How I dramatically improved the stability of my internet connection

kvikram

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Nov 16, 2010
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My ISP is BSNL. My home is located outside the city and is at a distance of more than 5 km from the nearest exchange. As a result, I'm getting an SNR value of 6 and line attenuation of 55 (too low and too high respectively). So, my connection is extremely unstable, and my internet disconnects and reconnects at least 10 times, and sometimes as much as 50 times per day, and sometimes gets completely shut off.

Then, based on the ISP's advice, I changed the "DSL modulation type" from "ADSL2+" to "G.dmt". This setting apparently limits the speed to 8 Mbps, but can dramatically improve the stability of my internet connection.

And it did. My connection is now rock-solid and is on 24x7 (so far).

This might help you out. :)

This might not be the only factor to my newly stable connection, so I will update this thread if there is any change in my situation. If your connection is unstable, try it out and see if it works for you.

Here's the setting on my modem:

 
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6pack

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Sep 19, 2005
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Nothing new. Everyone knows this from years and its been mentioned here umpteen times.
 
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blr_p

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Nothing new. Everyone knows this from years and its been mentioned here umpteen times.
Took me many years to discover this trick :(

its a dramatic improvement in stability and can understand the OP's excitement over this discovery. They sell us adsl2+ compliant modems when we just get by with adsl let alone 2 or +, everybody thinks the default setting is the best. No, it ain't.

The reason it works is the error checking is less strict at lower speeds.
 

cisco_tech

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Aug 25, 2005
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Does this help with packet loss?
Modulation doesn't help. For that you need to know what profile are you on.
Fast path or interleaved
Some routers shows data path = fastpath/interleaved.

Fastpath means ping response to first hop should be under 30 ms.
Interleaved gives around 60-70 ms to first hop.

Also setting up the correct MTU does help for packet loss.

All in all it depends on the quality of our sarakri BSNL cable as well.
 
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6pack

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Sep 19, 2005
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Took me many years to discover this trick :(

its a dramatic improvement in stability and can understand the OP's excitement over this discovery. They sell us adsl2+ compliant modems when we just get by with adsl let alone 2 or +, everybody thinks the default setting is the best. No, it ain't.

The reason it works is the error checking is less strict at lower speeds.
The analogy I'm going to make might be wrong. Its like buying a car. Every car can run at 130+ km per hr. In reality do people really get to run at that speed with traffic congestion, bad roads etc?
Similarly every modem can run at the fastest speed depending on certain conditions.

Adsl2+ is for the best line conditions and nearest distance from exchange. Beyond 200 metres it does not work at full 24Mbps. For distances of a km or more only Gdmt works.
 

raksrules

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Aug 30, 2007
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I came here to thank @kvikram
I use MTNL in Mumbai and the connection is pretty unstable many a times. Yesterday it was more than usual unstable. So i went into the settings of my ADSL2+ modem and found the DSL settings. In my modem there is no dropdown to select modulation but instead have something like this..

DSL Settings

Select the modulation below.
G.Dmt Enabled
G.lite Enabled
T1.413 Enabled
ADSL2 Enabled
AnnexL Enabled
ADSL2+ Enabled
AnnexM Enabled

There is s tick mark to be done in front of each of these and there was one already present in front of "ADSL2+ Enabled" as well as "G.Dmt Enabled". So i just removed the tick from the ADSL2+ and saved/applied the settings and since then i have a feeling that my connection is pretty stable now.
May be a placebo effect, not sure.
 

logistopath

Molar Police
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May 25, 2007
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What does the line attenuation actually indicate?
My modem statistics are as follows:
D Link DSL 2750U.png

Is the attenuation too high? Anything that can be done to correct it?
 

kvikram

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Nov 16, 2010
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@raksrules Glad it worked out for you. :) G.DMT definitely offered a good improvement in the stability for me, so I think it's not really a placebo effect. See if it continues to be stable.

@logistopath Your values aren't too bad. SNR margin should ideally be above 10 dB and line attenuation (which is basically the amount of noise) should be below 40. Yours is at 9.1 and 40 respectively. If you enable G.DMT, you should be getting a stable connection.

Not sure if enabling G.DMT actually affects the SNR and line attenuation values. My current values are 10 and 44, which is a remarkable improvement from the old values of 6 and 55. Not sure if enabling G.DMT had anything to do with it.
 

raksrules

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Aug 30, 2007
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My connection has been On since yesterday 5 PM and it was on entire night also. I believe it never disconnected anytime (cannot confirm but i feel).
Currently the stats of my MTNL modem show this..


DownstreamUpstream
SNR Margin (dB):6.2 6.3
Attenuation (dB):34.5 20.5
Output Power (dBm):12.4 17.2
Attainable Rate (Kbps):1704 889
Rate (Kbps):923 893
 

xtremevicky

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Apr 16, 2011
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I did not knew this.

Told this to a friend also who has this problem. Let see if it works out.

Thanks mate.
 

mrnikhilsudo

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Does this work for DSL PPPOE connection? I am using a 5mbps cable connection (fibre optic) provided by local ...ahem.... monopolists. My router is running dd-wrt.
 

kvikram

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Nov 16, 2010
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Are my modem's stats of SNR and attenuation good ? I have no idea actually.
Ideally:
SNR > 10
Line attenuation < 40

Your values:
SNR=6
Attenuation=35

which is not too bad. It might not be stable on ADSL2+, but it will stay stable on G.DMT.