What is the purpose of TCP's sliding window mechanism?

• A. To regulate the number of unacknowledged bytes and provide flow control between sender and receiver.
• B. To fix the route path.
• C. To ensure encryption.
• D. To determine IP address.

Answer: (A)

The sliding window in TCP controls how much data can be in flight at once. The sender is allowed to send up to a certain number of bytes before it needs an acknowledgment, and that limit is the window size advertised by the receiver. As ACKs come back, the window slides forward, freeing space to send more data. This keeps data flowing efficiently without overflowing the receiver’s buffer, providing flow control and supporting reliable, in-order delivery. It’s not about fixing route paths, encryption, or IP addresses, which are handled by other layers or mechanisms.