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TCP’s “Three-Way Handshake”
With TCP, there’s work to be done before data transmitted. The two devices have to agree on some basic parameters before segments can be sent – and this negotiation has the curious name three-way handshake. If that’s the first time you’ve heard this term, you’re probably wondering how a handshake can be three-way! They again, maybe you don’t want to know – but to pass the CCENT and CCNA exams, we gotta know! Let’s take a step-by-step look at this process. .
Before the sender can start sending, there’s going to be negotiation between the two devices regarding rules for data transmission, That negotiation is the three-way handshake itself, which begins with the sender transmitting a TCP segment with the Synchronization(“SYN”) bit set. The primary value being negotiated here is the TCP sequence number, which we’ll discuss in more detail in the next section. This is the first part of the three-way handshake.
The recipient responds with a TCP segment with both the synchronization and acknowledgement bits set – a “SYN/ACK”. This is part two of the three-way handshake.
The sender responds with an ACK, and the three-way handshake is complete.
UDP does not use a three-way handshake.
In addition to the orderly construction of the communication channel, TCP uses the FIN (“Finish”) to bring the channel down when the communication is closed.
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TCP’s “Three-Way Handshake”
With TCP, there’s work to be done before data transmitted. The two devices have to agree on some basic parameters before segments can be sent – and this negotiation has the curious name three-way handshake. If that’s the first time you’ve heard this term, you’re probably wondering how a handshake can be three-way! They again, maybe you don’t want to know – but to pass the CCENT and CCNA exams, we gotta know! Let’s take a step-by-step look at this process. .
Before the sender can start sending, there’s going to be negotiation between the two devices regarding rules for data transmission, That negotiation is the three-way handshake itself, which begins with the sender transmitting a TCP segment with the Synchronization(“SYN”) bit set. The primary value being negotiated here is the TCP sequence number, which we’ll discuss in more detail in the next section. This is the first part of the three-way handshake.
The recipient responds with a TCP segment with both the synchronization and acknowledgement bits set – a “SYN/ACK”. This is part two of the three-way handshake.
The sender responds with an ACK, and the three-way handshake is complete.
UDP does not use a three-way handshake.
In addition to the orderly construction of the communication channel, TCP uses the FIN (“Finish”) to bring the channel down when the communication is closed.
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