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Author Topic: Can you see anything?  (Read 3349 times)

Simondup

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Can you see anything?
« on: July 17, 2012, 12:18:09 PM »

Hi,

Firstly thanks for the great work some of you have done with the modem scripts and graphs, very helpful.

I had BT Infinity installed just over a month ago and had a pretty solid 76Mbps for about 3 weeks. The dlm kicked in last Saturday (7th july) and reduced my speed to around 54Mbps on the fly without an actual disconnect. So at first my iprofile was still at 76 while my connection was clearly operating at about 54. After a modem reboot this updated to the actual profile of 54Mbps.

I left the connection alone for a while to see if it would rectify itself but it has stayed around 54 since then. I am pretty close to my cab and on installation the engineer said the line could theoretically carry 123Mbps according to his testing equipment.

Can you spot anything on my stats that points to there being a fault on the line ? I have attached current stats and about 3 days worth on on goings.

Thanks in advance
Simon
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Bald_Eagle1

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Re: Can you see anything?
« Reply #1 on: July 17, 2012, 01:37:40 PM »

Hi Simondup & welcome to the Kitz forum,



I had BT Infinity installed just over a month ago and had a pretty solid 76Mbps for about 3 weeks. The dlm kicked in last Saturday (7th july) and reduced my speed to around 54Mbps on the fly without an actual disconnect. So at first my iprofile was still at 76 while my connection was clearly operating at about 54. After a modem reboot this updated to the actual profile of 54Mbps.


Firstly, are you aware of how often the connection has resynced on the fly?
The modem's inbuilt logs should confirm that.
You may need to enable the logging & also set the modem's date & time following each reboot/power cycle. The date & time are maintained through on the fly resyncs though.

Secondly, on the fly resyncs are usually very quick (around 16 seconds on my own connection) & are thus usually NOT detected by the ISP & as a result a new PPP session is NOT initiated & BT's IP Profile is not updated.

The SAFER way to update IP Profiles is to just disconnect/reconnect the ROUTER. A MODEM reboot is not necessary.
Too many MODEM reboots can have a negative effect, making DLM believe that a connection is unstable & reducing sync speed & increasing interleaving etc. as an attempt to provide connection stability.

Quote
I left the connection alone for a while to see if it would rectify itself but it has stayed around 54 since then. I am pretty close to my cab and on installation the engineer said the line could theoretically carry 123Mbps according to his testing equipment.

Can you spot anything on my stats that points to there being a fault on the line ? I have attached current stats and about 3 days worth on on goings.

I can' see anything in your recent/current stats/graphs to suggest you will be able to achieve much higher sync speeds than you are currently achieving.

You QLN looks a little noisy, your SNRM levels don't have much spare margin & I would like to see your SNR & Hlog graphs.

Could you post a Plink log & possibly a modem_stats.log for me to plot using the newer format (not quite ready for public release yet)?

You would probably need to zip the log files & possible post them in separate messsages in this forum (unless you could post them somewhere else so that I could download them).

On a positive note, your connection seems fairly error-free, if anything with DS better than US.
The newer scripts will actually include a bit more US detail.


EDIT:

I see you had attached SNR & Hlog graphs separately.
The newer scripts produce smaller file sized montages that can be uploaded here as they fit within the size limits.

A new GRAPH6.BAT is attached if you want to use it.
« Last Edit: July 17, 2012, 01:42:41 PM by Bald_Eagle1 »
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NewtronStar

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Re: Can you see anything?
« Reply #2 on: July 17, 2012, 08:25:08 PM »

Thats good 80/20 from where I am sitting if you could move your house closer to the Cab by 100 meters you would be hitting a nice 70Mbps download  :P
« Last Edit: July 17, 2012, 08:27:54 PM by NewtronStar »
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Simondup

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Re: Can you see anything?
« Reply #3 on: July 18, 2012, 09:47:06 AM »

Thanks for the reply Bald_Eagle.

I have attached my logs and an updated graph using graphs6.bat.

If the line looks ok, how was it able to carry more data before ? Does the snr start at 3 and then move up if it detects instability ?
Is interleaving currently on ?

Thanks
Simon
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Bald_Eagle1

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Re: Can you see anything?
« Reply #4 on: July 18, 2012, 10:29:48 PM »


If the line looks ok, how was it able to carry more data before ? Does the snr start at 3 and then move up if it detects instability ?


The line looks pretty perfect, very few errors, really steady SNRM, attenuation quite low etc.

The only downside seems to be QLN levels, indicating a general & steady noise issue.
Values around -140 would be typical. However your values are only around -100 (noisier).
My own connection has QLN values closer to -140, but it does exhibit spikes of noise.

I suspect you are asking about SNRM, not SNR values.
Target SNRM is 6.0dB & your connection seems to more or less flatline around 6.0dB.

If SNRM was higher, you would expect to see higher attainable rates, possibly achieving higher sync speeds if diconnecting/reconnecting at that time.
However, as you have no spare margin, your sync speeds & attainable rates wouldn't really change much.
In other words, it looks like your connection is currently achieving the highest speed with good stability that the current conditions will allow.

I can only imagine that your connection may have started off on a wide open speed profile, possibly with higher sync speed than attainable rate due to SNRM dropping to much lower levels (maybe 3dB or less).
Eventually DLM probably lowered speeds which had the effect of raising SNRM back to 6.0dB.

This is pure guesswork & it's a shame that you don't have any stats from the higher speed period for comparison purposes.

Quote

Is interleaving currently on ?


No, the values of 1 & 1 shown against D: signify that interleaving is OFF for both DS & US.


Do you hear a constant & steady noise on the phone when running an audible quiet line test that maybe wasn't present when your speeds were higher?

3 days of stats look like a really solid, trouble-free connection.
It is therefore a complete mystery to me that your connection did achieve higher speeds, with the engineer reporting a really high attainable rate.

How far would you say you are from the cabinet to which you are connected?
Your stats suggest around 600m or so.

The engineer's comment actually suggests around 100m or so.
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Simondup

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Re: Can you see anything?
« Reply #5 on: July 19, 2012, 10:35:44 AM »

Hi Bald_Eagle,

I paced out the distance from my flat to the cab. It is about 45m to the old cab. The run between old and new cab is about 35m and I am on the 4th floor so add approx 20m for the vertical distance and you are looking around 110-120m.

About 4 years ago the line was intermittently noisy and BT came out and move me onto another pair which seemed to stabilise my adsl at the time, there might still be a problem.

The wiring in the building was all done by the builders so I would not be surprised if they have run the electrical and telephone cables together and here might be some type of interference but then I suppose we would see more error spikes.

I will leave it alone or a few weeks and see what happens. Do a few more quiet line tests see if I can hear anything.

Thanks
Simon



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