单项选择题
If node 2 is accepting line timing from node 1, node 2 will send （）to node 1 as its SSM message.
A. ESF B. PRS C. DUS D. SMC E. B8ZS
单项选择题 SONET Code Violations (CVs) totals in the PM tables are actually an accumulation of the number of （）.
单项选择题 Scrambling of SONET signals is done to （）.
单项选择题 A Channel ID mismatch occurs when （）.
