Which statement best describes a connectionless, best-effort protocol?

• A. TCP
• B. UDP
• C. ARP
• D. ICMP

Answer: (B)

A connectionless, best-effort approach means sending data in independent packets without establishing a session, and without guarantees about delivery, order, or integrity. This is exactly what the transport layer protocol UDP provides: it transmits datagrams with port numbers but with no connection setup and no reliability mechanisms. Because there’s no acknowledgment or retransmission handled by UDP, it’s fast and low overhead, but you might lose packets or see them arrive out of order.

Other options don’t fit this description. TCP, for instance, is connection-oriented and guarantees delivery and in-order delivery, with retransmissions when needed. ARP is used to map IP addresses to MAC addresses on a local network, not to transport application data. ICMP handles control messages and diagnostics at the network layer, not end-to-end data transport for applications.