Table of contents
Classification by information exchange method
what is network
A network is composed of several nodes and links connecting these nodes, representing many objects and their interconnections. In mathematics, a network is a kind of graph, which is generally considered to refer specifically to weighted graphs . In addition to mathematical definitions, networks also have specific physical meanings, that is, networks are models abstracted from a certain type of practical problem. In the computer field, the network is a virtual platform for information transmission , reception, and sharing. It connects information from various points, surfaces, and bodies together, thereby realizing the sharing of these resources. The Internet is the most important invention in the history of human development, improving the development of science and technology and human society .
Overview of the Internet
The Internet, which originated in the United States, has grown into the world's largest computer network with global coverage. Computer network (hereinafter referred to as network): It consists of several nodes and the links connecting these nodes. Nodes in the network can be computers, hubs, switches or routers, etc. Networks can also be interconnected through routers to form a computer network with a larger coverage; such a network is called the Internet; therefore, the Internet is a network of networks. A network connects many computers together, and the Internet connects many networks together through routers. The computers connected to the network are often called hosts.
Four elements of network
1. Communication lines and communication equipment;
2. A computer with independent functions;
3. Network software support;
4. Realize data communication and resource sharing .
Network classification
Edit Broadcast
Classified by topology
Bus type, ring type , star type, mesh type
Classification by information exchange method
Circuit switching , message switching , message packet switching
Sort by coverage
Local area network LAN ( the range is generally a few meters to dozens of kilometers). Metropolitan Area Network MAN (between WAN and LAN).
Wide Area Network WAN (range is generally tens to thousands of kilometers).
local area network
Local area network (local area network) is usually referred to as " local area network ", abbreviated as LAN. A local area network is a computer network with the least structural complexity . A local area network is simply a group of computers in the same location that are connected via a network. LANs are usually very close together and are the most widely used type of network today. A network with the following characteristics is usually called a local area network.
1. The geographical scope covered by the network is relatively small. Usually no more than a few dozen kilometers, or even just within a building or a room.
2. The information transmission rate is relatively high, ranging from 1Mbps to 10Mbps, and has reached 100Mbps. The transmission rate of WAN operation is generally 2400bps, 9600bps or 38.4kbps, 56.64kbps. Dedicated lines can only reach 1.544Mbps.
3. The operation and management rights of the network belong to a certain unit.
Wan
Wide area network (WAN) is a complex network system with wide impact .
A WAN consists of two or more LANs, and the connections between these LANs can traverse a distance of more than 30mile*. A large WAN can consist of many LANs and MANs on various continents. The most well-known WAN is the Internet, which consists of thousands of LANs and WANs around the world.
Sometimes the boundaries between LAN, MAN and WAN are very unclear and it is difficult to determine where the LAN ends and the MAN or WAN begins. But the type of network can be determined by four network characteristics - communication medium , protocol, topology , and boundary points between private and public networks . Communication media refers to the electrical cables, fiber optic cables, radio waves , or microwaves used to connect computers to networks . Typically LANs end where the communication medium changes, such as from wire-based cables to fiber optics. A wire and cable LAN is usually connected to other LANs through optical fiber cables .
About network security
Cybersecurity is an important issue related to national security and sovereignty, social stability, and the inheritance and development of national culture . Its importance is becoming more and more important with the acceleration of global informatization. “The door to the home is the door to the country”, and security issues are urgent.
Network security is a comprehensive discipline involving computer science , network technology , communication technology, cryptography technology , information security technology, applied mathematics , number theory, information theory and other disciplines.
Network security means that the hardware, software of the network system and the data in the system are protected from damage, alteration, or leakage due to accidental or malicious reasons, and that the system operates continuously, reliably and normally, and network services are not interrupted.
Network security is essentially information security on the Internet . Broadly speaking, all related technologies and theories involving the confidentiality , integrity , availability , authenticity and controllability of information on the network are the research fields of network security.
The specific meaning of cybersecurity changes with the "perspective." For example: From the perspective of users (individuals, enterprises, etc.), they hope that information involving personal privacy or commercial interests will be protected by confidentiality , integrity, and authenticity when transmitted over the Internet . Prevent other people or opponents from using eavesdropping, impersonation, tampering, denial and other means to infringe on the interests and privacy of users, access and destroy it.
From the perspective of network operators and managers, they hope that operations such as access, reading and writing of local network information will be protected and controlled to avoid " trapdoors ", viruses, illegal access, denial of service and illegal occupation and illegal control of network resources. and other threats, stop and defend against attacks by network hackers.
For the security and confidentiality departments, they hope to filter and prevent information that is illegal, harmful or involving state secrets, to avoid the leakage of confidential information , avoid harm to society, and cause huge losses to the country.
From a social education and ideological perspective, unhealthy content on the Internet will hinder social stability and human development, and must be controlled.