[ih] principles of the internet

[Noel Chiappa]

    > From: John Day <jeanjour at comcast.net>

    > Yes, this was the basic datagram innovation pioneered by CYCLADES,
    > which is the fundamental shift in the thinking. I sometimes
    > characterize the distinction as packet switching was "continental
    > drift" but datagrams were "plate tectonics."

Going to disagree with you there.

Don't get me wrong, CYCLADES was a _HUGE_ step forward, and considering the
gap from the ARPANET to the Internet, CYCLADES is much close to the latter
than the former. So it was a critical trail-breaker. Still...

The ARPANet really did pretty well implement the radical Baran/etc model of
the world, the model of packets. That was the really fundamental change in the
world, the strata-breaking event (to continue the geological metaphor).  Prior
to that, circuits (with a whole range of key attributes, such as explicit
setup/tear-down, fixed sharing of resources, stream service model, etc,
etc). After that... And everything else since then has been adjustments to
that major change in direction, IMO.

The ARPANet really did expose the datagram paradigm to the users (from its
perspective, the hosts): for example, there was no 'connection open' or
'connection close' _from the host to the IMP_ - the host just sent packets to
whereever, and whenever, it wanted.

Yes, it had to obey flow-control restrictions, or it could be blocked - but
even if a host did obey flow-control, it could be blocked for reasons beyond
its control/understanding.

And, yes, the Host-Host protocols sort of 'made' the actual users use the
network as VCs, but that was I think for other reasons (which I can only
guess, but I would guess that keeping the circuit paradigm made getting into
that whole new world easier).


The big change going from the ARPANET (not Host-Host Protocol, see above) to
the Internet (in terms of the _placement_ of function - the Internet of course
added other capabilities, such as being able to use a diverse range of
technologies, but that's different) was to make the hosts responsible for
reliable transmission (checksums, sequence numbers, timeouts,
retransmissions). Was that as big as going to packets to begin with? It was
big, sure, but as big as going to packets?

	Noel