The Simple Network Management Protocol (SNMP)is an  （）protocol that facilitates the exchange of management information between  （） . It is part of the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol suite. SNMP enables network  （） to manage network performance, find and sole network problems, and plan for  （） . An SNMP-man-aged network consists of three key components: managed devices, （） , and network-management systems.

The Simple Network Management Protocol (SNMP)is an （）

A．Physical Layer

B．Link Layer

C．Network Layer

D．Transport Layer