"Normal SNR and LA" on lines for acceptable DSL?

antonfh

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If the title was not too clear, here is a more elaborated explanation and question.

Would like to know what is a good and acceptable Statistic on DSL 384/128 line would wrt to SNR and Line Attenuation.

Reason I’m asking, is because of noticeable degradation of service since Friday. I have tried to run some Speed Test (iburst, gamco etc) and mostly get Downstream between (worst to best) 119 - 275, and about 90 - 100 up.

I checked my routers' status and because I have checked this in the past noticed my downstream LA was at 51. Which I thought was a bit high since I noticed this in the past to be around 29 - 30.

Before I continue here is my full set of stats:

Downstream Upstream

SNR Margin:26.0 12.0 db

Line Attenuation:50.5 29.5 db

Data Rate:384 128 kbps


Sometimes my SNR Upstream jumps to 22 or 29 also

What made me concerned also was the Downstream Line Attenuation, at one point it jumped to 61 even, but now seems to fluctuate between 49 - 52 the whole time (like I said where I used to see this figure at 30).

I checked al my wires first, checked all socket secure. "Rebooted" the router and unplugged tel wires and pushed back in also, did a SysRestart on router, and even rebooted. Still got same results and slow connections.

I phoned Telkom Saturday afternoon, the voice channel was extremely fussy and static by then also, much line noise. Spoke to technical guy, checked extension and line, asked questions like if i have a virus, or any spyware. This is a brand new PC just installed a week before and assured him I have updates and Spyware and Antivirus (which I checked also before calling) etc.

Told me line seems fine, said its funny because I’m getting this reading of 51 on my Line Attenuation and even voice is experiencing lots of line noise. Said I must reset cookies etc, reset modem etc, finally tried to put me through to Internet dept.? Got nowhere from there.

Went back did a iburst test, got DL link of about 119, and UL just under 90 I think it was. Tried to download something from Tucows, Stellenbosch mirror and then MWeb mirror ...got avg speeds of about 1.5Kb and 5.5Kb

Phoned Telkom again, said they need to check again. did their thing, made me reset modem, switch it off, pull out power cable, switch of PC (switch of Freezer and Television and make sure car was full of petrol)...well not last part but I guess I would of done so, have they asked just to get it working at that stage ;-) Ok to make a long story short ...it ended up with ...No sir the line seems fine, can you open a website? ....well yes... mostly at dialup speed ...o wonderful sir! then your internet seems to be fine, thank you for calling Telkom ....

So I thought stuff this, tried to look at my wires (nothing broken etc) checked wall unit, fine, nothing loose. Unplugged all phones and cables (just kept DSL connected). Used a friends account, reset router, got Laptop connected too. Tried again. Downloaded some files, went to YouTube and StumbleOn. Went to open picture gallery ... was not impressed with how visibly things have degraded. Checked my router management interface again ...and still Downstream LA was at 51.
Today my LA is still at 51, but Speed tests on my PC and later from laptop, improved to about 257 DS and later (hour or so) dropped again to about 170 DS (downstream)


BTW router is Telkom ADSL 5102G
So what is normal SNR and LA ratios ? and if I have a bad voice and data line, what is my rights for improvement of service and services and how to best get resolve for these ?
 
well - how far do u stay from the local exchange? (DSLAM)

my 2cents - you have a problem on the line itself.

if u have checked these - then its time to request a tech for callout

i know u have checked some - but these are my personal checklist at customer sites:

-use another RJ11 cable from wallsocket to router
-if possible use a UPS (line interactive) to supply power to your router (eishkom not very well these days)
-use another RJ45 cable from router to pc/switch/hub
-unplug all your filters (just use ADSL)
-use alternative ISP accounts (I.S -,Saix - and Verizon based (2 at least if possible))
-and on another pc!

tell tech to check d/p , e side , v side , and air cable .

cheers
 
Will do so

Thanks for the reply, need confirmation to insist they look.

I have done the following and that did not help :

-unplug all your filters (just use ADSL)
-use alternative ISP accounts (I.S -,Saix - and Verizon based (2 at least if possible))
-and on another pc!


As far as changing cables .. I sure wil give that a try and see. But I think as you say there is a line problem/trouble...but yes better to make sure you did all your side before calling them out..also much faster that way

Thanks
 
For interest's sake, I'm also on a 384 line, here is my stats:

Downstream , Upstream
SNR Margin : 42.5 , 27.0 db
Line Attenuation : 26.5 , 15.5 db
Data Rate : 384, 128 kbps


:)
 
I upgraded to 4MB today and my stats is like this:

Us Rate (Kbps) 384
Ds Rate (Kbps) 4096
US Margin 14
DS Margin 13

LOS Errors 0
DS Line Attenuation 28
US Line Attenuation 15

I know my attenuation is fairly good, but im worried about the DS margin.. is it acceptable for a 4mb line? Im not getting any errors or anything..

thanks
 
Ok if i got this rite ur DS/US Line Attenuation should be low and ur US/DS Margin should be high.I got my dsl last week tho i applied 2 years ago the line was faulty till now.Luckaly they got a new line. Im a bit far from exchange bout 4.2-4.5km and i get this reading.

Us Rate (Kbps) 128
Ds Rate (Kbps) 384
US Margin 14
DS Margin 17
Trained Modulation ADSL_G.dmt
LOS Errors 0
DS Line Attenuation 56
US Line Attenuation 31
Peak Cell Rate 301 cells per sec
CRC Rx Fast 14
CRC Tx Fast 18
CRC Rx Interleaved 0
CRC Tx Interleaved 0
Path Mode Fast Path

My question is this can i upgrade to let's say a 512k or even 1 MB line?My connection is stable tho thus far doesnt drop.
 
Ok if i got this rite ur DS/US Line Attenuation should be low and ur US/DS Margin should be high.I got my dsl last week tho i applied 2 years ago the line was faulty till now.Luckaly they got a new line. Im a bit far from exchange bout 4.2-4.5km and i get this reading.

Us Rate (Kbps) 128
Ds Rate (Kbps) 384
US Margin 14
DS Margin 17
Trained Modulation ADSL_G.dmt
LOS Errors 0
DS Line Attenuation 56
US Line Attenuation 31
Peak Cell Rate 301 cells per sec
CRC Rx Fast 14
CRC Tx Fast 18
CRC Rx Interleaved 0
CRC Tx Interleaved 0
Path Mode Fast Path

My question is this can i upgrade to let's say a 512k or even 1 MB line?My connection is stable tho thus far doesnt drop.

correct-

SNR-higher-better
Attenuation-lower-better

17 SNR with 56 Attenuation...hmmm

512k yeah - it should be fine!

1024 - sorry my friend....your SNR is gonna almost go down half - to about 8-9 - which puts it borderline to minimum operation which is 6-8...and would then bump your Attenuation up to 60..which in turn is also on the edge.

my 2cents would be - upgrade to 512 - altho the speed diff aint much from 384-512 - it does help in checking the stability of a lower SNR/higher Attenuation.

then after a while , if ok , pump it up to fixed 1024.
 
Ta for reply.....heard there are projects to further better the line so ....ya think i will upgrade to 512k for now.
 
Well to extend their range their putting up "mini"exchanges.I heard it from a telkom techi.So just ask a local techi if there are such projects underway in your area
 
/necro

Is this normal:
Downstream Upstream
SNR Margin (dB): 206 140
Attenuation (dB): 360 210

Attenuation seems a bit high?
 
Last edited:
/necro

Is this normal:
Downstream Upstream
SNR Margin (dB): 206 140
Attenuation (dB): 360 210

Attenuation seems a bit high?

There is an entire stickied thread dedicated to this: http://mybroadband.co.za/vb/showthread.php/186156-Understanding-SNR-and-Attenuation-Rates

Just drop off the last 0 in your stats and compare:

Heres is my table of comparisons
SNR:

6dB or below is very bad and will experience no synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with little or no sync problems
20dB-28dB is excellent
29dB or above is outstanding

Attenuation:

20dB and below is outstanding
20dB-30dB is excellent
30dB-40dB is very good
40dB-50dB is good
50dB-60dB is poor and may experience connectivity issues
60dB or above is bad and will experience connectivity issues

The following guide (distance vs. attenuation vs speed) gives you an guestimate what you can achieve:
<1km should be 23-24Mbit (nice speed, but doesn't it bug you that Telkom people walk through your bedroom?)
1.0km = 13.81dB = 23Mbit
1.5km = 20.7dB = 21Mbit
2.0km = 27.6dB = 18Mbit
2.5km = 34.5dB = 13Mbit
3.0km = 41.4dB = 8Mbit
3.5km = 48.3dB = 6Mbit
4.0km = 56dB = 4Mbit
4.5km = 62.1dB = 3Mbit
5.0km = 69dB = 2Mbit
>5.0km (you are pretty much poked --- sorry for you)
 
/necro

Is this normal:
Downstream Upstream
SNR Margin (dB): 206 140
Attenuation (dB): 360 210

Attenuation seems a bit high?

Seems fine to me, those values are well above the average, though I bet you won't get higher than 8Mbit/sec, 6Mbit/sec stable.
 
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