TCP/IP host-to-host data transmission, as well as a simple understanding of three handshakes and four waves

Data packet transmission from the host to the host

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SYN is the signal for TCP connection establishment.

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Host 3.1 2-layer encapsulation of frame ARP requests

 

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Host 3.1 sends ARP request Broadcast

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Host 3.2 receives ARP request Broadcast

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Host 3.2 receives ARP requests

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Host 3.2 receives and responds to a frame

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Host 3.2arp response

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Host 3.2 sends ARP response

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Host 3.1 receives a response, unpacks the two-layer frame, and adds an ARP entry

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ARP ing completed

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Host 3.1 requires the first session handshake

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Host 3.2 confirm to accept and respond to the second handshake of the session

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Host 3.2 Response session

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Host 3.1 unpacking

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Three-way handshake completed

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Host 3.1 package and send data

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Host 3.2 unpack and extract data

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Confirm received data

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TCP connection establishment (three-way handshake)

SEQ is the serial number

Ack is the validation character and the serial number of the data packet to be sent.

Three-way handshake

Step 1 A sends SYN and randomly generates an initial seq such as seq = 100

Step 2 B confirm that SYN is received, that is, seq = 100 packets

And want to accept the next packet ACK = 100 + 1 that is 101 packets

At the same time, B will also tell a to randomly generate the initial aeq, such as seq = 300.

Send seq = 300, ACK = 101 packets

Step 3 A receives ACK = 101 from B, and sends its seq = 100 + 1 to B.

At the same time, B is expected to continue to send data packets, then ACK = 300 + 1

In step 2, Ack confirmation and SEQ packet transmission are synchronized.

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TCP connection termination (four waves)

Step 2 and Step 3 are not synchronized. It is often because you have finished sending and I have not finished collecting

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TCP/IP host-to-host data transmission, as well as a simple understanding of three handshakes and four waves