SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietio

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问题 SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the(71)protocol called NRM is essentially the same as SDLC.
   SDLC is(72)protocol like HDLC, Frame Relay or X.25.An SDLC network is made up of(73)that controls all communications, and(74).It is capable of(75).operation, but almost all practical applications are strictly half duplex.

选项 A、halfduplex
B、full duplex
C、half or full duplex
D、half and full duplex

答案B

解析 同步数据链路控制SDLC是IBM开发的用来取代二进制同步协议以连接广域网中的IBM设备。高级数据链路控制规程HDLC协议的一个版本是NRM(普通响应模式),它基本上与SDLC相同。
   SDLC与HDLC、帧中继或者X.25不一样,它不是对等协议。SDLC由一个控制所有的通信的初级站与一个或者多个二级站构成。它支持全双工通信操作,但是几乎所有的实际应用都是半双工的。
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