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SNR reset and Ip Profile kick please

Uncle_Meat
Grafter
Posts: 167
Registered: 04-08-2007

SNR reset and Ip Profile kick please

Evening all. Long time no see....
Bit of a story first.. Been having line problems lately which culminated in the line being blown down in those strong winds we had here in West Wales the weekend before last.  Anyway, the offending branches that were knackering the line have been cut, those nice folk from BT Openreach have (finally, a week or so later)  reconnected things with a cheery smile and a "That'll be bombproof now" and we have phone and ADSL service again.  Well. Sort of.  My ADSL is not much better than dialup at the moment, Noise Margin is high (15db where it used to lurk around 6) and my IP profile is woeful.
First, results from BTOW speedtest.

Download speed achieved during the test was - 0.05 Mbps
For your connection, the acceptable range of speeds is 0.05 Mbps-0.25 Mbps.
Additional Information:
Your DSL Connection Rate :1.18 Mbps(DOWN-STREAM), 0.45 Mbps(UP-STREAM)
IP Profile for your line is - 0.14 Mbps

Router stats as follows.
Statistics Downstream Upstream 
Line Rate 1184 448 
Noise Margin 14.8 dB 14.0 dB 
Line Attenuation 58.0 dB 31.5 dB 
Output Power 12.5 dBm 16.6 dBm

Historically, I used to sync up at around 2200 downstream and margin used to lurk around 6db.
I know my line is not the best out there, huzzah for rural living, but it would be nice to get back to the above...

Finally, and a general question for folk out there.. I'm using an elderly BT Voyager 2100 at the moment. Any recommendations for a new 802.11n router which is also adept at handling poorer lines? Got a few wireless devices around and waiting for them to talk to each other over 11g requires a certain amount of patience.
Cheers all.
6 REPLIES
Plusnet Alumni (retired) chrispurvey
Plusnet Alumni (retired)
Posts: 5,369
Fixes: 1
Registered: 13-07-2012

Re: SNR reset and Ip Profile kick please

I've placed a SNR reset on your line, you should hopefully see an improvement within the next four hours.
Uncle_Meat
Grafter
Posts: 167
Registered: 04-08-2007

Re: SNR reset and Ip Profile kick please

Cheers for that!  I'll find out tonight when I get home..
Before I left for work, I tweaked the noise margin using DMT (The tool, not the chemical...)  as far  down as I could get it, 9db, which gave me a sync speed of 1888 or thereabouts, and then left DMT to log changes in Attn/SNR over the day.    Will this interfer with the reset, or will that only go through next time I drop and resync?
Cheers!
Uncle_Meat
Grafter
Posts: 167
Registered: 04-08-2007

Re: SNR reset and Ip Profile kick please

Yep, that worked. Cheesy
BT Speedtest
Download speedachieved during the test was - 1.82 Mbps
For your connection, the acceptable range of speeds is 0.6 Mbps-7.15 Mbps.
Additional Information:
Your DSL Connection Rate :2.18 Mbps(DOWN-STREAM), 0.45 Mbps(UP-STREAM)
IP Profile for your line is - 2.5 Mbps
Router
Statistics Downstream Upstream 
Line Rate 2176 448 
Noise Margin 6.3 dB 14.0 dB 
Line Attenuation 58.0 dB 31.5 dB 
Output Power 12.3 dBm 17.5 dBm

I noticed, referring my previous post where I was fiddling with noise margin via DMT tool and had reduced the margin by 6db, that when I came home my line sync was at 3072, but margin was 0.3 as you would expect from my fiddling, but unsure as to how the line was hanging on to that. I did see a few line up/down counts in my logs as it was trying to hang on to that. As you can see from the above I've untweaked to defaults and it's sitting quite reliably at 6.3db or thereabouts at the moment.
If this stays relatively stable, would I be stumbing to a fall if I tweaked my router, for example, 3db in order to squeeze out a little extra speed or would I be in danger of the exchange knocking my SNR margin back up again if that proved to be unreliable?
Superuser
Superuser
Posts: 9,573
Thanks: 947
Fixes: 54
Registered: 06-04-2007

Re: SNR reset and Ip Profile kick please

Your IP Profile will decrease from the present value to 1.75Mbps due to sync speed having reduced to 2.176Mbps. So expect to see slightly lower speed test results soon.
I believe the ADSL1 protocol is less tolerant of lower noise margins than ADSL2/2+, and the lowest target SNR margin available from the DLM is 6dB (compared with 3dB on ADSL2/2+). Does your router show you CRC error counts? Those give an idea of how the line is performing.
How much Noise Margin variation do you normally experience between daytime and night time conditions?
David
Uncle_Meat
Grafter
Posts: 167
Registered: 04-08-2007

Re: SNR reset and Ip Profile kick please

Ta for that!  Yep, I'm expecting the profile to drop, but that'll be back to what I was used to before my line started going Gallipoli on me.
Over the last 18 hours or so, the SNR has been fairly stable, only deviating +/- .3db from the above reading.
I'll give it a few days, see how it goes. When the line started playing up, one notable variation was in adverse weather conditions, a spell of wet and windy weather would play havoc with it but fingers crossed now the suspect branches have been lopped and the last couple of drops of cable replaced.
As for CRC and so on, can't give you an exact figure, but when I was watching it last night after fiddling things back ot normal, it reported 13 CRCs in a period of 30 minutes so I assume that's within tolerance. I also noticed I'm on fast path rather than interleaving for the time being.
As before, leave it for now and see if it stays happy over the next few days. If so, I might try tweaking things again to see if I can squeeze a bit more bandwidth out of it.
Superuser
Superuser
Posts: 9,573
Thanks: 947
Fixes: 54
Registered: 06-04-2007

Re: SNR reset and Ip Profile kick please

That daily variation of noise margin is fine, and the DLM should be happy with under 1000 CRC errors per day.
Once the 10 day training period is past you could try biasing the target noise margin to 5dB aiming to get sync speed to 2272kbps which would give you an IP Profile of 2000kbps.
David