In the context of TCP connections, when is an ACK packet typically sent?

The correct answer is that an ACK packet is typically sent for every packet after the first SYN. This behavior is a fundamental part of the Transmission Control Protocol (TCP), which establishes a reliable connection between sender and receiver.

In the TCP three-way handshake process, an initial SYN packet is sent from the client to the server to request a connection. The server responds with a SYN-ACK packet, acknowledging the receipt of the SYN packet and also sending its own SYN to establish a two-way connection. The client then sends an ACK packet back to the server to acknowledge the server's response.

Once this initial connection is established, ACK packets are sent with each subsequent data packet to confirm that the data was received. This acknowledgment process ensures reliability in the TCP protocol, allowing both parties to track sent and received packets. If an ACK is not received within a specified timeframe, the sender will retransmit the data, which is a crucial aspect of how TCP maintains a reliable data transmission channel.

Considering other options, ACK packets are not limited to secure transactions, nor are they only sent during connection establishment. They are integral to maintaining the consistent flow of data during an active connection.