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

Richard Bennett richard at bennett.com
Wed Nov 11 16:08:26 PST 2009

Classical Ethernet - the co-ax cable-based, Aloha-derived CSMA/CD system 
- is one of the canonical examples of a purely edge-managed network. It 
actually hails from the era during which the Internet protocols were 
designed, and expresses a similar set of engineering trade-offs. 
Thirty-five years after the design of Ethernet, we've dropped the purely 
edge-managed approach to building layer 1 and 2 networks in favor of 
somewhat more centralized systems: Switched Ethernet, DOCSIS, DSL, 
Wi-Max, and Wi-Fi are the leading examples. These systems aren't purely 
centralized, of course; they're more like multiply-centralized meshes 
than either edge-managed or core-managed systems.

While we now know that edge-managed LANs and MANs are not the way to go, 
we still use edge-managed protocols to operate the Internet. The 
Jacobson Algorithm is probably the purest example.

The triumph of switched and semi-centralized systems at layer 2 suggests 
that it might be beneficial to revisit some of the design tradeoffs at 
layer 3 if for no other reason than to bring them up-to-date. In 
principle, IP isn't supposed to care what's happening at layer 2, but in 
practice it makes a great deal of difference; this is one reason that 
people design networks nowadays with the express intention of being good 
for IP; e.g., MPLS.

That's the general idea.


Detlef Bosau wrote:
> Richard Bennett wrote:
>> In other words: does the success of Switched Ethernet suggest that 
>> it's better to think of network protocols as units of recursion than 
>> as collections of statically-placed functions that operate once and 
>> only once in the lifetime of a packet?
>> RB
> I've just had a very first glance at this discussion. (Thanks god, I 
> first wrote the post by Joe....)
> However, I'm a bit curious what this discussion is all about.
> Many of us enjoy Switched Ethernet, me too. However, what is the very 
> issue with switched Ethernet from the end to end arguments point of view?
> And second: Shall switched Ethernet replace TCP/IP?
> If not: What is this argument all about?
> Just curious.
> Detlef

Richard Bennett
Research Fellow
Information Technology and Innovation Foundation
Washington, DC

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