is ANYTHING more annoying that drop out?

[Zak33]

thanks fella, although that's exactly what the Zen site says too.

Just WISH is was sorted on the phone calls, nothaving a week long wait for an appointment.

[Zak33]

adsl status
--------------------------- ATU-R Info (annex A) ---------------------------
Running Mode : G.DMT State : SHOWTIME
DS Actual Rate : 6368000 bps US Actual Rate : 448000 bp
DS maximum Rate : 7456000 bps US maximum Rate : 768000 bp
DS Path Mode : Interleave US Path Mode : Interleave
NE Current Attenuation : 42.5 dB Cur SNR Margin : 6.5 dB
DS actual PSDM(C) : 00000007 US actual PSDM(R) : 00003e77
ADSL Firmware Version : 41e2be2c
-------------------------------- ATU-C Info --------------------------------
Far Current Attenuation : 30.0 dB Far SNR Margin : 15.0 dB
CO ITU Version[0] : 000f414c CO ITU Version[1] : 43420000
DSLAM CHIPSET VENDOR : < Alcatel >
----------------------------------------------------------------------------
INTL, DSTREAM bytes/depth= 16, symbols/codewords = 0, latency= 0*0.25ms
, USTREAM bytes/depth= 2, symbols/codewords = 0, latency= 0*0.25ms
CODE, DSTREAM fast parity bytes= 0, fast codeword= 0.
DSTREAM intl parity bytes= 14, intl codeword= 214.
CODE, USTREAM fast parity bytes= 0, fast codeword= 0.
USTREAM intl parity bytes= 16, intl codeword= 136.
Setting>>
FDQ : Enable, TCM : Enable, EC : Disable, Framing Mode : 3.
Running>>
FDQ : In Use, TCM : Off, EC : Off.
DS : Framing Mode 3, US : Framing Mode 3.
ADI ADSL Firmware Version: 41e2be2c
adsl status

What is the Far SNR Margin of 15dB?

Is that what the Alcatel DSLAM is set at? Or is it the SNR margin that the local DSLAM is working with? If so, tonight, when it slows down, I'll telnet this again and compare.

(ATU-R is ADSL Terminal Unit Remote (my router) and ATU-C is Central)

[jamin]

I might be wrong, but I am looking at this from an engineers point of view.

To me, SNR margin is the clear gap between the usable top edge of the signal, to the top of the noise floor, I don't think it can be "set" by the ISP. However, in this case, an SNR of 6.5db is far too close for comfort (The adsl signal is about 4 times the magnitude of the noise). On the HDSL circuits I work on, an SNR of anything less than about 13db will cause problems. 6.5db seems too low to me (but as I say, I may be reading it wrongly). I'd be interested to know the signal level being received by your router. But as usual, manufacturers never give you access to useful info!

Does this SNR change much when you remove all of your telephone extensions (Take the bottom plate off the master socket to dis extensions) and plug the router directly in the socket behind?

[Zak33]

that IS plugged into the main plug socket! It is the exact same amount if it's plugged into the normal wall plug too, the only thing that changes is the line speed, though it doesnt equate to a speed increase sadly. I therefore have no phones plugged in.

The SNR margin can be set by BT. That's what Zen tell me. I believe it auto detects normally but can be forced by BT.

I don't know that actual SNR, just the margin.

[Agent]

Zak, which model exactly is this ?
You need about 7-9db at a bare minimum to stay reasonably synced IIRC,

[Steve]

Time to clear up a few misconceptions.

SNR

Signal to Noise Ratio is a measure of the magnitude of the desired signal over other crap on the transmission medium. It's measured in decibels. I believe the absolute low-limit for ADSL Max is 3db, but SNR varies constantly... it's not a fixed thing. The higher your SNR margin, the stronger your signal is over the noise. If your SNR margin gets too low, or fluctuates a lot, then chances are you're in for a dropped line.

Downstream/upstream SNR

Seeing as a router is receiving one signal and sending another, there's SNR at both ends of the line. There's SNR as the router sees it - the strength of the incoming signal, and there's SNR as the DSLAM sees it - the strength of the signal it's receiving from the router.

'Setting' the SNR margin

As far as I'm aware, all they'll do to 'set' the SNR margin is to monitor the line for drops and low SNR figures, throttling back the speed at which the ADSL link operates at until it's within satisfactory bounds. It's usually automatic. The more bandwidth ADSL uses, the worse the SNR gets.

Attenuation

Basically the resistance of the line reduces the strength of the signal as it is carried over it. In turn this may well reduce the SNR as the signal will be smaller once it reaches where its going. This is why long lines can't always negotiate to full speeds.


There, I've not gone into too much detail, because I'll trip over my own lack of really in-depth knowledge.

[Zak33]

good info: does that mean my SNR margin FROM my router TO the Alcatel DSLAM is 15dB?

If so, I rock, they don't

[madman045]

Zak, are you using the UK2 firmware on your router?

I have a 2600, it syncs at 6mb but i actually get 4mb true speed....

[Agent]

There is another firmware you can try for issues like this. From the readme :

***********************************************************************************

Release Notes

Firmware Version : v2.5.9 UK
Modem Firmware : 41E2BE2C (Standard) / 43E2EAA1 (UK2)
Firmware Build Date : Fri Jan 27 2006 15:55
Status : Formal Release
Release Date : 13 Feb 2006
For Models : Vigor2600plus, Vigor2600G, Vigor2600Gi, Vigor2600i
Locale : For UK use only

Note : This firmware is not compatible with other models; do not
attempt to upgrade it to other models as it may make them inoperable.
If your router was not purchased in the UK please check with local
distributor for the correct firmware as physical hardware varies.

For support for the UK, please visit www.support.draytek.co.uk

***********************************************************************************


The 'UK2' firmware is intended for use only when the regular UK firmware
is unable to reliably sync. with your line in situations of poor
quality ADSL signal/lines. Use regular firmware otherwise. To obtain
the UK2 firmware, download from the same URL, using 'uk2' instead of 'uk'
to the end of the filename

You can download it from : http://www.draytek.co.uk/support/dow...0p_259_uk2.zip

edit - just beaten too it while typing it up

[Zak33]

ok dudes...I'll try that

I avoided it as it seemed to be a bit of a "beta" firmware...and Agent knows my history with any kind of BIOS

Tonight I 'll leave it as it is, with this connection to see when it drops....then rush outside and shout at the Ionosphere for ruining my game or my neighbour for having an electric garage dooor I didn't know about (joking...though it'sa thought)

and then try the new firmware

[Zak33]

here;s a good read for anyone interest....
http://bbs.adslguide.org.uk/showthre...anded&sb=5&o=0

[Steve]

good info: does that mean my SNR margin FROM my router TO the Alcatel DSLAM is 15dB?

If so, I rock, they don't

There's also a lot less bandwidth on your upstream, resulting in the higher SNR

[jamin]

Well said guys, all great info.

Steve, didn't realise the snr limit was so low! 3db is tight, REALLY tight.

Zak, if the SNR doesnt change when you remove your extensions from the master, it is more than likley a fault outside. However if the minimum is 3db, then I'm stumped! lol!

Interested to find out what is causing this, as a lot of peeps are having probs with MAX. I would wait for the test results on the line, then hit the ISP with them. Gives you a bit of a bargaining chip and stops them blaming BT.

Just for the record, we soak tested about 10 different adsl filters from different manufacturers and they all came out rubbish. Poor signal rejection and they pretty much all clipped frequencies in the wrong place! The cheaper ones came out worse, but the more expensive ones were only marginally better.

[Agent]

I wouldnt normaly ask being you, Steve, my darling , but where have you got the 3db figure from ?, it just seems waaaaayyy too low.

[jamin]

@ Agent...... Phew, not just me!

[Zak33]

10:06........went from 5 to 3.5...and then bang...dead!
I took a screeny first....

Here....


then I rushed outside to beat the crap outta the nieghbours, but nothing had changed...no neighbous to kill.

and now it's resynced I'm fine....slightly slower but hey ho.