– 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 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.