Which of the following protocols is commonly associated with returning network diagnostic information?

The protocol associated with returning network diagnostic information is the Internet Control Message Protocol (ICMP). ICMP plays a critical role in network management and diagnostics, as it allows devices to send messages about network conditions. For instance, tools such as Ping and Traceroute utilize ICMP to test connectivity between devices and to measure response times. When a packet is sent using these tools, ICMP can return messages indicating whether the destination is reachable and provide information about any network issues that may arise along the path.

ICMP is integral for troubleshooting and monitoring network performance, as it helps identify problems like packet loss or unreachable destinations, which are essential for maintaining healthy network operations. Other protocols mentioned, such as DHCP, FTP, and SMB, serve different primary functions—DHCP is for dynamic IP address assignment, FTP is for file transfer, and SMB is for shared access to files and printers—thus, they do not focus on diagnostic messaging in the way ICMP does.