Do you understand the TCP/IP protocol?
A set of communication protocols used to implement network interconnection, containing complete rules from data transmission to application services.
Core Protocols:
TCP: Transport layer protocol that provides reliable, connection-oriented byte stream services (such as file transfer, web browsing).
IP: Network layer protocol responsible for addressing and routing data packets (for example, sending data from a server in Beijing to one in Shanghai).
Other protocols:UDP (connectionless transmission), ICMP (network diagnostics), DNS (domain name resolution), HTTP (web page transmission), etc.
Characteristics: Protocols operate independently but work together to achieve end-to-end communication.
What are the specific implementation steps of the TCP protocol?
The TCP/IP protocol is a connection-oriented, secure, and reliable transport protocol at the transport layer. The three-way handshake mechanism ensures a secure and reliable connection. The first handshake is initiated by the client, which sends a message to the server with the SYN flag set to 1, indicating a request to establish a new connection. When the server receives this message, it knows that the client wants to establish a new connection, so it sends a confirmation message back to the client with the ACK flag set to 1, confirming the client’s initial connection request. After these two handshakes, the client is aware that it can successfully send messages to the server and receive responses. However, for the server, two handshakes are not enough because, so far, it only knows that it can receive messages from the client, but it does not know if the client can receive messages from it. Therefore, a third handshake is needed. The third handshake occurs when the client receives the server’s confirmation response and sends another acknowledgment message back to the server, also with the ACK flag set to 1. Through these three connections, both the client and server know that they can send messages to each other and receive responses, thus establishing a secure connection.
The four-way handshake is initiated by the client. In the first wave, the client sends a message with the FIN flag set to 1, indicating that it wants to disconnect. When the server receives this message, it knows that the client wants to disconnect, but it may not be ready yet because there may still be unsent messages. Therefore, the server can only send a message confirmation (the second wave), indicating to the client that it knows the client wants to disconnect but may not be ready yet and will inform the client later (the third wave). After sending this message confirmation, the server may take a moment before sending a disconnection message (the third wave) with the FIN flag set to 1, indicating that it is ready to disconnect. When this message is sent to the client, the client must also send a message confirmation back to the server (the fourth wave). After these four exchanges, both the client and server know that they are ready to disconnect, and the connection is terminated.
What are the roles of each layer in the TCP/IP layered model?
Application Layer: Format definition;
Transport Layer: Confirms the application programs communicating through both parties’ port numbers;
Network Layer: Confirms both parties’ IP addresses, establishing their network locations;
Link Layer: Adds both parties’ MAC addresses, confirming their physical locations;