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Topic: Building an Ethernet bandwidth monitor - Suggestio (Read 3 times) previous topic - next topic

Luca

Westfw,
Interesting you mentioned this. Going analog was my original plan but then I got a digital oscilloscope connected to an Ethernet line and I couldn't really tell the amount of traffic just by looking at the wave.
I learned that 100Mbps uses a three-levels encoding -1, 0, +1 and even with no traffic the signal would still constantly change within those three values to provide clock synchronization.
http://www.erg.abdn.ac.uk/users/gorry/course/phy-pages/4b5b.html


Luca

kg4wsv,
I was simply planning to "tap" on the Tx and Rx wires that run between  the broadband router and the cable modem. kind of like you would do by connecting an oscilloscope to the line.

Tim Stamp

Just don't forget how UTP works - when one wire in each twisted pair is high, the other is low - so the same amount of current is always passing through the line. This method allows countering for noise on the line by simply examining the difference in voltage level between the paired wires.

You could theoretically tap the Tx and Rx pairs and monitor them both for wave changes, simply counting the wave changes would give a good idea of the very lowest fundamental level of traffic on the network.

Luca

Mark S,
That's some good information you provided. Basically I would have to use the wiznet adapter at a MAC level (layer 2) and count the bits.
Do you know if bps data is readily available off the chip or I would have actually count the bits?
Looks like I would have to use either one of those WIZ811 or WIZ810 but I am a little afraid at the fact that these devices use SPI. How do you interface SPI with the Arduino?
Also you mentioned some sample code on their website. I looked everywhere (FAQ, Support, Q&A, forum) but I couldn't find anything. Do you happen to have a copy you can send to me?

Thanks

MikMo

I think that tapping into the RX / TX cables can easyli introduce noise that  can have a very bad influence on the quality of the line.

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