I may not have been clear enough in my post.

It is not a case of the infrastructure provider (Openreach in this case) providing more bandwidth than the advertised rate. I am aware that depending on your distance from the street box it will vary.

In this case I actually had an Openreach engineer stood next to me with his very sensitive test kit. The Deco is reporting a max connection of 93mbps and his equipment was showing 82mbps. This was measured at both the street box and at the master socket by Openreach.

It isn't a case of the provider giving more than advertised (they are by 2mbps), it is a case of the Deco reporting over 11mbps more than is being provided.

The actual sync'd rate shown is about right and pretty close the speed tests show about 6mbps below that rate which is about right for a wireless endpoint.

Having a sync rate which is 30mbps below the max rate when it is 150m to the street bax on new cabling and a new card in the box with a very low resistance is not what you would see.

Oh, should have also mentioned if I plug in the Plusnet provided Smarthub 2 it does show a max sync speed of 82mbps which matches the Openreach engineers figures.

To me there is a bug in what the Deco is reporting for the max rate as professional test equipment has shown it to not be correct. And this is the view of several BT engineers.

I also approve of this feedback. While the VR2800 modem accurately reflects the actual attainable VDSL speed, the DSL-X73 VDSL modem displays an unattainable speed value. This has been physically tested, and the displayed speed is at least 12Mbps higher than the attainable speed. Additionally, please improve the effectiveness of the web interface. By the way, somehow the VR2800 performs better than the DSL-X73. The DSL-X73 is a complete disappointment...

  @ARGamingPK1

I contacted my ISP to request a VDSL speed upgrade.
They informed me that I was already receiving the maximum possible speed (which was confirmed by the VR2800).
I explained that I had changed my modem and observed—based on the DSLAM—that I could reach the speed offered by the higher-tier plan.
Although the ISP insisted that there were no restrictions on their end and that I wouldn’t be able to reach that speed, they agreed to let me try.
In the end, nothing changed.

ARGamingPK1 wrote

  @Tahtakale You don't have to worry about your speed. You can check your actual speed on Ookla Speed Test Website or Application.

 

https://www.speedtest.net

  Thats like saying you don't need the speedometer in your car to be accurate as you can use GPS on your mobile phone.

Also, speedtest.net will not give you either your maximum potential sync speed, or current sync speed to your ISP. It will only give you the current throughput from the device you are running it from. 

This is about reporting a bug in the software which is giving misleading information.

Now that my line has settled, according to the router I have a max sync speed which is over 20% higher than the line or service can deliver and similar for what it is actually delivering. Its a bug which needs fixing, bit embarrising for a network company really.

  @400ixl 

 

There could be other reasons as well. For example, compatibility between the modem and the DSLAM might be a requirement for accurate data. When I tested with a Keenetic modem using the EN7516GT = MediaTek (formerly known as Ralink or Econet) SoC, I observed the same data as with the DSL-X73. Of course, these data were not accurate for my line either.

"Broadcom Modem & Broadcom (DSLAM) somehow show the correct values for my VDSL line."