OSI Layer 3 - ICMP and IGMP

C.

The Open Systems Interconnection (OSI) model is a conceptual framework for understanding how network communication works. It divides the communication process into seven layers, each with its own set of functions and protocols.

The Internet Control Message Protocol (ICMP) and the Internet Group Management Protocol (IGMP) are both network-layer protocols used in the transmission of data across the internet.

ICMP is used to send error messages and operational information about network conditions. It is used by network devices to communicate error messages, such as "destination unreachable," to other network devices. ICMP messages are typically sent in response to errors that occur during the transmission of data packets.

IGMP, on the other hand, is a protocol used by hosts to join and leave multicast groups. Multicasting is the transmission of data from a single source to multiple destinations simultaneously. IGMP is used to manage multicast group membership and to notify routers when hosts join or leave a multicast group.

Therefore, ICMP and IGMP both work at the network layer, which is layer 3 of the OSI model. The network layer is responsible for addressing, routing, and forwarding data packets between networks. It uses IP addresses to identify devices on the network and determine the best path for data to travel from the source to the destination.

To summarize, the correct answer is C. The Network layer.