erratic sync

The house I moved into 2 years ago had some very old and dodgy wiring - several unused extensions, no master socket, generally a mess. I'd been having very erratic dsl performance after my LLU 'upgrade' (!), which seemed to have sattled down somewhat. However, I've noticed my Netgear routing routinely going very slowly and reporting a Noise Margin of a very large number. When this happened I could reboot the router and it would reconnect with a decent speed and sensible Noise Margin.

Today I had a BT engineer out to rationalise the mess of wiring. I've now got a new line coming into the house, which goes direct to a new master socket into which I have my router plugged. The router now takes about 1/2 hour to sync (!). However, when it does sync I'm getting a connection speed approx double what I was getting.

Right now I'm connected at 4096Mb with an Attenuation of 50 db and Noise Margin of 5 db.

Can anyone suggest why my router is taking so long to sync? Superficially the fact that I've doubled the connection speed with the new wiring looks good, so why is it so reticent to sync?

In reply to:

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I've noticed my Netgear routing routinely going very slowly and reporting a Noise Margin of a very large number. When this happened I could reboot the router and it would reconnect with a decent speed and sensible Noise Margin.

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Duff router ?

In reply to:

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The router now takes about 1/2 hour to sync (!).

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Getting duffer ?

I agree. Try to borrow a router, and see if that's the same. If it is, take it up with your ISP as a fault. (Assuming you have the necessary filters on all your other phones/Sky boxes/answering machines/faxes)

Depending on the modem/router, a very large number for the SNR can also indicate a negative SNR Margin because a negative number in binary is usually displayed as a one in the left most bit which then translates into a decimal figure of at least 2^(how ever many bits used-1).

Duff router ?

The Netgear DG834 series do report a stupidly large number when the margin drops just below zero (i.e. becomes negative).
So it's probably not duff (well, no more than a Speedtouch is duff for reporting a 99ms ping on the first step of a traceroute). My guess is they didn't think about negative noise margins so the negative number reported by the chipset (presumably using a floating point variable) shows up as a very large db number (in the order of a few million).

The slowness probably being caused by the high level of noise (compared to signal).
When I used to have a Netgear it often did this, and if left for longer enough it would either recover (rare), or would drop sync anyway.

"When I used to have a Netgear it often did this, and if left for longer enough it would either recover (rare), or would drop sync anyway."
...and you don't call that duff ?

Well not duff as in a faulty one (as they all do it).
What appears to be the problem is the ability of the Netgears to hold onto a zero margin signal when other routers would have long since let go and re-sync'd.

Admittedly I'd rather it dropped and re-established sync, rather than it holding onto a (usually) hopeless situation and dropping out anyway.
I discovered, for this very reason, Netgears are not as well suited to long or noisy lines than other routers, but are fine if a line can sync with plenty of margin (either because it's a short line, or has a higher than normal target margin), but they're of little use on lines where the noise margin regularly visits zero.

Well, I just noticed that Netgear have released a new firmware for the DG834 - installed it and I sync straight away and with an increased noise margin, now up to 12db.