CEH

34 Chapter 2 ■ System Fundamentals

FigurE 2.7 TCP three-way handshake

Sending System Receiving System

System 2

System 2

ACK System 2

SYN-ACK

System 1 SYN

System 1

System 1

FigurE 2.8 TCP sequencing

Sending System Receiving System

System 1 System 2

System 1 System 2

Seq. No. 884562 (SYN)

Seq. No. 776825 (SYN-ACK)

System 1 Seq. No. 776826 (RESPONSE) System 2

System 1 Seq. No. 884563 (SYN-ACK) System 2

System 1 Seq. No. 884563 (DATA) System 2