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[Stephen71]

Hi There,

I'm having problem with my new VDSL connection to the extent that my download throughput can be as low as 2Mbps at peak times. My latency also seems very high - I'm pinging www.bbc.co.uk at 40ms where I used to get 29ms on my old ADSL line. I have ruled out any issues with my home network by connecting directly to the OR modem using my laptop and configuring a PPOE connection. The results are the same. I'm guessing there's a congestion problem somewhere.

I've had a BT engineer out 3 times and initially he found an earth on the line which he fixed but on his latest visit he said he believed the problem lies with my ISP.

I've obtained an unlocked modem and have had a look at the line stats to try and confirm what BT are saying and, using the excellent information provided by this site everything looks ok to me except the downstream SNRM looked a bit low?

Given that all this is new to me I was wondering if someone with some experience could comment on my stats (I am experiencing extremely low download speeds just now).

# xdslcmd info --show
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 22672 Kbps, Downstream rate = 67176 Kbps
Path:   0, Upstream rate = 17613 Kbps, Downstream rate = 55208 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):        5.8             6.2
Attn(dB):        0.0             0.0
Pwr(dBm):        12.6            7.7
                        VDSL2 framing
                        Path 0
B:              37              24
M:              1               1
T:              64              64
R:              12              10
S:              0.0219          0.0451
L:              18269           6204
D:              1571            621
I:              50              35
N:              50              35
                        Counters
                        Path 0
OHF:            2782569         968083
OHFErr:         7               0
RS:             890421651               4191980
RSCorr:         38453           1883
RSUnCorr:       962             0

                        Path 0
HEC:            118             0
OCD:            0               0
LCD:            0               0
Total Cells:    519483350               0
Data Cells:     5638765         0
Drop Cells:     0
Bit Errors:     0               0

ES:             2               0
SES:            0               0
UAS:            24              24
AS:             4895

                        Path 0
INP:            4.00            4.00
PER:            1.75            5.05
delay:          9.00            7.00
OR:             114.18          44.31

Bitswap:        1449            24

# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 22661 Kbps, Downstream rate = 67176 Kbps
Path:   0, Upstream rate = 17613 Kbps, Downstream rate = 55208 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):        5.8             6.1
Attn(dB):        0.0             0.0
Pwr(dBm):        12.6            7.7
                        VDSL2 framing
                        Path 0
B:              37              24
M:              1               1
T:              64              64
R:              12              10
S:              0.0219          0.0451
L:              18269           6204
D:              1571            621
I:              50              35
N:              50              35
                        Counters
                        Path 0
OHF:            2948057         1025851
OHFErr:         7               0
RS:             943377590               6585
RSCorr:         41289           1883
RSUnCorr:       962             0

                        Path 0
HEC:            118             0
OCD:            0               0
LCD:            0               0
Total Cells:    550378530               0
Data Cells:     5640565         0
Drop Cells:     0
Bit Errors:     0               0

ES:             2               0
SES:            0               0
UAS:            24              24
AS:             5186

                        Path 0
INP:            4.00            4.00
PER:            1.75            5.05
delay:          9.00            7.00
OR:             114.18          44.31

Bitswap:        1528            26

Total time = 1 hours 26 min 52 sec
FEC:            41289           1883
CRC:            7               0
ES:             2               0
SES:            0               0
UAS:            24              24
LOS:            0               0
LOF:            0               0
Latest 15 minutes time = 11 min 52 sec
FEC:            4811            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:            4002            0
CRC:            0               0
ES:             0               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
Latest 1 day time = 1 hours 26 min 52 sec
FEC:            41289           1883
CRC:            7               0
ES:             2               0
SES:            0               0
UAS:            24              24
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 25 sec
FEC:            41289           1883
CRC:            7               0
ES:             2               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
#

Thanks for taking a look!

[Stephen71]

Thought I'd attach the SNR graph too which seems low to me.

[NewtronStar]

I've had a BT engineer out 3 times and initially he found an earth on the line which he fixed but on his latest visit he said he believed the problem lies with my ISP.

Welcome to the forums Stephen71

Yes the ISP has some control on your SNRM have witnessed this first hand after a call to my ISP two weeks ago the DS has not gone below 5.9dB but whatever they did it only lasted for 14 days and the DS SNRM has started to drop below 5.4dB again.

So give your ISP a call but it's only going to be a short term fix (14 days) 

[Bald_Eagle1]

Thought I'd attach the SNR graph too which seems low to me.

Your throughput does seem very low at 2 Mbps.

What is the highest throughput speed you achieve?

Ping times are likely to be fairly high as you have quite high Interleaving depths:-

D:              1571(DS)            621(US)


There could be a fault or a noise issue affecting your connection or it could simply be that a large number of user initiated resyncs have caused Interleaving to be applied as such depths.



It may be useful to post your full 'snapshot' montage (in portrait format).
I have attached mine as an example.

Also, posting the xdslcmd info --stats data would give us a little more information.



FWIW, as we can see some blue coloured 'shared' tones in your graph and a couple of other indications from your raw stats, it appears that your modem is running very old firmware.

Given time, unless you have disabled updates, BT are likely to remotely update your modem's firmware to the current version.

The latest firmware version does appear to help some users reduce Interleaving depth. i.e. increase sync speed.
Bitswapping also appears to be more effective with newer firmware & we believe that PHYR is also effective to allow some FEC, without needing such high Interleaving depths.


If you are still using v 3 of HG612 Modem Stats, allowing it to be updated to the current versions will also give you some more Ongoing stats data/graphs that may assist a little with diagnosing any issues.

[Stephen71]

Hi Bald_Eagle1,

Thanks very much for looking at this.

Yes 2Mbps is slow but this is the worst case I see. Generally at peak times it drops as low as 3Mbps. First thing in the morning I'm up at 37.5Mbps. I'll need to ask my employer if I can work night shifts

I have had an OR engineer out twice since the installation at the start of December last year. On the first occasion I reported frequent disconnections and poor speeds and he discovered that my line was earthing between the house and the cabinet. He moved me onto a new pair and I assumed it was fixed. The trouble is that the slowdowns only happen at peak times so the speedtests I ran while he was still on the premises looked good.

The work he carried out seemed to fix the disconnections but the speed remained slow at peak times so he was called on again last week. This time he could find nothing wrong with the line and after phoning BT said the issue was at my ISP's end (Plusnet). Plusnet are now investigating whether there are capacity issues.

Due to the work which has been carried out on the line and me changing the modem firmware I have probably had several user initiated disconnects so that may explain the high interleaving values. When I first updated the modem firmware the downstream interleaving was high but upstream interleaving was off.

I am also currently running a ping test at Plusnet's request and I am also getting 4->5% packet loss.

Thanks for pointing out that my firmware is old. I will try and update it over the weekend once the ping test has done 24 hours. I understand that disconnecting the modem for 30 minutes does not cause DLM to intervene?

I will attach my portrait snapshot stats.

Below is the output of xdslcmdinfo --stats

# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 22714 Kbps, Downstream rate = 66988 Kbps
Path:   0, Upstream rate = 17613 Kbps, Downstream rate = 55208 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):        5.8             6.2
Attn(dB):        0.0             0.0
Pwr(dBm):        12.6            7.6
                        VDSL2 framing
                        Path 0
B:              37              24
M:              1               1
T:              64              64
R:              12              10
S:              0.0219          0.0451
L:              18269           6204
D:              1571            621
I:              50              35
N:              50              35
                        Counters
                        Path 0
OHF:            54558479                2384594
OHFErr:         93              0
RS:             278843621               3182182
RSCorr:         560457          33849
RSUnCorr:       4374            0

                        Path 0
HEC:            794             0
OCD:            0               0
LCD:            0               0
Total Cells:    1595704627              0
Data Cells:     14253681                0
Drop Cells:     0
Bit Errors:     0               0

ES:             23              0
SES:            0               0
UAS:            24              24
AS:             95940

                        Path 0
INP:            4.00            4.00
PER:            1.75            5.05
delay:          9.00            7.00
OR:             114.18          44.31

Bitswap:        19328           113

Total time = 1 days 2 hours 39 min 26 sec
FEC:            560457          33849
CRC:            93              0
ES:             23              0
SES:            0               0
UAS:            24              24
LOS:            0               0
LOF:            0               0
Latest 15 minutes time = 9 min 26 sec
FEC:            2990            628
CRC:            2               0
ES:             1               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
Previous 15 minutes time = 15 min 0 sec
FEC:            2423            0
CRC:            0               0
ES:             0               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
Latest 1 day time = 2 hours 39 min 26 sec
FEC:            54615           1256
CRC:            7               0
ES:             3               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
Previous 1 day time = 24 hours 0 sec
FEC:            505842          32593
CRC:            86              0
ES:             20              0
SES:            0               0
UAS:            24              24
LOS:            0               0
LOF:            0               0
Since Link time = 1 days 2 hours 38 min 59 sec
FEC:            560457          33849
CRC:            93              0
ES:             23              0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
#

Once again, thanks very much for your help. I work in the telecomms industry but I've never needed to look at DSL before so I'm learning in my free time. This website and it's members is the best source of information I've found.

[Bald_Eagle1]

Do you have a full 24 hours worth of Ongoing stats for which you could post the line_stats__FULL_MONTY_P-xxxxxx montage (from the Ongoing_Stats folder?


Your DS SNRM is just below the target 6dB at 22:49.
It probably improves slightly during daylight periods.

That suggests your connection is maxing out whatever is available, apart from being sync speed restricted by the Interleaving depth, INP & delay values:-

D:              1571            621
INP:            4.00            4.00
delay:          9.00            7.00


For the first layer of interleaving depth, the INP & delay values would usually be these:-

INP:            3.00            0.00
delay:          8.00            0.00

It is not often that US Interleaving etc. is switched on at all.

Depending on how DLM has interpreted the resyncs & error counts, your connection may now be stuck in some sort of time bound mechanism where, subject to stability, low Errored Seconds & low CRC/OHFErr errors, it may take a few days, a few weeks or even a few months to reduce Interleaving etc.

Other forum members may be able to explain that a bit better than I have.



My connection is around 1100m in length & it was almost always Interleaved at around 400 on the DS & OFF for US until the modem's firmware was updated & BT seeming to introduce PHYR (lower quantities of FEC can be seen at lower Interleaving depths or as in my case, complete removal of any Interleaving measures).

My stats:-

Code: [Select]

xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 5180 Kbps, Downstream rate = 24152 Kbps
Bearer: 0, Upstream rate = 4912 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): 7.3 6.7
Attn(dB): 24.4 0.0
Pwr(dBm): 12.7 6.6
VDSL2 framing
Bearer 0
MSGc: 26 52
B: 237 143
M: 1 1
T: 49 37
R: 16 12
S: 0.3378 0.9293
L: 6016 1343
D: 1 1
I: 254 78
N: 254 156
Counters
Bearer 0
OHF: 373530656 470643
OHFErr: 41826 334
RS: 1123121185 3677330
RSCorr: 3402444 880
RSUnCorr: 215984 0

Bearer 0
HEC: 175143 0
OCD: 12828 0
LCD: 12828 0
Total Cells: 2386507620 0
Data Cells: 438876606 0
Drop Cells: 0
Bit Errors: 0 0

ES: 19156 314
SES: 62 0
UAS: 22 22
AS: 1551594

Bearer 0
INP: 0.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 4.15 17.25
OR: 61.63 26.88
AgR: 22460.42 4939.47

Bitswap: 991763/991767 4433/4439

Total time = 1 days 23 hours 16 sec
FEC: 3402444 880
CRC: 41826 334
ES: 19156 314
SES: 62 0
UAS: 22 22
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 16 sec
FEC: 1 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: 18 1
CRC: 7 1
ES: 5 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 23 hours 16 sec
FEC: 8318 22
CRC: 1615 10
ES: 970 6
SES: 1 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 21075 42
CRC: 1596 11
ES: 1038 10
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 17 days 22 hours 59 min 53 sec
FEC: 3402444 880
CRC: 41826 334
ES: 19156 314
SES: 62 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0




You are connected a Huawei DSLAM, so Vectoring to help combat some crosstalk should be available whenever BT roll it out.

Your Hlog graph looks good (smooth curves & no evidence of bridged taps/internal star wiring etc.

QLN looks 'reasonably' O.K., although not the 'quietest' connection we have seen (values closer to -140 than -120 indicate quiet connections.

Bitloading looks quite good (no obvious gaps).

SNR looks clean too (no gaps or sudden dips other than the 'V' shape that is from power cutback or PSD masks to avoid your connection swamping ADSL/ADSL2 frequencies for other users).


  for an eventual improvement (it won't be massive, but if you are a gamer, a return to or closer to fastpath would no doubt be welcomed).

24 hours Ongoing stats from my connection are attached, as obtained at 06:00 this morning, for reference.

[Stephen71]

Hi Bald_Eagle1

Thanks for that.

I guess the slowdowns must be a caused by a congestion issue further up the network then. I don't have much time for online gaming anymore so I can live with the latency. The big issue for me is streaming which can stall at peak times. My old ADSL link didn't drop below 6mbps so the whole VDSL experience has been somewhat underwhelming so far. I just hope Plusnet manage to sort the problem sooner rather than later.

I guess there is nothing I can do about the SNRM dropping below target. This is something that has got worse with time. I'm about 400m from the cabinet.

I have attached the 24hour graphs you requested.

Thanks once again for your help.

[Bald_Eagle1]

Your ongoing connection stats look pretty good, with quite low error counts.

No doubt the highish levels of interleaving are assisting there.

I have recently been reading of other PlusNet users seeing effects of congestion, but I'm a PlusNet user & am not really seeing any (perhaps because my longer connection doesn't achieve higher speeds anyway).

On speed tests, I generally achieve around 20 Mbps regardless of the time of day or night.





Hopping PlusNet gateways by disconnecting/reconnecting the router (not modem) sometimes helps in that you may land on a less congested Plusnet gateway.

Your DS SNRM is pretty steady & from your ongoing graphs, the drops only appear to be the expected natural daily fluctuations.

I'm not sure how you would do that without causing a resync if you are still connected directly to the modem though as I've never needed to run my connection that way.

[Stephen71]

Thats good, at least It confirms what the OR engineer was saying - the line to the cabinet is fine. I had considered buying better cable than the stock RJ11 which Plusnet provide but I guess it will make no difference.

Hopefully the interleaving will reduce with time provided the OR Engineer isn't sent back out.

Your latency is impressive - On my old ADSL line I was getting around 29ms whereas my new VDSL connection is averaging around 45ms. A good reason not to take up gaming again.

I checked out my quality monitor this morning and the 4-5% packet loss I was seeing after I started the monitor at 7pm gradually reduced after 12am. This morning there is no packet loss which ties up with the automated speed test cron job I set up a few days ago.

I'm wondering if the issues I am seeing are related to my geographical location - I'm in Central Scotland. I have noticed that there is a thread on the Plusnet forums where people are experiencing congestion issues ofa similar pattern albeit not as pronounced as the problems I have.

Your constant download speed of 20.46 Mb/s also makes me envious.

Unfortunately I think there is not much more I can do to investigate at my end now. I've been getting a bit frustrated with the ping-pong between Openreach and Plusnet. The last Openreach engineer I had out said the problem was with my ISP while Plusnet are saying they need their supplier to investigate.

I have made a small donation to the running costs of the site as thank you for the help I have received.

[Bald_Eagle1]

Your latency is impressive - On my old ADSL line I was getting around 29ms whereas my new VDSL connection is averaging around 45ms. A good reason not to take up gaming again.

It was much better when FTTC was first installed back in 2011.
It was often around 5 to 10ms back then.

Your constant download speed of 20.46 Mb/s also makes me envious.

It was regularly around 30 Mbps back in the day (before crosstalk from additional users started to have an increasingly  noticeable effect).

Unfortunately I think there is not much more I can do to investigate at my end now. I've been getting a bit frustrated with the ping-pong between Openreach and Plusnet. The last Openreach engineer I had out said the problem was with my ISP while Plusnet are saying they need their supplier to investigate.

Please keep us posted regarding how you get on and/or if DLM decides to relent in due course.

I would definitely recommend the modem firmware upgrade after another week or so more of connection stability (unless it is updated remotely anyway).
It does appear to help, certainly with bitswapping etc.

[WWWombat]

Note: I wrote this yesterday, but forgot to post it. BaldEagle has added some updates since, but I don't think it clashes with anything I put.

As BaldEagle has noted, your line has been bad enough that it has triggered DLM intervention, which has taken the unusual step of intervening on both downstream and upstream.

DLM specifies how much intervention is necessary by setting the INP and delay values, which act as requirements to the modem; all other parameters are then negotiated by the modems during sync in order to provide the amount of protection demanded by "INP", but limited to a maximum extra latency demanded by "delay".

• INP = "Impulse Noise Protection", and the amount is an indication of the length of noise bursts that most be protected against. 3 is a low setting, 4 is high.
• delay = "maximum extra latency" in milliseconds. 8ms is low when only one direction has intervention.

DLM doesn't often intervene for upstream, but when it does, it often seems to compromise the downstream settings so that the combined process doesn't add too much delay to the combined round-trip; for example a low setting of 8ms for one direction can be changed into 4ms in each direction.

With that in mind, your case has pretty heavy intervention all around. High INP settings in both directions, and a total of 16ms delay.

The obvious thing to figure out now is whether this level of intervention represents the current state of your line, or the state prior to the last fix by the engineers.

Question: Did you get a DLM reset done by the openreach engineer who fixed your line, and stopped the disconnections? How long ago was this, incidentally?

The good news is that the most important factor - the ES rate  - seems low enough both upstream and downstream that DLM may well de-intervene. The thinking seems to be that an ES rate of over 2880/day triggers intervention, below 288/day triggers de-intervention, and in-between triggers nothing. De-intervention levels have to be maintained for a while, before any action is taken.

There is some evidence that DLM monitors the FEC rate too, as part of de-intervention criteria, but less is known about the thresholds for this aspect. Your FEC level doesn't feel too bad to me.

There doesn't appear to be much evidence that the slow throughput speeds of 2Mb-ish are caused by the DSL component of your line, but the longest uptime we see in the stats is only 1 day. If you can see the modem staying in sync for days on end, while the throughput drops and rises, then this will rule out your line.

I know what you mean about the interaction between Plusnet and Openreach, but remember that "their supplier" is actually BT wholesale - and they own a whole section of connectivity that could also be the cause of congestion as well as either of the other two. Other plusnet users are experiencing some issues in both of these areas at the moment.

If you are suffering packet loss, then you might find a TBB BQM tool useful, but it only works with a static IP - or at least only gives you a result for as long as you can keep the one IP allocated. Take a look at http://www.thinkbroadband.com/ping

You'll find a whole bunch of Plusnet ones to compare with at http://community.plus.net/ping-graphs/

[Stephen71]

Hi WWWombat

Thanks very much for your input.

I don't know whether the OR engineer performed a DLM reset or not but I do know that when I originally connected my unlocked modem there was to Interleaving on my upstream.

I have been running a ping test - I've attached one from Thursday / Friday. It seems to show latency increases and packet loss at peak times. I have another one running just now.

I have read the threads about other people having problems on Plusnet and the symptoms seem the same albeit a lot less severe. I wonder if this has anything to do with my geographical location in the central belt of Scotland.

My speed is appalling this evening to the extent I can't use any streaming services. My old ADSL connection which I had until the start of December last year always gave me a constant 5Mbps which at least allowed me to stream SD.

A link to my current speed results is below.

[WWWombat]

Oh wow, that is dire!

In this PN thread, I had to question my understanding of BQM graphs; congestion used to be obvious (lots of chunks of yellow and blue), and serious congestion was even more obvious (the green area would increase in height). Newer queuing mechanisms seem to mean that plain congestion is harder to spot nowadays, except for some packet loss.

Your BQM, however, seems to show signs of severe congestion.

Going back to that PN thread, congestion seems to be better spotted using the TBB speed tests, and showing big differences between the single-threaded and multi-threaded results.

Your result seems to show that too. You might want to post some results over on that thread (or maybe you already did); at least PN's networking team will pick it up.

I see Kitz has been posting over there recently. I wish BT had got my connection sorted, so I could experiment too...

BTW, Scottish lines might add a few ms to round-trip down to London, but there shouldn't be any additional likelihood of congestion or loss.

[Stephen71]

I'm actually thinking about digging out my old dial up modem 

I've added my graphs to the plusnet thread on your advice - thanks.

Havin read through the thread there is no admission from Plusnet that a problem exists which is rather frustrating.

I'd much prefer that they admitted they took on too many customers over Christmas and didnt't increase their capacity enough rather than blaming BT. I know BT users nearby and they do not have these problems.

'We made a mistake, we'll fix it' earns  much more respect than 'It wasn't me'

My advice, for what it's worth, to anyone thinking of taking out a contract with Plusnet is to wait and see if they sort their capacity issues out first.

[WWWombat]

Havin read through the thread there is no admission from Plusnet that a problem exists which is rather frustrating.

I'd much prefer that they admitted they took on too many customers over Christmas and didnt't increase their capacity enough rather than blaming BT.

I agree that it is frustrating to not hear anything, but I don't think the problem is as simple as not ordering capacity. If it were, there'd be a *much* larger group of people complaining.

Your case is so severe, that is smacks of congestion somewhere closer to you.