TCP/IP has achieved success in large part due to its universality: it has been implemented on virtually every major computing platform. While the suite is thus not specific to any operating system, there is no denying that its history is closely tied to a particular one—UNIX. Most of the computers on the early Internet used UNIX, and the development of TCP/IP has paralleled that of UNIX in a number of respects.

One of the most important organizations involved in the development of UNIX, and thus TCP/IP indirectly, was the University of California at Berkeley. Their well-known Berkeley Software Distribution (BSD) UNIX has been in widespread use for over 20 years. A set of commands was developed for BSD UNIX to facilitate various remote operation functions over a TCP/IP internetwork. Each of these programs begins with the letter “r” (for “remote”), so they have come to be known as both the Berkeley remote commands (or utilities) and also simply the “r” commands. Since their initial creation, they have been adopted for most variations of UNIX, and some other operating systems as well.

In this section I provide a brief description of the Berkeley remote protocols and how they are used. I begin with a discussion of the main protocol in this group, rlogin, and how it is used to enable remote host access. I then describe the remote shell program, rsh, and how it allows a command to be executed on a network host. I conclude with a brief summary of the other members of the “r” protocol family: rcp, ruptime and rwho.