单选题 71
in the strength of the carrier signal is varied to represent binary 1 or 0.
72
is a system that can map a name to an address and conversely an address to an name.
73
is a three-way handshaking authentication protocol that it"s packets are encapsulated in the point-to-point protocol
74
is an approach that enables an ATM Switch to behave like a LAN switch.
75
is an guided media which is made of glass or plastic and transmits signals in the form of light.