According to abbreviationfinder, ARPANET is a network that made up of about 60,000 computers (computers) in the 1960s, developed by the Advanced Research Projects Agency (ARPA) of the United States Department of Defense. Its origin is in the Cold War. It was feared that, in the event of an attack, the telephone exchanges would be destroyed, so an attempt was made to create a fully decentralized data switching system. The communication protocols that were developed gave rise to the current Internet. In 1990, Arpanet was replaced by the National Science Foundation Network (NSFNET).) to connect its supercomputers with regional networks. Today, the NSFNET serves as the high-speed core of the Internet.
Introduction Communication Networks
Possibility of universal sharing of information between groups of computers and their users; a vital component of the information age. The generalization of the computer or personal computer (PC) and the local area network (LAN) during the 1980s has given rise to the possibility of accessing information in remote databases, loading applications from overseas points, sending messages to other countries and share files, all from a personal computer. The networks that allow all this are advanced and complex equipment. Its effectiveness is based on the confluence of very diverse components. The design and implementation of a global computer network is one of the great ‘technological miracles’ of recent decades.
Modem and service companies
Even in the 1970s, computers were expensive and fragile machines that were cared for by specialists and kept in guarded rooms. To use them and access them from a remote place, a terminal could be connected directly or through a telephone line and a modem.. Due to their high cost, they used to be centralized resources that the user accessed on their own. During this time, many organizations emerged, the service companies, that offered processing time on a mainframe. Computer networks were not commercially available. However, one of the most significant advances for the world of technology began in those years: the experiments of the United States Department of Defense with a view to distributing computing resources as protection against failures. This project is now called the Internet.
Local Area Networks (LAN)
One of the most critical events for networking is the emergence and rapid spread of the local area network (LAN) as a way of standardizing connections between machines used as office systems (see Office). As its name suggests, it is a way of interconnecting a series of computer equipment. At its most basic level, a LAN is nothing more than a shared medium (such as a coaxial cable to which all computers and printers connect) along with a set of rules that govern access to that medium. The most widespread LAN, Ethernet, uses a mechanism known as CSMA/CD. This means that each connected computer can only use the cable when no other computer is using it. If there is a conflict, the computer that is trying to establish the connection aborts the connection and tries again later. Ethernet transfers data at 10 Mbits/s, fast enough to make the distance between multiple computers negligible and give the impression that they are directly connected to their destination. There are very diverse typologies (bus, star, ring) and different access protocols. Despite this diversity, all LANs share the characteristic of having a limited range (usually spanning a building) and being fast enough to make the connecting network invisible to the computers using it. In addition to providing shared access, modern LANs also provide the user with a host of advanced features. There are packages ofmanagement software to control the configuration of the equipment in the LAN, the administration of the users and the control of the network resources. A widely used structure consists of several servers available to different users. Servers, which are usually more powerful machines, provide services to users, usually personal computers, such as print control, file sharing, and email.
Roads and bridges
Services on most LANs are very powerful. In general, organizations do not want to find isolated cores of computing utilities; they prefer to spread such services over a wider area so that groups can work regardless of their location. paths (routers) and bridges (bridges) are special equipment that allow two or more LANs to be connected. The bridge is the most elementary piece of equipment and only allows several LANs of the same type to be connected. The path is a more intelligent element and enables the interconnection of different types of computer networks. Large companies have corporate data networks based on a series of LANs and paths. From the user’s point of view, this approach provides a physically heterogeneous network with the appearance of a homogeneous resource.
Wide Area Networks (WAN)
When a certain point is reached, it becomes impractical to continue expanding a LAN. Sometimes this is imposed by physical limitations, although there are usually more convenient or cheaper ways to expand a computer network. Two of the important components of any network are the telephone network and the data network. They are long-distance links that extend the LAN into a wide area network (WAN). Almost all national network operators (such as DBP in Germany, British Telecom in England or Telefónica in Spain) offer services for interconnecting computer networks, ranging from simple, low-speed data links based on the public telephone network to complex high-speed services (such as frame relay and SMDS-Synchronous Multimegabit Data Service) suitable for the interconnection of LANs. These high-speed data services are often referred to as broadband connections. They are expected to provide the necessary links between LANs to enable what have come to be called information highways.
It seems logical to assume that computers will be able to work together when they have a broadband connection.. How to get, however, that computers from different manufacturers in different countries work in common throughout the world? Until recently, most computers had their own interfaces and had their own particular structure. A team could communicate with another from the same family, but had great difficulty doing so with a stranger. Only the most privileged had the time, knowledge and equipment necessary to extract what they needed from different computing resources. In the 1990s, the level of agreement between different computers reached the point where they could be effectively interconnected, allowing anyone to take advantage of a remote team. The main components of this process are client/ server systems., object technology and open systems.
Instead of building computer systems as monolithic elements, there is general agreement to build them as client/server systems. The client (a PC user) requests a service (such as printing) that is provided by a server (a processor connected to the LAN). This common approach to the structure of computer systems results in a separation of functions that previously formed a whole. The details of the implementation range from simple approaches to the real possibility of handling all computers in a uniform way.
Another of the approaches for the construction of systems is based on the hypothesis that they should be composed of perfectly defined elements, enclosed objects, defined and materialized, making them independent agents. The adoption of objects as means for the construction of computer systems has contributed to the possibility of exchanging the different elements.
This definition refers to computer systems whose architecture allows for easy interconnection and distribution. In practice, the open system concept translates into unlinking all the components of a system and using analogous structures in all the others. This involves a mix of standards (which tell manufacturers what they should do) and associations (groups of like-minded entities that help them do it). The end effect is that they are able to talk to each other. The ultimate goal of all the effort invested in open systems is that anyone can buy computers from different manufacturers, put them wherever they want, use broadband connections to link them together, and make them work as a composite machine capable of taking advantage of high speed connections.
Information security is becoming increasingly important with the increasing volume of important information found on distributed computers. In this type of system it is very easy for an expert user to surreptitiously access confidential data. The Data Encryption System (DES) standard for computer data protection, implemented in the late 1970s, has recently been supplemented by public key systems that allow users to easily encrypt and decrypt messages without the intervention of third parties..
Having fast computer networks capable of interconnection is not the end point of this approach. The figures of “information highway user” and “information highway jobs” remain to be defined.
The task of maintaining the operation of a LAN requires complete dedication. Keeping a globally distributed network running smoothly is even more of a challenge. Lately, much attention has been devoted to the basic concepts of managing distributed and heterogeneous networks. There are already enough tools for this important area to effectively monitor global networks.