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Upstream Speed Cap?

gp
Dabbler
Posts: 11
Thanks: 1
Registered: ‎08-04-2016

Upstream Speed Cap?

I am on ADSL2+ and get a decent downstream speed, given the distance from the exchange.  Upstream was supposedly uncapped some time ago but I never got more that 828 kbps in the upstream direction.  As we nowadays have to meet our friends online due to the lockdown, it would be nice to have as much upstream bandwidth as possible (some of our friends complained that we had really bad video quality).

The line stats from my router show

    Receive direction Send direction
Max. DSLAM throughput kbit/s 6656 1280
Min. DSLAM throughput kbit/s 3328 32
Attainable throughput kbit/s 9128 1501
Current throughput kbit/s 6652 828
       
Latency   8 ms 5 ms
Bitswap   on on
Seamless Rate Adaptation   off off
Impulse Noise Protection (INP)   2.0 2.0
Energy-saving mode L2 NA - -
       
Signal-to-noise ratio dB 10 8
Line attenuation dB 47 24
Power reduction dB 0 0
Carrier record   A43 A43

 

According to Wikipedia, ADSL2+ can provide upstream bitrates of up to 1.4Mbps.  According to my router stats, the max. DSLAM throughput is 1280kbps, so slightly less than the spec.

I appreciate that the connection may sync at a lower speed if the Signal-to-noise ratio drops, but why is my upstream speed arbitrarily capped at 828kbps?

Is it possible to get that restriction lifted? 

4 REPLIES 4
MisterW
Superuser
Superuser
Posts: 9,308
Thanks: 2,308
Fixes: 173
Registered: ‎30-07-2007

Re: Upstream Speed Cap?

The DSLAM has decided to apply an interleaving (G.INP) depth of 2 on both your upstream and downstream profiles. I believe the upstream interleaving will limit the maximum synch, presumably to 828k.

PlusNet still have some control of the ADSL DSLAM (as opposed to the FTTC one) so if one of the experienced staffers sees this , they could do a GEA test and look at the error counts to see whether it would make sense to switch interleaving off.

Gandalf
Plusnet Help Team
Plusnet Help Team
Posts: 18,317
Thanks: 5,958
Fixes: 996
Registered: ‎21-04-2017

Re: Upstream Speed Cap?

Interleaving is indeed been switched on at the exchange which would be causing the slow upload speed. I'm not sure it's a good idea yet to remove interleaving because your connection's been dropping and download speed's banded as a result: WBC 3M - 6M Medium delay (INP 2) 6dB Downstream, UC Medium delay (INP 2) 6dB Upstream (ADSL2+)

I've attached a picture below showing the drops:

I'd recommend going through the troubleshooting steps Here and raising a fault ticket Here as we'd likely need to arrange an engineer visit to investigate further (if there are further issues or things don't improve)

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team
gp
Dabbler
Posts: 11
Thanks: 1
Registered: ‎08-04-2016

Re: Upstream Speed Cap?

Hi Gandalf

many thanks for looking into this.

You are right, the line was not particularly stable recently (due to the weather?). The Upstream noise margin had been going up and down like a jojo, causing frequent resyncs.  Since Saturday 13/2 afternoon, the upstream noise margin has been good again (6-8 dB) with sync speed at 828kbps. The resync this morning at 8:39 was me resetting the router and I suspect the resync at 14:12 today was you testing?

So, for the moment I will put up with 828kbps, but maybe you could look into removing the downstream banding at some point in the future, as the problems appear to be upstream related and the downstream banding does not help much to mitigate the issue.

I will keep an eye on the performance for a while before raising a ticket.

 

Gandalf
Plusnet Help Team
Plusnet Help Team
Posts: 18,317
Thanks: 5,958
Fixes: 996
Registered: ‎21-04-2017

Re: Upstream Speed Cap?

Hello,

There's interleaving activated (INP2) on both the downstream and upstream.

I'm happy to remove the banding and/or turn off interleaving but I fear it may cause further issues.

Let me know if you'd want me to though.

If this post resolved your issue please click the 'This fixed my problem' button
 Anoush Mortazavi
 Plusnet Help Team