Network Learning notes-Computer Network Basics

Network Learning notes-Computer Network basics 1 What is network: The network is the interface between several computer hosts or network printers, through the network cable or wireless network technology, connect these hosts or devices so that data can be transmitted through network media (network cable or wireless network technology. 2. Computer network components node: A node is a device with a network address (IP. Server: the host that provides data to respond to user requests can be called a server in the network connection direction. Workstation or Client: any device that can be input on the computer network can become a workstation, the client initiates a connection to request data. NIC (Network Interface Card: NIC): Mainly used to provide Network connections, most Network interfaces are currently trial RJ-45 Interface ethernet Card. Network Interface: the network interface designed by the software mainly provides the network address (IP) task. Network form or topology: the connection mode of each node on the network. Generally, it refers to the physical connection mode. Gateway: A gateway with more than two network interfaces that can connect two or more devices with different network segments (an IP router is a common gateway device ). 3. Computer Network range LAN Wide Area Network 4. Computer Network Protocol: OSI Layer 7 network protocol application layer: the application layer is not owned by the application, instead, it defines how the application enters the communication interface at this layer to receive or send data to the application and finally display the data to the user. Presentation layer: the data format generated by applications does not necessarily conform to the standard encoding format for network transmission. Therefore, the main operations of presentation layer are: convert (or recode) the data format from the local application to the standard format of the network, and then hand it to the following transport layer and other protocols for processing. Therefore, at this level, we mainly define the conversion of data formats between network services (or programs), including data encryption and decryption. Session Layer: This layer mainly defines the connection and interruption of the connection channels between two addresses. In addition, you can also establish application communication and provide other enhanced services, such: network Management, sign-in and sign-off, and communication control. If the transport layer is determining whether data packets can arrive at the destination correctly, the Session Layer is confirming that the network service is established online. Transport Layer: defines the connection technologies (such as TCP and UDP) between the sending end and the receiving end, and also includes the packet format of the technology, transmission of data packets, control of processes, detection and re-transmission of transmission processes, etc., to confirm that each data packet can arrive at the target end correctly. Network Layer: IP (Internet Protocol) is defined at the network layer. At the same time, the network layer also defines the online establishment, termination and maintenance between computers, and the transmission path selection of data packets. Therefore, in addition to Ip addresses, this is the concept of whether a packet can reach its destination. Data link layer: the bottom layer of the data link layer is the definition of entities, while the top layer is the definition of software encapsulation. Therefore, the data link layer is divided into two child layers for data conversion. In the hardware aspect, MAC is mainly responsible for Media Access Control. MAC is the main data packet that can be processed by network Media. This is also the data that is finally encoded as a bit string by the physical layer. The software-biased part is controlled by the logical link control (LLC). It mainly processes packets from the upper layer and converts them to the MAC format, responsible for information exchange, traffic control, and error handling. Physical Layer: because the network medium can only transmit strings 0 and 1, the physical layer must define the voltage and signal of the transmission medium used, and must also understand the data encoding method, finally, link the solid media to send/receive bits.