多项选择题
Which two statements about MPLS label-switched paths (LSPs) are true? （）
A. LSPs are bidirectional. B. LSPs are unidirectional. C. LSPs must follow the IGP's shortest path. D. LSPs can follow paths other than the IGP's shortest path.
单项选择题 Which statement is correct regarding IPv6 addresses?（）
单项选择题 At which layer of the OSI model does error checking occur with IPv6?（）
多项选择题 Which two statements are true about optical networks?（）
