Hi Arthur, Sorry to be slow with this... was away for the weekend.
I have to say though, that I have the opposite opinion to Bru here. Here's my read on the various figures you provide: Downstream Line Attenuation: The 63dB is a pretty high figure, and means that the signal level is pretty low. Your figure might actually be even higher than this (and the signal level lower), because 63dB is the highest value the Netgear can report (apparently BT will try ADSL on lines up to 75dB). Still, 63dB isn't a surprise, given the distance from the exchange. Upstream Line attenuation: Almost never varies, and isn't too important here. Connection Speed Downstream: If the "connection speed downstream" value keeps changing, then that means that the modem is re-synchronising with the exchange. And with numbers ranging from 249 kbps to 992 kbps, it is getting very different answers whenever it does so. A re-synchronisation is forced when the modem detects too many errors on the incoming data, and each time it performs a resync, it takes 30 seconds, perhaps longer. While re-synchronising, you will not be able to connect to *anything* on the internet - so login to AOL will fail, browsing will fail, as will all DNS operations. Note that while the modem is resyncronising, the PC just experiences long delays, and slow downloads. You may get errors indicating timeouts - and usually these messages will indicate a timeout while trying to connect to DNS. A stable line almost *never* re-synchronises, and doesn't change the speed value. Downlink Noise Margin: The value that may be the most telling is the "downlink noise margin"... On a perfectly stable connection, the exchange equipment will try to target a noise margin of 6dB, and the synchronisation process will work out what amount of data can be carried underneath this 6dB margin. It is an allowance for future noise - a belief that for most stable connections, the random noise on the line will be less than the 6dB, and won't actually interfere with the data on the line. Short burst of interference can thus be ignored by the modem & exchange (or at least handled). However, too many bursts of interference, or noise that is too loud, *will* cause errors. If the modem/exchange see too many errors in too short a period, they will re-synchronise to see if they can work around the new interference. When they do this, the extra interference would mean that the new connection can carry less data... and gets a lower connection speed. So "normally", you would expect to see a modem react to interference by going slower, but becoming stable again. If the "connection speed" numbers keep changing, and go up and down, then it is a sign that (a) re-synchronisations are happening, and (b) the noise on the line is just too unreliable, and the modem/exchange cannot establish a coherent way around it. Eventually, the exchange notes that there have been too many re-synchronisations, so it changes the target to 9dB. With a larger margin, the synchronisation between modem & exchange will result in a slower connection, but the benefit should be less susceptibility to noise, so more stability. The exchange then allows connections to be made, and if these *still* need too many re-synchronisations, then it would lift the target to 12dB, and try again. If this still failed, it would lift the target to 15 dB, and try again. So what do your values of 9-11 dB tell us? Well, they certainly suggest the noise is changing over time (by at least that 2dB range), and the fact they are higher than 9 suggest that the exchange is not using the default 6dB target - suggesting in turn that the exchange doesn't think this is a stable line. My parents had similar readings when they had this problem, but would often see that figure drop to 0, 2 or 4 dB - and then frequently drop the connection. If you watch carefully at a time your connection is being "dodgy", are you seeing such low values? Connection Speed Uplink: Finally, the "connection speed uplink" also tells us a little something too. The uplink data actually uses the "best" part of the frequency spectrum over your phone line, and is the part that is (generally) least susceptible to interference. If that is altering too, then this backs up the proposition that you are suffering too much noise. My conclusion is thus... You are getting re-synchronisations. This means that you were getting sufficient errors to trigger a resync (so you will start having problems getting any data), and for the resync period itself, you will have no available connection. The resynchronisations then don't result in stable connections. >From experience, these suggest that you have too much interference on the >line, and that is pretty much the root cause of the problems. Where to go next...? I'd either get BT in, or get extra figures to back up the suspicions. You could monitor the line some more, to decide whether this is really the problem. There are a few ways... a) You can monitor the router's idea of "connection time". When logged in to the router, use the "Connection Status" button. Whenever this goes back to zero, you have re-synchronised. If it is doing this at 5-10 minute intervals, then you are definitely having problems. b) Get more regular readings of the downlink noise margin, and the downlink connection speed, to determine how often you get re-synchronisations. Watch for how often the speed value changes (so showing a resync), and whether the noise margin ever goes particularly low. c) Read different statistics off the modem (that aren't so easy to get), which will tell us how many errors you are *really* getting. We're after the CRC values for the router, which tells us how many packets of data are received containing errors. If you want to go the whole hog on this, it means running some software to monitor & graph these figures. The graphs are especially useful, as they give you an idea of how often you are seeing changes. Software such as "RouterStats" is a good start... http://www.vwlowen.co.uk/internet/files.htm This package is capable of extracting and graphing the CRC values, but it is more complicated. Given that you weren't sure about involving BT just yet, I'd probably want to get some extra confirmation about just how often your line is re-synchronising. I suspect, though, this is going to end up back at AOL/BT at some point. Do you know someone with a working ADSL connection nearby? You could always try plugging your modem in there, and reading the same line statistic values. That would give some direct comparison values. Or borrow their modem, and see how it handles your line. Now... I could be wrong on all this, so don't ignore Bru's advice either Cheers, Mike --- In [email protected], "Bru" <br...@...> wrote: > > OK, you're line attenuation is just a wee bit on the high side but > consistent with your distance from the exchange. Noise looks about par for > the course. Your speed figures are also consistent with the attenuation > levels and distance. > > The critical point is that if I read you right whilst you were obtaining the > stats on your ADSL line you could not log in to your ISP > > That is a pretty clear indication that the problem is *not* your ADSL line > (as I've been saying all along). Never say never but it doesn't sound like > it's a noise problem nor does it sound like your router is getting it's > knickers in a twist > > However it *does* sound like you are having problems beyond that. It could > be anything from routing problems at your local exchange onwards. > > I can't tell you where to find the following on your particular router but > you need to find and right down the IP addresses ... > > Default Gateway > Primary DNS > Secondary DNS > > Then the net time you can't connect to your mailserver or a web site, try > pinging each of those IP addresses and see what happens > > Bru > > > > > > > -----Original Message----- > > From: [email protected] [mailto:[email protected]] > > On Behalf Of arthurnaylor2...@... > > Sent: 07 February 2010 10:39 > > To: [email protected] > > Subject: Re: [canals-list] Re: Home Broadband Questions for the > > technocrats > > > > In a message dated 06/02/2010 09:00:46 GMT Standard Time, > > brassed...@... writes: > > > > However, knowing roughly from whence Mr Naylor hails, assuming this > > map [1] is up to date, sadly the nearest he's going to get to fibre > > optic is two torches and a length of hosepipe. > > > > I think the battery on one of the torches is flat! > > > > > > > > AS requested I have managed to get some stats from my router. I don't > > know > > what they mean of course but a selection of the data may mean something > > to > > someone out there. It is interesting that although it said I was > > connected > > and the connection had been successful I still couldn't log- in to my > > ISP > > to read my email. > > > > Connection speed downstream has varied from 249 kbps (11:49pm on > > 4.2.2010) > > to 992 kbps (16:45 on 6.2.2010), generally it is around 500 -700 kbps). > > Upstream is fairly consistent at 448kbps (but has dropped to 379 on > > the > > occasion of the slowest downstream (11:49pm on 4.2.2010). > > Line attenuation is consistent at 63db downstream and 15.5db upstream. > > Noise margin varies between 9 and 11 downstream and is steady at 9 > > upstream. > > Finally UPI is 0, VCI is 38 and I'm tuned to Channel 11. > > > > My firmware version on my Netgear DG834G is V4.01.28 > > > > > > Arthur Naylor. > > > > > > [Non-text portions of this message have been removed] > > > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > > > > >
