The concept of computer networks

  • Generally speaking, computer network is a willdecentralizedHaving or having a different geographical locationindependentThe function ofComputer systemThrough theCommunication equipment(routing, etc.) andline(optical fiber, etc) connected by functionalsoftwareimplementationResource sharingandInformation transferIn the system.
  • Computer networks are someA collection of interconnected, autonomous computer systems

The composition of computer networks

(1) In terms of components

A complete computer network is mainly composed of hardware, software and protocols. Hardware is mainly composed of host (also known as end system), communication links, such as twisted-pair cable, optical fiber, exchange equipment (such as routing, switches, etc.) and communication processor (such as network card), etc Software mainly includes various realize resources sharing of software and the user’s convenience tools software (e.g., network operating system, email program, FTP, chat program, etc.). Protocol is the core of computer network, the protocol defines the network transmission data to follow the specification. Just like the law in our real life, there are certain rules that must be followed in the online world.

(2) From the way of working

  • Computer networks (mainly the Internet) can be divided intoThe edge and the core.
  • The edge section consists of all the hosts connected to the Internet for direct use by users for communication (such as data, audio, or video transmission) and resource sharing
  • The core consists of a large number of networks and the routers that connect them. It provides connectivity and switching services to the edge.

(3) From the perspective of functional composition

Computer network is composed of communication subnet and resource subnet Communication subnet by all sorts of transmission medium, communications equipment and corresponding network protocol, it is the network data transmission, exchange, control and storage capability, data communication between the computer resource subnet is to realize the resource sharing of the set of equipment and software, Network users can share hardware resources, software resources, and data resources on other computers

Computer network functions

(1) Data communication

(2) Resource sharing

(3) Distributed processing

(4) Improve reliability

(5) Load balancing

(6) Others

  • Computer network can also achieve electronic office and service, distance education, entertainment and other functions

Classification of computer networks

The largest computer network is the Internet, which connects the world’s local and wide area networks (Lans) to each other and has a nationwide reach (2) Classified broadcast networks by transmission technology. All networked computers share a common communication channel. When one computer sends a packet using a shared communication channel, all other computers hear the packet. The computer receiving the packet will decide whether to accept the packet by checking the destination. Peer to peer networks. Each physical line connects to a pair of computers. (3) Classification by topology Network topology refers to the network structure represented by the geometric relationship (such as bus, ring) between the total network nodes (routers, hosts, etc.) and communication lines (network cables), mainly refers to the topology structure of communication subnets. Divided into four categories: bus, star, ring, network

(4) Classification by users

  • Public Network. Also known as the public network. A large network funded by a telecommunications company.
  • Private Network. A network built by a department to meet its special business needs. This network does not provide services to people outside the unit. Such as railways, ceremonies, military and other departments dedicated network.

(5) Classify circuit switched networks by switching technology. A dedicated path is established between the source node and the destination node for data transmission, including connection establishment (occupying communication resources), data transmission (occupying communication resources all the time) and disconnection (releasing communication resources) three stages. The most typical circuit switching network is the traditional telephone network. The characteristic of this type of network is that the whole packet bit stream from the source point to the end point continuously, as if in a pipe transmission. Packet switching network. Also known as store-and-forward network. The user data is added with auxiliary information such as the source address, destination address, and verification code, and then encapsulated into a packet. The packet is sent to the adjacent node. After all the packets are stored, the packet is forwarded to the next node. Packet switched network. Also called packet switched network. The principle is to divide the data into short fixed-length data blocks, add the destination address, source address and other auxiliary information to each data block to form a group (packet), and transmit the data in store-and-forward mode.

(6) Classification by transmission medium

  • Transmission media can be divided into wired and wireless two categories
  • The wired network can be divided into twisted-pair network, coaxial cable network, etc
  • Wireless networks can be divided into bluetooth, microwave, radio and other types