[e2e] Protocols breaking the end-to-end argument

Dave Eckhardt davide+e2e at cs.cmu.edu
Thu Oct 29 11:05:58 PDT 2009

> It strikes me that your 90% claim is a bit of an exaggeration,
> and more importantly that it misses the point.

Actually, I was trying to get you to define what you meant by
"Ethernet became dominant" by proposing a definition, since
you hadn't.

> Define "the market" as all the places where switched Ethernet
> is used today, crank in some realistic shares, and tell me
> what you get; by guess is that coax Ethernet was deployed in
> around 10-20% of the places where twisted pair and optical
> Ethernet LANs, MANs, and WANs are used today

Now I get it:  when you wrote "Ethernet only became dominant
when we dumped CSMA/CD for the collision-free, flow controlled,
full duplex switches that we use today" you meant something
like "Switches were a necessary addition to Ethernet before
it could grow from a single-building LAN to a campus-spanning
technology".  I buy that, because treating an entire campus
or medium-sized company as one collision domain wouldn't have
worked out very well.

On the other hand...

> ARCNet was very big in desktop connections, as far as that
> goes, especially in IBM shops because it used the 3270 PHY.

I don't think any of Ethernet's competitors would have scaled
very well either--ARCNet had single-byte node addresses; Token
Ring would have been painful if you had to share a transmit
token with thousands of other machines; etc.  So it's unclear
that CSMA/CD was a structural limit of Ethernet--the reality
is probably more like "It doesn't matter much how you contend
among a few hosts, but you can't build large networks unless
you limit contention domains to less than the size of the
large network", which is almost a tautology.

Dave Eckhardt

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