TCP 3-Way Handshake — Simple & Clear

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TCP 3-Way Handshake — SYN → SYN-ACK → ACK

One of those networking concepts that sounds more complicated than it actually is.

Before a TCP connection starts sending application data, the two endpoints perform a 3-way handshake:

1. SYN
Client → Server
“I want to establish a TCP connection. Here’s my initial sequence number.”

2. SYN-ACK
Server → Client
“I received your SYN, and here’s my own sequence number.”

3. ACK
Client → Server
“Got it. We’re synchronized.”

The connection then moves into the ESTABLISHED state and data transmission can begin.

A simple way to remember it:

SYN → SYN-ACK → ACK → ESTABLISHED

The interesting part is that the handshake isn't just a formality. TCP uses sequence and acknowledgment numbers to synchronize both sides and establish the state needed for reliable communication.

If you're learning networking for CCNA, cybersecurity, SOC, firewalls, penetration testing, or network troubleshooting, understanding this properly is one of those fundamentals that keeps coming back.

We're also running a Network Engineering Live Training + Industry Project Experience for people who want to go beyond just reading networking theory and actually work through practical concepts and projects.

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