Which protocol provides reliable, ordered, and error-checked delivery of a stream of packets across the Internet?

• A. UDP
• B. TCP
• C. ICMP
• D. SCTP

Answer: (B)

The main concept is a transport-layer protocol that guarantees a reliable, in-order delivery of a stream of bytes across the network. TCP does this by establishing a connection, dividing data into segments with sequence numbers, and using acknowledgments and retransmission to recover any lost segments. Each segment includes a checksum to detect corruption, so erroneous data is discarded and retransmitted. The receiver reassembles the bytes in their original order and hands a continuous stream to the application. TCP also uses flow control (a sliding window) and congestion control to manage throughput and avoid overwhelming the network.

The other protocols don’t fit this description. UDP is connectionless and offers no reliability or ordering guarantees. ICMP is used for control messages and network diagnostics, not for delivering a data stream. SCTP is reliable and supports multi-streaming, but it is typically message-oriented rather than a simple byte-stream transport, and TCP remains the standard for reliable, ordered byte streams across the Internet.