Has the computer 3 handshake agreement English description?
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1st, TCP handshake agreement
In TCP/IP protocol, TCP protocol to provide reliable connectivity, using three shook hands with the establishment of a connection.
The first handshake:establish a connection, the client sent syn packets (syn = j) to the server and access SYN_SEND state, waiting for the server to confirm;
Second handshake:Server received syn package, customers must confirm the SYN (ack = j +1), while himself a SYN packet sent (syn = k), that is, SYN + ACK packet, then enter the server SYN_RECV state;
Third handshake:client server received the SYN + ACK packet, send confirmation to the server package ACK (ack = k +1), this package sent completed, the client and server into the ESTABLISHED state, complete the three shook hands.
Complete the three shook hands with the client and server start sending data, in the process, there are some important concepts:
Not connected cohort:the three shook hands with the agreement, maintaining a server is not connected queue, as the team each client SYN packet (syn = j) creation of an entry, the entry server that has received SYN packet, and customers identified, Is awaiting confirmation, the package.These entries by the logo of Syn_RECV connected to the server in the state, when the client server received the confirmation package, delete the entry into the server ESTABLISHED state.
Backlog parameters:that is not connected to accommodate the largest number of the queue.
SYN-ACK re-sent the number of servers End SYN-ACK packets, if customers have not received confirmation package, the first re-server, waiting for customers for a period of time has not yet received confirmation package, the second-Chuan, if re – More than the number of requirements for re-largest number of systems to connect information from the semi-connected in the queue to delete.Note that each re-waiting time does not necessarily the same.
Semi-connected survival time:connect queue is half the entry of the most prolonged survival, or services received from the SYN packet to confirm that the text was invalid, the longest period, the time value of all repeat request of the longest wait for the package The total time.Sometimes we also said that the survival time for the semi-connected Timeout time, SYN_RECV survival time.
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