Four-way handshake
A four-way handshake is a protocol exchange consisting of four messages for terminating a TCP connection or establishing WPA encryption keys.
Acing the CCNA Exam: Volume 1 Fundamentals and Protocols
A four-way handshake is the typical four-message TCP procedure for terminating a connection using FIN and ACK control flags.
- How it is used
- Explains how TCP terminates a connection after data exchange.
- How deep it goes
- Shows the FIN, ACK, FIN, ACK sequence and notes combined flags, while deferring unusual termination details.
- Examples
- Uses PC1 and SRV1 to illustrate the four termination messages after TCP data exchange.
- What you can do after
- Understand TCP termination by recalling and identifying the typical FIN, ACK, FIN, ACK exchange.
Read how Acing the CCNA Exam: Volume 1 Fundamentals and Protocols explains four-way handshake →
Acing the CCNA Exam: Volume 2 Advanced Networking and Security
A four-way handshake is a WPA key-establishment exchange between a wireless client and authenticator that generates encryption keys for data communication.
- How it is used
- Uses post-association key establishment to verify a shared PSK and protect wireless data communication.
- How deep it goes
- Explains purpose, placement, security limitation, and WPA3 relationship but does not detail individual handshake messages.
- Examples
- Uses a client–access point exchange, an 8- to 63-character passphrase, and captured-handshake brute-force attempts.
- What you can do after
- Evaluate WPA-Personal authentication order, key generation, and the security difference between WPA2 PSK and WPA3 SAE.
Related concepts
- pre-shared keyuses · A pre-shared key is secret keying material provisioned in advance to communicating parties for authentication or cryptographic operations.
- tcp connection terminationkind of · TCP connection termination is the process of closing a TCP connection after the necessary data has been exchanged.
- three-way handshakecontrasts with · A three-way handshake is the exchange of SYN, SYN/ACK, and ACK messages that establishes a TCP connection between endpoints.
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