单项选择题
Which Frame Relay feature is responsible for transmitting keepalives to ensure that the PVC does not shut down because of inactivity?（）
A. DLCI B. BECN C. FECN D. LMI E. CIR F. DE
多项选择题 Which characteristics are representative of a link-state routing protocol?（）
多项选择题 Which of the following contribute to congestion on an Ethernet network?（）
多项选择题 Which of the following correctly describe steps in the OSI data encapsulation process?（）
