kre is quite correct.  To fill in a few minor points...  3Com had a
(mostly user-level) TCP/IP for Unix, called UNET; it was certainly 
available in 1982 but not, I think, much earlier.  BBN did a kernel 
implementation that was apparently ancestral to the 4.2bsd Berkeley 
version.  I seem to recall a TCP (or was it NCP) for PDP 11-based 
Unixes around then, too.

As for MVS -- there was no notion of a "directory".  File names had 
levels, but these were separated by periods.  Creating a new level 
in the "system catalog" (as opposed to a reference that also required 
you to specify the disk drive type and "volume serial") required a
moderately arcane operation, much less common than mkdir.  The notion 
of treating a level as a file would have been quite foreign; the 
catalog was not part of the disk in anything like the way it is on Unix.

I don't know when Multics came online; I know that I used it via the 
ARPAnet in the (northern hemisphere) summer of 1976.

		--Steve Bellovin, http://www.research.att.com/~smb