what is internet

The Internet is a collection of global information resources. It is a worldwide computer network. It is a logical network interconnected by many small networks (subnets). Each subnet is connected There are several computers (hosts); the Internet aims to exchange information resources with each other, is based on some common protocols, and is formed through many routers and the public Internet. It is a collection of information resources and resource sharing.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

What is the Internet

The Internet (Internet) is a collection of global information resources. Roughly speaking, the Internet is a worldwide computer network; that is, it is a network that interconnects billions of computing devices around the world.

The Internet is a logical network composed of many small networks (subnets) interconnected. Each subnet is connected to several computers (hosts). The Internet aims to exchange information resources with each other, is based on some common protocols, and is formed through many routers and the public Internet. It is a collection of information resources and resource sharing.

The Internet began in the United States in 1969. It was first used for military connections by the US military under the agreement established by ARPA (Arpanet, US Defense Research Project Agency), and later used by the University of California, Los Angeles, Stanford University Graduate School, UCSB (University of California) and Utah in the southwestern United States. State University's four main computers are connected. The agreement was executed by BBN Technologies of Cambridge, Massachusetts, which built the IMP (Interface Information Processor), a custom Honeywell DDP-516 Minicomputer. After BBN's design and construction of software design, routing, traffic control and network control, they are assigned to various sites to serve as gateways to ARPANET. BBN successively manufactured 4 IMPs between August 30, 1969 and the end of the year, and began to go online.

Another wide area network that promotes the development of the Internet is the NSF network. It was originally funded by the National Science Foundation and was designed to connect five supercomputer centers in the United States for more than 100 American universities to share their data. resource. The NSF network also uses TCP/IP protocol and is connected to the Internet.

Both the ARPA network and the NSF network originally served scientific research, and their main purpose is to provide users with valuable resources to share large mainframes. As the number of connected hosts increases, more and more people use the Internet as a tool for communication and exchange. Some companies have also launched commercial activities on the Internet. With the commercialization of the Internet, its huge potential in communications, information retrieval, customer service, etc. has been tapped, making the Internet a qualitative leap and eventually going global.

Features

The reason why the Internet has developed so rapidly is mainly due to the following characteristics:

1. It is a global computer interconnection network .

2. It is a huge information material.

3. The most important thing is that the Internet is a big family, with tens of millions of people participating and sharing the wealth (i.e. resources) created by humans themselves.

Disadvantages

1. No overall planning and design, unclear network topology, and lack of fault tolerance and reliability.

2. In the commercial field, security issues are another major factor that troubles users.

3. The Internet is a centerless network.

Basic Internet Services

WWW Service

World Wide Web (World Wide Web, referred to as WWW) It is a global information resource network on the Internet that integrates text, sound, images, videos and other multimedia information. It is an important part of the Internet. Browser is a bridge for users to access the WWW and a window for obtaining WWW information. Through the browser, users can roam in the vast ocean of the Internet, search and browse all the information they are interested in.

WWW web page files are written in Hyper Text Markup Language (HTML) and run with the support of Hyper File Transfer Protocol (Hype Text Transmission Protocol). Hypertext not only contains text information, but also multimedia information such as graphics, sounds, images, and videos (so hypertext is also called hypermedia). More importantly, hypertext contains implicit links to other hypertexts. Such links Called Hyper Links. Using hypertext, users can easily link from one web page to other web pages with related content without having to care about where the web pages are scattered in the host.

HTML is not a programming language in the general sense. It embeds special tags in documents to describe the semantics of a piece of text. After interpretation, it produces multimedia effects and can provide hyperlinks to the text. .

The WWW browser is a client program whose main function is to enable users to obtain various resources on the Internet. Commonly used browsers are Microsoft's Internet Explorer (IE) and Netvigator/Communicator. SUN also developed a browser written in Java, HotJava. Java is a new type of dynamic interpreted language that is independent of various operating systems and platforms. Java enables browsers to have animation effects and provides real-time interactive functions for connected users. Commonly used browsers support Java.

E-mail service

E-mail is the most widely used service on the Internet. As long as the user can connect to the Internet, has a program that can send and receive e-mails, and a personal e-mail address, he or she can easily, quickly and economically exchange e-mails with all users on the Internet who have e-mails. E-mails can be exchanged between two users. You can also send the same email to multiple users, or forward received emails to other users. In addition to text, emails can also contain various computer files such as sounds, images, and applications. In addition, users can also subscribe to e-magazines online via email, obtain required documents, participate in relevant announcements and discussion groups, and even browse WWW resources.

Sending and receiving emails must be supported by corresponding software. Commonly used software for sending and receiving emails include Exchange, Outlook Express, etc. These software provide the functions of receiving, editing, sending and managing emails. Most Internet browsers also include the ability to send and receive email, such as Internet Explorer and Navigator/Communicator.

The protocols used by the mail server include SMTP (Simple Mail Transfer Protocol), MIME (Multipurpose Internet Mail Extensions), and POP (Post Office Protocol). POP services need to be provided by a mail server, and users must obtain an account on the mail server to use this service. The more commonly used POP protocol is version 3, so it is also called the POP3 protocol.

Usenet Internet News Group Service

Usenet is a collection of various topic discussion groups organized by many users with similar interests. It is also often referred to as a global bulletin board system (BBS). Usenet is used to publish announcements, news, comments and various articles for online users to use and discuss. The discussion content is organized according to different topic categories. Each category is a topic group, called a news group, and more subtopics can be divided within it.

Every news in Usenet is guided by a tag that distinguishes types. Each news group revolves around a theme, such as comp. (computer content), news. (news and information about Usenet itself), rec. . (Sports, art and entertainment activities), sci. (scientific branches), soc. (social issues), talk. (discussion and communication), misc. (other miscellaneous topics), biz. (business issues), etc.

In addition to choosing to participate in the topic groups of interest, users can also open new topic groups themselves. As long as there are people participating, the topic group can continue to exist; if no one participates for a period of time, the topic group will be automatically deleted.

File Transfer Service

Text transfer service, also known as FTP service, is one of the earliest service functions provided on the Internet and is still widely used.

FTP (File Transfer Protocol) protocol is the basis for file transfer on the Internet. What is commonly known as FTP is a service based on this protocol. The 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 compression files, etc., can be transferred to another computer. Can be transferred using FTP.

FTP is actually a set of file transfer service software. It uses 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 systems, but ordinary users can also use FTP easily through Windows 95 or Windows 98.

The biggest feature of FTP is that users can use numerous anonymous FTP servers on the Internet. The so-called anonymous server refers to a system that can be entered without a special user name and password. When users connect to an anonymous FTP server, they can use "anonymous" as the username and their own email address as the password to log in. After successful login, the user 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. Due to security concerns, most anonymous servers do not allow users to upload files.

Remote login service

The remote login service is also called the Telnet service. It is one of the earliest service functions provided on the Internet. Many people are still using this service. Function.

Telnet is a protocol for Internet remote login services. This protocol defines how remote login users interact with the server. Telnet allows users to log into a remote time-sharing system on a networked computer and then use the remote system as if they were 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 acts like a normal terminal and directly accesses the resources of the remote computer system. Remote login software allows users to interact directly with remote computers through keyboard or mouse operations. The client application sends relevant information to the remote computer, and the server returns the output results to the user. After the user logs out remotely, the user's keyboard and display control rights return to the local computer. General users can log in remotely through the Windows Telnet client program.

Electronic Bulletin Board Service

BBS (Bulletin Board Service, Bulletin Board Service) is an electronic information service system on the Internet. It is a popular contemporary means of communication for individuals and groups. Today, BBS has formed a unique online culture. Netizens can freely express their thoughts and ideas through BBS. BBS is actually a kind of website. From a technical point of view, the electronic bulletin board is actually a public information storage area set up in a computer on the network in a distributed information processing system. Any legal user can access information in this storage area through the Internet or LAN. Early BBSs could only provide text-only forum services. BBSs could also provide email, FTP, newsgroups and other services. BBS is divided into multiple columns according to different themes. The division of columns is based on the needs and preferences of most BBS users. The usage rights of BBS are divided into browsing, posting, sending emails, sending files and chatting. Almost any Internet user has the right to browse freely, and only formally registered users can enjoy other services. The biggest difference between the communication characteristics of BBS and the Internet is that, as its name describes, it is a "bulletin board", that is, the vast majority of emails running on BBS sites are public letters. Therefore, users will be faced with almost all the information on the site. China's Internet was first developed from universities and scientific research institutions. Universities generally set up campus networks. Therefore, students and teachers have naturally become the largest user groups of BBS.

Other Internet services

1. Internet telephony

Internet telephony is the latest technology on the Internet, which allows people to make calls to Fantasy becomes reality on any ordinary telephone in the world. As a pioneer in communications and Internet services, the Internet phone developed by the American IDT company occupies a leading position in global network communications. Its Internet phone system allows any multimedia computer user equipped with a sound card on the Internet to make international long-distance calls. Transmitted to IDT's server in the United States via the Internet, it will be automatically transferred to any ordinary telephone of the called party. The other party's phone will ring, and the two parties can communicate in real time and in full duplex. When using this system to make international calls, the cost can be saved by up to 95% compared to traditional international long-distance calls, because the signal is transmitted to the server in the United States through the Internet and then transmitted to the called phone instead of traditional telecommunications. transmission to reduce costs. With Internet phone calls, you can make calls from a PC to any ordinary phone, changing the technical limitations of the previous Internet phone calls from PC to PC.

2. IRC

IRC (Internet Relay Chat) is an online instant chat system. Its biggest advantage is that it is extremely fast, users basically do not feel the stagnation of information when sending messages, and it supports online file transfer and secure private chat functions. Compared with BBS, it has a more intuitive and friendly interface. IRC has developed at an astonishing speed. More and more people around the world are investing in the secondary development of IRC and the production of client software. There are also several IRC chat rooms in China. IRC chat will replace other chat methods and enter the life of every Internet user.

IRC uses a wide range of software, such as PERCH, SCHAT, etc. The more popular one is the IRC client software mIRC produced by the British company mIRC. Once launched, it became popular all over the world. Through this software, as long as everyone uses the same address and enters the same server (even without entering the server), information can be instantly transmitted to one or more other users who are online at the same time. It is a very practical and powerful real-time chatting software.

3. ICQ

ICQ is the abbreviation of I seek you in English. It is often called "network pager" and is a free network software. The main function is to send information or communicate with users who also have ICQ installed on the Internet. It is an instant messaging software developed by the Israeli company Mirabilis in 1996. It can send text messages, voice messages, chat and send files instantly, and allows users to detect the network status of their friends. And it also has a strong "integration" function, which can integrate multiple communication methods such as pagers, mobile phones, and emails.

4, contact chat

5, online shopping

6, online video

7, Weibo

8, online community

Network Core Protocol

A computer network is composed of many computers. To transmit data between computers in the network, two things must be done: the data transmission destination address and measures to ensure rapid and reliable data transmission. This is because the data is transmitted during the transmission process. It is easy to be lost or mistransmitted. The Internet uses a specialized computer language (protocol) to ensure that data reaches the designated destination safely and reliably. This language is divided into two parts: TCP (Transmission Control Protocol) and IP ( Internet Protocol)sure Internet marketing theory.

Data transmission process of TCP/IP protocol: The communication method used by TCP/IP protocol is packet switching. The so-called packet switching simply means that data is divided into several segments during transmission. Each data segment is called a data packet. The basic transmission unit of the TCP/IP protocol is a data packet. The TCP/IP protocol mainly includes two main protocols, namely TCP protocol and IP protocol, these two protocols can be used in combination or with other protocols. They mainly complete the following functions during the data transmission process:

(1) First, the TCP protocol divides the data into several Data packets, write a sequence number on each data packet so that the receiving end can restore the data to its original format.

(2) The IP protocol writes the addresses of the sending host and the receiving host for each data packet. Once the source address and destination address are written, the data packet can transmit data on the physical network. The IP protocol also has the function of utilizing routing algorithms for routing selection.

(3) These data packets can be transmitted through different transmission channels (routing). Due to different paths and other reasons, order reversal, data loss, data distortion or even duplication may occur. These problems are handled by the TCP protocol, which has the function of checking and handling errors, and can also request the sending end to resend when necessary. In short, the IP protocol is responsible for the transmission of data, while the TCP protocol is responsible for the reliable transmission of data.

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