[e2e] on local ethernet throughput?

[David P. Reed]

At 09:33 PM 10/21/2001 -0700, Cannara wrote:
>What Vernon says is quite right and I'll only add that Collision sensing and
>recovery happens in times on the order of 200 uS to a few mS, on even
>extremely highly contended Ethernet segments (many stations ready with pkts to
>send all the time).  This is far faster than Token passing (many mS), in any
>of its forms, as a very pertinent graph from the original IEEE 802
>standarization simulations shows (it can be faxed to anyone who wishes a
>copy).  This graph is particularly telling in that CSMA/CD become better in
>relation to Token as the number of contending nodes increases -- yes, better.

I'd love to see the chart - but can you make a scanned image on a server, 
and send the URL (why fax it?).

Token rings introduced essentially one bit/node of propagation delay 
(actually slightly less), plus 8 bits of token overhead at the end of each 
packet.  At 10 Mbit/sec, that is hardly "many mS", if you have only 
hundreds of nodes on the ring (as N grows, you can make it as large as you 
like).  You are absolutely right that the corresponding "arbitration time" 
for CSMA/CD Ethernet is flat with regards to the number of nodes.  It 
actually grows with the diameter of the collision domain due to "speed of 
light", but the standard fixes it to a constant.

I suspect that is what the graph you are suggesting will show, which is why 
I'd like to see it.

It's sad to look back at these old marketing  battles and see how the 
distortions of fact arose and stuck with us.

Religion seems to work because it places much less burden on detailed 
thinking and analysis than does science.  Technical "religions" seem to 
work the same way.

- David
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