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bjvyas

join:2005-06-09
El Sobrante, CA

Sudden drop in modem connect speed

Hi,

My modem connect speed has suddenly dropped form 4.1 mbps to 3 mbps. Any way to fix this problem?

B. J. Vyas



leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

said by bjvyas:

Any way to fix this problem?

Depends on what the problem actually is. All you have told us is that you have about 25% decrease in "connect speed". Without a few more details a lot of guesses could be made but it wouldn't be helpful to you (if the guess is wrong, the suggested remedy may do nothing to solve your speed issue).

In the absence of any details the generic troubleshooting advise is:

- does power-cycling the DSL mdem resolve the issue (at least temporarily) ?
- do you get better results when plugging in the DSL modem into the test jack at the NID ?
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire!

bjvyas

join:2005-06-09
El Sobrante, CA

Hi,
Tried both of your suggestions but it did not do anything.
Following are stats from my modem. Any help would be greatly appreciated.

ADSL Line State: Up
ADSL Startup Attempts: 4
ADSL Modulation: DMT
ADSL Data Path: Interleave
Datapump Version: DSP 5.2.2.0, HAL 5.2.2.0
Downstream Upstream
---------- ----------
SNR Margin: 4.00 8.00 dB
Line Attenuation: 56.50 31.50 dB
Output Power: 17.55 12.34 dB
Errored Seconds: 0 0
Loss of Signal: 0 0
Loss of Frame: 0 0
CRC Errors: 0 16
Data Rate: 3072 928



NormanS
I gave her time to steal my mind away
Premium,MVM
join:2001-02-14
San Jose, CA
kudos:11
Reviews:
·SONIC.NET
·Pacific Bell - SBC

said by bjvyas:

Tried both of your suggestions but it did not do anything.
Following are stats from my modem. Any help would be greatly appreciated.

Downstream Upstream
---------- ----------
SNR Margin: 4.00 8.00 dB
Line Attenuation: 56.50 31.50 dB
Data Rate: 3072 928

Margin (4.00 dB) is worse than marginal. For the given attenuation (56.50 dB) it should be closer to a marginal 9.0 dB, if not a better 10.0 dB.

Since there is no difference at the test jack, I would guess something changed for the worse in the premises wiring. You might get an improvement with a whole house splitter at the NID, and a home run to the modem location.
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum


leibold
Premium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:10
Reviews:
·SONIC.NET

said by NormanS:

Margin (4.00 dB) is worse than marginal.

Agreed.

Different modems vary in how they determine this number and as a result also in how low it can be. Generally a SNR of 9dB or more is desirable for error free operation even in fast-track mode. Below 9dB modems generally are more stable in interleave mode because of its better error handling capability but when SNR goes below 6dB expect at least occasional disconnects. At 3dB and less the line becomes unusable (frequent loss of sync and retraining).

There is a direct relationship between SNR Margin, Attenuation and Sync/Data Rate. Attenuation tends to be fixed and is primarily determined by the loop distance between home and CO (however poor inside wiring can increase Attenuation!). Therefore the typical remedy for a SNR Margin that is too low is to decrease the Sync/Data Rate.

bjvyas See Profile, you only posted one set of stats but it is unlikely that the stats are completely identical between testing at the NID test jack and inside the home. Try to leave the modem connected for some time (at least 15 minutes) before getting the stats (the modem may initially train at a higher speed and then drop down as a result of errors).
--
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