From the course: Cisco Networking Foundations: Fundamentals of Cisco Networking

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TCP three-way handshake

TCP three-way handshake

From the course: Cisco Networking Foundations: Fundamentals of Cisco Networking

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TCP three-way handshake

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- [Instructor] What makes TCP so reliable? Well, it begins with a three-way handshake between the sender and receiver. The first step in the three-step process is where the sender sends a synchronization message, which we call a SYN message to the receiver, which is essentially saying, "Hey, I'd like to talk to you." And when the receiver gets that send message, if it's willing to communicate with the sender, it's going to send a couple of messages back to the sender. First, it sends a SYN message of its own saying, "Awesome. I'd like to talk to you too." And second, it sends an acknowledgement message, which we call an ACK back to the sender that acknowledges receipt of the send message that was received from the sender. And after the sender receives that set of SYN-ACK messages, it needs to acknowledge the SYN sent by the receiver. So it's going to send an ACK of its own saying, "Great, I'm willing for you…

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