Upstream Speed Cap?

[#1]

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? 

[#2]

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.

[#3]

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)

[#4]

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.

[#5]

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.