Question

The three way handshake for TCP connection establishment is shown below.

Which of the following statements are TRUE?
S1 : Loss of SYN+ACK form the server will not establish a connection
S2 : Loss of ACK from the client cannot establish the connection
S3 : The server moves LISTEN $\to$ SYN_RCVD $\to$SYN_SENT $\to$ ESTABLISHED in the state machine on no packet loss
S4: The server moves LISTEN $\to$ SYN_RCVD $\to$ ESTABLISHED in the state machine on no packet loss.

• A. S2 and S4 only
• B. S1 and S3 only
• C. S2 and S3 only
• D. S1 and S4 only

Answer 1

The correct option is D S1 and S4 only

Initially server is in LISTEN mode when a SYN is received, the server sends SYN + Ack and goes to SYN_RCVD state. When ack form client is received it moves to ESTABLISHED state.
$\therefore$ S3 is false and S4 is true.
The loss of SYN+ Ack form server will not allow the client to move to ESTABLISHED state.
Hence connection cannot be established.