Why is the TCP three-way handshake used?

Why is the TCP three-way handshake used?

• A. To establish a connection before data transfer
• B. To terminate a connection
• C. To encrypt the data
• D. To discover the path between hosts

Answer: (A)

TCP is a connection-oriented protocol, so a reliable data exchange starts only after both sides agree to communicate and set up state. The three-way handshake coordinates this start: the initiator asks for a connection with a synchronization signal, the responder acknowledges and transfers its own sequence information, and the initiator confirms the acknowledgement. This establishes the connection, negotiates initial sequence numbers, and puts both ends in a known state so data can be sent reliably with correct ordering, error checking, and flow control. Without this handshake, data could be sent without agreed parameters, risking misordered or lost packets. The other options don’t fit because ending a connection uses a separate closing process, encryption is provided by higher-layer protocols like TLS over TCP, and discovering a route between hosts is handled by the network layer routing mechanisms rather than TCP.

TCP is a connection-oriented protocol, so a reliable data exchange starts only after both sides agree to communicate and set up state. The three-way handshake coordinates this start: the initiator asks for a connection with a synchronization signal, the responder acknowledges and transfers its own sequence information, and the initiator confirms the acknowledgement. This establishes the connection, negotiates initial sequence numbers, and puts both ends in a known state so data can be sent reliably with correct ordering, error checking, and flow control. Without this handshake, data could be sent without agreed parameters, risking misordered or lost packets.

The other options don’t fit because ending a connection uses a separate closing process, encryption is provided by higher-layer protocols like TLS over TCP, and discovering a route between hosts is handled by the network layer routing mechanisms rather than TCP.