4-layer architecture of TCP/IP and role of each layer

Briefly describe the layer-4 architecture of TCP/IP and the role of each layer. data Link Layer 2. network Layer 3. transport Layer 4. the application layer, where IP is in the Layer 2 network layer, TCP is in the layer 3rd transport layer, the most important thing about the Internet architecture is the TCP/IP protocol, it is the key to achieving interconnection network connectivity and interoperability. It connects various networks on the Internet of many machines. Other Internet protocols use the functions provided by the TCP/IP protocol. Therefore, we are used to calling the entire Internet protocol family the TCP/IP protocol family, the TCP/IP protocol is also known as the layer-4 architecture of TCP/IP. data link layer: the data link layer is a physical transmission channel that can be transmitted using a variety of transmission media and can be established on any physical transmission network. For example, optical fiber and twisted pair wires. 2. Network Layer: The main function is to transmit packets between hosts in the network. There are four Protocols: (1) the Internet Protocol IP address is responsible for the transmission of grouped data, and each IP address data is independent of each other. (2) The special message mechanism in the ICMPIP layer of the Internet control protocol, which plays a controlling role and can send report errors or provide information about unexpected situations. Because ICMP data packets are sent through IP addresses, the function belongs to the layer 3rd of the network. (3) address translation protocol ARP must know the physical addresses of each other in order to allow erroneous or unexpected information to be transmitted to the destination on the physical network, in this way, there is a requirement to convert an Internet address (a 32-bit IP address, a logical address) to a physical address, which requires a set of services (Protocols) at the network layer) the IP address can be converted to the corresponding network address, which is the APP. (Internet addresses can be considered as external and physical addresses.) (4) reverse address translation protocol RARP is used in special cases, when only your physical address does not have an IP address, you can obtain the IP address through RARP. in case of power failure or restart, you must use RARP to obtain the IP address again after the instance is started. It is widely used to obtain the IP address of a diskless workstation. 3. Transmission Layer: the main task is to provide reliable End-to-End services to the upper layer to ensure that "packets" are transmitted without errors, order, loss, and repeat. It shields the details of lower-layer data communication from the top layer and is the most critical layer in the computer communication architecture. It includes the following two important protocols: (1) TCP: TCP is the transport layer protocol in the TCP/IP system, responsible for reliable data transmission ("three handshakes"-establish connections, data transmission, and close connections ). (2) UDP: Compared with TCP, data transmission has low reliability and is suitable for a small amount of data transmission with low reliability requirements. 4. Application Layer: the application layer determines the nature of inter-process communication to meet user needs. Multiple common protocols are provided at the application layer. -- Telnet (Remote Login): File Transfer Protocol: SMTP (Simple Mail Transfer Protocol): Simple Mail Transfer Protocol POP3 (Post Office Protocol 3 ): third-generation Post Office Protocol HTTP (Hyper Text Transfer Protocol): Hypertext Transfer Protocol NNTP (Network News Transfer Protocol): Network News transmission Protocol