Computer networks can be divided into "private networks and public networks" according to their scope of use. The public network is established, managed and controlled by the telecommunications department or other operating departments that provide communication services. The transmission and switching devices within the network can be used by any department or individual. The private network is a network established and operated by the user department and is not allowed to be used by other users and departments.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Computer network refers to the connection of multiple computers and their external devices with independent functions in different geographical locations through communication lines. Under the management and coordination of network operating systems, network management software and network communication protocols , a computer system that realizes resource sharing and information transfer.
Computer networks are divided into private networks and public networks according to their scope of use.
The public network is established, managed and controlled by the telecommunications department or other operating departments that provide communication services. The transmission and transfer devices in the network can be used by any department and individual; Public networks are often used in the construction of wide area networks to support users' remote communications. Such as my country's telecommunications network, radio and television network, China Unicom network, etc.
A private network is a network established and operated by the user department and is not allowed to be used by other users and departments. Due to investment factors, private networks are often local area networks or are constructed by leasing lines from the telecommunications department. Established wide area network. Such as the campus network established by the school, the enterprise network established by the enterprise, etc.
Characteristics of public network
1. Public Switched Telephone Network (PSTN)
The Public Switched Telephone Network is the telephone transmission network we usually use. It is a circuit-switched network based on analog technology. The transmission rate of PSTN is low and the quality is poor. Network resource utilization is low. Bandwidth is limited. No store-and-forward functionality. It is difficult to achieve transmission between devices with different speeds. It can only be used in situations with low requirements. [1]
2. Packet switching data network (X.25)
China Packet Switching Public Data Network (CHINAPAC) is a packet switching network covering the entire country. Its main agreement is X. 25. X. 25 is a data terminal equipment (DTE) interface specification for public switched networks. X. 25.com emphasizes providing reliable services to the public. Its design philosophy focuses on the reliability of data transmission. Its bit error rate is very low. X. The 25 network is a network with excellent performance. Allows users to obtain hundreds or thousands of virtual circuit connections through a physical channel. It has error control capability for transmitted information within the network. Because it is an interface with store-and-forward and provides various packet disassembly and assembly equipment. Therefore, asynchronous, synchronous, and terminal interconnection communications at different rates are allowed. The public packet switching data network also provides value-added services such as electronic mailbox, electronic data interchange and video and text.
3． Digital Data Network (DDN)
Digital Data Network (DDN) is a high-bandwidth, high-quality public digital data communication network. The channel through which information is transmitted is a digital channel. DDN is a synthesis of digital communications, computers, optical fiber, digital crossover and other technologies. Can provide and support multiple services and applications.
4． Integrated Services Digital Network (ISDN)
Integrated Services Digital Network (ISDN) and telephone network, X. 25. DDN is also designed as a public network. "Integrated services" means that its telecommunications business scope is diverse. It includes and integrates all the services of various existing communication networks (telephone network, packet switching network, etc.). ISDN is suitable for services with high real-time requirements such as telephone and image. It can also adapt to highly sudden information services such as digital data. It can also adapt to various types of business that may arise. In terms of data transfer rate adaptability. It can adapt to both low speed and high speed user network interface transmission rate. It can also accommodate the transmission of variable rate information. Narrowband ISDN (N-ISDN) provides 164kbit/s bandwidth. Its applicable business scope is quite limited. It cannot adapt to the needs of new services such as high-speed data, image services, and high-definition television. ATM technology is the core technology for realizing broadband ISDN. ATM (Asynchronous Transfer Mode), as its name implies, is the asynchronous transfer mode. The emergence of optical fiber laid the foundation for the development of ATM. The capacity of optical fiber can meet the speed requirements of ATM.
Reason for using private network
The reason why it is called "private network" is because this kind of network is used for internal communication of the organization's host, and It is not used to communicate with hosts outside the network that are not part of the organization.
If communications between different sites on a private network must pass through the public Internet, but there are confidentiality requirements, then all data transmitted through the Internet must be encrypted.
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