[e2e] Switched Ethernet is Not an End-to-End System; was Protocols breaking the end-to-end argument

rick jones perfgeek at mac.com
Sun Nov 1 10:45:28 PST 2009

On Oct 31, 2009, at 2:46 PM, Richard Bennett wrote:

> Dave Eckhardt wrote:
>> 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.
> That's part of the story, but the implications of the switched  
> Ethernet killing off CSMA/CD Ethernet are much larger, and relate  
> the end-to-end arguments principle. CSMA/CD Ethernet was an end- 
> point managed system sharing a dump pipe, while switched Ethernet is  
> a system that deploys intelligence - switching, flow control,  
> buffering, QoS discrimination, VLANs - inside the network at  
> multiple points. Switched Ethernet is scalable, manageable,  
> diagnosable, and future-proof, while CSMA/CD Ethernet is none of  
> these things. So the competition of CSMA/CD and Active Switching for  
> markets demonstrates something about which approach to the design of  
> layer 2 networks is superior.

I think you left-out how Power over Ethernet will replace the global  
power grid and that it also juliennes fries :)

Color me a cynic, but I rather thought that today's switched  
"Ethernet" needed flow control and buffering precisely because CSMA/CD  
was removed from Ethernet when it went full-duplex?  I seem to recall  
that flow-control was not initially present in full-duplex Ethernet.   
I'm still not sure how much of the rest of the laundry list above has  
been added to Ethernet has been in response to folks going "Routing is  
hard, lets go shopping for switches" and the switch vendors being  
quite happy to provide a solution to encourage people to buy new  

rick jones
there is no rest for the wicked, yet the virtuous have no pillows

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