Unanswered Question
May 8th, 2008

Not an expert at ATM/DSL stuff but this is a show command from a HWIC-1ADSL in an 1841 router. Curious of how to see if the issues are related to the ISP or line. Most curious about Noise Margin, Output Power, and Attenuation.


I have this problem too.
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sirdudesly Thu, 05/08/2008 - 18:58

Noise Margin, Output power and attenuation are relative to how far away you are from the telephone exchange providing the xDSL service.

At home I live about 6km from the exchange and have an attenuation figure of about 60db, so my glorious 24mbit ADSL2+ connection runs in at about 3mbit.... (isp's here in australia only sell ADSL2+ in one speed)

dennis_range Thu, 05/08/2008 - 19:03

So help me out with the actual numbers and what they mean. I am looking for specifically which levels I need to look for and where they can cause me problems. Do any of those numbers raise any concerns?

sirdudesly Thu, 05/08/2008 - 19:20

they seem relatively normal, if your attentuation was around 70db I would be concerned but the figures you provided are perfectly normal.

Higher your attentuation the lower your speed.

dennis_range Thu, 05/08/2008 - 19:22

Is there a document anywhere out there that shows what levels are good and which are bad? I am not excited to call Pacific/Telstra just yet.

sirdudesly Thu, 05/08/2008 - 20:53

oh dear, telstra :(

Not much you can actually do about your attentuation levels unless there is actually a line fault but your readings are perfectly normal.

As I said before bad would be around the 70db mark,based on your figures I could make an educated guess and say you're about 2-3km away from the exhange

americain Fri, 05/09/2008 - 10:25


Your down/ upstream speed is 2464/768.

I can see some Header, Reed-Solomon EC and CRC Errors, EC =Corrected errors.

Noise margins lower than 10dB are not good.

An other thing you have to look at is the used capacity, if this is higher than 80% you could say that there is a problem.

Or if it is high, like in your case, look at it as an indicator that there is somthing not like it should be.

A high attenuation can also be an indicator of a problem, sometimes the DSLAM-CPE distance, but if you have a high attenuation you should not worry too much.


Paolo Bevilacqua Fri, 05/09/2008 - 10:46

All correct but a correction on the meaning of capacity.

When you have very high speed ADSL, like 12 Mbps or so, you will see that capacity is very high anyway, simply because all the frequency bins are used to the maximum.

On the other hand, an high capacity for a low speed, would indicate that some bins cannot be used, hence a potential problem.


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