SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the (50) protocol called NRM is essentially the same as SDLC.
SDLC is (51) protocol like HDLC, Frame Relay or X.25.An SDLC network is made up of (52) that controls all communications, and (53) .It is capable of (54) .operation, but almost all practical applications are strictly half duplex.
A.HDLC
B.Frame Relay
C.X.25
D.X.21
A.2
B.3
C.4
D.5
A.存放指令地址
B.存放操作数
C.存放正在执行的指令
D.存放操作数的地址
A.DES
B.UNIX
C.SNMP
D.RSA