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[supercooper]

Hi Guys,

Thought you might like to hear a weird one.

I am looking at a sites Broadband that we support which has suffered dropouts and dramatic changes in the SNR.
The line has been tested many times by Bt as ok.  I requested an Engineer attend site and spoke to him about this problem, after the visit the Engineer completed a left n shift at the exhange.   Guess what the fault remins but its gone a bit differant.

so whats happening??

Well a while ago i ran Router stats on this connection using a Draytek Vigor router on site, the SNR was all over the place. Raised with BT "no fauts found" :s

We went tp site and replaced the filter and confirmed all internel cabling was ok. The fault remained.

Went back to site once more and replaced the Router with a Zyxel 660. The fault remained.

BT as i said before attended and now the connection is showing -1db on the SNRM ? Re-booted the router and again -1db??

The router stats that i have linked to this page is on the draytek before any action was taken.

Current stats taken from the Zyxel are:

3968 kbps / 448 kbps
noise margin upstream: 24 db
output power downstream: 19 db
attenuation upstream: 29 db
tone   0- 31: 00 00 00 04 45 66 77 77 77 77 77 77 77 76 65 50
tone  32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
noise margin downstream: -1 db
output power upstream: 12 db
attenuation downstream: 47 db
tone   0- 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  32- 63: 9b bc cc cc cc cb cb bb bb cc cc cc c9 bb bb bb
tone  64- 95: 0b bb bb bb bb bb bb bb aa ab aa aa aa aa 98 60
tone  96-127: 35 99 99 99 88 88 88 78 88 67 88 77 88 78 77 77
tone 128-159: 77 76 50 24 27 77 66 66 66 66 65 44 05 55 44 44
tone 160-191: 20 33 44 43 30 00 00 02 44 44 32 33 44 43 23 00
tone 192-223: 22 22 33 02 33 44 33 22 00 00 00 30 22 22 22 22
tone 224-255: 22 22 00 22 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
LAN Information:
IP Address: 192.168.1.1
IP Subnet Mask: 255.255.255.0

The connection has been online for over 10 hours and has dropped very early this morning.  I always thought that DSLMax could never have an SNR above 16db, am i wrong?

Your thoughts please

Thanks, Chris


[attachment deleted by admin]

[roseway]

>> I always thought that DSLMax could never have an SNR above 16db, am i wrong?

Yes you are The highest target noise margin which you can have is 15 dB, but that only defines the noise margin at the time of making the connection. After that it can drift up and down by any amount, depending on interference conditions.

Regarding the - 1 dB noise margin, some routers are capable of holding the connection down to such low levels. Netgear routers have often been found to do this. It depends on the chipset used in the router and the firmware which controls it.

[kitz]

Thats some hellish fluctuation in SNRM - especially over such short time spans

Just to clarify - the "Re-booted the router and again -1db?"

Was that -1dB immediately after a resync?
It would be interesting to see what the SNRM is immediately after a resync to try and find out what the Target SNR is.
It looks like the line could still be suffering from possible interference.

[supercooper]

Hi Guys,

Thanks for youre replies.

Well i did a remote re-boot of this router today and it stepped in at the below stats:

4128 kbps / 448 kbps
noise margin upstream: 24 db
output power downstream: 19 db
attenuation upstream: 29 db
tone   0- 31: 00 00 00 04 45 66 77 77 77 87 77 77 77 76 65 40
tone  32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
noise margin downstream: 13 db
output power upstream: 12 db
attenuation downstream: 47 db

So it would appear the SNRM reduces over time.  I will watch this connection throuout today and let you know what happens. 

Thanks, Chris

[kitz]

>> noise margin downstream: 13 db

The target SNR is probably set at 12dB then.

>> So it would appear the SNRM reduces over time.  I will watch this connection throuout today and let you know what happens. 

Yes probably well worth monitoring with routerstats to see what happens and if its still fluctuating all over the place or if it is a gradual decline.
Since the router has sync'd up at a higher speed than previous it doesnt look like its a permanent ever decreasing.
If the router was showing -1db then a reboot sync up at a higher speed, rather than a lower one (which is what should normally happen), then something is a little strange and not what youd expect to see.

[supercooper]

Hello again,

Hmmm ok the SNRM has changed but due dropouts on the connection.

Here is the RAD Log:
2008-07-25 13:04:56  <>  <>  Login OK   
2008-07-25 11:33:42  <>  <>  Login OK   
2008-07-25 10:32:09  <>  <>  Login OK   
2008-07-24 06:15:10  <>  <>  Login OK   
2008-07-24 06:10:33  <>  <>  Login OK   
2008-07-23 14:33:28  <>  <>  Login OK   
2008-07-22 13:46:49  <>  <>  Login OK   
2008-07-22 11:51:26  <>  <>  Login OK   
2008-07-22 10:25:01  <>  <>  Login OK   
2008-07-22 09:55:52  <>  <>  Login OK 

The connectio at 10:32:09 was me requesting a re-boot from the router and the other two dropouts are unkown. I know the router has not lost power.

New Stats are:
3872 kbps / 448 kbps
noise margin upstream: 24 db
output power downstream: 19 db
attenuation upstream: 29 db
tone   0- 31: 00 00 00 04 45 66 77 77 77 87 77 77 77 76 65 40
tone  32- 63: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  64- 95: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone  96-127: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 128-159: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 160-191: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 192-223: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 224-255: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 256-287: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 288-319: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 320-351: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 352-383: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 384-415: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 416-447: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 448-479: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
tone 480-511: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
noise margin downstream: 14 db
output power upstream: 12 db
attenuation downstream: 47 db

All i can see here is that the profile has stepped down casing the SNRM to increase   I'm still no closer to finding why this site has problems.  Interesting to see the SNR has not moved but i could have missed it before the dropout.

I will be honest with you that I cannot get Routerstats to work with this router   The last set of stats was taken from a Draytek Vigor. I will have another try to get it working on the Zyxel.

Thanks, Chris

[kitz]

It looks like the SNRM must have continued to fall after the last boot this morning until it reached a point where the connection could no longer hold causing the lower syncs afterall :/

Its hard to say without seeing an SNRM record, but tbh I wouldnt be surprised if the old underlying problem was still there..  a wild guess would perhaps lead me to suspect a REIN issue.  The old graph had signs of it and if it is, then that would explain why the lift and shift hasnt made that much difference.
The wild erractic spikes could either be REIN or even a line fault - neither of which would be cured by a lift and shift. :/

[supercooper]

Thanks Kitz,

That was an interesting read

Well the connection has been up for just over 3 hours and the SNRM is steady between 14-15db at the moment.

I think in light of what you have said i will send one of my Engineers back to site to check around for such devices, the only think is that on the old RouterStats the connection was consistantly all over the place and now it seems to drop over time???  Maybe the Zyxel tolerates this differantly than what the Draytek did.

I will keep my eye on this for a while and let you know what happens soon.

Thanks again, Chris

[kitz]

The wild and erratic spikes are more typical of something more background electromagnetic noise rather than something being switched on, which materialises as a very sharp drop.  Could also be something like an oxidised joint which has some weird symptoms.
Have you got someone to try a quiet line test? - Dial 17070 and select option 2 to see if you can hear any noise on the line.

[supercooper]

Hi

The line has been tested many times as ok :\

Something has caught my eye this morning on the RAD log here:
2008-07-25 13:04:56  <>  <>  Login OK   
2008-07-25 11:33:42  <>  <>  Login OK   
2008-07-25 10:32:09  <>  <>  Login OK   
2008-07-24 06:15:10  <>  <>  Login OK   
2008-07-24 06:10:33  <>  <>  Login OK   
2008-07-23 14:33:28  <>  <>  Login OK   
2008-07-22 13:46:49  <>  <>  Login OK   
2008-07-22 11:51:26  <>  <>  Login OK   
2008-07-22 10:25:01  <>  <>  Login OK   
2008-07-22 09:55:52  <>  <>  Login OK 

They have not dropped out over the weekend (They dont work weekends).  Current SNRM is 14db.

I'm now wondering if the fault is happening when passing excessive traffic or maybe some kind of hidden filtering issue. 

Very confuesed at the moment

Chris

[kitz]

>> They have not dropped out over the weekend (They dont work weekends). 

Some other equipment in the office not switched on?
CRT Monitor, radio, air con, heating?

[supercooper]

Hi,

We are due to go back to this site to look for the possibility of a RIEN issue.

I have spoken to the tech guys who provide our BB and they agree the connection is not acting in a correct way if it was a line fault. 

Not sure when we will be going to take a good look on site just yet, i was amazed my Technical Manager did not laugh at me when i requested an AM radio    He said no

I will update you all once we go back to site also im thinking about putting the Draytek back in so we can monitor this with Routerstats again.

Cheers, Chris

[kitz]

>> i was amazed my Technical Manager did not laugh at me when i requested an AM radio

 

>> He said no

lol you mustnt have been convincing enough 

[supercooper]

Hi Guys,

I'm still waiting on a time slot for an Engineer to attened site on this now suspected REIN issue.

I was reading through a post and came accross a comment by "Roseway" (Sounds like a clever chappy) and he mentioned that an NTE2000 stops the internal cabling being like an airel for interferance.  If this site does in fact have a REIN issue then at a guess changing for an NTE2000 may in fact reduce the interferance or eliminate it, so with that i have a nice shiny NTE2000 sat on my desk ready to try. 

The post was here if anyone is interested: http://forum.kitz.co.uk/index.php?topic=2199.0

Also i still cannot get Routerstats to work woth the router we swapped so im going to send the Engineer with another Draytek Vigor.

Once all is setup i will let you know how it all went. 

Fingers crossed for now.

Thanks, Chris

[kitz]

Thanks for the update
and good luck with the faceplate