From: Johnny Billquist
the switch to TCP/IP only happened in 1982-1983. So
while the
"internet" (well, ARPANET actually) existed before then, it was not
TCP/IP based.
The conversion of the _ARPANET_ from NCP to TCP/IP happened on 1 January,
1983. However, 'the Internet' (in the sense of a grouping of networks over
which TCP/IP packets flowed) had been around for some time before that, both
as i) a testbed for developing the TCP/IP protocols and software used for
that cutover, and ii) for network service to machines which couldn't get an
ARPANET port (remember that at that point in time, there were no personal
computers, just time-sharing systems).
The history of TCP/IP and the Internet up until that point is complicated (I
lived through it, so I should remember, but alas the memory dims :-), but the
first use for actual service (as opposed to testing software, demos, etc)
would have been a year or two before that - exactly when is somewhat lost in
in the mists of time.
Although the ARPANET pre-dated the Internet, it was used to carry TCP/IP
traffic (directly, not inside NCP - the protocol used between hosts on the
ARPANET before TCP/IP) long before the cutover; it was _the_ long-haul
network in the early Internet, and connected together all the various local
TCP/IP 'hot spots' (to use modern jargon).
'All' that happened on January 1, 1983 was that the ability of the ARPANET to
carry NCP packets was disabled. Of course, in the months prior to that, all
the ARPANET hosts which didn't _already_ have TCP/IP running (many did, to
speak to other machines locally which didn't have ARPANET ports) went through
a big thrash to get TCP/IP software, and get it installed, tested and running.
Noel