Final answer:
The protocol used in network management systems to monitor network-attached devices is SNMP, or Simple Network Management Protocol, which operates at the application layer.
Step-by-step explanation:
The type of protocol used in network management systems to monitor network-attached devices is called SNMP, which stands for Simple Network Management Protocol. SNMP allows for the management and monitoring of networked devices like routers, switches, and servers.
It operates at the application layer of the Internet protocol suite. TCP/IP is a set of protocols governing communication over the internet, HTTP is used for data transfer on the web, specifically web pages, and FTP is a protocol for transferring files across a network.