Finite State Machines (FSM)

Published by Keyboard Banger on

– network protocol states, events and actions can be captured in FSM – a state describes a unique configuration of the protocol – the FSM describes how a protocol behaves from both client and server points of view – FSM can describe all or some of the states. If only some states are described, this leaves the door open to improvements – the bridges between states describe the transition from one state to another. – the transition is described by two things: – the event that led to the transition – the action that the system takes when the transition happens. If there is no action, then we leave it blank


A sample Finite State Machine in TCP, at the sender side. This is Stop-and Wait protocol.

– a protocol can be in only one state at a time – in FSM, a protocol starts in the Closed state, which is a fictional state. The following diagram depicts the TCP Finite State Machine.


TCP Finite State Machine – copyright TCP/IP Guide



The TCP/IP Guide: A Comprehensive, Illustrated Internet Protocol Reference
Computer Networking: A Top Down Approach, Kurose and Ross

Categories: Networking Basics

Keyboard Banger

Keyboard Banger is a network engineer from Africa. He has been working in network support and administration since 2008. He started writing study notes about certification exams and technology topics a couple of years ago. When he's not writing articles, he can be found wandering on technical forums.


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