UNIX and Networking

One of the greatest advantages of the UNIX system is its inherent network−related structure. From its very beginnings, UNIX included a number of network−based characteristics that made it quite different from other existing operating systems. At a time when network technologies were in the very early stages, UNIX already provided certain network services and powerful tools to cope with network issues between remote hosts. From a network standpoint, the concept of UNIX was so well done that it allowed an easy integration of UNIX into network technologies. It is even more appropriate to say that UNIX and networking merged, making UNIX the core operating system in the new emerging network environment.

Today, even after so many years of intensive commercial
use, UNIX is still far from being considered an obsolete operating system. UNIX was the first
commercially successful and available network−oriented OS, and UNIX's use in networked
environments was perhaps the biggest factor leading to the end of the supremacy of mainframe
computers and gigantic OSs. Despite its advancing age, UNIX is still the leading OS, offering more than any other OS alone, and permanently keeping pace with newcomers.
The primary advantages of UNIX are its openness and flexibility, which make it suitable for almost any kind of upgrade.
Most of these upgrades were made in the network arena, which makes sense,given the incredible advances in the field of networking. However, this flexibility and UNIX's ability to
integrate so many changes only prove the sound conceptual approach that UNIX designers had
while creating UNIX.

Regardless of where the credit should go, UNIX's main contribution to the overall development of computer technologies was, and still is, in networking; it is fair to say that the network−oriented UNIX concept practically enabled the tremendous growth of networking technologies.
Networks have grown so prolifically because they provide an important service: to share informationamong users. Computers generate and process information that is often useless unless it is shared among a group of people; the network is the vehicle that enables data to be easily shared.
Once a computer has been networked, users will likely not want to return to an isolated system. Such a trend does not stop at the local level; forming a local network and cooperating with neighboring computers lead to global, worldwide networking. Today, this global network is known under the generic name Internet, which is named after what was once the worlds largest experimental network.
Computer networking has brought new challenges and duties to system administrators.
It is not enough to simply maintain the systems; the network requires a great deal of ongoing work.
This issue is very important, because it affects not only a single system, but also other systems on the network.
A familiarity with basic theoretical issues will make this job easier, and that is the purpose
of this chapter and those following

Computer Networks
A computer network is a communication system that connects end computers, usually referred to as hosts. The hosts can range in size from small microcomputers to the largest supercomputers.
From a network point of view, a host is any machine participating in network communication,
independent of its basic function and configuration (single−user or multi−user, general purpose
systems, dedicated servers, terminals, any kind of client, etc.).