Simple Network Management Protocol (SNMP) is an Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device（）. SNMP is a component of the Internet Protocol Suiteas defined by the Internet（ ）Task Force. SNMP operates in the（请作答此空）layer of the Internet protocol suite. All SNMP messages are transported via User（ ）Protocol. An SNMP-managed network consists of three key components: a) Managed devices, b) （ ）(i.e.，software which runs on managed devices), and c) Network management station (NMS) (i.e.， software which runs on the manager).

答案：

解析：