An Application Layer utility transmits network administration and control messages. Which service should it use if it needs to minimize bandwidth usage and handle retransmissions?

The most suitable service for transmitting network administration and control messages while minimizing bandwidth usage and managing retransmissions is TCP (Transmission Control Protocol).

TCP is designed for reliable communication, ensuring that all transmitted data packets are received correctly. It employs a method of acknowledgment and retransmission where each segment sent must be acknowledged by the receiving end. If an acknowledgment is not received, the sender will retransmit that segment, which is crucial for applications that require data integrity and assurance, such as network administration tools.

In contrast, while UDP (User Datagram Protocol) is more efficient in minimizing bandwidth usage because it sends messages without establishing a connection or confirming receipt, it does not handle retransmissions or guarantees delivery. Therefore, while UDP may handle some use cases with lower overhead, it would not be suitable for tasks that require reliable message transfer.

IP (Internet Protocol) is responsible for addressing and routing packets across the network but does not function as a transport layer protocol; it lacks the mechanisms for ensuring data integrity and reliability that are key requirements in this scenario. ICMP (Internet Control Message Protocol) is primarily used for sending error messages and operational information regarding IP processing but does not support a full communication model with retransmissions like TCP.

Thus, TCP is the correct choice for utility applications