but we can't tell *when* it happened.

FEC is currently using 19% of your bandwidth for error recovery, and you can see from the number of FEC in the "since line time" stats, you are getting lots of errors fixed through this. 15,000 FEC in 9 minutes (or 40,000 FEC in 22 minutes) seems like quite a rate to me - about 30 errors per second.

Again, we can't tell how long this has been going on, nor can we tell the cause. Nor can we tell why DLM has decided your line needs "FEC+interleaving" to fix the issue instead of G.INP retransmission (though perhaps retransmitting 30 blocks per second is considered excessive).

It is a fair bet, though, that the extra noise from crosstalk (ie other subscribers) has stolen some of your speed. It has likely also added some of that noise has also caused errors, which has triggered DLM intervention ... and stolen more of your speed.

There are likely things you can do to check the physical setup of your phone line to make sure you aren't inadvertently causing the errors, but I'll leave others to help there...

[ejs]

xdslcmd info --vectoring to see the vectoring status. If vectoring doesn't do much for long lines, I suppose crosstalk must also be a relatively minor issue for long lines.

[NewtronStar]

I suppose crosstalk must also be a relatively minor issue for long lines.

I don't see 5Mbps lost by crosstalkers on a 1000 meter line as minor issue every 1Mbps you gain is like gold dust on a long line.

[ejs]

And for this 1.8km line, I don't see why the 21Mb to 15Mb drop must be due to crosstalk, although that seems to be what 3 different people have assumed must be the most likely reason.

Has anyone else noticed the total time being only 22 minutes (since the device was rebooted?), and yet there's already been one drop in connection?

[NewtronStar]

I suppose it must be easy for users to blame it on crosstalk and most of the time you never get to see your crosstalker unless your gathering 24/7 stats and it shows up as plain as day when the crosstalker turns off their modem your SNRM suddenly rises +2.0 - 3.0dB that's crosstalk for ya.

[lewisp8]

I didn't mention that recently i have just changed from plusnet to BT, it was shortly after that the connection speed dropped. Would the switch of provider have caused a DLM reset and the loss of G.INP?

[ejs]

Yes, that could well be it. I'm still questioning the modem uptime and the drop within only 10 minutes, although it could have just been bad timing.

[j0hn]

I didn't mention that recently i have just changed from plusnet to BT, it was shortly after that the connection speed dropped. Would the switch of provider have caused a DLM reset and the loss of G.INP?

if you added that in your 1st post your answers would have reflected that 
when g.inp comes back on you may notice a slight increase in sync. it's certainly caused a dlm reset, it's removed g.inp, and added interleaving + FEC which is taking a chunk of your bandwidth. when g.inp comes back the interleaving/fec may drop back off, increasing speed further.

[lewisp8]

It would appear that G.INP has been re applied from what i can tell, although no increase in DL speed is observed

xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason:   1
Last initialization procedure status:   0
Max:   Upstream rate = 3080 Kbps, Downstream rate = 20048 Kbps
Bearer:   0, Upstream rate = 3080 Kbps, Downstream rate = 19883 Kbps
Bearer:   1, Upstream rate = 0 Kbps, Downstream rate = 0 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):    6.6       6.2
Attn(dB):    27.2       0.0
Pwr(dBm):    10.4       6.7
         VDSL2 framing
         Bearer 0
MSGc:      -6      56
B:      243      95
M:      1      1
T:      0      34
R:      10      12
S:      0.3908      0.9841
L:      5200      878
D:      8      1
I:      254      108
N:      254      108
Q:      8      0
V:      0      0
RxQueue:      16      0
TxQueue:      8      0
G.INP Framing:      18      0
G.INP lookback:      8      0
RRC bits:      0      24
         Bearer 1
MSGc:      90      -6
B:      0      0
M:      2      0
T:      2      0
R:      16      0
S:      10.6667      0.0000
L:      24      0
D:      1      0
I:      32      0
N:      32      0
Q:      0      0
V:      0      0
RxQueue:      0      0
TxQueue:      0      0
G.INP Framing:      0      0
G.INP lookback:      0      0
RRC bits:      0      0
         Counters
         Bearer 0
OHF:      0      214994
OHFErr:      0      12
RS:      207731064      1192834
RSCorr:      56783      17
RSUnCorr:   0      0
         Bearer 1
OHF:      1268420      0
OHFErr:      0      0
RS:      7610148      0
RSCorr:      35      0
RSUnCorr:   0      0

         Retransmit Counters
rtx_tx:      6915796      0
rtx_c:      510      0
rtx_uc:      0      0

         G.INP Counters
LEFTRS:      22      0
minEFTR:   19872      0
errFreeBits:   6173227      0

         Bearer 0
HEC:      0      0
OCD:      0      0
LCD:      0      0
Total Cells:   778982937      0
Data Cells:   42388755      0
Drop Cells:   0
Bit Errors:   0      0

         Bearer 1
HEC:      0      0
OCD:      0      0
LCD:      0      0
Total Cells:   0      0
Data Cells:   0      0
Drop Cells:   0
Bit Errors:   0      0

ES:      58      47
SES:      11      0
UAS:      59      48
AS:      20375

         Bearer 0
INP:      46.00      0.00
INPRein:   0.00      0.00
delay:      0      0
PER:      0.00      16.79
OR:      0.01      29.53
AgR:      19903.35   3109.63

         Bearer 1
INP:      2.50      0.00
INPRein:   2.50      0.00
delay:      0      0
PER:      16.06      0.01
OR:      47.81      0.01
AgR:      47.81   0.01

Bitswap:   9942/9942      348/348

Total time = 14 hours 28 min 33 sec
FEC:      3911363      224
CRC:      1773      48
ES:      58      47
SES:      11      0
UAS:      59      48
LOS:      1      0
LOF:      8      0
LOM:      0      0
Latest 15 minutes time = 13 min 33 sec
FEC:      2301      0
CRC:      0      0
ES:      0      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Previous 15 minutes time = 15 min 0 sec
FEC:      2973      0
CRC:      0      0
ES:      0      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Latest 1 day time = 14 hours 28 min 33 sec
FEC:      3911363      224
CRC:      1773      48
ES:      58      47
SES:      11      0
UAS:      59      48
LOS:      1      0
LOF:      8      0
LOM:      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
LOM:      0      0
Since Link time = 5 hours 39 min 33 sec
FEC:      56783      17
CRC:      0      12
ES:      0      13
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
#

Stats recorded 16 Aug 2016 11:11:43

DSLAM/MSAN type:           BDCM:0xa48c / v0xa48c
Modem/router firmware:     AnnexA version - A2pv6C038m.d24j
DSL mode:                  VDSL2 Profile 17a
Status:                    Showtime
Uptime:                    5 hours 40 min 33 sec
Resyncs:                   0 (since 16 Aug 2016 11:05:40)
         
            Downstream   Upstream
Line attenuation (dB):     27.2      0.0
Signal attenuation (dB):   Not monitored      
Connection speed (kbps):   19883      3080
SNR margin (dB):           6.6      6.2
Power (dBm):               10.4      6.7
Interleave depth:          8      1
INP:                       46.00      0
G.INP:                     Enabled      Not enabled

RSCorr/RS (%):             0.0273      0.0012
RSUnCorr/RS (%):           0.0000      0.0000
ES/hour:                   4.01      3.25


            Downstream      Upstream
General
   rtx_tx             6915797            0               
   rtx_c              511                0               
   rtx_uc             0                  0               
   LEFTRS             22                 0               
   minEFTR            19872              0               
   errFreeBits        6191407            0               
Bearer 0
   RxQueue            16                 0               
   TxQueue            8                  0               
   G.INP Framing      18                 0               
   G.INP Lookback     8                  0               
   RRC Bits           0                  24             
   Interleave depth   8                  1               
   INP                46.00              0.00           
   INPRein            0.00               0.00           
   Delay              0                  0               
Bearer 1
   Interleave depth   1                  0               
   INP                2.50               0.00           
   INPRein            2.50               0.00           
   Delay              0                  0               

[j0hn]

before g.inp: Connection speed (kbps): 17877      3117
with g.inp: Connection speed (kbps): 19883      3080

looks like over 2mb increase to me?

[digitalnemesis]

It would appear that interleaving has been disabled and G.INP enabled increasing your ds sync from 17877 to 19883.