The Internet is the world's largest, open, computer network composed of many interconnected networks. It is the product of the combination of modern computer technology and communication technology.

The Internet originated from the US military's computer network-ARPANET in the 1960s.

The Internet is a complex system that covers all countries in the world and contains thousands of various devices that require precise management and scheduling. Generally speaking, it can be divided into two parts: network hardware and network software.

Commonly used network hardware includes workstations, servers, network interface cards, hubs, switches, routers, transmission media, etc.

Network software is a collection of various protocols, protocols, programs and management methods that support the realization of network functions. Network software mainly includes network protocols, communication software, network operating systems, etc.

TCP/IP includes four layers: application layer, transport layer, network layer and network interface layer

The most commonly used transport layer protocol is the Transmission Control Protocol TCP, which provides connection-oriented reliable data transmission, flow control and congestion control. Another transmission protocol is the User Datagram Protocol UDP, which provides a connectionless, unreliable, best-effort transmission method.

Internet Protocol IP is the most important protocol in the network layer. It defines a uniquely identifiable IP address for each computer in the network, thereby enabling the smooth transmission of data of different application types on the Internet. The network layer also includes ARP, RARP, ICMP and other protocols

The network interface layer of the TCP/IP protocol supports multiple interface protocols, such as IEEE, 802.2, Token-ring.FDDI, X.25, ATM, etc.

A traditional IP address (IPv4) is represented as a 32-bit unsigned binary number, usually represented by four decimals connected by dots.

The length of the IP address in IPv6 is 128 bits, which can provide 2 to the power of 128 - 1 address

In a computer network, with computers as nodes and communication lines as connections, geometric figures with different relative positions can be formed, which is called network topology.

Basic network topology can be divided into: bus structure, ring structure, star structure, tree structure and mesh structure

The most promising new Internet applications that have emerged in the past year or two mainly include the Internet of Things, cloud computing and big data.

At present, my country's main ISP service providers are China Mobile, China Unicom, China Telecom and local radio and television agencies.

Internet access methods: dial-up telephone line access to PSTN; integrated services digital network ISDN: asymmetric digital subscriber line ADSL; CABLE MODEM; optical fiber broadband access; wireless network

The basic element of www application is the web page

Web pages are written using the Hypertext Markup Language HTML, and the information in the web pages is transmitted on the Internet through the Hypertext Transfer Protocol HTTP.

Every web page on the Internet has a unique identifier called a Uniform Resource Locator URL.

Portal website refers to an Internet application system that provides access to comprehensive Internet information resources and can provide related information services.

The English abbreviation of social networking site is SNS, which is an Internet application service used to help people establish social connections.

E-government websites are websites established by government agencies and administrative institutions at all levels to better conduct public management, improve administrative service efficiency, and publish policies, regulations, notices and other information.

The characteristics of email are fast speed, large amount of information, low price, sending multiple letters in one letter, and supporting multimedia information.

The email address is a standard format, consisting of two parts, the first part is the user name, and the second part is the special separator "@". The third part is the mail server name. A complete email address is: username@mailservername

As an Internet application, email requires the support of network protocols. The network protocols used include Simple Mail Transfer Protocol SMTO, Post Office Protocol POP and Internet Message Access Protocol IMAP, all of which belong to the TCP/IP cluster.

Web pages are the carrier of Internet information. They are written in hypertext markup language HTML and displayed on the client through browser software.

The <p> tag appears alone to indicate the end of a paragraph, and the following text will wrap.

The function of <pre> and </pre> is to indicate that the text between the two will be displayed in the browser as it is without changing the format.

The function of <br> is to interrupt a certain line of text, and the following text will start a new line.

Blog, also known as weblog, is a tool for personal writing and interpersonal communication on the Internet.

Weibo, which has emerged in recent years, is an evolution of the traditional blog form and is the abbreviation of MicroBlog.

There are many technologies to prevent and control computer network threats, including data transmission technology, intrusion detection technology, access control technology, audit technology, anti-virus technology, backup technology, etc., in addition to corresponding network security management laws, regulations and good practices. operating specifications, etc.

Computer viruses refer to a set of computer instructions or program codes compiled or inserted into computer programs that destroy computer functions or destroy data, affect computer use, and can replicate themselves.

A network worm is a safe and independent program that can replicate itself. Its propagation process does not require the help of other programs on the infected host and can run without human intervention.

To prevent viruses on personal computers, the most direct prevention is to install and use anti-virus software

A firewall is a system or a group of systems, including hardware and software, that implement access control policies between a protected network or host and an external network. It achieves effective management of network security by controlling and monitoring information exchange and access behavior between networks.

Firewall products used by individual users mainly exist in the form of software