| Connecting to other machines is an important part of every UNIX network. This means connecting both to other UNIX machines as well as to non-UNIX machines. The machines must be physically connected to one another as well as functionally connected to one another, so that you can perform such tasks as transferring files and logging into other systems. Many commands exist on your UNIX system that provide you with the functionality to log in and transfer files between systems. These are known as the ARPA commands, telnet and ftp. The telnet command allows remote logins in a heterogeneous environment. From your UNIX system, for instance, you can telnet to non-UNIX systems and log in. After login on the remote system, you need to have an understanding of the operating system running on that system. If you need to connect to a different computer only for the purpose of transferring files to and from the system, then you can use ftp. This command allows you to transfer files between any two systems without having an understanding of the operating system running on the remote system. These commands are somewhat primitive compared to the commands that can be issued between UNIX systems. To UNIX systems, networking is not an afterthought that needs to be added on to the system. The ftp and telnet commands come with your UNIX system, as well as more advanced commands and functionality that you can use to communicate between your UNIX system and other UNIX systems. These more advanced commands, known as Berkeley commands, allow you to perform many commands remotely, such as copying files and directories and logging in. This function-ality continues to increase to a point where you are working with files that can be stored on any system on the network, and your access to these files is transparent to you with the Network File System (NFS). Let's take a look at some of the basics of UNIX networking. | 
