Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[snadge]

Im trying to find out if my low SNR is causing more errors on my line, currently my SNR is between 2.0db and 2.5db, download speeds are fine although from a 19,000k sync I can only max out at 15.8Mbps which is 3Mbps lower than the sync rate - even on standard SNR of 6db I get 17,000k sync and 14Mbps download speed

I dont know what a 'high' amount of errors are and DMT does not display FEC although ive since learnt it displays RS (corrected) which I believe is what Iam looking for, the figure looks high but not sure - am I right in saying it has 441 million RS counts and 1 million corrected... this means the correction rate is about 0.25% of all traffic? I would imagine that is low, looking for re-assurance that my line is ok on such a low SNR.

here is my routers stats from DMT (DG834GT on DG team 1018 - 18,800k sync on 26.5db Line Atten with 2.0-2.5db SNR)

thanks


Counters        Down            Up

SF:             9251683         9364687
SFErr(CRCErr):  213             10683
RS:             441894752               0
RSCorr:         1645623         0
RSUnCorr:       6923            0

HEC:            155             9982
OCD:            0               0
LCD:            0               0
Total Cells:    2363087815              1585223560
Data Cells:     81647498                3424987357
Drop Cells:     0
Bit Errors:     0               1015005

ES:             176             1326679
SES:            0               0
UAS:            16              0
AS(Uptime):     149835

INP:            2.04            0.00
PER:            16.19           16.18
delay:          6.07            0.24
OR:             31.61           10.87

Bitswap:        15344           16
Total uptime:   149835


Total time = 1 days 17hours 37min 51sec
SF  = 9251683   CRC = 213
LOS = 0   LOF = 0   ES = 176

Latest 1 day time = 17hours 37min 51sec
SF  = 3919071   CRC = 87
LOS = 0   LOF = 0   ES = 73

Previous 1 day time = 24hours 0sec
SF  = 5332612   CRC = 126
LOS = 0   LOF = 0   ES = 103

[roseway]

103 errored seconds in 24 hours, that's roughly 1 ES per 15 minutes or 1 ES in 900 seconds. Unless it all comes in one burst, that's quite insignificant.

[snadge]

thanks

am I right abut the RS error count and correction figures? (0.25% of all traffic) and if so is that acceptable?
also, do you know why I get 3Mbps difference between sync and actual throughput?

I cant think on how much it was used yesterday, I may reset the router and monitor usage vs errored seconds.

[waltergmw]

Hi Snadge,

I think Eric's gone to tea so here's a quick reply

All will be revealed if you read here and pages before and after

http://www.kitz.co.uk/adsl/IPprofile.htm

The sync speed is used to select  the bRAS which is lower to ensure there are reasonably error free transmissions.
Then there are overheads so your actual throughput is bound to be a bit lower still than the bRAS.

I wouldn't bother about your error rates as Eric says. He and Kitz know best !

Kind regards,
Walter

[razpag]

Also to back the boys up Snadge, various ISP's use various ES counts (Errored Seconds), to determine what they regard as faulty. Some allow 12 ES per minute, some 20 ES per minute.

The key in stabilising a circuit is looking at incrementation and using ones judgement. I genuinely think your error count is way within parameters. Regarding Reed/Solomon and corrections, this place is a mine of information about that. Way over my head mate.

PS ... hope yer well and good ?? 

[snadge]

thanks for the replies guys

Hi Razpag, Iam fine, nice to see a familiar face

Im not on a Bras Profiling line, im on LLu ADSL2+ where I always have 3Mbps difference (which is a lot IMO) between sync and throughput regardless of SNR Margin at 2db or 6.5db - at my previous address I noticed on a longer 39db line it was the same (or thereabouts)... is that much difference normal? and why such a large amount?

old line:
39db - 2db - 16,000k / 13Mbps

new line:
26db - 2db - 19,000k / 16Mbps

if I dont apply SNR tweak I get 17,000k / 14Mbps
as you can see there is a difference of 3Mbps..  now my friend who is also on o2 LLu gets 9,000k sync and 8.1Mbps throughput...that seems 'normal' to me - so in that respect surely my 19,000k line should be yielding speeds of about 17.5Mbps or 18Mbps..?

Regarding the Error Count it seems acceptable, I suppose I'm just trying to understand the figures from DMT, this website has been an amazing tool for me too learn from (and still is), I know that the DSLam is setting an Interleaving Depth of 160, 192 or 224 and this is high so im trying to determine if this is because of a high error count and if my latency (and loading of web pages) is affected by high Interleaving Depth and Error Count, and if so raising the SNR to see if it can compensate, it seems though no matter what the SNR is at the Interleaving Depth setting is not related, ive had 224 @ 6db and 160 @ 2db, one would think that a lower SNR (and more chance of errors) it would set a higher Interleaving Depth... but it doesnt seem that way

...anyway, error counts aside now, I want to find out why i have 3Mbps difference instead of about 1.3Mbps (or thereabouts)

[burakkucat]

Old Line

39db - 2db - 16,000k / 13Mbps

Assuming 1000k to 1M, then throughput is ~81% of sync speed.

New Line

26db - 2db - 19,000k / 16Mbps

Using the same assumption, then throughput is ~84% of sync speed. According to my understanding, that is spot on for what you should expect.

[waltergmw]

BUT

Playing with Kitz's estimator Snadge's guess looks as if he should be getting less of a drop.


I've put a couple of 2Wire O2 diagnostic pictures just for comparison but they are on longer lines as you'll see.
Is there any way O2 could have put you on a different Mode?

Kind Regards
Walter



[attachment deleted by admin]

[attachment deleted by admin]