GIAC Foundational Cybersecurity Technologies Practice Test

Which packet type is used when a graceful TCP Teardown fails?

1. FIN

2. RST

3. EXIT

4. ACK/FIN

The correct answer is: RST

When a graceful TCP teardown fails, the appropriate response is to use a reset packet, which is indicated by the RST flag in the TCP segment. In the TCP protocol, a graceful teardown typically involves a sequence of FIN packets, where each side of the connection indicates it has finished sending any remaining data. However, if something goes wrong in this process, such as the connection being interrupted or one side becoming unresponsive, the RST packet is employed to immediately terminate the connection. The RST packet serves a critical function; it signals to the other party that the connection should be stopped immediately, without the normal closing process. This is particularly useful when one side is no longer available or has encountered an error that requires an abrupt cessation of communication. The other options do not apply in the context of handling a failed graceful teardown. The FIN packet initiates a normal connection termination, while ACK/FIN is part of the graceful teardown process itself. 'EXIT' is not a recognized TCP packet type. Therefore, a RST packet is the correct response when a graceful TCP teardown fails, demonstrating its role in ensuring that connections can be forcibly closed when necessary.