Puzzled about line speed readings in router

[#1]

I recently opened a new account with PlusNet, all of which is working OK. However, I'm puzzled by some of the broadband speed readings I'm getting.
An on-line speed check site shows that I get around 6Mbps download and 400Kbps upload speeds. But when I look at my Thompson router DSL Link Information screen (see attached screenshot) it shows a download speed of about 15Mbps and an upload speed of around 450Kbps.
The PlusNet Help & Support pages say that my current connection should provide me with 'Up To'  20Mbps. So the questions seems to be, if my reported line speed is managing 15Mbps, why am experiencing only 6Mbps?

[#2]

If you login to your account using this link - https://portal.plus.net/my.html?action=data_transfer_speed
what does it say for "Current line speed" ?

[#3]

It says:  Estimated speed 5Mb.  Current speed 21Mb.

[#4]

Those figures are pretty puzzling... Your max upload speed shouldn't be so high (afaik), so might be worth restarting your router to see if you get some more sensible figures...
You should only expect 88.2% of the speed that your router syncs at, so that 15,192Kbps should work out 13.3Mbps (which the current line speed in the above post should match, but there's a known issue with delays in these figures updating)
Have you tried running the speed tests in different browsers/using different sites (speedtest.net is usually pretty accurate for me)
What results do you get from a BT speed test?
http://www.speedtester.bt.com/

[#5]

I rebooted the router and still got the same upload/download speed results. Ran the BT speed test, which gave a line speed of 4.9Mbps.
BT have recently finished installing fibre to all the distribution boxes in the town. The box which serves my street is about 300m away. Don't know if this could be anything to do with the odd speed readings.

[#6]

getwitty,
I'm wondering if this is related to the issues reported here: http://community.plus.net/forum/index.php/topic,102123.msg866715.html#msg866715 let me know if you think otherwise

[#7]

This doesn't appear to be related to the post you mention. I'm not getting any worse speeds than when I was with BT, slightly better in fact. I'm just curious to understand why I appear to be on a line that could give me around 15Mbps, but in practice only delivers 5 to 6Mbps. That was what got me wondering about whether the recent fibre upgrade on the local network had anything to do with it.

[#8]

Having looked at your account again your line looks OK and is on a 20mb profile. I'd advise raising a fault https://portal.plus.net/apps/kbdfaults

[#9]

When you do the speed tests are you using a wired or WiFi connection?

[#10]

I'm using Ethernet, connected over Devolo Homeplugs, which give me up to 100Mbps, so I don't think there's any problem there.
I'll post a fault report and see what that turns up.
Thanks for all the help

[#11]

Quote

which give me up to 100Mbps

'Up to' are the crucial words there. Homeplug speed is very dependent on the wiring and whether plugs are on the same circuit.
Is it possible to test with a direct wired ethernet connection to the router ? just to eliminate the Homeplugs as a restriction.

[#12]

That certainly seems to be a limiting factor. Plugging a netbook directly into a router Ethernet port gives a speed reading of 11Mbps. Running the same test across the Homeplug network gives a reading of 6Mbps.

[#13]

11Mb sounds more reasonable for your synch speed. I've not used Homeplugs myself but I've heard that some of the claimed speeds are wildly optimistic. At least you now know what the problem is.

[#14]

My guess is that it's less to do with the Homeplugs and more to do with the building. It's two hundred years old, with two foot thick walls (which makes wireless pretty difficult). Admittedly, the wiring is probably a bit more recent, but even so, it may be the most significant factor.
I'll just have to nail proper Ethernet cable around all the door frames and skirting boards. But for some reason my wife says she'd kill me if I did. 

[#15]

Have you looked at your network using Devolo Cockpit ?
Are all the LEDs on the front of both homeplugs green ? or are some orange or red ?