ADSL Actual Rate Higher Than Attainable Rate

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Handle9

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#111594 8-Nov-2012 13:37

Hi There

I've just switched to Telecom from Vodafone. As I expected my speed dropped a bit but I have noticed something a little odd. The actual sync rates I'm getting are higher than the attainable rates. Is this what you would expect?

I have a new master fliter in the ETP with a single CAT5e running from the filter to my modem (Draytek Vigor 120).

Line stats are as below.

Cheers
Duncan

--------------------------- ATU-R Info (hw: annex A, f/w: annex A) -----------
DSL Modulation : ADSL2+(G.992.5)
State : SHOWTIME
DS Actual Rate : 8301872 bps US Actual Rate : 993204 bps
DS Attainable Rate : 7828000 bps US Attainable Rate : 993000 bps
DS Path Mode : Fast US Path Mode : Fast
DS Interleave Depth : 96 US Interleave Depth : 1
NE Current Attenuation : 34 dB Cur SNR Margin : 11 dB
DS actual PSD : 18. 7 dB US actual PSD : 12. 1 dB
ADSL Firmware Version : 321311_A
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 17 dB Far SNR Margin : 11 dB
CO ITU Version[0] : 00004244 CO ITU Version[1] : 0000434d
DSLAM CHIPSET VENDOR : < BDCM >

cbrpilot

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Spark NZ

#715536 11-Nov-2012 20:42

This is fairly normal behaviour of DSL.

What happens is that for stability reasons you never connect at the absolute maximum connect rate. Instead there is a certain margin left to deal with the fluctuating state of a copper line. This is completely normal - line conditions will change slightly throughout a day.

So what has happened in this instance is that you have connected, and the line was slightly better. You got a good connect rate, and as per Telecom's network, there is 12db left to deal with noise. Since that time your line has got slightly worse, but because there is a margin there for things like this, the connect rate stays the same, but you lose some of your margin - you'll notice your noise margin is no longer 12db - it's dropped to 11db. If you restarted the modem now, you'd connect at those "attainables", and your SNR margin will be 12db again.

All in all, this is normal behaviour of any DSL line.

My views are my own, and may not necessarily represent those of my employer.

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Handle9

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#715538 11-Nov-2012 20:44

That makes sense, thanks for the reply:)