Speed variation

Can anyone explain why my download speed should be 4.5Mbps this morning http://www.thinkbroadband.com/speedtestcomplete.html?id=11867283498337761271 and 0.3Mbps this evening http://www.thinkbroadband.com/speedtestcomplete.html?id=11867726073350513809. Synch speed is the same, connection not dropping off. I'm 1.2miles from exchange.
Standard ADSL2+
Bandwidth Down/Up(kbps) 5097/443
SNR Margin Down/Up(dB) 11.0/23.5
Attenuation Down/Up(dB) 31.0/18.5

This happens pretty much every day. Opal networks are on the case, but seem satisfied that the synch speed is consistent and have run line tests. This situation has existed precisely since I was LLU'd on 29th June. Is it possible that the wires at the exchange have been crossed? Could someone else's connection be gobbling up the speed? Surely the speed nosedive is too great for contention? Any ideas?

This seems to maybe a congestion issue within your exchange. Try performing 3 speedtests at 3 different times of the day and logging it as a speed issue with TalkTalks 2nd line support.

I've spent so much time on this with 2nd line and high level complaints; network engineers say the line is fine, nothing wrong; do you think contention could disable the connection to such an extent? Will talktalk ever admit that this is the cause? Because if they do, and don't increase their capacity, then obviously I'm off; I've tried to make this work and endured some really poor treatment from TT, and don't want to have wasted the last 7months. If it is contention, will this affect all TT customers at the Upton Park exchange, or even all of those 35 (I think) on my card? and as I write, I keep losing synch: is that an effect of contention?

If your loosing sync then it may be another issue. Maybe to do with intiferance on your line at night or somting inside your property causing interference on the phone line.

Can you post your line stats ?

The contention could be anywhere from your exchange along the backhaul circuits to one of Carphone Network's 3 POPs in Irlam, Brentford and Birmingham. The further away you live the worse it could be as you will inevitably be sharing links with AOL and other TT exchanges etc.

Just for your information the BT minimum acceptable speed on an up to 8Meg sync is 400kbps before they will declare it as a fault.

I have been plugged right into the test socket for weeks; the internal wiring is pretty simple and looks sound: just the two blue and white wires, no other extensions or devices other than dect phones; since my original post my stats have changed to:

Standard ADSL2+
Bandwidth Down/Up(kbps) 6728/443
SNR Margin Down/Up(dB) 6.5/24.5
Attenuation Down/Up(dB) 31.5/18.5

and my speed has increased to 1.5meg http://www.thinkbroadband.com/speedtestcomplete.html?id=118678703352911018289 or 4meg on Giganews... I have had ipstream on this line for a year or two and never had such low speeds, although it was generally around the 2.5mbps mark, until the day I was switched to Talktalk's kit at exchange

ETEE, I often drop to around 170kbps in the evening; I've been doing godknows how many speedtests recently, but don't know how to publish or link to the whole table in my thinkbroadband profile, which would show the shape things have been before and after LLU.

The only other things that vary with LLU are the MTU & RWIN settings but as you get good speeds in the morning I didn't mention it.

The fact that the sync speed increase also affected your speed throughput makes me think that you need to look again at these settings. Try starting with an MTU of 1400.

MTU already set at 1400; RWIN set according to tcpoptimizer, can't remember the number; I recently borrowed neighbour's laptop and plugged into router: same speeds, both good and bad.

Just a small observation.........
Do you notice that YOU the customer have to do speed tests, log results, make notes, change settings..........etc etc.
This is the job of a network engineer surely......not the customer.
ISP's are really taking the micky expecting customers to do their job to get problems on ex BT lines sorted.
It's about time ISP's were billed by the customer for their time in fixing their problems....unless of course the problem is at the customers end.

Thats my gripe for today, thanks for viewing.