Yet another numbers question

Hi folks,

Been browsing through the forum and would jusl like confirmation of some facts, please!

I have been on an upto 8Mb package since November and have never seen anywhere near that speed for downloading, whether it be surfing, Usenet or gaming.

Current ADSL stats are (Connexant AccessRunner PCI card)
Up Down
Noise Margin +18.0 +10.9 to +11.9 varying
Attenuation +30.5 +49.5

Reported line speed 448kbps 2624kbps,

Speednet tests this evening show something more realistic :
2/18/2007 7:38 PM GMT 66 kb/s 158 kb/s 1869 ms Dublin ~ 200 mi
2/18/2007 7:31 PM GMT 126 kb/s 287 kb/s 111 ms London ~ 200 mi
2/18/2007 2:25 AM GMT 129 kb/s 321 kb/s 119 ms Kiev ~ 1400 mi
2/18/2007 2:24 AM GMT 133 kb/s 334 kb/s 205 ms Dublin ~ 200 mi

I removed the link wire in the 2 sockets in the house a few weeks ago and saw an immediate speed increase - before it was less than the 2Meg line I was previously on!

Setup is - master socket in lounge with nothing else plugged into it - short extenstion wired into socket across under floor into room with PC's. Microfilter and base unit for cordless phones. I've tried without anything else plugged in to socket but no difference.

Is this indicative of a phone line wiring problem or something more serious with the ISP?

Numerous support tickets to ISP haven't changed anything.

I have just run the BT Speedtest and have this as a result:
Test1 comprises of Best Effort Test: -provides background information.
IP profile for your line is - 135 kbps
DSL connection rate: 448 kbps(UP-STREAM) 2624 kbps(DOWN-STREAM)
Actual IP throughput achieved during the test was - 119 kbps

Phone line or change ISP?

Comments?

Ta muchly!

Regards,

Simon

Phone line.

At 49.5db line attenuation, you're never going to see 8Mbps.
The most you could hope for, and only if you have a really quiet 'phone line, and connect using an ADSL filtered face-plate (on the BT master socket), is around 5Mbps.

Given your DS noise margin (10.9 - 11.9db), it appears you've been placed on a 12db noise margin target (presumably, because of sync/stability problems).

Have you been getting a lot of re-syncs?

Although you say there's nothing else plugged into your master socket, you mention you removed the "link wire" between the two sockets in your house.
Are you talking about the "ring wire" or the entire cable.

Also, as you're still on a 135kbps IP profile (despite your 2624kbps sync), I assume you're either still getting low sync events, or you haven't left it the full three days to recover.

Even when it has recovered (after waiting a full 3+ days), you'll still be on a 12db noise margin target (which will hold your speed down).
To get this reduced (providing you've removed the cause of the re-syncs), you need to either wait for a 14 day continuous sync (no drops at all) - some mention this works (never seen any evidence though), or contact your ISP to get a request put through to BT (although this rarely works either).

Ta muchly for the reply.

I am 1.5km from the exchange, which I forgot to mention, I don't know if this makes a difference to your answer.

As far as link wire goes, yes, I meant ring wire....just have wires on 2 and 5 now in both sockets.

With a 49.5 dB attenuation, is it worth me getting BT to check the phone line itself?

As far as re-syncs go, do you mean line drop and reconnect? I have been tending to disconnect and reconnect myself to see if line rates improve, as recommended by my ISP, but once it's connected it tends to stay connected.

Occasionally I check and see that the line speed has dropped from when I last reconnected it, in which case I usually disconnect and get it to reconnect to see if it goes back up again. Is this causing adverse affects on my profile and should I stop doing it?

To be honest I'd be happy with 5Mbps, I know that you only tend to get 6 - 8 if you live in the BT Exchange!

Once again, thanks for your input, one and all!

Regards,

Simon

Try just the modem into the master socket, and use the internal 'test' socket - that way you'll be eliminating your internal 'phone wiring (just in case there's a problem with that).

Also, if you can borrow one, try a different modem/router (just in case that's the problem).
For the time being, don't go by speedtest results (as they're going to be badly affected by your dodgy IP profile) - just try and see if you can get your sync up.

Although you're only 1.5km from the exchange, your line could be anything from 1.5km to 4km+. It really depends on how imaginative BT were when routing the telephone cables serving your area.
The typical multiplier is around 1.4x. So if your line was typical, it would be around 2.1km. Average db/km is around 10-12, so that would imply your line is closer to 4km in length (assuming your 49.5db is about right).
As a comparison, I'm 2.65km from the exchange, BT have my line length at 6.94km (so my multiplier is 2.6), yet my line attenuation is 58db (making my db per km to be 8.35 - much lower than average).

So, as you can see, there's a wide variation in line quality, so unless you've a voice fault (crackling, loss of dial tone, etc.) I don't think BT will even bother to look at your line.

As your target noise margin seems to be 12db, you'll be losing quite a bit of speed there.
Typically you can expect around 250kbps for every 1db change in the target noise margin, so if you can get your target noise margin/SNR back down to 6db, you could a sync increase of up to 1500kbps.

However, there is definately something wrong.
You have an IP profile of 135kbps (implying a sync as low as 180-200kbps at some point during the last three days).

I would suggest, you firstly invest in an ADSL filtered face-plate (to fit on the front of your master socket, in place of the un-filtered one).
Then, if you can make them understand, get your ISP to request a line re-train from BT. This should reset your target noise margin back to 6db, reset your IP profile, and start your 10 day training period again (as your line seems to have got itself into such a mess, you'll be extremely lucky if it fixes itself without manual intervention).

Edited by adebov (Mon 19-Feb-07 19:38:06)

Many thanks for a most detailed explanation.

Will do the tests you recommend and get an ADSL faceplate and will see what happens. Was debating whether to get an external ADSL router anyway. Any recommendations as far as that goes?

Regards,

Simon

Speedtouch routers seem to be dirt cheap these days.
DSL Source are selling the ST546v6 for