Which protocol is defined as used to control and manage information transmitted using TCP/IP?

The correct answer is ICMP, which stands for Internet Control Message Protocol. This protocol plays a critical role in managing and controlling the behavior of the TCP/IP network. ICMP is primarily used for error reporting and diagnostics, helping to determine whether data is being transmitted correctly across a network. For instance, it can communicate messages regarding unreachable destinations or time exceeded for packets, helping network administrators troubleshoot issues effectively.

ICMP operates at the network layer and is essential for the overall health and management of network communication. It facilitates the exchange of control messages, allowing devices to communicate problems and anomalies that may occur in the transmission of data packets over the network.

In contrast, the other protocols mentioned serve different purposes: IGMP (Internet Group Management Protocol) is used for managing multicast groups; HTTP (Hypertext Transfer Protocol) is used for transmitting web pages and files over the web; and FTP (File Transfer Protocol) is designed for transferring files between systems. Each of these protocols has specific functionalities unrelated to overseeing and controlling information flow within TCP/IP, which is the reason they are not the correct choice in this context.