单项选择题
A.IETF B.HDLC C.Q9333-A Annex A D.ANSI Annex D
Which layer 2 protocol encapsulation type supports sync...
单项选择题Which layer 2 protocol encapsulation type supports synchronous and asynchronous circuis and has built-in security mechanisms?（）
A.Frame Relay B.HDLC C.x.25 D.PPP
Which two options are valid WAN connectivity methods?（）...
多项选择题Which two options are valid WAN connectivity methods?（）
A.PPP B.WAP C.DSL D.Ethernet E.L2TPv3
At which layer of the OSI model dose PPP perform?（）A.La...
单项选择题At which layer of the OSI model dose PPP perform?（）
A.Layer 3 B.Layer 4 C.Layer 2 D.Layer 5
