100Mb Ethernet cable waveforms etc

I've Googled but not found any helpful articles. I am aware there is a preamble to a packet but not found any further information. Can anyone point to a useful website?

What is the theoretical maximum throughput with 100Mb Ethernet? Does the

100Mb include any other characters in addition to the preamble and the packet?

Many thanks in advance.

Reply to
Fred
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Asfair it's just the preamble + data. Ofcourse there's numerous twists to it but the basic is just those two. Search for MLT-3. Waveform consist of three levels Vmax, Vneutral, Vmin. Where highest voltage is 3.3v asfair. To calculate maximum throughout, you have to consider preamble, overhead data and minimum packet spaceing.

So what are you going to construct ..? ;)

Reply to
pbdelete

Many thanks for the steer. It was a great help and found some useful articles.

I was trying to see what overheads there were to limit theoretical data rates. I see the only overhead symbols are the Start of Stream and End of Stream.

Reply to
Fred

For the 100 Mbit/s Ethernet, there is one point to note if you're going to scope the signal: the clocks are embedded in the stream by a 4 bit to 5 bit coding, so the base speed is 125 million encoded bits / second.

There are more signifcant overheads in the upper-level protocols, if you're not going to use raw Ethernet frames. A raw Ethernet frame has a 14 byte overhead for addressing and 4 bytes for CRC after the payload of the frame, and this is in addition of the framing overhead (preamble & co).

HTH

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Tauno Voipio
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Reply to
Tauno Voipio

the

of

Hint for a single point to point like about 85 Mb/s to 90Mb/s is attainable, but not reliably. For realistic networks about 30 Mb/s to 40 Mb/s is all you can get. The limiting factor has a curve on the order of v=t*e^-t.

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JosephKK
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Reply to
joseph2k

This is a dedicated connection so not contentions.

Many thanks for the posts.

Reply to
Fred

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