Almost any of the common definitions of a process would suit the needs of this paper.
Or perhaps there is only one permanently known port, which belongs to a directory-process that keeps a table of permanent-process/well-know-port associations.
That program which prints file directories, tells who is on other teletypes, runs subsystems, etc.
The reader should have noticed by now that I do not like to think of a new process (consisting of a new conceptual copy of a program) being started up each time another user wishes to use the program. Rather, I like to think of the program as a single process which knows it is being used simultaneously by many other processes and consciously multiplexes among the users or delays service to users until it can get around to them.
I use operating system rather than time-sharing system in this section to point up the fact that the autonomous systems at the network nodes may be either full blown time-sharing systems in their own right, and individual process in a larger geographically distributed time-sharing system, or merely autonomous sites wishing to communicate.
For a SEND FROM ANY message, the rendezvous site is the destination site.
For readers familiar with the once-proposed re-connection scheme for the ARPA Network, the above system is simple, comparatively, because there are no permanent connections to break and move; that is, connections only exist fleetingly in the system described here and can therefore be remade between any pair of processes which at any time happen to know each other's port numbers and have some clue where they each are.
Crowther says this is not the virtual net concept.
As one of the builders of the ARPA communications subnet, I am partially responsible for these constraints.
The reader having access to the ARPA working documents may want to read Specifications for the Interconnection of a Host to an IMP, BBN Report No. 1822; and ARPA Network Working Group Notes #36, 37, 38, 39, 42, 44, 46, 47, 48, 49, 50, 54, 55, 56, 57, 58, 59, 60.
This also allows messages to be completely thrown away by the IMP subnet it that should ever be useful.