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Internet (Internet)

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What is the Internet

The Internet is a network connected to the Internet, which is the largest in the world at presentcomputer network

Just as the Internet is called "international" between countries, the huge network connected between networks can be translated as“internet”, also transliterated“Internet”Or“Internet”, refers to the world's largest global interconnection network developed on the basis of the ARPA network (the advanced research projects agency network, the world's first operational packet switching network developed for the advanced research projects agency of the U.S. Department of defense, which is the ancestor of the global Internet). The Internet is translated into the Internet in Taiwan“Internet”, i.e“Network connected to the network”It can be a collection of any separate physical networks, which are connected by a set of general protocols to form a logical single network. This method of connecting computer networks to each other is called "network interconnection".

The Internet is a collection of global information resources. There is a rough saying that Internet is a logical network formed by the interconnection of many small networks (subnets), and several computers (hosts) are connected in each subnet. Internet aims at exchanging information resources with each other. It is based on some common protocols and is formed through many routers and public Internet. It is ainformation resourcesAnd resource sharing.

When it comes to the Internet alone, it is generally the Internet or a network connected to it, sometimes referred to as the net or the net. The use of the Internet is called "surfing", "browsing" and "roaming", while those who use the Internet are called "netizens", and online friends are called "netizens".

History of the Internet

In the 1950s, communication researchers recognized the need to allow routine communication between different computer users and communication networkssignal communication。 This promptedDecentralized networkqueuing theoryAnd packet switching. In 1960, the ARPA network established by the defense Frontier Research Project Agency (ARPA) of the U.S. Department of defense due to the consideration of the cold war aroused great concerntechnical progressAnd make it the center of Internet development. In 1973, ARPA network was expanded into the Internet, and the first access computers were British and Norwegian computers.

In 1974, Bob Kane of ARPA andStanfordWenden Zeff ofTCP / IP protocol, the method of transmitting messages between computer networks is defined. On January 1, 1983, ARPA changed its network core protocol from NCP to TCP / IP protocol.

In 1986, the National Science Foundation (NSF) established NSFNET, the backbone network of interconnection between universities, which is an important step in the history of the Internet. In 1994, NSFNET became a commercial operation. In 1995, with the opening of the network to commerce, other important networks successfully accessed in the Internet include Usenet, bitnet and a variety of commercial X.25 networks.

In the 1990s, the whole network was open to the public. In August 1991, inTim Berners-Lee Two years after he founded HTML, HTTP and the first few web pages of CERN in Switzerland, Tim Berners Lee began to promote itwebWorld Wide Web)Project. In 1993, mosaicWeb browserVersion 1.0 was released in late 1994,public interestBefore the Internet, academic and technological growth. In 1996, the term "Internet" was widely circulated, but it refers to almost the whole world wide web.

Meanwhile, after a decade, the Internet has successfully accommodated most of the original computer networks (although some networks such as fidonet remain independent). This rapid development is due to the lack of central control of the Internet and the non private nature of the internet protocol. The former has led to the organic growth of the Internet, while the latter has encouraged compatibility between manufacturers and prevented onecompanyDominate the Internet.

The success of the Internet can be seen from the confusion of the term "Internet". At first, the Internet represented those networks built using IP protocol, but today, it is used to refer to various types of networks, which is no longer limited to IP networks. An Internet (Internet, the first "I" is a lowercase letter) can be a collection of any separate physical networks, which are connected by a set of general protocols to form a logical single network. The Internet (Internet, "I" at the beginning is a capital letter) specifically refers to the United States, formerly known as ARPA network, which uses IP protocol to connect various entitiesNetwork linkInto this single logical network.

Characteristics of the Internet

Structural features

The Internet adopts the most popular client / server working mode. Any computer that uses TCP / IP protocol and can communicate with any host of the Internet, no matter what type and operating system, can be regarded as a part of the Internet.

Strictly speaking, users do not directly link their computers to the Internet, but connect to one of the networks, and then the network is connected to other networks through the network trunk. Network trunks are interconnected through routers, so that computers on each network can communicate with each otherinformation transmission。 For example, a user's computer passes throughDial up internet access, connect to a local Internet service provider (ISP) host. The ISP host is connected with countless hosts in the country and all regions of the world through the high-speed trunk line. In this way, users can visit the Internet only through the host of the first-order ISP. It can also be said that the Internet is a network connected by ISPs around the world through high-speed communication trunk lines.

The structure of the Internet has the following characteristics:

  1、Flexible network access methods. This is because TCP / IP successfully solves different hardware platformsNetwork products. compatibility between operating systems.

  2、The most popular client / Server Mode in distributed network is adopted, which greatly improves the flexibility of network information service.

  3、takenetwork techniquemultimedia technologyIntegration, reflecting the modern multiinformation technologyThe development trend of mutual integration.

  4、Easy to operate. Any place can access the Internet only through telephone line and ordinary computer.

  5、Provide users with extremely rich information resources, including a large number of free resources.

  6、With perfect service function and friendly user interface, it is easy to operate without users mastering more professional computer knowledge.

Characteristics of information exchange

  1. Openness.The Internet is an information network connected by packet switching, so there is no closed boundary in its scope. It breaks the time and geographical restrictions.

  2. Real time.People can exchange information through the Internet at a very high speed, and time is no longer an obstacle to information exchange.

  3. Interactivity.With the multimedia and Hypertext Technology of the Internet, people's information communication mode has changed from traditional linear communication to associative multi-directional communication, and users have becomeNetwork information resourcesofconsumerAnd producers.

  4. No mediation.The Internet has no intermediate management level. It presents a non central and discrete management structure.

  5. Low communication cost.The cost of using the Internet is much lower than that of traditional telecommunications tools.

  6. Massive information.Internet toinformation explosionForm forms a torrent of information and data.

Key technologies of Internet

  1. TCP / IP Technology

TCP / IP is the core of the Internet. Using TCP / IP protocol can easily realize the seamless connection of multiple networks. Usually, a certain host is on the Internet, the Internet address (i.e. IP address) and runs TCP / IP protocol. It can send IP packets to all other hosts on the Internet.

The hierarchical model of TCP / IP is divided into four layers, and the highest layer is equivalent toOSILayer 5 ~ 7, which includes all high-level protocols, such as common protocolsFile transfer protocolFTP, email, SMTPDomain name systemDNS、Network management protocolSNMP, access to WWWHyper Text Transfer ProtocolHTTP, etc.

  TCP/IPThe sub high layer of is equivalent to the transport layer of OSI, which is responsible for providing end-to-end data transmission services between the source host and the destination host. Two protocols are defined on this layer:Connection orientedofTransmission control protocolTCP and connectionless user datagram protocol UDP.

The second layer of TCP / IP is equivalent to the network layer of OSI. This layer is responsible for independently transmitting packets from the source to the sink. It mainly solves the problems of routing and blocking control level Internet Interconnection. This layer defines Internet Protocol IP, address translation protocol ARPReverse address translation protocolRARP and Internet control message protocolICMPAnd other agreements.

The lowest layer of TCP / IP is the network interface layer, which is responsible for encapsulating IP packets into a frame format suitable for transmission on the physical network and sending them, or unloading the frames received from the physical network and taking IP packets to the upper layer. This layer is related to the specific implementation of physical network, and there is no special protocol. In fact, any protocol that can transmit IP packets can run. Although this layer generally does not need a special TCP / IP protocol, and each physical network can use its own data link layer protocol and physical layer protocol, slip or PPP protocol still needs to be run when using serial line for connection.

  2. Marking branch

1) Host IP address. In order to ensure mutual recognition during communication, each host on the Internet must have a unique identification, that is, the IP address of the host. IP protocol realizes information transmission according to IP address.

IP addresses are composed of 32-bit (i.e. 4-byte) binary numbers. For the sake of writing convenience, each byte is often taken as a segment and expressed as a decimal number, and each segment is separated by ".". For example, 202.96.209.5 is a legal IP address.

IP address consists of network identification and host identification. There are three types of IP addresses commonly used: A, B and C. each type specifies the number of bits of network ID and host ID in 32 bits. Their representation ranges are:

  • Class a address: 0.0.0.0 ~ 127.255.255.255
  • Class B address: 128.0.0.0 ~ 191.255.255.255
  • Class C address: 192.0.0.0 ~ 233.255.255.255

Class a addresses are generally allocated to networks with a large number of hosts, class B addresses are usually allocated to medium-sized networks, and class C addresses are usually allocated to small networksLANuse. In order to ensure uniqueness, IP addresses are managed and assigned by the authority inter NIC (Internet Network Information Center) in major regions of the world.

A network ID of an IP address can contain a large number of hosts (for example, the host ID domain of class a address is 24 bits and the host ID domain of class B address is 16 bits). In practical application, it is impossible to connect so many hosts to a single network, which will bring inconvenience to network addressing and management. In order to solve this problem, the concept of "subnet" can be introduced into the network.

The host identification domain is further divided into subnet identification and subnet host identification. By flexibly defining the number of bits of subnet identification domain, the scale of each subnet can be controlled. After a large network is divided into several relatively independent and interrelated subnetworks, each subnetwork within the network can be addressed and managed independently, and each subnetwork is connected through a router across subnetworks, which also improves the security of the network.

The subnet mask can be used to determine whether two hosts are in the same subnet. Like the IP address, the subnet mask is also a 32-bit binary number, except that its subnet host identification part is all "0". If the IP addresses of the two hosts are the same as their subnet masks, it means that the two hosts are in the same network.

2)Domain name systemAnd uniform resource locator. The IP address of 32-bit binary number is very effective for computers, but it is very inconvenient for users to use and remember. To this end, the Internet has introduced a character form of IP address, that is, domain name. The domain name adopts a hierarchical naming scheme based on "domain". Each layer is separated by a sub domain name with "." in the format of:

Machine name, network name, organization name and top domain name

On the Internetdomain nameIt is uniformly managed by domain name system (DNS). DNS is a distributed database system, which is composed of domain name space, domain name server and address translation requester. With DNS, any domain name defined in the domain name space can be effectively converted to the corresponding IP address. Similarly, the IP address can also beDNSConvert to domain name.

Each home page on the WWW has an independent address, which is called the unified resource locator(URL), as long as you know the URL of a web page, you can open the web page directly.

3) User e-mail address. The format of user e-mail address is: user name @ host domain name. The user name is the user's mailbox name on the mail server, usually the user's registered name, name or other code, and the host domain name is the domain name of the mail server. The user name and host domain name are separated by "@".

Because the host domain name is unique on the Internet, as long as the user name in the e-mail address is unique in the mail server, the e-mail address is also unique on the whole Internet.

Internet access

Access technology

Network connection technology (Internet access technology) is the general name of the connection mode and structure between users and the Internet. Any computer that needs to use the Internet must be connected to the Internet in some way. The development of Internet access technology is very rapid:bandwidthFrom the initial 14.4kbps to the current 10Mbps or even 100Mbps bandwidth; The access mode has also developed from a single telephone dialing mode in the past to a variety of wired and wireless access modes; Access terminals also began to develop towards mobile devices. And newer and faster access methods continue to be usedresearch and development

According to the speed of data transmission after access, the access mode of Internet can be divided into broadband access and narrow-band access.

Common civil broadband access:

  • ADSL(Asymmetric Digital dedicated line) access, access bandwidth, uplink rate (up to 640kbps) and downlink rate (up to 8mbps);
  • Cable TV Internet access (through cable TV network) with 3-34mbps;
  • Optical fiber access, access bandwidth 10-100-1000mbps;
  • Wireless (using IEEE 802.11 protocol or using3G technology)Broadband access, 1.5mbps-540mbps;
  • Satellite broadband access.

Common civil narrowband access:

  • Telephone dial-up access, access bandwidth 9600-56kbps (V.92 standard);
  • Narrow band ISDN access with access bandwidth of 64 / 128kbps;
  • GPRSMobile Internet accessbandwidthMaximum 53kbps;
  • UMTS Mobile Internet access, 384kbps;
  • CDMA mobile Internet access:(2G) cdmaOne,150Kbps。

Access mode

  1. ISP access mode

1) Frame relay mode.Frame relayIts main characteristics are low network delay, high transmission rate and high reliable connection in star and mesh networks. These characteristics are that frame relay is especially suitable for unpredictable, high-capacity and burst data services on the Internet, such asE-mail, client / server and other systems. However, frame relay is not suitable for applications that transmit a large number of large capacity (100MB) files, multimedia components or continuous traffic.

2) Dedicated line (DDN) mode. DDN (digital data network) is a data network that provides users with voice, data and image signal transmission through digital channel. DDN can be public data exchange network and variousprivate network Provide user data channel and provide inter network connection for frame relay, LAN and interconnection of various networks. DDN has the characteristics of fast speed and high quality, but it is less flexible than simulation, and the investment cost is large.

3) ISDN mode. ISDN isdigital technique The product combined with telecommunication services can be used to replace leased lines to realize the interconnection between domain networks. In this connection mode, ISDN can provide users with high-speed and reliable digital connection, and the host or network port can share the access of multiple remote devices. fromnarrowbandISDN(N-ISDN)Developed fromb-isdn B-ISDN), it can also support different types of services with different rates, including not only continuous broadband services, but also sudden broadband services.

  2. User access mode

1) Simulation terminal mode. The terminal can be connected with the remote host through the telephone line, and the ordinary computer can install the correspondingsimulation software After, it can also realize the connection with the ISP host like a real terminal. This access method is simple, economical and has no special requirements for user computers. But the disadvantage isClientWithout IP address, it is impossible to run advanced interface software. All kinds of files and e-mails of Chuang AI users are stored on the ISP host, affecting the Internet speed and time.

2) Dial IP mode. Dial up IP mode, also known as slip / PPP mode, adopts serial line internet protocol (slip) orPoint by point agreementPPP(Point to Point Protocol), connect the user's computer to the ISP host through telephone line dialing. The advantages of dial-up IP areClientWith independent IP address, users can use their own environment and user interface (such as windows, UNIX, Macintosh, etc.) for networking operation, and all kinds of files and e-mail can be directly transmitted to the user's computer. At present, most individual users use this way to surf the Internet. Because a large number of interface software needs to be run on the user's computer, the requirements of the computer are relatively high.

3) LAN connection mode. There are two ways to realize the connection between LAN and Internet host. One method is to use high-speed modem to connect with Internet host through telephone line through LAN server. In this method, all workstations share an IP address of the server. Another method is to connect the LAN with the inserter host through the router, which is to add the whole LAN to the Internet to become an open LAN. In this approach,LANAll workstations in can have their own IP addresses.

Application of Internet

  1. World Wide Web

The world wide web (WWW) is a global information resource network integrating text, sound, image, video and other multimedia information on the Internet. It is an important part of the Internet. Browser is a bridge to the WWW and a window for users to obtain WWW information. Through the browser, users can roam in the vast ocean of Internet, search and browse all the information they are interested in.

The web page files of WWW are written in Hyper Text Markup Language (HTML) and run under the support of hyper text transmission protocol (HTTP). Hypertext contains not only text information, but also multimedia information such as graphics, sound, image and video (so hypertext is also called hypermedia). More importantly, hypertext contains links to other hypertext, which are called hyper links. Using hypertext, users can easily link from one web page to other related content web pages without worrying about where these web pages are scattered in the host.

  HTMLNot in a general senseProgramming language, it embeds special tags into the document to describe the semantics of a paragraph of text, produces multimedia effect after interpretation, and provides text hyperlink.

WWW browser is aclientIts main function is to enable users to obtain various resources on the Internet. Common browsersMicrosoftInternet Explorer (ie) and NETVIGATOR / communicator.Sun CorporationA browser hot written in Java is also developedJava。 Java is a new dynamic explanatory language independent of various operating systems and platforms. Java makes the browser have animation effect and provides real-time interaction function for connected users. Currently commonly used browsers support Java.

  2. E-mail

E-mail is the most widely used service on the Internet. As long as users can connect to the Internet, have programs that can send and receive e-mail and personal e-mail addresses, they can exchange e-mail with all users with e-mail on the Internet conveniently, quickly and economically. E-mail can be exchanged between two users, send the same e-mail to multiple users, or forward the received e-mail to other users. In addition to text, e-mail can also contain various computer files such as sound, image, application program and so on. In addition, users can also subscribe to e-magazines online by e-mail, obtain required documents, participate in relevant announcements and discussion groups, and even browse WWW resources.

Sending and receiving e-mail must be supported by corresponding software. Commonly used software for sending and receiving e-mail include exchange, Outlook Express, etc. these software provide e-mail receiving, editing, sending and management functions. Most Internet browsers also include the ability to send and receive e-mail, such as Internet Explorer and navigator / communicator.

The protocol used by the mail server is the simple mail transfer protocolSMTP(Simple Mail Transfer Protocol)、Email extension protocolMime (Multipurpose Internet mail extensions) andPost office agreementPOP(Post Office Protocol)。 Pop service needs to be provided by a mail server. Users must obtain an account on the mail server before they can use this service. At present, the pop protocol widely used is version 3, so it is also called POP3 protocol.

  3. Special discussion

Usenet is a collection of various thematic discussion groups jointly organized by many users with similar interests. It is also commonly known as the global electronic bulletin board system (BBS). Usenet is used to publish announcements, news, comments and various articles for online users to use and discuss. The discussion contents are organized according to different topics. Each category is a topic group, called newsgroup, and more sub topics can be divided within it.

Each Usenet news is guided by a type distinguishing mark. Each newsgroup focuses on a theme, such as comp (computer content), news (Usenet's own news and information), rec (sports, art and entertainment activities), SCI (Science Branch), SOC (Social Issues), talk (discussion and exchange), misc (other miscellaneous topics), biz (commercial issues), etc.

Users can not only choose to participate in the topic group they are interested in, but also create a new topic group. As long as someone participates, the topic group can always exist; if no one participates for a period of time, the topic group will be deleted automatically.

  4. File transfer

File transfer(File Transfer Protocol,FTP) Protocol is the basis of file transfer on the Internet. FTP is a service based on this protocol. FTP file transfer service allows users on the Internet to transfer files from one computer to another. Almost all types of files, including text files, binary executable files, sound files, image files, data compressed files, etc., can be transferred by FTP Send.

FTP is actually a set of file transfer service software. It takes file transfer as the interface and uses simple get or put commands to download or upload files, just like executing file copy commands on the Internet. Most FTP server hosts use UNIX operating system, but ordinary users can also easily use FTP through Windows95 or Windows98.

The biggest feature of FTP is that users can use many anonymous FTP servers on the Internet. The so-called anonymous server refers to a system that can enter without a special user name and password. When users connect to an anonymous FTP server, they can use "anonymous" Log in as your user name and your e-mail address as your password. After successful login, users can download files from the anonymous server. The standard directory of the anonymous server is pub, and users can usually access files in all subdirectories under this directory. Considering security issues, most anonymous servers do not allow users to upload files.

  5. Remote login

Remote login (telnet) is a protocol of Internet remote login service, which defines the interaction between remote login users and servers. Telnet allows users to log in to a remote time-sharing system on a networked computer, and then use the remote system like their own computer.

To use the remote login service, you must start a client application on the local computer, specify the name of the remote computer, and establish a connection with it through the Internet. Once the connection is successful, the local computer directly accesses the resources of the remote computer system like a normal terminal. The remote login software allows users to interact directly with the remote computer through the keyboard Or mouse operation, the client application sends the relevant information to the remote computer, and then the server returns the output result to the user. The user exitsRemote loginAfter, the user's keyboard and display control return to the local computer.

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Comments (8 in total)

Tip: the content of the comment is the user's comment on the item“internet"The discussion has nothing to do with our views and positions.
222.205.120. * published at 14:48 on May 1, 2011

Thank you.

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219.135.4. * published at 14:54 on December 11, 2015

For what?

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60.251.47. * published at 10:59 on January 4, 2016

There's too much to thank. Thank God

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Internet luck(Talk| contribution)Published at 02:02 on June 12, 2017

U is the classic invariant, and I is the totem. East asked west home, Chinese and English exchange?

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113.135.80. * published at 09:59 on August 5, 2019

Can't the checked encyclopedia be collected?

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111.173.136. * published at 16:42 on May 13, 2020

sixty-six thousand six hundred and sixty-six

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203.72.122. * published at 21:17 on June 23, 2020

60.251.47. * published at 10:59 on January 4, 2016

There's too much to thank. Thank God

Chen Zhifan

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219.77.128. * published at 18:46 on August 23, 2020

Why is the Internet automatically interrupted.

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CommentPlease surf the Internet in a civilized way, speak rationally and abide by relevant regulations.

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