I sometimes got higher speeds than the BT IP profile would suggest the connection should get and my connection is 20CN, I put it down to occasional error within the BT software if that is actually possible in the BT non virtual reality???

Edit > typo

Edited by Apprentice (Fri 18-Apr-14 23:27:09)

There have been a couple like that in the last week. None before that I remember. It could be BT Wholesale are mucking about modifying the test again and screwing up. Not for the first time.

The reason I asked about the Internet Security is that some firewalls can cause weird effects on speed tests. Avira and Kaspersky being common suspects.

The sequence is:- Connect, sync speed is determined >> IP Profile is determined almost straight away >> IP Profile change is logged by BTW >> a few times a day Plusnet interrogate that log and apply a slightly lower Current line speed, which is what ultimately limits your line download speed.

The links in that chain are not robust. It shouldn't be possible for throughput to exceed IP Profile on the BT test. However, it's my understanding there are at least two copies of the IP Profile in the BTW system. What we see in the speed test report is just a figure used for reports. The other one is what actually controls the speed. The two do seem occasionally to get out of step, with the Plusnet CLS being set by the real limiting one.

ISPs are expected to monitor the IP Profile and make sure nothing arrives at the DSLAM from them faster than it, as that would mean the DSLAM would have to drop random packets because they couldn't all go down your line. Plusnet and a few others certainly do this, and Plusnet are able to buffer your line to some extent.

Thanks Roberto. I am still left with an underperforming line. The TBB speedtest is consistently returning 4.13Mbps with a sync of 5312. So I too do not believe the BT speed figure logged.
I can't seem to get Plusnet to do anything about it. They blame DLM, my house wiring or filtering, the BTW maximum speed estimate of 4Mbps and so on..........

In reply to a post by RobertoS:

And on WBC ADSL2+ the IP Profile is 88.2% of the sync.

Edit - so the IP Profile for 5300kbps is 4.67Mbps. CLS possibly 4.66Mbps. Looking at the OP, I'd be very surprised if the IP Profile is still 4.14Mbps.

Well you will be surprised in that case. [IMG]http://i18.photobucket.com/albums/b137/jbuk/btiptst1...[/IMG]

This morning nothing has changed : still synced at 5312, diurnal variation of snr from 7-5db and the line profile stuck down at 4.14 for 11 days. It is just not resetting and following the sync speed any more. Running the TBB speedtest the throughput is always at 4Mbps not the false result in the BT test above. Also the upload speed is not right either I think.

Plusnet are not responding to my ticket asking them to do something. Their last reply said they had looked at some statistics for my line and it is not capable of running any faster than 4Mb reliably !!! There is no evidence for this plus it is synced at 5312 without dropping ever.

It is true that the BT test result does show the maximum speed for my line is 4Mbps but this is obviously refuted by the 20% higher sync speed.

What should I do - nothing, hassle Plusnet or just ask for a MAC ?

In reply to a post by jaba:

What should I do - nothing, hassle Plusnet or just ask for a MAC ?

I'd do nothing. Look at RobertoS' figures. 88.2% of 5312 is 4.7Mb/s. A PN profile of 4.14 sounds a bit low but not hugely so. Take off 15% for TCP overheads and you have 3.5Mb/s.

Even without the PN line speed you're still only looking at 3.95Mb/s which is probably where PN's statement that you can't get better than 4Mb/s comes from. They are right - you will never see throughput higher than 4Mb/s.

But it does seem that being with PN is costing you .5Mb/s. If it were me I'd ignore it but if you feel it's worth changing ISPs over then go for it.

In reply to a post by Andrue:

In reply to a post by jaba:

What should I do - nothing, hassle Plusnet or just ask for a MAC ?

I'd do nothing. Look at RobertoS' figures. 88.2% of 5312 is 4.7Mb/s. A PN profile of 4.14 sounds a bit low but not hugely so. Take off 15% for TCP overheads and you have 3.5Mb/s.

Even without the PN line speed you're still only looking at 3.95Mb/s which is probably where PN's statement that you can't get better than 4Mb/s comes from. They are right - you will never see throughput higher than 4Mb/s.

But it does seem that being with PN is costing you .5Mb/s. If it were me I'd ignore it but if you feel it's worth changing ISPs over then go for it.

The TBB speedtest is consistently returning 4.13Mbps with a sync of 5312

Which is actually better than I'd expect for that sync so speed and to my mind nothing to complain about. But perhaps I'm confused.

In reply to a post by Andrue:

But perhaps I'm confused.

I think you are! By this:

Take off 15% for TCP overheads and you have 3.5Mb/s.

IPP accounts for most of that.

Uh uh .

The PN Current Line speed was 4.66. It's the IP Profile that was 4.14, but is apparently being ignored.

That comes down to the one reported by the BT Test not being the one applied to the line. We've seen that a few times.

You seem to have copied a link incompletely. It doesn't work, because the actual link is exactly what we can see in the post.

Edited by RobertoS (Tue 22-Apr-14 18:59:00)

It's a copy of this one:

In reply to a post by jaba:

http://i18.photobucket.com/albums/b137/jbuk/btiptst1...

but as that was 4 days old the 'still' is suspect.