Which transport protocol provides reliable data delivery with acknowledgments and retransmission?

• A. UDP
• B. ICMP
• C. TCP
• D. SCTP

Answer: (C)

Reliable data delivery with acknowledgments and retransmission is a feature of the transport-layer protocol that is connection-oriented and uses sequence numbers, ACKs, and retransmission mechanisms. This protocol establishes a connection before any data is sent, tracks data with sequence numbers, requires the receiver to acknowledge received segments, and retransmits segments when ACKs are missing or when timeouts occur. It also provides ordered delivery and incorporates flow and congestion control to prevent overwhelm and ensure efficiency. That combination of connection-oriented setup, acknowledgments, and automatic retransmission is what makes this protocol the standard example of reliable transport in most CCNA-focused discussions.

UDP is a connectionless protocol that delivers best-effort data without guarantees, ACKs, or retransmission. ICMP operates at the network layer for error reporting and diagnostics, not for delivering application data reliably. SCTP does provide reliable delivery with acknowledgments and retransmission and adds features like multi-streaming and multi-homing, but TCP is the most widely covered reliable transport protocol and is the typical reference in CCNA contexts.