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Three-way Handshake

The process used by TCP to establish a reliable connection between a client and a server.

Categorynetwork

Overview

The three-way handshake ensures that both the sender and receiver are ready to communicate and have agreed on initial sequence numbers.

The Steps

  1. SYN (Synchronize): The client sends a packet with a random sequence number (ISN) and the SYN flag set.
  2. SYN-ACK (Synchronize-Acknowledge): The server responds with its own ISN, the SYN flag set, and an acknowledgement of the client's ISN.
  3. ACK (Acknowledge): The client sends a final packet acknowledging the server's ISN.

Purpose

This process prevents old or delayed packets from interfering with a new connection and synchronizes the sequence numbers used for reliable delivery.

Related Terms

TCPTransport LayerFlow Control