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In article <Oct.26.21.11.02.1992.5329@skate.rutgers.edu> manolis@skate.rutgers.edu (Chris Manolis) writes:
>Hi out there!
>I have a question regarding Ethernet.  Can anyone tell me if the
>expression, "the current bandwidth of an Ethernet network is 10Mbps".
>I do not agree with that, so please let me know if I am right or
>wrong.
>Thanks
>*******************************************************************************
>Christos Manolis			manolis@clam.rutgers.edu
>                                        manolis@pilot.njin.net
>                                        manolis@nsvm.atlantic.edu
>*******************************************************************************
Actually, this is a complicated question, but I'll take a crack at it.

Ethernet, the 10Basex (with x being 2,5,T ) uses Manchester encoding, with
two states, (call them high and low for now). It is capable of bursts
of information at 10 million bits per second. Actual throughput is lower due
to an interframe gap. Character information from a computer is lower still
due to the overhead that each frame has (preamble bits, destination bits,
a bit here a bit there, it adds up). And file transfer speeds are lower still
if you take into account such things as bus speed of the computer, ram
clock cycles, disk speed (slower still), and on and on.
On a quiet Novell network file throughput is somewhere around 1.6 million 
bits per second. (As measuured with Norton Utilities sysinfo diskspeed test).
This includes the disk access of the two computers, the 2 computers
bus speed, the cpu cycles. 
Risc-based computers with fast network cards can get something like 5 megabits
per second betwween themselves.

From a communications theory standpoint, one could argue that the bandwidth
is a theoretical minimum of 10mhz, since for 10 megabits of data it would
be 5 megahertz for bipolar signalling, but the Manchester encoding doubles
this to 10 Mhz. In actuallity, the manchester ecoded signals have to pass
through a 30 Mhz filter (I forget the number of poles), because of FCC high
frequency radiation rules, so you could say it is bandlimited to 30Mhz.

Of course the best answer to the question 
What is the bandwidth of ethernet?
is:
It depends.
    
Comments appreciated. Hope I was able to help you.