Intermittent connection and upstream SNRM dropping
I have a fault that is logged and has been under investigation since early May however after 9 visits by various OpenReach engineers it seems no closer to being resolved.
This post is not to cricise the PN faults team, who now I can get hold of them are good at getting the engineers to visit. The latest BT OR Engineer, who is one of the more senior ones, seems to have run out of thing to test, swap or replace. He was able to give me his mobile number and I could call him when the fault started to occur. The faults team have escalated this with BT OR.
This post is in case anyone can provide help in identifying what the cause may be based on my description and stats from the router. Any suggestions or information that might help point BT/PN in the right direction?
My normal sync speed is about 25/4.5. I am about 900m from the cabinet, with the last 75-100m overhead.
The fault manifests itself as broadband disconnects usually mid to late afternoon as a result of a deterioration in the Upstream SNRM.
- It can happen by itself or
- Can be triggered by making or receiving a call on the landline; if not straight away then within 5 or so minutes.
- Any call usually drops the upstream SNRM by 3dB or more
This behaviour normally continues until early evening then after the next re-connect it is all back to normal speed, SNRM etc. Occasionally this gets sufficently bad that the upstream sync speed is only 500kps. Quiet line test is quiet, though when the speed is really bad there is crackling.
If I make a call that causes an upstream SNRM drop but not a reconnect then once back on hook the SNRM is back to the normal 6dB. This happens whether DECT phone or analog phone plugged straight into master socket.
I have followed all the advice/requests - a micro-splitter plugged into the master socket with just one phone and the router. Different routers - HubOne, Fritzbox, HG612 and a replacement HubOne. Different phones - Fritzbox DECT or old BT analog corded.
I have had router stats programs running (depending on the router) collecting stats and can see the upstream SNR drop away, spike etc. The download SNRM is stable through most of this.
On every single visit so far the engineers have not been able to detect any faults with their test equipment. Various BT OR Engineers have replaced the Mk3 faceplate for a Mk5; replaced the external connection box that joins the dropwire; replaced some external overhead line where probably a squirrel had chewed part way through. All to no avail.
Two attachments:
- HubOne from Monday 20th, including engineer visit with line disconnected
- HG612 today (after I swapped the router last night
xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 3686 Kbps, Downstream rate = 29916 Kbps
Bearer: 0, Upstream rate = 3200 Kbps, Downstream rate = 22399 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): 7.8 2.3
Attn(dB): 25.4 0.0
Pwr(dBm): -0.5 -0.6
VDSL2 framing
Bearer 0
MSGc: 34 424
B: 47 32
M: 1 1
T: 51 1
R: 16 16
S: 0.0681 0.3187
L: 7520 1255
D: 951 69
I: 64 50
N: 64 50
Counters
Bearer 0
OHF: 3819492 971516
OHFErr: 24 89
RS: 973913144 2686308
RSCorr: 43957 194717
RSUnCorr: 545 0
Bearer 0
HEC: 139 0
OCD: 17 0
LCD: 17 0
Total Cells: 715947787 0
Data Cells: 156068697 0
Drop Cells: 0
Bit Errors: 0 0
ES: 241 182
SES: 190 73
UAS: 509 336
AS: 16643
Bearer 0
INP: 8.00 3.50
INPRein: 0.00 0.00
delay: 16 5
PER: 4.35 17.19
OR: 73.43 200.01
AgR: 22472.21 3400.31
Bitswap: 8339/8515 185/190
Total time = 23 hours 33 min 19 sec
FEC: 1716077 3269052
CRC: 43497 537
ES: 241 182
SES: 190 73
UAS: 509 336
LOS: 13 0
LOF: 117 0
LOM: 36 0
Latest 15 minutes time = 3 min 19 sec
FEC: 1336 30669
CRC: 0 7
ES: 0 3
SES: 0 1
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 1724 47440
CRC: 0 24
ES: 0 6
SES: 0 1
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 23 hours 33 min 19 sec
FEC: 1716077 3269052
CRC: 43497 537
ES: 241 182
SES: 190 73
UAS: 509 336
LOS: 13 0
LOF: 117 0
LOM: 36 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 = 4 hours 37 min 21 sec
FEC: 43957 194717
CRC: 24 89
ES: 1 29
SES: 0 3
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
#
The saga may have completed 
After the engineer trying some more things (temporary length of overhead line; swapping onto a different pair of the underground section), all of which made some improvement to speed but not reliability; i was finally moved onto a different fibre port in the cabinet. It took the engineer 3 hours plus an overnight loss of broadband as he had difficulty in getting the service centre in India to transfer the connection.
A day and a half in the line seems stable, doesn't drop by itself or when making a phone call. I have a stable 4.5/27 connection. Hopefully I wont lose too much speed as DLM does its stuff.
The tantalising bit is that when the engineer swapped pairs after taking out the temporary overhead line, for ten minutes I synced at 6.9/45. Then he put me on another pair and I was back to 4.5/29. He tells me that DLM might get me to those speeds but currently attainable is only 5/30 at best so I don't really believe him. I have a suspicion that I might still be on a section of alu cable underground whereas the other pair was patched through a new section of copper cable they installed earlier in the year.
