Re: [tcpm] Is this a problem?

[Ethan Blanton <[e-mail]>]

Lloyd Wood spake unto us the following wisdom:
> At Tuesday 20/11/2007 20:11 -0500, Ethan Blanton wrote:
> >Joe keeps making this point because it is _very important_.  Any
> >feature which can be accomplished at Layer N can be accomplished at
> >Layer N - 1, and vice-versa.  
> 
> One obvious exception: end-to-end reliabililty.
> 
> Another: error-coding for the channel.

Not to digress, but ... I think this makes the argument beautifully.
Either of these *can* be handled at any layer, but we obviously agree
that it's a Bad Idea to push these all the way down to the MAC layer.
There is nothing magical about layering, that says "a protocol can
only work if layered".  Separation of concerns simply makes the model
easier to grasp, and easier to Get Right.

We could do end-to-end flow control, reliability, and link
error-coding all in Layer 1 (or Layer 2, depending on which way you
want to push), but we don't, and for a very good reason.

Ethan

-- 
The laws that forbid the carrying of arms are laws [that have no remedy
for evils].  They disarm only those who are neither inclined nor
determined to commit crimes.
		-- Cesare Beccaria, "On Crimes and Punishments", 1764

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