Knowledge of TCP/IP required by programmers

The TCP/IP knowledge that programmers need to know may not be available for most project development projects. However, as a technical engineer, the basic TCP/IP knowledge is essential, it is also helpful for future development in this area. Www.2cto.com TCP/IP protocol is the most basic protocol of the Internet and the basis of the international Internet. It consists of the IP protocol at the network layer and the TCP protocol at the transmission layer. TCP/IP defines how electronic devices connect to the Internet and how data is transmitted between them. The protocol uses a layer-4 hierarchy. Each layer calls the network provided by its next layer to meet its own needs. In layman's terms: TCP is responsible for discovering transmission problems. When there is a problem, it sends a signal and requires a re-transmission until all data is securely and correctly transmitted to the destination. The IP address specifies an address for each computer on the Internet. The TCP/IP protocol is not the combination of the TCP/IP protocol and the IP protocol, but the entire TCP/IP protocol family of the Internet. In terms of protocol layered model, TCP/IP consists of four layers: network interface layer, network layer, transmission layer, and application layer. Www.2cto.com the TCP/IP protocol does not fully comply with the OSI Layer-7 Reference Model. OSI (Open System Interconnect) is a traditional reference model for Open System Interconnection, it is a layer-7 abstract reference model for communication protocols, where each layer executes a specific task. This model aims to make various hardware communicate with each other at the same level. These seven layers are: physical layer, data link layer (network interface layer), network layer (network layer), transmission layer, Session Layer, presentation layer and application layer (Application Layer ). The TCP/IP communication protocol uses a layer-4 hierarchy. Each layer calls the network provided by its next layer to meet its own needs. 1. TCP/IP layered model the Internet uses TCP/IP protocol. Like the OSI reference model, TCP/IP is also a hierarchical model. It is composed of four conceptual layers on the hardware layer, namely the network interface layer, IP layer, transmission layer, and application layer. Network Interface Layer: Also known as the data link layer, which is the bottom layer of TCP/IP. Function: receives IP data packets and sends them to the selected network. IP layer: the IP layer processes communications between machines. Function: it receives requests from the transport layer and sends the group with the destination address. Encapsulate the group into the datagram, fill in the Data header, use the routing algorithm to decide whether to directly send the datagram to the target host or to the router, and then submit the data to the corresponding network interface for transmission. Transport Layer: Provides communication between application layers, that is, end-to-end communication. Function: manages information flows and provides reliable transmission services to ensure data arrive in order without errors. 2. TCP/IP model demarcation line Protocol address demarcation line: to distinguish between high-rise and low-level addressing, high-level addressing uses IP addresses, and low-level addressing uses physical addresses. Protocol software on the application IP layer only uses IP addresses, while the network interface layer processes physical addresses. Operating System demarcation line: to distinguish between systems and applications. Between the transport layer and the application layer. 3. When a message is reused and decomposed, the sender adds additional information such as the message type and Protocol to the message. All packets are transmitted repeatedly in the network in the form of frames to form a Grouped stream. When receiving packets from the receiver, refer to the additional information to separate the received groups.