First, the concept of computer network
Computer network is the product of the combination of modern communication technology and computer technology. Computer network means that computers distributed in different geographical areas are connected by communication equipment and lines, and equipped with related network equipment and software, thus forming an organic system of network communication and resource sharing.
A computer network must have three elements: first, at least two computers with independent operating systems and shared hardware, software and information resources. The second is the communication medium or communication channel connected to the computer. The third is to standardize the network protocol of information transmission.
Second, the classification of computer networks
1, Lan, Lan, Wan
LAN: Also called LAN. Used for data transmission between computers within a limited distance. The distance is generally within the range of 10 km, which belongs to the nature of the unit private network. LAN can be connected to WAN or public network, so that LAN users can enjoy the resources provided by external networks.
Local area network (LAN): Also known as metropolitan area network (MAN), it is larger than LAN, and usually covers a region or a city, with a geographical range from tens of kilometers to hundreds of kilometers. It can be private or public.
WAN: A network covering a large area, usually a country.
2. Remote communication network
A network used for data transmission between computers in two places, also called communication private network.
3. Private network and public network
Private network is a network established and used by a certain department or unit. Public networks are generally organized, managed and controlled by telecommunications departments. Transmission lines and switching equipment in the network can be rented.
Third, the concept and characteristics of the Internet
Internet is a collection of computer networks, also known as Internet. Based on TCP/IP network protocol, it connects many different types of computer networks and thousands of computers around the world, so that hardware, software and information resources scattered on computer networks and computers can be easily exchanged and shared. The Internet has the following characteristics:
First of all, it is open. As long as you follow the prescribed network protocol, you can connect freely, without time and space restrictions and the concept of geographical distance. Anyone can join and use the Internet anytime and anywhere.
Second, the resources are huge. The information on the Internet is almost all-encompassing. Which is the largest in the world? Library? And an information database.
Third, the transmission speed is fast. E-mail can be sent to computers in different corners of the world in a few minutes or even seconds, and a large amount of data can be processed and transmitted quickly.
Fourth, it is convenient to use. As long as you have a computer, a modem and a telephone line, or a network card and a dedicated line, you can access the Internet after applying to an Internet access service organization. The Internet is rapidly spreading all over the world and has increasingly become the central nervous system of the world. According to the statistical report of American computer and network industry market research consulting company, in 2005, the number of global netizens exceeded 1, 654,380+billion.
Fifth, it is easy to leak. When data is transmitted on the Internet, it is easy to be intercepted and copied.