Is congestion causing a dip of around 10Mbps...?

[#1]

Hello,

I am on the NE26 Exchange and have an 80 Megabit VDSL connection which most of the time is usually spot on and would normally get the full bandwidth of 75Mb/s at any time of day, however, tonight I noticed my throughput has dropped by circa 10Mb/s (5-15) and latency also has a small difference reflecting this, it has been like this since around 7pm. I do appreciate that it isn't a very serious issue and almost negligable in these early stages but just thought I would share it anyway in case it doesn't rectify and/or gets worse.

Sync is still 79,987k on a Fastpath 17a profile (INP Error Correction and Interleaving disabled by the DLM) and I use the Gigabit LAN from my PC to a Zyxel VMG8924-B10A xDSL Modem/Router that has a Broadcom 63168 chipset and a Common-Mode Noise Filter, which in turn is fed from an Openreach NTE5 Phone Socket thats fitted with a Mk3 Pressac Filtered VDSL Faceplate and feeds it with 3 meters of copper CW1308 Twisted Pair Telecoms Cable.

I use a program called DSL-stats installed on a Raspberry Pi and the 'unlocked' broadcom modem to monitor and record my connection statistics as they are & over time (a smart meter for broadband connections of sorts), this doesn't show any increases in Error rates or Noise on the line, the Signal to Noise Ratio Margin (SNRM), and Bitswaps-Per-Minute (BPM) are also normal, see stats & graphs below....

.

• DSLAM type / SW version:    IFTN:0xb206 (178.6) / v0xb206
  Modem/router firmware:      AnnexA version - A2pv6F039v.d26a
  
  DSL mode:                   VDSL2 Profile 17a
  Status:                     Showtime
  Uptime:                     1 day 7 hours 0 min 37 sec
  Resyncs:                    0 (since 17 Jan 2019 20:53:53)
  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

• Max: Upstream rate = 26029 Kbps, Downstream rate = 79993 Kbps
  Bearer:  Upstream rate = 20000 Kbps, Downstream rate = 79987 Kbps
  
                          VDSL2 framing
                   Downstream    Upstream
  Line attenuation (dB):      14.2        0.0
  Signal attenuation (dB):    Not available on VDSL2       
  Connection speed (kbps):    79987        20000
  SNR margin (dB):            6.0        9.6
  Power (dBm):                3.2        3.1
  Interleave depth:           1        1
  INP:                        0        0
  G.INP:                      Not enabled        Not enabled
  Vectoring status:           5 (VECT_UNCONFIGURED)       
  RSCorr/RS (%):              N/A        0.0032
  RSUnCorr/RS (%):            N/A        0.0000
  ES/hour:                    33.5        0.24
  SNR (dB):        6.0             9.6
  Attn(dB):        14.2            0.0
  Pwr(dBm):        3.2             3.1
  MSGc:           18              150
  RS:             0               1264905
  RSCorr:         0               90
  RSUnCorr:       0               0
  Bit Errors:     0               0
  ES:             796             5
  SES:            6               0
  UAS:            28              28
  AS:             110257
  INP:            0.00            0.00
  INPRein:        0.00            0.00
  delay:          0               0
  PER:            1.65            6.15
  OR:             116.09          202.87
  AgR:            80103.09        20203.27
  Bitswap:        16565/16565             7/7
  FEC:            0               90
  CRC:            5235            5
  ES:             796             5
  SES:            6               0
  Total time = 1 days 6 hours 38 min 6 sec
  
  
  
• SNR-Per-Tone and Bit-Loading map
• SNR Margin over time
• Bitswaps per hour (2 hours)
• Cyclic Redundancy Check Errors per Hour(2 hours)

[#2]

Hi 

I've checked your line and our tests aren't showing any signs of congestion, or rather enough congestion for a problem to flag up as I believe our suppliers have a certain threshold where if it passes then it'd be classed as a hot S-VLAN.

I'd recommend keeping an eye on it and let us know if things get worse.

If you're interested, here's a copy of our testing including from a back-end system called BRAG:

GEA Test Detail
Circuit ID	NA	Service ID	BBEU00000000

Test Outcome	Pass
Test Outcome Code	GTC_FTTC_SERVICE_0000
Description	GEA service test completed and no fault found .
Main Fault Location	OK
Sync Status	In Sync
Downstream Speed	80.0 Mbps
Upstream Speed	20.0 Mbps
Appointment Required	N
Fault Report Advised	N
NTE Power Status	PowerOn
Voice Line Test Result	Pass
Bridge Tap	Not Detected
Radio Frequency Ingress	Not Detected
Repetitive Electrical Impulse Noise	Not Detected
Cross Talk	Not Detected
Estimated Line Length In Metres	353.4
Upstream Rate Assessment	Very Good
Downstream Rate Assessment	Very Good
Interference Pattern	Not Detected
Service Impact	No Impact Observed
Home Wiring Problem	Not Detected
Downstream Policing Discard Rate	0.0
Customer Traffic Level	Upstream and Downstream Traffic Detected
Technology	VDSL
Profile Name	0.128M-80M Downstream, Error Protection Off - 0.128M-20M Upstream, Error Protection Off
Time Stamp	2019-01-05T07:45:00

Parameters	MIN	MAX	AVG
Down Stream Line Rate	78.3 Mbps	79.9 Mbps	79.1 Mbps
Up Stream Line Rate	20.0 Mbps	20.0 Mbps	20.0 Mbps
Up Time	776.0 Sec	900.0 Sec	899.3 Sec
Retrains	0.0	1.0	0.0

Current and Last 15 Minute Bin Performance
Parameters	Last Traffic Count(Upto 15 mins)	Current Traffic Count(Upto 15 mins)
Start Time Stamp	2019-01-18T07:16:34.314+00:00	2019-01-18T07:31:34.314+00:00
Ingress Code Violation	0	13
Egress Code Violation	0	0
Errored Seconds	8	7
Severely Errored Seconds	0	0
Unavailable Seconds	0	0

Service Layer Data
Circuit ID:	NA	Service ID:	BBEU00000000
Telephone No.:	NA	Test Executed On:	18-01-2019 07:41:39

Date	BRAG		Brandenburg Code
	Line Reach Rate	Line Stablity
17-01-2019	Very Good	Good	OK
16-01-2019	Good	Good	OK
15-01-2019	NA	NA	NA
14-01-2019	NA	NA	NA
13-01-2019	Good	Good	OK
12-01-2019	Good	Very Good	OK
11-01-2019	NA	NA	NA
10-01-2019	Good	Good	OK
09-01-2019	Good	Good	OK
08-01-2019	Good	Good	OK
07-01-2019	NA	NA	NA
06-01-2019	Good	Good	OK
05-01-2019	Good	Very Good	OK
04-01-2019	Good	Good	OK
03-01-2019	Good	Good	OK
02-01-2019	Good	Very Good	OK
01-01-2019	Good	Very Good	OK
31-12-2018	Good	Very Good	OK
30-12-2018	Good	Very Good	OK
29-12-2018	Good	Very Good	OK
28-12-2018	Good	Very Good	OK
27-12-2018	Good	Very Good	OK
26-12-2018	Good	Very Good	OK
25-12-2018	Good	Very Good	OK
24-12-2018	Good	Very Good	OK
23-12-2018	Good	Very Good	OK
22-12-2018	Good	Very Good	OK
21-12-2018	Good	Very Good	OK

[#3]

@snadge

Hi

You are not alone, I observe a drop in throughput every evening from around 18:30 for about six hours, 

which is the time I would expect heavy use on the internet for such services as gaming, tv.

During this period ping latency increases, snr and sync speed are stable, throughput drops to around 3Mbs

I recently downloaded, overnight, a large file, approx 40Gb, and the traffic graph showed a steady 20Mbs.

The only difference between us is Location, Speed (20Mbs fttc) and I have had crosstalk since November 2018.

I am assured there is no issues with the exchange or backhaul.

There are more reports  from users showing a slowdown, some of these are due to wifi or modem issues.

I am trying to get a correlated report from a BT customer.

I am using a Vigor 2860 router modem to a Huawei dslam.

Yes a ticket has been raised, though I suspect this may be external to PN, unless the whole locality has piled onto PN.

[#4]

@dws1900 Sorry to hear that you're having similar issues.

I've tested your line and there's no congestion issues reported in your area.

So we can investigate further can you connect your computer/laptop to the router with an ethernet cable and run the BT Speedtester service at http://speedtest.btwholesale.com when you're having issues

You must ensure that you have no other programs running at the same time such as streaming, general browsing and the most common one is antivirus programs downloading updates in the background. This must be done on a wired connection and not wireless

Once the initial result is completed please click Further Diagnostics. Please type in your phone number and click run diagnostic test. This will run a test and send the results to the server for investigation

[#5]

@MatthewWheeler

Hi

This issue is already subject of another ticket, 186397515 , to do as you ask would be pointless as the instructions provided have been carried out and reported on another thread, and PN informed on said ticket.

As stated I am trying to get a neighbour to do the test, they is not too tech savvy on the internet, so will take a bit of time.

I will report via the ticket.

Thanks

[#6]

@ Gandalf - thanks for those details, I have saved them. I work in Broadband Technical Support for Sky & as you can probably tell I love all the technical jargon, our systems are similar to yours, its called LAMA, I will monitor the throughput of an evening and see if it continues and/or gets worse.

@dws1900 - I once went around all my neighbours with my unlocked broadcom modem and took stats from almost every line in the street in order to help pin down a fault lol...

just for extra info I am connected to an ECI DSLAM (Lantiq chipset).

[#7]

Ah fair, I imagine the Sky systems would be quite different as we'd use BTwholesale infrastructure, but there's bound to be some similarities. 

Keep us posted on how your monitoring goes.

[#8]

18/1/19 - 7:30pm : (79,000k sync) 74Mbps down / 18Mbps up - 13ms latency - ok so far tonight

[#9]

@snadge

Lucky you, did a BT wholesale test, at 19:15 , speed dl 6.56, ul 2.52.

This was with one computer, wifi disabled, using the PN modem, so that rules out the Vigor.

[#10]

Hello @dws1900,

We are sorry to see that you are experiencing an issue with your speed as the connection reaches your end.

Our faults team are currently investigating it with our supplier and will keep you updated via the ticket here.

[#11]

@ dws1900 - I had issues with the Plusnet Hub One, I had TWO of them and both yielded the same results which were after a few days my throughput would dip from 37Mbps to 15-25Mbps and stay that way, it could only be fixed by a reboot, I got another one from Plusnet and the same thing happened, the Plusnet Hub One is a BT Home Hub 5A (Lantiq VRX200 chipset) in white, some time ago the HH5A was reported as having issues and was one of the reasons BT rushed out the Home Hub 5B (Broadcom 63168 chipset), however, I can no longer find any evidence supporting this, I just remember it being a topic of discussion on a forum.

I swapped it for a BT Home Hub 5B and the result was slightly better speed, no dips and slightly better wifi, I have 2 of each but currently use a Zyxel VMG8924-B10A which has the same chipset as the BT-HH5B but is unlocked (can access modem stats) and has a common-mode noise/RF filter built in, since using that DLM has put my sync up and put me on Fastpath

[#12]

@snadge

Hi

Interesting.

I was told the Vigor uses a lantiq chip, and if I knew what 

Vendor ID:

b5004244 434db12d [BDCM]

means (router or dslam which is huawei) I might be wiser!!

I am still waiting for my neighbour who is on the same dslam to do a few BT checks, he is on BT, using apparently the latest modem.

I did a test with the PN1, it was slow in the evening, but ok during the day.

Curiously, the slowdown commenced earlier on Saturday.

Attached are the latency and traffic graphs (ignore the gaps, thats when I was testing with the pn1, so there will be no data,

and also ignore vigor.adsl, its vdsl, not got around to altering the legends yet)

My router stats show

Downstream             Upstream                 Actual Rate 22079 Kbps 2641 Kbps Attainable Rate 22059 Kbps 2641 Kbps Path Mode Fast Fast Interleave Depth 1 1 Actual PSD 7. 3 dB 11. 7 dB       Near End                  Far End                    Trellis ON ON Bitswap ON ON ReTx 0   1   SNR Margin 3 dB 6 dB Attenuation 31 dB 36 dB CRC 11 8511 FECS 0 s 2764 s ES 5 s 6851 s SES 0 s 51 s LOSS 0 s 0 s UAS 38 s 1326912 s HEC Errors 0 0 RS Corrections 0 0 LOS Failure 0 0 LOF Failure 4 0 LPR Failure 0 0 NCD Failure 0 0 LCD Failure 0 0 NFEC 88 32 RFEC 8 16 LYSMB 737 16

and all the GEA/KBD's show a good line, but with crosstalk.

The dslam has had another 128 lines added in a big bit on the side, annoying as the best cabinet is 500m away and half the street are on that one,  guess which one I am on!!

[#13]

@ Plusnet STAFF - My throughput is iffy again tonight - same results as previously, a circa 10Mbps dip and latency jittering 23-30ms when it's usually 13ms, definitely a sign of congestion heading this way, I do hope it gets nipped in the bud before it gets out of control.

 @ dws1900 -The VENDOR ID is brand and firmware version of the hardware your router is connected to in the cabinet (DSLAM) or exchange (DSLAM, MSAN or ISAM), BDCM or BCM is referencing Broadcom (Huawei cabinet) which is the best to be on as they support G.INP and VECTORING (although only some cabinets are enabled),  most (80% or so) are ECI Cabinets (Lantiq chipsets) and do not support G.INP or VECTORING and are considered the 'weaker' less performing chipsets when compared to Broadcom (which are famous for holding onto long/noisey lines and giving good sync), your Vigor is a  Lantiq VRX288 chipset, if I were you I would swap it out for a Broadcom modem/router as your lucky enough to be connected to a Huawei chipset, I would say you might find improvement over time (and that may still be true) but I can see your already on Fastpath with a 3db SNRM... so any difference should be immediate I think

[#14]

@snadge

Thanks for the informative reply.

Re changing the vigor, not likely in the near future, too expensive!!

Re the other comments, the snr drops from 6 to 3db quite quickly, the throughput from 00:00 to approx 18:00 is around 20Mbs, about as good as it gets for the line length, 1.5km.

Not sure what Fastpath is, and the interleave depth of 1, is that good?

Sorry to hear you are having issues again, I suspect my issues are very similar, and hope PN pass it on to OR as I requested so they may be able to as you say nip it in the bud.

I am also concerned that crosstalk is now apparent since Nov 2018 which suggests to me that the dslam + 128 extra lines may be the issue.

[#15]

Cheers for the update, how are things looking today? I just ran a full set of diagnostics but no issues are being identified.