what is Network
The human society has entered the era of Internet, network becomes the basis of our life. When you in network information retrieval, the network is a huge library, almost to provide all the information you need; When you are looking for a friend, network network is a circle on which you can find all kinds of people; When you on the network send E-mail, the web and like a real post office… The network is it
The network is we communicate, Narrows bridge and the space and time; Nets winding is human exchange of information facilities; The network is the basis of electronics, equipment, cable and agreement.
About the computer network, the americans have ever given a standard definition: “network is connected to each other the autonomy of the set of computer.” The reason this definition “standard”, because almost all of the network course in university, when introduce the concept of network to mention this sentence.
This definition has three key content: connect with each other, autonomy, and computer. We can say more specific point, the so-called computer network, is to use communication and line for a different geographical position, function of independent DuoGe HP CQ50 battery computer system interconnection up to the function is perfect network software (i.e., network communication protocol, information exchange network operating system and way of sharing resources network) and information transmission system.
Should say, the definition of network as the change of time and develop. Early, people will be dispersed computer, terminal and affiliated equipments, connected by using communication medium, can realize mutual communication system called network.
In 1970, in the United States at the information processing association spring computer joint meeting first gives a be accepted definition: “network is to share information source (hardware, software and data, etc > way connected with independent, and their respective functions of the computer system of the set.”
The aim is to build up a network resource sharing, and this is the nature of the network,
The definition of computer network involves the following four points: in a computer network contains more than two sets of different geographical position with “autonomy” function of the computer. The so-called “autonomy” meaning, it is to point to the computer does not depend on the network and be able to work independently. Usually, will have “autonomy” function of the computer says, in the network mainly machine is also known as the node. The network node is not only the computer, also may be the other communication equipment, such as, on, routers;
Each node in the network the connection between the need to have a way, that is, by the transmission medium to achieve physical interconnection. Article the physical channel can be twisted pair, coaxial cable or light fiber, etc “cable” transmission medium, also can be the laser and microwave or satellite, “wireless” transmission medium;
Each node in the network communication between each other or exchange information, need to have some agreement and rules, these conventions and the set of rules is the agreement, its function is to realize the quarter point of logic interconnected. For example, Internet use on the communication protocol is the TCP/IP protocol;
The computer network is based on data communication and network resources to realize (including hardware and software resources information source > sharing for the purpose to achieve this purpose., network the need to have power can improve network software, including the network communication protocol and network operating system.
The computer network is the computer technology and communication technology, the combination of the this is mainly embodied in two aspects: on one hand, communication technology for computer data transmission and exchange between provides the necessary means; On the other hand, the development of computer technology to penetrate the letter in the technology, and also to improve the communication network in all sorts of function.
The development of computer network process can be divided into four stages: the first stage, with a single computer as the center of the remote online system, a computer network for terminal (the 1950.
In 1946, world’s first electronic computer ENIAC was born in the United States, the computer and communication technology project technology and no direct link. In the 1950 s, the beautiful countries in order to its own security, in the United States and Canada northern territory, established a semi-automatic ground air defense system, the SAGE computer technology and communication technology, the combination of trying.
The people with the individual computer as the center of the online system called for the remote terminal online system. The system is a computer technology and communication technology, combining the form the prototype of the computer network, so also called for the computer terminal communications network. The 20 th century 60 s American airline reservation system SABRE-1 is the typical application of computer network communication network, the system by a computer and distribution center in the United States within the scope of the 2 000 DuoGe terminal composition, the terminal through telephone lines connected to a central computer.
With communication function of single machine system is the typical structure of computer through multiple lines controller and a remote terminal is linked together, along with the rapid development of computer and network, the size of the increase with the center for single remote online system soon exposed its inherent disadvantages:
The host should not only responsible for data processing, and management and terminal communications, burden, can not adapt to a large number of data processing tasks;
Each terminal used alone a root line, line utilization rate is very low, especially when it is the end of the links to increase the number of causing certain investment pressure;
Lines of software and hardware not universal, controller when access terminal, need to change to making a large adjustment.
To reduce the burden of the host, in the communication lines and between computer set to an FEP processor, the former special charge and terminal of communication between the control, and let the Lord machine data processing; In order to improve the communication efficiency, reduce communication costs, in a remote terminal most densely populated add a focus, focus on the role of the device is to place several a terminal at low speed on the communication lines up, connected to the high-speed lines, and then, after the high speed line road and front-end processor connection. Front and concentrators, the common processor by a small computer bear, so, the structure also called has the correspond dencefunction many system,
By definition, in the first stage of development network with single center for remote online system cannot be called the true network. On this point, in the field of network technology has become a consensus. But the system has the essential feature of the network resources sharing, also is the prototype of the network development and the foundation.
The second phase, DuoGe autonomy function host through the communication lines, formation of the Internet information sharing source of computer network (the 1960 s).
In this stage, realize the Internet, thus forming the real computer network. At the same time, during this period, there was a in the history of network often overlooked but for the development of the network landmark event: resources and communication subnet subnet separation.
Communication subnet and resources, eliminate the subnet separation technology barriers, to avoid the network of monopoly, reduce the network technology, a large number of outstanding threshold to the manufacturers, research institutions and scientists in the field, the network is human HP Presario c700 battery society, the network technology to the rapid development of the very important basis.
What, then, are the resources subnet and communication subnet?
By all of the network resources subnet host, terminals, terminal controller, peripherals such as; network printers, disk array, etc.) and all kinds of software resources, responsible for the entire network of several according to treatment and to network users (workstation or terminal) provides the network resources and services.
Communication subnet of communication equipment and the circuitry for resources, the data transmission, allowable subnet and transform and other communications work.
The third stage, form a unified network system structure, follow the international standardization agreement (the 1970 s computer network; ) .
The third stage of computer network development is accelerated system structure and agreement of international standards of the research and application. At the end of the 1970 s, ISO’s computer with XinXiChu
Richard standardization technical committee established a special institutions, research and make network communication standards to achieve the network system structure of international standardization. 1984 ISO formally promulgated a called “open systems interconnection basic reference model of” international standards, “ISO7498 OSI RM, the famous OSI seven layer model. The OSI RM and standard agreement and improve dramatically accelerated the development of computer network. Many large computer manufacturers have announced its support for OSI standards, and actively research and development conforms to the OSI standard product.
Follow the international standardization agreement with united network of computer network system and structure, the manufacturer should be recognized in accordance with the international standard develop their own network products, which can ensure the different products can be in same communication network. This is the meaning of “began to put”.
At present there are two dominant network system structure: one kind is the international standard organization must change ISO proposed OSI RM (open system interconnection reference model >; another kind is Internet use in fact industrial standard TCP/IP RM (and test model).
The fourth stage, to the Internet, high speed, intelligent direction development of computer network (beginning in the 1980 s >.
From the end of 1980 s, computer network technology into the new development order section, its characteristic is: Internet, high speed and intelligent. Displays in: development with the Internet as a representative of the Internet; High-speed network. In 1993 the United States government has announced a “national information infrastructure” action plan, namely the information highway plan. Here the “information superhighway” refers to the large capacity of optical fiber communication network digital, to put the government institutions, enterprises, universities, scientific research institution and the family of the computer network project. The United States government and respectively in 1996 and 1997 to investigate more quickly and with the development of Internet 2 and the next generation of the Internet.
Can say, the network interconnection Dell Inspiron 1464 battery and high-speed computer network is becoming the latest generation of the development of computer network direction;
Research intelligent network. Along with the increase of the network size and network service function, increase of the number of countries is developing intelligent network of IN research,
In order to improve the communication network began to send business ability, and more reasonable network all kinds of industry affairs management, true to distribution and open forms to customers. Intelligent network is the concept of the United States in 1984, put forward the definition of the intelligent network and no people usually Richard solution “intelligent” meaning, it is just a kind of “network”, the purpose is to improve the communication network development business ability. The emergence of the world telecom department has caused the attention of international report couplet additionally began in 1988 as its research subject. 1992 the formal definition itu-t T intelligent network, made a fast, convenient and flexible, economy, have effect to generate and implementation of new business system. The goal of this system is applied to all communications network; That not only can be applied to the existing network, N-ISDN nets and group nets, also apply to mobile telecommunication network and B-ISDN nets. With the passage of time, the purpose of intelligent network applications to a higher level.
