The ISO/OSI model is helpful for visualizing the way in which the networking layers interact. The model does not, however, tell you how to use the networking. Two widely used networking services that may be running on your system(s) and are worth taking a look at are ARPA and NFS.
The first networking product to try on your system is what is sometimes called ARPA Services - what I have been calling ARPA. ARPA is a combination of "ARPA Services" and "Berkeley Services." ARPA Services supports communications among systems running different operating systems, and Berkeley Services supports UNIX systems. The following sections are a list of the most common ARPA and Berkeley commands. Although many programs can be run under each of these services, the following are the most commonly used ones in the UNIX world. In some cases, there are examples that show how these commands are used. For most of the examples, the local host is system1 and the remote host is system2.
