This picture shows a normal three-way TCP/IP handshake.

Which of the following will cause VPN-1/Firewall-1 to reset TCP connections with a server
protected by SYNDefender?

A.
The client never completes the handshake with an SYN packet.

B.
The client never completes the handshake with an SYN/ACK packet.

C.
The server never completes the handshake with an SYN packet.

D.
The client never completes the handshake with an ACK packet

E.
The server never completes the handshake with an ACK packet.

Explanation:

: This is true, since the 3 way normal handshake process is SYN, SYN/ACK, ACK, the client
needs to complete this step to establish the TCP connection. If the user never send this ACK, the
gateway running SYNDefender will reset the connection with a RST packet, this is because
SYNDefender is not going to leave the connection in waiting state for more than the configured
time, if SYNDefender does not reset the connection, your network is vulnerable to the Denial of
Service Attack “SYN Flood”.