GATE CS 2026 Set 1 Q8 — Transport Layer: Flow Control, Congestion Control, UDP, TCP, Sockets

The correct option is D.

Let us analyze each statement to understand why option D is correct:

• Option A is incorrect: TCP uses a three-way handshake (SYN $\rightarrow$ SYN-ACK $\rightarrow$ ACK) to establish a connection before data transmission begins, not a two-way handshake.
• Option B is incorrect: Either the client or the server can initiate the connection teardown. The side that sends the first FIN segment is known as the active closer. There is no restriction preventing the server from initiating the close first.
• Option C is incorrect: TCP is a full-duplex protocol, meaning both endpoints can transmit and receive data simultaneously over the same connection.
• Option D is correct: TCP supports a scenario called simultaneous close. If both the client and the server send a FIN segment at the same time, their segments cross in the network. Both endpoints transition from the ESTABLISHED state to FIN-WAIT-1, then to CLOSING upon receiving each other's FIN, and finally to TIME-WAIT before fully closing the connection.