Broadband Related > ADSL Issues
Major line problem
MikeS:
Hi
I knew I shouldn't have posted a noise margin graph a few days ago
My line went pear shaped day before yesterday, voice line crackly, dsl dropping. Today BT came and switched pairs and cleaned up the voice line. However I am now syncing now at 160K down and 320K up with what looks like a target margin of 9dB, despite the line attenuation having improved by 6dB. For the last 8 weeks I have been syncing at 4000-4500 with an IP profile of 3000-3500 and a target SNR of 6. Phoned Plusnet who said the reason was that because my line had been dropping and as I had been trying different routers the DSLAM had cut my sync rate, so I should leave my router on and wait three days and it should go up
My experience with noisy lines has been that the sync rate didn't change to this extent. I may have gone from 4000 to 2000 during noisy periods. The method used to control downstream speed was to reduce the IP profile, which would go down to 250K in very noisy periods and maybe increase SNR margin.
I guess my question is - is the sync rate determined by what the line can support, or does the DSLAM say 'despite the fact that the line can support higher speeds I am going to physically reduce sync speed because of recent poor performance' . By this I mean actually reduce sync speed directly rather than reducing IP profile or increasing SNR margin
Basically I don't want to waste three days at 160K if the Plusnet advice is wrong. Any thought welcome
roseway:
DSLAMs don't make executive decisions in that way. Your router negotiates with the DSLAM to get the highest speed which can be achieved for the target noise margin. This will depend on the attenuation and the amount of interference (noise). What are your current router stats?
MikeS:
Stats are as shown below
Connection Status Connected
Us Rate (Kbps) 320
Ds Rate (Kbps) 160
US Margin 6
DS Margin 9
Trained Modulation ADSL_G.dmt
LOS Errors 0
DS Line Attenuation 48
US Line Attenuation 30
Peak Cell Rate 754 cells per sec
CRC Rx Fast 0
CRC Tx Fast 0
CRC Rx Interleaved 5
CRC Tx Interleaved 0
Path Mode Interleaved
DSL Statistics
Near End F4 Loop Back Count 0
Near End F5 Loop Back Count 0
My understanding was that the DSLAM/router negociated the highest sync speed for the line conditions. The actual download speed would then be modified by the IP profile in place at the time, mine will almost certainly be rubbish due to the disconnections I have had. If that is the case then waiting 3 days will be a waste of time. Is there any way that switching pairs could confuse the DSLAM or does it look as if there is yet another fault somewhere. I should say that I am coming directly out of the master socket and have tried 3 routers and three filters
I can't get on the BT speed tester to find my IP profile, but I would guess it is 250 ish.
roseway:
On the face of it, those stats don't make any sense. You should get a much higher connection speed, in the region of what you had before. Waiting three days isn't going to make any difference - it's your actual connection speed which is the problem, not the IP profile. I think you're going to have to go back to PlusNet and make it clear that the connection speed is much too low, so the IP profile is never going to recover until this is fixed.
(I'm assuming that you haven't changed anything else at your end, and you're still using the same filters in the same places, etc.)
MikeS:
Yes you are correct in terms of filters etc. I'll have another go at them. What I was told did not make sense to me, but I wanted to check it out with the experts before going back to Plusnet.
Thanks for the input Roseway
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