Fred is the network administrator for his company. Fred is testing an internal switch. From an external IP address, Fred wants to try and trick this switch into thinking it already has established a s

A packet with both RST (reset) and SYN (synchronize) bits set is contradictory and would typically result in an error or connection reset, not the establishment of a session.

Sending an IP packet with only the SYN bit set initiates a new connection attempt, rather than tricking a system into thinking a session is already established.

An ACK bit set to zero means the packet is not an acknowledgment, which would not help in tricking a system into believing a session is established, as established sessions heavily rely on ACKs.

Sending an IP packet with the ACK bit set is characteristic of an established TCP session, as ACKs acknowledge received data. By sending such a packet with his own source address, Fred attempts to make the switch believe that an ongoing, active session from his machine is already in progress, possibly by guessing or predicting sequence numbers.