[e2e] Lost Layer?

[Detlef Bosau]

May I ask an indecent question?

Do we talk about line switching or about packet switching?

It was, amongst others, Vint Cerf himself in RFC 675 who denied the
difference. And since these days, we take the internet as a "magic
cloud" where isolated (!!!!!!! in the very meaning of Härder/Reuter and
the ACID transcations) flows exist - and appear to the user exactly in
the same way as they would in line switched networks.

Replace the line by endpoints in the cloud - and play the
Telix/Kermit/xmodem/ymodem/zmodem/UUCP game - hopefully, it will work.

My idea of layers is that a layer n provides services to layer n+1. And
these services are transparent and isolated, hence when two TCP flows
use the "IP cloud"  the two flows expect an isolated view. So the
service as seem by flow 1 does not depend on whether flow 2 is active or
not.
(When you hear your neighbour while you both do a phone call - not to
each other, this should be due to the thin walls or your neighbour's
loud voice. Not to the telephone system. )

(Of course, this concept of isolation is extreme and not sound in a
network where ressources are shared. However the question is which view
is presented by a "network layer" to upper layers? And are "layers" in
this context are a useful idea at all?)

Detlef

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