Computer network is a system that connects many computer systems with different geographical locations and independent functions through communication equipment and lines, and realizes network resource sharing with well-functioning network software (network protocol, information exchange mode and network operating system, etc.). ).
The word network has many meanings, which can be interpreted as:
1, the streaming network is also called the network. It is generally used for modeling pipeline system, transportation system and communication system. Sometimes it refers to a computer network, or a system in which the Internet is composed of related individuals, such as interpersonal network, traffic network and political network.
2. A graph composed of nodes and lines. Represents the research object and its relationship. Sometimes lines with arrows indicate that there is a certain order relationship from one node to another. The numerical values marked next to nodes or lines are called point weights or line weights, and sometimes they are not marked with numbers. In mathematical language, the network is a graph, which is generally considered as a weighted graph. In addition to the mathematical definition, the network also has a specific physical meaning, that is, the network is a model abstracted from a certain kind of practical problems, and what kind of network is customarily called, such as switching network, transmission network, communication network, planning network and so on. In a word, the network is a model abstracted from similar problems and expressed and studied by graph theory in mathematics.
Computer network is a system that connects several autonomous computer systems distributed in different places with communication lines and communication equipment, and shares hardware, software and data resources according to the same network protocol.
[Edit this paragraph] The birth of the network
Contrary to many people's imagination, the Internet is not the result of an optimal plan, and the founders of the Internet would never have thought that it could develop to its present scale and influence. At the beginning of the birth of the Internet, no one thought that it would enter thousands of households, and no one thought of its commercial use.
In a sense, the internet can be said to be the product of the cold war between the United States and the Soviet Union. In the United States, the 1960s was a very special era. In the early 1960 s, the Cuban nuclear missile crisis occurred and the cold war between the United States and the Soviet Union warmed up. The threat of nuclear annihilation has become a topic in people's daily life. At the same time that the United States blocked Cuba, the Vietnam War broke out and political crises occurred in many third world countries. Due to the stimulation of American federal funds and the influence of public fear, the "cold war in the laboratory" also began. People think that maintaining the leading position in science and technology will determine the outcome of the war. The progress of science and technology depends on the development of computer field. By the end of 1960s, every major federally funded research center, including purely commercial organizations and universities, had the latest computer equipment provided by the emerging computer industry in the United States. The idea of sharing data among computer centers is developing rapidly.
The U.S. Department of Defense believes that if there is only one centralized military command center, in case this center is destroyed by the nuclear weapons of the former Soviet Union, the military command of the whole country will be paralyzed and the consequences will be unimaginable. Therefore, it is necessary to design such a decentralized command system consisting of decentralized command points. When some command points are destroyed, others can still work normally, and these scattered points can get in touch through some form of communication network. From 65438 to 0969, ARPA- Advanced Research Projects Agency of U.S. Department of Defense began to build a network called ARPAnet, which connected several military and research computer mainframes in the United States. At first, ARPANET only connected four hosts. As far as military requirements are concerned, it is under the protection of high-level secrets of the US Department of Defense. Technically, it does not have the conditions for external promotion.
1983, ARPA and the us department of defense communications bureau successfully developed the TCP/IP protocol for heterogeneous networks. The University of California, Berkeley took this protocol as a part of its BSD UNIX, which made it popular in the society and gave birth to the real Internet.
From 65438 to 0986, the National Science Foundation (NSF) established NSFnet WAN on the basis of five supercomputers for scientific research and education services by using the TCP/IP communication protocol developed by ARPAnet. With the encouragement and support of the National Science Foundation of the United States, many universities, government-funded research institutions and even private research institutions have incorporated their local area networks into NSFnet. At that time, the military part of ARPAnet had left the home network and established its own network-Milnet. ARPANET, the father of network, was gradually replaced by NSFnet. At 1990, ARPANET withdrew from the historical stage. Nowadays, NSFnet has become one of the important backbone networks of the Internet.
1989, CERN successfully developed the World Wide Web, which laid the foundation for wide-area hypermedia information interception/retrieval on the Internet.
By the early 1990s, the Internet had actually become a "network within a network"-each subnet was responsible for its own erection and operation costs, and these subnets were interconnected through NSFnet. Since NSFnet was funded by the government, the biggest boss of the Internet at that time was the American government, but to some extent, some small private bosses were also added. The expansion of the Internet in 1980s not only brought quantitative changes, but also brought some qualitative changes. Due to the entry of various academic groups, enterprise research institutions and even individual users, Internet users are no longer limited to computer professionals. New users find that joining the Internet can not only enjoy the supercomputer of NSFnet, but also communicate with each other, which is more attractive to them. As a result, they gradually regard the Internet as a tool for communication, rather than just enjoying the computing power of the NSFnet supercomputer.
Before the 1990s, the use of the Internet was always confined to research and academic fields. Commercial organizations' access to the Internet is always troubled by laws or traditional problems of one kind or another. In fact, government agencies such as the National Science Foundation, which once funded the construction of the Internet, are not interested in commercial activities on the Internet.
199 1 year, three companies in the United States operated their own CERFnet, PSInet and Alternet networks, which can provide customers with internet networking services to some extent. They set up the Commercial Internet Association (CIEA), announcing that users can use their Internet subnets for any commercial purpose. The emergence of Internet business service providers has enabled industrial and commercial enterprises to finally enter the Internet in an upright manner. As soon as commercial organizations step into the unfamiliar Internet world, they find its great potential in communication, information retrieval and customer service. As a result, its situation is out of control. Countless enterprises and individuals from all over the world have flooded into the Internet, which has brought a new leap in the history of Internet development.
At present, the Internet has contacted 160 countries and regions, more than 40,000 subnets, more than 5 million computer hosts and more than 40 million direct users. It is the most abundant computer network in the world. Internet is considered as the embryonic form of the future global information expressway.
Four elements to realize the network
1, communication lines and communication equipment
2. Computers with independent functions
3, network software software support
4. Realize data communication and resource sharing.
The development history of computer network
1946 the world's first electronic computer came out more than ten years ago, because of its high price, the number of computers was very small. The so-called computer network in the early days was mainly produced to solve this contradiction. Its form is to directly connect a computer with several terminals through communication lines. We can also regard this method as the simplest prototype of LAN.
The earliest Internet was established by the Advanced Research Projects Agency (ARPA) of the US Department of Defense. Many concepts and methods of modern computer network, such as packet switching technology, all come from ARPAnet. ARPAnet not only studied the packet switching technology of leased line interconnection, but also studied the packet switching technology of wireless and satellite networks, which led to the emergence of TCP/IP.
In 1977- 1979, ARPAnet introduced the current TCP/IP architecture and protocol. Around 1980, all the computers on ARPAnet started the conversion of TCP/IP protocol, and the initial Internet with ARPAnet as the backbone network was established. 1983, all ARPAnet computers completed the conversion to TCP/IP, and realized TCP/IP on UNIX (BSD 4.1). The biggest contribution of ARPAnet in technology is the development and application of TCP/IP protocol. Two famous science education networks have been established successively: China Science Network and BITNET. 1984, NSF of the National Science Foundation planned to establish 13 National Supercomputing Center and National Education Science and Technology Network. Then it replaced the backbone position of ARPANET. 1988 the internet began to open to the outside world. 199 1 June, 2006, among computers connected to the Internet, commercial users surpassed academic users for the first time, which was a milestone in the development history of the Internet, and the growth rate of the Internet was out of control.
The development stage of computer network
First Generation: Remote Terminal Connection
In the early 1960s.
Terminal-oriented computer network: the host is the center and controller of the network. Terminals (keyboards and monitors) are distributed everywhere and connected to the host computer. Users use remote hosts through local terminals.
Communication between terminals and hosts is only provided, and communication between subnets is impossible.
The second generation: computer network stage (LAN)
The mid-1960s
Multiple hosts are interconnected to realize communication between computers.
Comprise a communication subnet and a user resource subnet.
End users can access the hardware and software resources of local hosts and all hosts on the communication subnet.
Circuit switching and packet switching.
The third generation: computer network interconnection stage (wide area network, Internet)
198 1 year, the International Organization for Standardization (ISO) formulated the basic reference model (OSI/RM) for interconnection between computers produced by different manufacturers.
The birth of TCP/IP protocol
The fourth generation: information expressway (high speed, multi-service, large data volume)
Broadband Integrated Services Digital Network: Information expressway
ATM technology, ISDN, gigabit Ethernet
Interactive: Internet TV on demand, video conference, videophone, online shopping, online banking, online library and other high-speed, visual.
Development history of China's network
1, the phased development of the Internet
From 65438 to 0987, China Academic Network sent the first e-mail to the world, marking the development of Internet in China. After decades of development, four mainstream network systems have been formed, namely: CSTNET, Science and Technology Network of China Academy of Sciences; CERNET Education and Scientific Research Network of the Ministry of Education; CHINANET of the former Ministry of Posts and Telecommunications and CHINAGBN of Jinqiao Network of the former Ministry of Electronics.
The development of Internet in China can be roughly divided into three stages:
The first stage is1987-1993, which is also the stage of research and experiment. During this period, some scientific research departments and universities in China began to internetize Internet technology, and carried out scientific research projects and scientific cooperation, but the network application at this stage was limited to a small range of e-mail services.
The second stage is 1994 to 1996, which is also the initial stage. 1In April, 1994, Zhongguancun Education and Scientific Research Demonstration Network Project entered the Internet, and China was officially recognized as a country with Internet. After that, many Internet networking projects such as Chinanet, CERnet, CSTnet and Chinagbnet were launched nationwide, and the Internet began to enter public life and developed rapidly in China. By the end of 1996, the number of Internet users in China had reached 200,000, and the services and applications developed by the Internet were gradually increasing.
The third stage, from 1997 to now, is the fastest and fastest stage of Internet in China. After 1997, the number of netizens in China basically doubled every six months. Today, the number of netizens has exceeded100000. According to the statistical report released by China Internet Network Information Center (CNNIC), as of June 30, 2003, the total number of Internet users in China was 68 million. This figure increased by 8.9 million compared with the beginning of the year and 22.2 million compared with the same period in 2002.
At present, there are five commercial Internet backbone units with independent international import and export routes in China, as well as non-profit Internet backbone units for education, science and technology, economy and trade. At present, there are more than 600 Internet access service providers (ISPs), of which 140 operate across provinces.
With the improvement of network foundation, the adoption of new technologies for user access, the diversification of access methods and the improvement of service capabilities of operators, the bottleneck problem caused by slow access network speed will be further improved, and the internet access speed will be faster, thus promoting more applications to be realized online.
Network classification
By coverage:
Local area network LAN (the range of action is usually several meters to dozens of kilometers)
Man (between Wan He Lan)
Wide area network WAN (the scope of action is generally tens to thousands of kilometers)
Classification by topological structure:
Bus type
toroidal
star
reticulation
According to the way of information exchange:
circuit switching
Message exchange
packet switching technology
According to the transmission medium, wired network, optical fiber network, wireless network and local area network usually use a single transmission medium, while metropolitan area network and wide area network use multiple transmission media.
Classification of Point-to-Point Transmission Networks by Communication Mode Broadcast Transmission Networks
According to the purpose of the network, it enjoys resource network, data processing network and data transmission network. At present, the purpose of network use is not unique.
Peer-to-Peer Network Classification of Client/Server Network Based on Service Mode
【 China public computer Internet (CHINANET)
Also known as Internet of Ministry of Posts and Telecommunications and China Public Internet, it is an electronic information network based on Internet network technology managed by Ministry of Posts and Telecommunications. 1995 started networking and provided services to the society in May. CHINANET consists of backbone network and access network. Backbone network is its main information channel, which is composed of network nodes of municipalities and provincial capitals. Access network is a network formed by network connection established in various provinces (regions). CHINANET's flexible access mode and access points all over the country can easily access the Internet, enjoy the rich information resources and various services on the Internet, and provide a convenient network environment for the interconnection of domestic computers and the enjoyment of domestic information resources.
China Education and Research Network (CERNET)
1994 started, and 1995 completed the first phase of the project, including Beijing (network center), Shanghai, Nanjing, Guangzhou, Wuhan, Xi 'an, Chengdu and Shenyang. There is an international special line connecting the United States. The national backbone network (*** 1 1 64Kbps DDN dedicated line) was opened in June 1995. After the completion of the second phase of the project, the national backbone network and international networking have been gradually upgraded, with the backbone network reaching more than 2Kbps and international networking reaching more than 8Kbps.
China science and technology network
Sponsored by China Academy of Sciences, jointly built by Tsinghua and Peking University. In April, 1994 opened a special line connection with the Internet. 65438+1May 2, 19941day, the setting of the main server of the highest domain name CN in China was completed, and the TCP/IP connection with the Internet was realized. By the end of 1995, the project of "networking 100 institutes" was basically completed. By the end of 1997, more than 100 Ethernet, more than 3,000 computers and more than 1000 users have been connected, making it a national scientific research and education network with large area, large consumption, good performance, large communication volume and complete service facilities.
China Jinqiao Information Network
That is, the national public economic information communication network managed by the former Ministry of Electronic Industry provides data communication and information services for the government, enterprises and institutions and the public. Jinqiao network was connected to the Internet at the end of the year, and 24 cities have been opened. More than 0/000 local and remote simulation terminals have been developed to provide comprehensive Internet services.
Rogue rabbit group
China Research and Development Center (Research on China &; The Development Center (hereinafter referred to as Rogue Rabbit Group) was established in Beijing, China in April 2006. By the end of April 2007, nearly 120 senior software engineers had gathered in just one year. The company will fully cover all the products and technical series of rogue rabbit network system company. The rogue rabbit network system reflects the Group's continuous strategic investment in China to meet the changing needs of customers in China, Asia and even the world. Adhering to the global R&D strategy of Rogue Rabbit Network System Co., Ltd., Rogue Rabbit Network System (China) R&D Co., Ltd. is determined to become the world's leading R&D institution and center of excellence, providing strategic, innovative and high-quality technologies, products and solutions in the global market. The establishment of R&D center of rogue rabbit network system (China) aims to take root in China, connect Asia and serve the world.
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