Question: In TCP, the _______ timer prevents a long idle connection between two TCPs.

Answer:

In TCP, the keepalive timer prevents a long idle connection between two TCPs.
When a TCP connection is established, it remains open until either end closes the connection. However, there may be cases where a connection is left open but not used for an extended period. This can happen if, for example, the application at one end crashes or if there is a network failure that prevents communication between the two ends. In such cases, the TCP connection may remain open indefinitely, tying up network resources.
To prevent this from happening, TCP uses a keepalive mechanism. The keepalive timer is a timer that is started when a TCP connection is established, and it is reset each time a segment is sent or received. If the timer expires without any segments being sent or received, then TCP sends a keepalive segment to the other end. The keepalive segment contains no data and is used only to elicit a response from the other end. If no response is received after a certain number of keepalive segments, the connection is assumed to be dead, and TCP closes it.
By using the keepalive timer, TCP can detect when a connection is no longer needed and close it, freeing up network resources for other connections. The keepalive timer value is typically configurable and can be set to a value appropriate for the specific network environment.

MCQ: In TCP, the _______ timer prevents a long idle connection between two TCPs.

Correct Answer: A. retransmission

In TCP, the keepalive timer prevents a long idle connection between two TCPs.
When a TCP connection is established, it remains open until either end closes the connection. However, there may be cases where a connection is left open but not used for an extended period. This can happen if, for example, the application at one end crashes or if there is a network failure that prevents communication between the two ends. In such cases, the TCP connection may remain open indefinitely, tying up network resources.
To prevent this from happening, TCP uses a keepalive mechanism. The keepalive timer is a timer that is started when a TCP connection is established, and it is reset each time a segment is sent or received. If the timer expires without any segments being sent or received, then TCP sends a keepalive segment to the other end. The keepalive segment contains no data and is used only to elicit a response from the other end. If no response is received after a certain number of keepalive segments, the connection is assumed to be dead, and TCP closes it.
By using the keepalive timer, TCP can detect when a connection is no longer needed and close it, freeing up network resources for other connections. The keepalive timer value is typically configurable and can be set to a value appropriate for the specific network environment.