TCP
The Transmission Control Protocol (TCP) is one of the protocols carried by IP. TCP accounts for over 90% of the traffic on the average LAN. TCP creates a connection between the client and server through a 3-way handshake.
First, the client, an FTP client, sends a TCP/IP packet from a randomly chosen high- numbered port to the server on port 21. In the header of this packet requesting to connect to the FTP server, the SYN bit is set and the others are clear (other bits include ACK, RST, FIN, URG, PSH, but most are not important to this discussion). The packet also contains a random sequence starting number.
When the server, sitting on the wait queue listening for an incoming connection request, sees this packet with the SYN bit set, it ...
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