[e2e] Layering vs. modularization

Joe Touch touch at ISI.EDU
Thu May 15 19:39:51 PDT 2008



David P. Reed wrote:
> Encasulation means that the "totally ordered stack of layers" suddenly 
> can grow to infinite depth, as the sequence of layers is laid on top of 
> a subsequence selected from the same layers.

Packets have finite length. Infinite layering is the layering equivalent 
of nonterminating recursion, which isn't useful either.

> Layering has nothing to do with "looking inside the packets".  That 
> concept is not layering, it is something quite different - having to do 
> with lack of "interpretation" of bit strings.

It's typically called "layer violation", and often means that the 
information needed at a particular layer has insufficiently been passed 
properly by the (typically higher) layer.

What those bits mean is "interpretation", but we're talking about 
peeking across the boundary, not how to map what you see to its meaning.

Joe

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