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Puzzling Speed Degradation

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Puzzling Speed Degradation

Am hoping the collective wisdom of this community can help resolve an issue that, so far, seems to have stymied Plusnet Tech Support. I have an open ticket because since early May a line that typically synched at 76Mbps and had an attainable speed of 56Mbps has been substantially degraded. There has been no change to the equipment at my end and if it matters I have a static IP address. To see the details of the circuit I am showing two GEA Tests and if anyone can point me in the right direction I will be most grateful.

 

 

20 REPLIES 20
Townman
Superuser
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Registered: ‎22-08-2007

Re: Puzzling Speed Degradation

Those reports do not give a lot to go on, beyond the change in profiles from HIGH retransmission to LOW retransmission.

I would be guessing that previously you might have had a higher sync rate, but that would be at the "cost" of a high transmission error rate.  You now have a lower sync rate which delivers a more stable connection with fewer errors requiring retransmission.  The latter should give you a more dependable DATA transmission rate.

The acid question is what is the real world issue you are encountering with this apparent change?

The router stats from then and now would be more informative.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

Kdog
Aspiring Pro
Posts: 160
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Registered: ‎26-01-2018

Re: Puzzling Speed Degradation

As townman says, not a lot apparent on those tests and a good 16 months between them as well.

I would say that that line length estimate would typically give about mid 40's download, and the fact that even with the high download speed your upload was always on the range for an 800 meter line leads me to think you were overperforming at 70, potentially with the higher errors and over time DLM has been slowing you down to a more appropriate range to balance the raw speed and the data stability.

What are your estimates? Check the contract, or put your phone number in here:

www.broadbandchecker.btwholesale.com
BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

Thanks for the comments. I get where you are coming from and I can of course post the current router stats [attached]. I wasn't in the habit of routinely monitoring but I have been over the past week.

The situation is that until late May and since the start of my current contract period in February 2020 I had a stable connection with, as I said, a 76Mbps synch and an attainable speed of around 56Mbps.The router was showing downstream SNRM of between 4.6 and 5.1 dB. Suddenly that changed and I know of no reason why.

I do not understand why the the profile on the line has changed so significantly unless it is connected with the load on my exchange?

 

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

Apologies - I didn't respond to your point about estimates etc. Firstly, I'm not a newbie to Plusnet I have been a customer for over 6 years. Secondly, estimates are one thing but I suggest the real life experience over a period of time is far more relevant.

If OpenReach are allowed to manipulate a line's behaviour simply so it matches their estimates, as opposed to allowing a line to achieve the best stable performance - then the estimate becomes a self-fulfilling prophecy and the user is being denied what they are paying for.

Townman
Superuser
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Registered: ‎22-08-2007

Re: Puzzling Speed Degradation

There is theory and then there is the practicality of real world physics.

In many areas as the uptake of VDSL increases, so does inter-circuit interference (know as cross talk) which means that to ensure everyone gets a workable service the power output an individual circuit needs to be reduced which can lead to slower attainable speeds.  As such that is what it is and we have to live with it.

In your case, I suspect that something else is "a foot..." for the DS SNRM is 16dB which suggests that there is noise being encountered on the line.

Broadband is not going to work well if the "phone" line is not working properly.

Please perform a quiet line test - dial 17070 select option 2 using a corded phone plugged into the test socket behind the face plate of the master socket. It should be silent. A noisy phone line (or no dial tone) will have a marked adverse impact on the performance of broadband.

If the line is noisy or there is no dial tone, then a PHONE LINE fault needs to be raised with your phone provider. If this is PlusNet, you can report a fault on line using the button below.  From the Q&A list, choose the one which matches the problem, 'open' the 'section' and click the trouble-shooter link.  NB: If you receive a failure message (rather than a log-in prompt) then log-in to the user portal in a different browser tab and attempt to use the trouble-shooter again.


 

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

First thing I did when the problem started was to run a quiet line test and the line is VERY quiet. But in the interest of following up any good suggestions I will do it again and post back in a few minutes.

MisterW
Superuser
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Registered: ‎30-07-2007

Re: Puzzling Speed Degradation



In your case, I suspect that something else is "a foot..." for the DS SNRM is 16dB which suggests that there is noise being encountered on the line.

The DSL has been up for over 5 days, could it just be a low sync event at the time?. What does the SNRM/speed show if you force a resynch ?

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

Took a while to find my corded phone! As I said the line is very quiet - several years ago now I did have a noisy line problem so I know what one sounds like.

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

@MisterW

I actually powered my router down for an hour earlier today to see if a resynch would help but it didn't.

BUT oh wow - after doing the QLT [which obviously dropped the VDSL2 connection] and putting the faceplate back I see my router is now reporting a downstream SNRM of 4.8dB which is much more like it. But interleaving depth has gone up from 4 to 8 and the max attainable to 70.566Mbps.

All of which suggests that something [the DLM?] has woken up. Hopefully as the connection settles down over time now it will re-stabilise to what I have been used to. Fingers crossed anyway.

 

 

Townman
Superuser
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Re: Puzzling Speed Degradation


@BobR wrote:

@MisterW

and putting the faceplate back I see my router is now reporting a downstream SNRM of 4.8dB which is much more like it.


Removing and reseating the faceplate has been known to make a significant difference before.  The contact pins can become tarnished resulting in poor quality electrical conduction.

Equally as @MisterW inferred, when the last resync took place their might have been electrical noise around.  When a line syncs it will do so at the line rate which delivers 6dB over the then present noise level.  That can then leave a much higher SNRM when the background noise abates ... possibly much like you have just proved.  The DLM does not do anything here in the sense you've sought to suggest.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

RealAleMadrid
Seasoned Champion
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Registered: ‎07-07-2009

Re: Puzzling Speed Degradation

@BobR Looks like like the resync has cleared the very high SNRM value so your speeds are better, I notice you are on a Vectored line which explains your high speeds for quite a long line, vectoring reduces the crosstalk between different users on the cabinet giving higher speeds. A previous poster suggested around 45Mbps for your line length but vectoring gives a a much better result. Unfortunately most cabinets do not have vectoring enabled so you are lucky.😊

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

@Townman

 

OK thanks for that information - as it happens I can't say I noticed tarnished contacts. But hey... I'll take whatever works!. Pity none of the Plusnet tech people were able to suggest that. Still, at least it's on record in the community so maybe it will help someone else.

BobR
Dabbler
Posts: 17
Registered: ‎23-02-2015

Re: Puzzling Speed Degradation

@RealAleMadrid

 

Can't say I'm feeling very lucky given it's taken quite a while to get to the bottom of the problem. However, thanks for the thought. 

I ran a BT Wholesale Speedtest which registered a 20Ms Ping and 59.26Mbps down and 9.44 Mbps up. As you say that is OK and more or less what I have been used to. 

Although I understand why the tech support guys have to look at problems through the lens of the contractual terms it doesn't help when a user who has been around for some time is looking at the problem through the lens of what has been reality in his/her experience.

 

Townman
Superuser
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Re: Puzzling Speed Degradation

Bob,

I suggest that you need to be a little kinder here ... the angles that agents take are the usual candidates responsible for the majority of issues.  When they do not fit / resolve the problem, then you need to turn to the wacky oddball causes of which there are many, some only gained from painful experience.

Of the contributions here, I would put my money on @MisterW 's observation ... however, I would also want to know what was happening on your line at the time of that last resync to drive down the connection speed to deliver the 6dB SNRM.  If you are using a router which plays nicely with RouterStats (there is a special version for the Plusnet Hub One router [aka BTHH5a]) monitoring the line stats would indicate if there are any REIN / SHINE issues on the line.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.