Beating my head against the wall

[#1]

Yet again I turn to the community for some help. A couple of days ago the power in my house was shut down for the electricity board to do some testing of the service from their sub-station.

When the power was restored I noticed from DSLstats that the downstream SNRM was very high at 16.9db compared to its usual level of 5.2 to 5.5db. The net result is a slower VDSL connection than I have been used to. I've been a Plusnet customer for some years and it is not the first time I've encountered this problem. It invariably drives me nuts trying to resolve the issue via Customer Support.

The router is currently synched at 68.379Mbps but instead of a usable down speed of somewhere between 52 and 55 Mbps i.e. afterI'm getting 45.293Mbps.

I know what my usually very stable connection achieves. Can anyone suggest how I get the line returned to its usual profile on the downstream side?

[#2]

Sorry guys bad form to reply to one's own post but need to correct a glitch. It should have read as:-

The router is currently synched at 68.379Mbps but instead of a usable down speed of somewhere between 52 and 55 Mbps i.e. after error correction and vectoring losses, I'm getting 45.293Mbps.

[#3]

Welcome to the forum.  🙂

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@BobR1 wrote:

Sorry guys bad form to reply to one's own post...

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For future reference - there's a 20 minute window after posting when you can modify your post (Post options drop-down menu).

[#4]

Thank you for that advice.

I see now that the fault ticket I raised has been arbitrarily closed.

Support have chosen to classify it as INTERMITTENT. It is NOT. The connection is stable but it is being throttled with a very high downstream SNRM setting.

I really cannot  figure out if they are being deliberately obtuse or just do not understand. 

[#5]

Going back I recalled a similar situation from March 2019. It wasn't fixed until an engineer was called to do a GEA test. It then got fixed along with an associated VLAN busy problem at the exchange which I did not understand.

Note the downstream speed highlighted in green in the file uploaded.

[#6]

@BobR1 

The attachment to your last post suggests to me that you were on the 40/10 fibre service not the 80/20 Fibre extra one. Which are you on now?

There was also an interim 55/10 running as the standard fibre service at one time. Have you upgraded or was the first problem due to you being put on the wrong service?

If you are on the 55/10 service then it might be that the line has been banded or that the power fail just resulted in the DLM automatically reducing the speed. If that is the case then all you can do is wait for it to automatically correct thespeed  back to normal.

As an aside, I was on the 55/10 service many years ago. When I came to recontract I found that by quoting competitors prices for the 80/20 service I could negotiate an upgrade at a lower price than if I stayed on the 55/10 service.

[#7]

@Baldrick1

Hi Baldrick, yes you are right. Tthe 2019 problem  was when I first subscribed to the 80/20 package and I had previously to that been on the 55/10 one. Plusnet maintained they had set up the 80/20 profile correctly but the engineer said that was not the case and he got things changed.

There was also a reference to a 'busy VLAN' at the exchange, which I didn't understand back then and barely do now.

What is really boiling my p**s is that I have spelled it out to Plusnet support as clearly as I can and they arbitrarily class it as an intermittent problem that has now gone away. It quite obviously has not while I'm still seeing 16.6db on the downstream SNRM.

[#8]

@BobR1 

My edit of the last post crossed with your reply so please ignore it.

A busy VLAN, also referred to as a hot VLAN, means that there is more internet traffic passing through the area BT infrastructure than can be handled at the normal speed, so all the subscribers feeding into that 'line' (fibre of course) have to wait their turn, causing a local slow down. This is corrected eventually by BT providing more capacity or rerouting some of the traffic.

Hopefully a Plusnet staffer will come along and do a GEA test for you. If the line is banded then it can be reset, but if it's just the DLM operating I'm afraid that you will have to wait until it improves.

[#9]

@Baldrick1

Thanks for that input Baldrick1 and I will persist until a Plusnet staffer who actually reads and understand the ticket does appear and does something about it. I am aware of the role of the DLM but thought that it would re-train from 6db when the router was powered up after the electricity was restored.

Upstream isn't an issue for me since I don't upload much traffic and anyway it's SNRM is 6.3db

[#10]

@BobR1 

if the line is not banded and DLM is working then it will retrain to the line. Unfortunately it does this at its own pace, which can be quite slow. You might have to monitor it over several days to see if there’s any improvement.

As I understand it Plusnet can only request a DLM reset if the line is banded and has a low error rate. Otherwise if you are getting above your minimum guaranteed speed you are likely to have problems getting a speedy resolution.

[#11]

@Baldrick1 

Noted. If I can establish that there is no banding I will probably have to hope the DLM responds reasonably quickly.

One thing is already certain - at my next renewal i will be a Zen customer.

[#12]

Thanks for your post @BobR1 and welcome to our Community Forums.

I'm sorry to see you're having issues with your speed.

I've checked this out our side and I can't find anything our end that'd be restricting your throughput.

In addition, as of yesterday your sync speed has dropped to 45293 and the profile is "Downstream: 0.128M-80M 4dB with Retransmission (High). Upstream: 0.128M-20M with no error protection" giving a line speed of 43.2mbps taking into account the high retransmission that DLM's enabled.

Before yesterday you were on the profile "0.128M-80M Downstream 3dB, Retransmission High - 0.128M-20M Upstream, Error Protection Off" so the SNRM target we can see has increased by 1dB. 

You're also not on a hot VLAN as there's no congestion seen at the exchange. 

We have absolutely no control over your sync speed or SNRM. All we can do remotely to a FTTC line is request a banding indicated by "0.128M-80M" on a GEA or RRT test reset but in this case you're on the highest banding already. 

As our testing isn't showing any issues with the line and you're within the estimated speed range for your line, an Openreach engineer sadly wouldn't investigate as your speed's within expectations. Appreciate you had higher speeds in the past, but that doesn't mean you'll always get that same speed.

I am though interested in the sync speed of 68mbps you were getting yesterday morning. Has anything changed since then? 

I've attached below a copy of the testing I've run:

GEA Test Detail

Circuit ID: N/A Service ID: [redacted BBEU] 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 43.2 Mbps Upstream Speed 10.1 Mbps Appointment Required N Fault Target Fix Time   Fault Report Advised N Estimated Line Length In Metres 778.4 Upstream Rate Assessment Good Downstream Rate Assessment Very Good Interference Pattern Regular Interference Observed Daily Service Impact No Impact Observed Interference Duration Longest Occurrence ;00:00to23:45 Interference Location Customer Premise Interference Observed In Days 0 Home Wiring Problem Not Detected Downstream Policing Discard Rate 0.0 Customer Traffic Level Upstream and Downstream traffic detected Technology VDSL DP Type External Current 15Min Bin Retrains 0 Last 15Min Bin Retrains 0 NTE Power Status PowerOn Voice Line Test Result Pass Bridge Tap   Radio Frequency Ingress Not Detected Repetitive Electrical Impulse Noise Not Detected Cross Talk Not Detected Profile Name 0.128M-80M Downstream 3dB, Retransmission High - 0.128M-20M Upstream, Error Protection Off Time Stamp 2021-09-28T10:45:00 Parameters MIN MAX AVG Down Stream Line Rate 43.2 Mbps 65.4 Mbps 60.2 Mbps Up Stream Line Rate 9.6 Mbps 10.0 Mbps 9.8 Mbps Up Time 0.0 Sec 900.0 Sec 896.2 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 2021-10-11T09:15:10Z 2021-10-11T09:30:10Z Ingress Code Violation 0 0 Egress Code Violation 0 0 Errored Seconds 0 0 Severely Errored Seconds 0 0 Unavailable Seconds 0 0

I do hope this helps. 

[#13]

Hi Gandalf - firstly, thank you for trying to help.

I'll attach what is being reported from my router via the DSLstats application. 

At the most fundamental level I do not understand the downstream SNRM level of 17.0db that is also being currently reported. Until the power drop on Friday last it would have been somewhere between 5.2 and 5.5db on the downstream side.

I grant that I may be misunderstanding how things work but doesn't a high SNRM value impede the speed obtained?

If you need any of the info available to me via the other tabs on the DSLstats application just tell me and I'll post them.

[#14 · Accepted solution]

Hi @BobR1 thanks for getting back to me.

68555's not actually your sync speed, it's the maximum attainable your modem's calculated your line can in theory achieve.

Your sync speed that your modem's negotiated to the cabinet (the green box in the road) is 45293.

The cause for this is going to be the high SNRM in turn likely caused by the power outage you've had. This wouldn't be a throughput or congestion issue as there's nothing our end or at the exchange that can affect your sync rate.

As DLM hasn't applied a banding to reduce your speed, it's just in effect panicked and risen the SNRM while keeping the 'target' SNRM <6dB (currently 4dB), we can't do anything to reset this back down to the target sadly. 

I'd personally recommend giving it a little more time for DLM to make changes to drop the SNRM. Based on the target and the maximum attainable, I'm quietly confident you'll get your speed back. 

Does this make sense? Let me know if not though.

[#15]

@Gandalf 

Hello again and thanks for straightening me out. I note that the 'Line Stability Assessment' on the test you attached changed to 'Pink' on 5th October. I'm not aware of any interruptions on that date - the power cut was 8th October. But it is what it is I guess.

So... I think I've taken this as far as it can go and my thanks to all who contributed.

I will therefore change the status of this problem to 'Fixed' and hope the DLM doesn't take too long to reduce that SNRM setting.