IPprofile-independent speed reductions?

[#1]

I have not been able to add a message to a ticket tonight, so I am posting here. In essence:
According to James (http://community.plus.net/blog/2007/07/02/broadband-speed-faults-how-to-diagnose/) and the most perceptive advice I have received (Bob Pullen, to previous ticket), DSL drops are critical. They affect IP profile, which PlusNet's speed profile follows, and which in turn determines actual download speed.
However, for more than four days now, my sync rate has been unchanged at 6304kbps and my IP profile unchanged at 2500. (No complaint at the difference, as it follows DSL breaks early on 16th.)
My exchange has been Green. PlusNet profile is given now as 5500.
So, why should my download speed have changed from constantly more than 2000 to constantly less than 1000 on the evening of 17th?
My ticket says it is due to connection drops. Does this mean speed is lowered independently of IP and PlusNet profile values, according to some other criteria? Or is this a misunderstanding (like suggesting I should not switch off my router, when I haven't since 11th anyway)?
[Download speedachieved during the test was - 476 Kbps
For your connection, the acceptable range of speeds is 600-7150 Kbps.
Additional Information:
Your DSL Connection Rate :6304 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 2500 Kbps ]

[#2]

Hmm.
The IP profile and Plusnet speed profile were raised yesterday while I was failing to post to my ticket and then posting here.
Both are now 5500 but download speed is not responding to that.
Today your link gives Plusnet line speed as 5500 and BT test gives
Download speedachieved during the test was - 795 Kbps
For your connection, the acceptable range of speeds is 600-7150 Kbps.
Additional Information:
Your DSL Connection Rate :6304 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 5500 Kbps
Still below 1Mbps since sometime 18.15 and 21.20 on 17th (previously above 2.5).

[#3]

Ugh!  final 2.5 should read 2M. !

[#4]

In practical terms, problem now solved. Now "Download speedachieved during the test was - 4675 Kbps". Thanks.
What lowered the speed for about 60 hours, in contradiction to both IP and Plusnet profiles though? What actually goes on? ?

[#5]

I have exactly the same problem as you.
Friday I went from a perfect connection to a very poor connection.
I can't even play low res youTube videos without it constantly buffering. The BT speedtest and speedtest.net both report aroun 400-500 a week ago I would have had around 5000-7000!
I have tested 2 different routers, multiple cables and filters, the master socket, wired and wireless... all the same result.
I raised a ticket and the latest response is to switch on interleaving.... however, I can't understand what has changed, it feels like the wrong thing to do to me. Why should it go from perfect to very poor overnight. What would switching interleaving on achieve. Surely the cause of the problem should be found?

[#6]

You have to take everything with a pinch of salt.
I was told on a ticket that interleaving would be switched on, when it had been all the time.

[#7]

I wrote too soon. Good speeds this morning. Now (and the BT test seems representative to me):
At 14.40 21st Sept.
Download speedachieved during the test was - 124 Kbps
For your connection, the acceptable range of speeds is 600-7150 Kbps.
Additional Information:
Your DSL Connection Rate :6304 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 5500 Kbps
Current line speed:
5500
Exchange status checker hangs. I cannot comfirm that it has remained green, but it always has  been until now.

[#8]

Hi Woodsider,
Your ticket wasn't raised as a fault, so I've managed to get one of our faults team to pick it up save re-raising it. He should update it shortly.
Jojo

[#9]

No. I didn't raise it as a fault.
My router, as far as I can tell, has worked perfectly since I last rebooted on 11th (including automatically reconnecting PPP).
My DSL sync has not dropped since then (and not without good reason for weeks). The line has increased in both sync speed and IP profile to above what I had been led to expect. The only breaks in sync were caused by my changes.
Plusnet's profile has followed the IP profile upwards. It all looks really good.
Now, this latest spate of low speeds comes against this background of my DSL service seeming better than ever and staying that way. So, it hardly looks like BTw's business.
I asked what else might step download speeds from a fairly constant speed over 2Mbps to constantly under 1Mbps.
Since then it has switched back up to speeds of about 5Mbps (in accord with the new raised profile) and then back down to even lower than before.
Now, as a fault, it has immediately been shunted to BTw without any attention to what I said, as far as I can tell,  or explanation (or, as far as I can tell, justification). Why?

[#10]

Hi woodsider,
As you are getting such poor speeds even though your profile and sync speed seem ok, rather than it going back and forth the best person to deal with it was a faults agent. If he didn't deem it necessary to pass it to BT then he wouldn't have done. The reason why, is that I think we would get a quicker resolution this way.
Jojo

[#11]

OK. I  do appreciate that you always try to explain in a helpful way.
Let's see how it goes.

[#12]

When i was getting speed problem and i had to do a disconnect and reconnect of my internet session via the routers config page to get plusnet's ip profile changes to take affect.

[#13]

That isn't my current problem. Both the steps down to bad speeds and the steps back up to decent ones happen without PPP break.
A simplistic view of this is that I am getting patchily bad service over perfectly good DSL and PPP connections.
(On a  slightly different tack, it looks like I only get an auto reconnection of PPP in absence of this speed problem. But that is an intuitive interpretation based on scant evidence so far.)

[#14]

Unable to bring up Help & Support page or my ticket, or anything with much graphic, for the last twenty four hours.
All terribly slow, as if someone else is using my rooter for megadownloads, only they aren't.
My guess is that if I could get as far as running a speed check it would be well under 100kbps.
Sync still 6304. Plusnet line speed still 5500. No change to noise levels. (from when download speeds were over 5M)

[#15]

HI woodsider,
we had an email back verifying that the VP was ok, so I guess we'll just have to wait to see what they come back with later.
Jojo