Introduction to TCP/IP protocol families from the underlying layer to the upstream Layer

Introduction of TCP/IP protocol families from the underlying layer to the upstream layer: 1. The network interface layer is a method for transmitting data packets from the network layer of a device to the network layer of another device. The Network Interface Layer encapsulates the upper-layer IP datagram into frames and sends them to the network. When a data frame reaches the receiving end through the network, the network interface layer of the node unblocks the data frame, check the MAC address contained in the frame. If the address is the MAC address or broadcast address of the local machine, it is uploaded to the network layer. Otherwise, the frame is discarded. 2. The network layer is responsible for converting data frames into IP data packets and selecting necessary routes. 3. The connection and establishment of the transmission protocol for the communication sessions at the end of the transport layer are determined by the data transmission mode. 4. the application layer is responsible for application network access and identifies different applications through port numbers. The TCP/IP protocol is a protocol family, and each layer contains many other protocols. Now we introduce several important protocols at each layer: Network Interface Layer: ARP: Address Resolution Protocol, converts an IP address to a MAC address. The Network Interface Layer encapsulates the upper-layer IP datagram as an Ethernet packet, and converts the IP address-marked destination B to the MAC address-marked destination B. When A does not know the MAC address of B, A broadcasts an ARP request packet with the IP address of B (192.168.1.2) in the request packet. All Ethernet computers will receive the request, under normal circumstances, only B will give an ARP response packet, and the packet will be filled with the MAC address of B, and will reply to. After receiving an ARP response, A puts the MAC address of B into the local cache for later use. RARP: opposite to ARP. Network Layer: IPv4, IPv6, ICMP, and IGMP are not detailed! Transport Layer: TCP: The application calls TCP program and uses the TCP Service to provide the data to be sent, which is used to distinguish the destination address and port number of the receiving destination. Three-way handshake protocol: establish a connection with the specified server port. The TCP packet with the synchronous serial number SYN set 1 and the initial serial number x is sent by the requester for the first time, indicating that the request establishes a connection packet. The SYN is sent by the receiver for the second handshake, and the ACK bit is set to 1, a tcp packet with the confirmation number x + 1 and the serial number y. If the SYN and ACK are set to 1, this indicates that this is the request response packet. The third handshake request end sends the confirmation number y + 1, A message whose serial number is z. Note that TCP has the timeout retransmission feature. FIN is used to release links. UDP: Non-connection is not reliable, simple, and not described. It is mainly used to solve real-time problems such as network video conferencing. Application Layer: telnet and ftp. Dns and so on!