Three Way Handshake

What is Three Way Handshake?

Three way handshake describes the initial process of communication for TCP . Three steps are required for TCP to open a new connection.

How Three Way Handshake works?

First The client will send a single SYN packet with a random sequence number (ID) . The server will response with an ACK acknowledging that it is indeed received the client's SYN,the ack ID will be +1 of the clients SYN id. The server will also send SYN of its own, combining the previous ACK and SYN into one packet, the server SYN id will be a random number. The client will send an ACK (server SYN's id + 1) to Acknowledge the server's SYN

Why we need Three Way Handshake?

Three Way Handshake process is required in order to assure reliable communication between the hosts. Some options are exchange between the hosts to agree upon the session parameters.

Simulation

In this simulation we focus on the sequence numbers between the hosts. We use the telnet application to start new session with the server Try to telnet to the server and observe the sequence numbers of the packets. understanding how TCP is ACK-ing is quite important for more advance topics.