[AusNOG] DSL Line Stats

[Shane Short]

That's... not strictly true.

SNR indicates the noise margin, but doesn't necessarily dictate if line 
is "good" or not. What're you really interested in are CRC errors, or 
Errored Seconds (ES). I've seen lines that have been able to run with a 
solid SNR of 3dB with minimal CRCs and a resync once a month.

It's also worth noting that if you're on Open 2 (20/1) on Telstra 
Wholesale, your default target SNR *is* 6dB, so assuming an SNR that low 
means the line is fubar is a bit of a red herring.

Different profiles on different ISPs/DSLAMS will often set a target SNR 
when they're initially syncing. From memory you can use the following 
profiles on some ISPs to hit an SNR target:

- Telstra Wholesale Default - 6dB
- Telstra Wholesale "Stability Profile" 15dB
- iiNet Thrillseeker - 7dB
- iiNet Standard - 9dB
- iiNet Controlled - 15dB

To recap, a low SNR doesn't mean you're having issues, but having a high 
one helps prevent them.

-Shane


adamn at eyemedia.com.au wrote:
> This was one I stumbled on the web sometime back, I can't find the 
> back reference for it :\
>
> *SNR is Signal to Noise Ratio* (aka Noise Margin or Signal to Noise 
> Margin)
> Relative strength of the DSL signal to Noise ratio. 6dB is the lowest 
> dB manufactures specify for modem to be able to synch. In some 
> instances interleaving can help raise the noise margin to an 
> acceptable level. The higher the number the better for this measurement.
>
> 6dB or below is 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 no synch problems
> 20dB-28dB is excellent
> 29dB or above is outstanding
>
> *Loop Att. is Line Attenuation*
> Measure of how much the signal has degraded between the DSLAM and the 
> modem. Maximum signal loss recommendation is usually about 60dB. The 
> lower the dB the better for this measurement.
> 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
>
> *Output Power*
> How much power modem (upstream) or DSLAM (downstream) is using. 
> Maximum recommended is about 15dB. The lower the power the better for 
> this measurement.
>
> Cheers,
> Adam
>
>
>
> From: Travis <mallik at internode.on.net>
> To: Jason Reid <jasereid at gmail.com>,
> Cc: "AusNOG at lists.ausnog.net" <AusNOG at lists.ausnog.net>
> Date: 30/09/2014 05:47 PM
> Subject: Re: [AusNOG] DSL Line Stats
> Sent by: "AusNOG" <ausnog-bounces at lists.ausnog.net>
>
> ------------------------------------------------------------------------
>
>
>
> I always thought this was a pretty good explaination:
> _
> __http://www.kitz.co.uk/adsl/linestats.htm_
>
> On 25 September 2014 17:12, Jason Reid <_jasereid at gmail.com_ 
> <mailto:jasereid at gmail.com>> wrote:
> I'd also be interested in this.
>
> Regards
> Jason Reid
>
>
> On Thursday, 25 September 2014, Jacob Kino 
> <_jacob at interconnekt.com.au_ <mailto:jacob at interconnekt.com.au>> wrote:
> Hi All,
>
> Someone in our team has asked for a good document to explain DSL line 
> stats, primarily in the context of interpreting wholesale DSL line 
> stats reports.
>
> I had a look at our carrier’s product definition document but it 
> doesn’t seem to speak much about layer 1, wondering if anyone had a 
> good reference they could point to, ideally that has some real world 
> reference values in an Australian context.
>
> Cheers,
>
> Jacob
>
> *Jacob Kino*
>
>
>
> Suite 5, 25-27 Izett St
> Prahran, VIC, 3181
> Hi *
> e-mail *jacob at interconnekt.com.au *
> phone*     1300 852 842*
> fax *         03 9011 6298*
> www * _www.interconnekt.com.au_ <http://www.interconnekt.com.au/>
>
>
>
> -- 
> Jason Reid
>
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