Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
   Glossary   Glossary
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Pages: [1] 2 3

Author Topic: FTTC Solid sync - poor upload  (Read 1257 times)

3tdk

  • Just arrived
  • *
  • Posts: 17
FTTC Solid sync - poor upload
« on: January 31, 2021, 06:36:33 AM »

Good morning, seeking advice from those more experienced than I (a new member but have been browsing this very useful forum & site for some time). I am a BT customer using HG612 in PPPoE bridge mode, Routerstats has been monitoring for over 2 weeks now.

I am trying to work out how to resolve an issue with what looks like speed capping in the OR cabinet my line is connected to. Both downstream and upstream syncs appear within the expected range, but real upload throughput is limited to somewhere near 2Mbit / sec. Depending on the speed tester used, I sometimes see a peak at the expected performance at the start of the test but this drops off almost instantly to a flat 2Mbit / sec.

Screengrab attached of a speed test from thinkbroadband that one of the helpful BT community staff pointed me to. The limit is the same whatever service I use.

I can't shift an ugly feeling that this line is somehow capped to the 2Mbit / sec performance that OR can provide, even though we are paying BT for the 10Mbit/sec upload profile and this seems to be reported correctly in their advanced diagnostics from the wholesale speed tester.
BT community forum support has been helpful at advising on DLM issues but unable to advise on the upload rate topic, and I have yet to call BT to raise an official fault since there are so many comments in other forums about "BT won't investigate upload problems"

So my obvious question... what can I do?

Thank you so much in advance for any steering to help me resolve this.

TLDR summary:
BT wholesale speed tester reports 5Mbit / sec but when you watch the numbers they quickly drop to 2Mbit / sec

I can recreate the issue using the following configuration: PC <-- cable / PPPoE --> modem (HG612) <-- cable VDSL2 --> cabinet. Other modems have produced similar results, but I'm reluctant to drop DSL as I am also waiting for DLM to relax on the upload side.




Full version (on BT community forum):
https://community.bt.com/t5/BT-Fibre-broadband/Fibre-1-upload-speed-limiting/td-p/2133518/page/2


Modem stats (I am waiting for DLM to release a bit more downstream speed - since resolving a wiring problem on my side the SNR has consistently been 9dB+ and achievable rates 39Mbit+):

Code: [Select]
Stats recorded 31 Jan 2021 06:25:37

DSLAM type / SW version: BDCM:0xc190 (193.144) / v0xc190
Modem/router firmware:  AnnexA version - A2pv6C038m.d24j
DSL mode:                VDSL2 Profile 17a
Status:                  Showtime
Uptime:                  12 days 23 hours 37 min 37 sec
Resyncs:                0 (since 18 Jan 2021 07:17:14)

Downstream Upstream
Line attenuation (dB):  26.2 0.0
Signal attenuation (dB): Not available on VDSL2
Connection speed (kbps): 32399 6758
SNR margin (dB):        9.7 7.3
Power (dBm):            12.1 3.1
Interleave depth:        8 1
INP:                    58.00 0
G.INP:                  Enabled Not enabled
Vectoring status:        5 (VECT_UNCONFIGURED)

RSCorr/RS (%):          0.0934 0.6640
RSUnCorr/RS (%):        0.0000 0.0000
ES/hour:                0 1.87
« Last Edit: January 31, 2021, 06:41:06 AM by 3tdk »
Logged

Ronski

  • Helpful
  • Kitizen
  • *
  • Posts: 4039
Re: FTTC Solid sync - poor upload
« Reply #1 on: January 31, 2021, 09:09:09 AM »

Welcome to the forums.

I'm not one of the experts, but I think there's two problems going on here.

Line conditions have either improved since your last resync, or your banded. You're downstream SNR is 9.7, which means this could sync with more speed at a target of 6.. There's also a little room for improvement on the upload. Banding is when the DLM caps the sync speed to reduce errors, too many disconnections of the modem can result in banding and lower sync speeds. This line shows what you are synced at: Connection speed (kbps):   32399      6758.

However, the upload is connected to the cabinet at 6758kbps. The DLM controls what speed you connect at, so not allowing for overheads your physical connection is capable of that speed, sped tests would be some where around 6 Mbps . I suspect the upload restriction lies elsewhere, when the DLM controls speed it restricts the line sync speed (the 6758) rather than bandwidth (the 2Mbps), so I think that bandwidth is being restricted elsewhere.

This could be a Quality of Service setting in the router, antivirus on the PC, or something at the ISPs end. Many years ago Plusnet used to cap package speeds in this way, and sometimes they would not get updated, although I don't recollect BT doing it.

It's odd that it's 2Mbps, was you ever on a 40/2 connection?
« Last Edit: January 31, 2021, 09:11:29 AM by Ronski »
Logged
Formerly restrained by ECI and ali,  now surfing along at 390/36  ;D

3tdk

  • Just arrived
  • *
  • Posts: 17
Re: FTTC Solid sync - poor upload
« Reply #2 on: January 31, 2021, 09:31:30 AM »

Thank you Ronski,

Regarding download, yes I'm sure this line has been banded. I had been rewiring a couple of weeks ago and wasn't smart enough about my disconnects / power downs, and then also had a bad crimp on an RJ11 which caused some noise. Nothing to do about that except wait for DLM to release the brakes. Sadly that is taking more than the basic 8 days, so no idea how big my DLM barriers have ended up.

Regarding upload, I'm glad you agree there is an issue. I did note in an Openreach document that there is a separate limiting system in the cabinet, which might not impact the sync speeds. so I'm not sure sure if the cap is happening outside of the cabinet or in another system. It definitely is not here, I have recreated the issue with 3x modems and a mix of direct PPPoE and through my router (separate device).

Yes, I'm pretty sure in the past we did have a 2Mb upload service; I recall one of the reasons I took out a new subscription with BT a while back was that they had removed this limit, but only if we recontracted... however I was clearly not smart enough at the time to check that the cap had actually been lifted!

(as an aside, here's where I read about the Openreach limits)

Note : The upstream throughput is also constrained on the DSLAM to the upstream rate requested in the order, i.e. 2 Mbit/s, 10 Mbit/s or 20 Mbit/s, so even if the VDSL2 upstream line speed is higher, the upstream throughput is constrained to the level ordered for the product.

The guide which contains that can be found here: https://www.cvf.openreach.co.uk/cpportal/content/dam/cpportal/public/images-and-documents/home/help-and-support/sins/documents/SIN_498_v7.7_apr_2020.pdf
Logged

Ronski

  • Helpful
  • Kitizen
  • *
  • Posts: 4039
Re: FTTC Solid sync - poor upload
« Reply #3 on: January 31, 2021, 10:29:28 AM »

Hi,

The upstream through put is restrained by the sync speed being limited, this is the case for both the upstream and the downstream. If you had a perfect very short line you would see an attainable speed of around 140/30, but the sync speed would show as per the package, so if on a 40/2 speed package it would sync at 40000/2000 or there about's, 80/20 would be 80,000/20,000. You wouldn't sync at 140,000/30,000 and be restricted at lower through put speeds. I'm not at all clued up on how it all works, this is just what I've remember and have seen.

You say you've tried three different modems, and I presume by direct PPPoE you mean direct from your PC thus taking the router out of the equation. Have you tried a different PC? Software or a configuration issue on the PC could be causing the problem, especially anti virus software.

I'm pretty sure there is no standard 8 days for a DLM to relent with banding, some lines stay banded for many months, I do believe you can request a DLM reset though. It would also be worth speaking with support, and see what they say.

I notice an absence of the attainable speeds from the modem stats, do you know what they are?

I'm sure someone far more knowledgeable will be along shortly.
Logged
Formerly restrained by ECI and ali,  now surfing along at 390/36  ;D

3tdk

  • Just arrived
  • *
  • Posts: 17
Re: FTTC Solid sync - poor upload
« Reply #4 on: January 31, 2021, 11:09:39 AM »

Thanks Ronski,

The modem reported attainable speeds are as follows.

Code: [Select]
Max: Upstream rate = 6666 Kbps, Downstream rate = 42376 Kbps
Bearer: 0, Upstream rate = 6666 Kbps, Downstream rate = 32399 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps

I did try a resync this morning for the first time in 2 weeks, hence upload has changed slightly.

The results are the same in every set-up but most recently I was using a completely clean linux USB live install on my PC and connecting direct to the modem over PPPoE - so have not added any QOS (the same device can manage a steady 60MB/s actual transfer around our home network). I'm happy I am not limiting the speeds at this end.

The question is where is the upload speed limit happening, and is it possible to fix (and is it possible to convince BT that they want to fix it)!

Thank you so much for the constructive comments so far,

Derek

 


Logged

Alex Atkin UK

  • Kitizen
  • ****
  • Posts: 2239
    • My Broadband History
Re: FTTC Solid sync - poor upload
« Reply #5 on: January 31, 2021, 11:43:03 AM »

Could have done with the stats when you resynced too as the upload sync has reduced even more so has the SNRm also reduced to 6dB or has it gone ever higher now?

Seeing if the SNR is fluctuating is one way to tell if there are issues on the line.
Logged
INTAKE (ECI) 2x Home Hub 5A OpenWrt:  1x Zen,1x Plusnet Hauwei B535-232: Voxi 4G Router: pfSense (i5-7200U) WiFi: Ubiquiti nanoHD
Thinkbroadband Quality Monitors & Zen Referral

tubaman

  • Addicted Kitizen
  • *****
  • Posts: 7055
Re: FTTC Solid sync - poor upload
« Reply #6 on: January 31, 2021, 11:54:30 AM »

The fact that the downstream rate has synced exactly the same as before confirms that the connection is banded as @Ronski mentioned earlier. So, you actually have two problems - banded downstream and seemingly wrong profile on the upstream.
You need to insist on this being passed to second line support, as the first line people likely won't have a clue what to do.
 :)
Logged
BT FTTC 80/20 Huawei Cab - Zyxel VMG8924-B10A

3tdk

  • Just arrived
  • *
  • Posts: 17
Re: FTTC Solid sync - poor upload
« Reply #7 on: January 31, 2021, 12:42:58 PM »

@Tubaman, @Alex Atkin, thank you both for your really helpful responses.

I can share you a DSLstats screenshot highlighting SNR stability. It follow the pattern I have come to expect from reading this forum; improving in the day, weaker at night, and a slower trend which mirrors the weather conditions (cold & dry is good, warm and wet is worse). The step at the end is the resync from this morning. The second attachment is the potential sync speed (and actual sync) shown by the HG612. I'm aware it is reported to be a bit optimistic but yes, it does clearly show the banding. I am no expect but both look pretty stable to me, much better than the 8800NL R2 I had on there before.

Question - in the "Additional diagnostic" section of the BTW performance tester at https://speedtest.btwholesale.com/ it tells me the following:
Quote
IP Profile for your line is 10 Mbps
. This is what  would expect, and does reflect the limit Fibre 1 package we are subscribed to.

Despite this I do see a 2Mb/sec limit in real performance, as per the screenshot in my original post.

For full disclosure I should say that the BTW performance tester will report around 6Mb / sec real performance, but that seems to be because it takes the peak upload speed as the measurement, and not the stable upload speed. I have attached a screengrab from speedtest.net which demonstrates this - a relatively high "burst" rate followed by a very consistent 2Mb / sec rate (upload is in purple). You can see this effect on the BTW speed tester, but only as the numbers flash past your eyes, before it reports the peak number.

I have seen this burst-and-stable pattern before in speed limiters, which is what makes me thing there is some limiter in effect here, separate from the raw syncs of DSL.

My conclusion is that I'm being limited at an IP / PPPoE level and not at the raw DSL level, but I don't know enough of the architecture of how my device actually appears "on the internet" to know where my traffic goes to once it gets into the cabinet and therefore how / where this would be done.

« Last Edit: January 31, 2021, 12:53:11 PM by 3tdk »
Logged

Ronski

  • Helpful
  • Kitizen
  • *
  • Posts: 4039
Re: FTTC Solid sync - poor upload
« Reply #8 on: January 31, 2021, 01:42:23 PM »

Just read you're BT thread, unfortunately they are just not seeing the issue which is clearly there. You're going to have to try telephone support, and hope you get someone who knows what they are talking about, hopefully second level support. It's not going to be easy, but won't be as painful as the issues I've had with Virgin  :wall: :wall: :wall:

There is no training period either, the line adapts all the time depending on line conditions. Looking on Codelook I can see you are on a Huawei cabinet, this is good news once you're problems are sorted out. Huawei cabinets support G.INP and dBx. G.INP is an error correction technology which doesn't impact speed, and dBx reduces the SNR target from 6dB to 3dB in 1dB steps until you reach the 40Mbps package speed if your line can support it.
Logged
Formerly restrained by ECI and ali,  now surfing along at 390/36  ;D

Alex Atkin UK

  • Kitizen
  • ****
  • Posts: 2239
    • My Broadband History
Re: FTTC Solid sync - poor upload
« Reply #9 on: January 31, 2021, 02:55:05 PM »

Huawei cabinets support G.INP and dBx. G.INP is an error correction technology which doesn't impact speed, and dBx reduces the SNR target from 6dB to 3dB in 1dB steps until you reach the 40Mbps package speed if your line can support it.

They already have G.INP on the line. ;)
Logged
INTAKE (ECI) 2x Home Hub 5A OpenWrt:  1x Zen,1x Plusnet Hauwei B535-232: Voxi 4G Router: pfSense (i5-7200U) WiFi: Ubiquiti nanoHD
Thinkbroadband Quality Monitors & Zen Referral

Ronski

  • Helpful
  • Kitizen
  • *
  • Posts: 4039
Re: FTTC Solid sync - poor upload
« Reply #10 on: January 31, 2021, 03:32:19 PM »

So they do, I forget to check.
Logged
Formerly restrained by ECI and ali,  now surfing along at 390/36  ;D

3tdk

  • Just arrived
  • *
  • Posts: 17
Re: FTTC Solid sync - poor upload
« Reply #11 on: January 31, 2021, 04:00:35 PM »

Well, thank you both for the bolstering words.

Regarding download speeds, I did read up a bit on DLM as best I could. I figured the advice from BT forum to "leave the line stable and it will retrain in time" tied in with the content I had seen about barrier levels and daily error/resync counts. I figured I just had a very high barrier to cross after my internal re-wire.

The upload issue though is a different matter, I just cannot se an explanation for it except that something somewhere still thinks we should have a 2Mbit rate.

One question; I have not been tracking the IP address and gateway assignment my router gets from BT. I figure some DHCP server is telling my local router a default route to ise for any external traffic. Is it possible that the gateway has the limiter on it? That would explain why the cabinet thinks the line has a 10Mbit profile but actual speeds are only 2.

Any hints to force a new DHCP lease? Maybe it is possible we have had the same one ever since upgrading from a 2Mbit service.

There must be a traceroute tool for that... which would help me If this thing is in the IP or packet world...

Thank you all for listening and quickly responding.
« Last Edit: January 31, 2021, 04:07:03 PM by 3tdk »
Logged

pob

  • Member
  • **
  • Posts: 32
Re: FTTC Solid sync - poor upload
« Reply #12 on: January 31, 2021, 04:11:38 PM »

Disconnect your modem from the phone socket for at least 60 minutes then re-connect (some say 30 minutes is enough)

I had an issue with my TalkTalk VDSL connection throttling upload about two weeks ago.  This fixed it.
Logged

3tdk

  • Just arrived
  • *
  • Posts: 17
Re: FTTC Solid sync - poor upload
« Reply #13 on: January 31, 2021, 04:13:47 PM »

OK, I will try the overnight tonight.
Logged

j0hn

  • Kitizen
  • ****
  • Posts: 3362
Re: FTTC Solid sync - poor upload
« Reply #14 on: January 31, 2021, 04:44:11 PM »

Regarding download, yes I'm sure this line has been banded. I had been rewiring a couple of weeks ago and wasn't smart enough about my disconnects / power downs, and then also had a bad crimp on an RJ11 which caused some noise. Nothing to do about that except wait for DLM to release the brakes. Sadly that is taking more than the basic 8 days, so no idea how big my DLM barriers have ended up.

Unfortunately the DLM usually takes considerably longer than 8 days to remove banding.
It's not as bad as it used to be (it used to get completely stuck) but it can still take weeks or months.

I did try a resync this morning for the first time in 2 weeks, hence upload has changed slightly.

The DLM will never make a positive change on the line from a manual resync.
You'll never see banding or Interleaving removed doing this.

It's actually counted as instability by the DLM that the line is resyncing.
Your best bet is to leave it alone, or to push BT for a DLM reset.

There's no doubt at all that the downstream is banded at 32.4Mb which is 1 of the common banding levels used by the OpenReach DLM.
Logged
BT FTTP 160/30 - BQM - speed test
Pages: [1] 2 3