High Attenuation, Low Noise Margin - Help!

Hi

Sorry to do another one of these stats posts but I am considering jumping from eclipse to be* as I am experiencing very bad quality of service recently. I am not entirely clear when this started but I did have a BT fault on my line recently which they resolved (but never contacted me to tell me what the problem was).

Previously I had always just looked at my router connection speed as a guide but reading around these forums I see that attenuation and noise margin are also important and this tallies with what I am seeing that upload speeds are good and download is bad. Heres my stats - all comments appreciated.

Downstream
Connection Speed - 5792Kbps
Attenuation - 46db
Noise Margin - 2db

Upstream
Connection Speed - 448kbps
Attenuation - 13.5db
Noise Margin - 16db

My router is a NetGear DG834G.. it also has the following stats on WAN but not sure if they are relevant:
Tx B/s - 24363
Rx B/s - 43354

Since the PPPoA uptime is less than LAN uptime I am assuming it drops connection sometimes


Thanks in advance
Alasdair

Your downstream noise margin at 2 dB seems low. Generally Max ADSL is meant to target 6 dB and set the sync speed accordingly. I guess if that falls any lower you will get disconnected and then reconnect at a lower sync speed with a 6 dB margin.

You say this is quite recent. Have you any idea what BT did? Have you ruled out any changes or failings with your internal wiring?

Thanks john - internal wiring hasn't changed but i will do some unplugging and checking / swapping of filters etc. when I get home.

How can the downstream and upstream figures vary so much?

I don't know why that is. My downstream margin is currently 16 dB versus an upstream margin of 25 dB.

upstream is at lower frequency which attenuates less.

Good - so compared to most other peoples, my download noise margin seems unacceptably low and my attenuation a touch on the high side. This would explain the problem and the symptoms experienced of upload performance being acceptable but download unacceptable.

Bit I am still confused is why my router reports a decent connection speed... this does not equate to throughput I guess.

FYI I get a speedtest.net result of 798kb/s...

your router said :-

Downstream
Connection Speed - 5792Kbps
Attenuation - 46db
Noise Margin - 2db

if the noise margin got so low (or errors so high) that it had to resync then it might lose a meg or so off the connection speed when it reverted to a 6 dB margin.

The sync rate is the speed at which your modem and the modem at the exchange communicate. There is a chain of computers between the exchange and the site you are browsing. The weakest link in that chain determines your internet throughput.

To demonstrate the chain on a PC open a DOS window and type

tracert bbb.co.uk

This will show the chain from you to that BBC site.

Thanks for all your help... I think I understand the problem. So given that everything used to be OK and now things are decidedly bad, what is the most effective way of getting something done?

I am with eclipse and in my experience they will just tell me to unplug the router etc. etc. I am convinced that when there was a fault on my line, something has changed with the set-up.

Given I am considering transferring from eclipse to be*, is this the most effective route as I have read other posts that suggest the transfer process will help (activity at the exchange etc.)

what does speedtester.bt.com say for your line ?

Also can you expand on what you see as the current problem.