单项选择题 A network administrator is verifying the configuration of a newly installed host by establishing an FTP connection to a remote server. What is the highest layer of the protocol stack that the nework administrator is using for this operation?（）

单项选择题 Acknowldgement, Sequencing, and Flow control are characteristics of which OSI layer?（）

单项选择题 The administrator is unable to establish connectivity between two Cisco routers. Upon reviewing the command output of both routers, what is the most likely caust of the problem?（）