What is the TCP state associated with closing a connection waiting for an acknowledgment?

The TCP state associated with closing a connection while waiting for an acknowledgment is LAST_ACK. In this state, the connection has already sent a final acknowledgment indicating that it is ready to close, and it is now waiting for the acknowledgment of that final segment from the other side before fully terminating the connection.

When a connection is in LAST_ACK, it means the endpoint has transmitted a FIN segment and is essentially waiting for the peer to acknowledge that FIN. This state is important because it ensures that both sides of the connection have a clear agreement on closing the session, preventing any loss of data that could occur if one side were to terminate the connection prematurely. Understanding the nuances of the TCP connection states, especially in the context of closing mechanisms, helps ensure robust and reliable network communication.

Other states, such as CLOSE_WAIT, FIN_WAIT, and TIME_WAIT, serve different roles in the TCP connection lifecycle, dealing with aspects like waiting for the application to close the connection, actively waiting for a remote connection closure, and ensuring that all data has been properly transmitted and received before fully closing, respectively. However, LAST_ACK specifically encapsulates the idea of waiting for acknowledgment as part of the closing process.