In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.Open Shortest Path First (OSPF) is a (1) routing algorithm that (2) work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (3) processing power. The (4) algorithm is used to calculate routes. OSPF routing table updates only take place when necessary, (5) at regular intervals. 3()
A. more
B. less
C. same
D. most
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设信道带宽为3000Hz,根据尼奎斯特(Nyquist)定理,理想信道的波特率为 (1) 波特,若采用QPSK调制,其数据速率应为 (2) ,如果该信道信噪比为30dB,则该信道的带宽约为 (3) 。设信道误码率为10-5,帧长为10Kb,差错为单个错,则帧出错的概率为 (4) 。若整个报文被分成5个帧,帧出错的概率为0.1,纠错重发以报文为单位,则整个报文的平均发送次数约为 (5) 次。 5()
A. 1.24
B. 1.33
C. 1.54
D. 1.69
In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet. Microwave communication uses high-frequency (26) waves that travel in straightlines through the air. Because the waves cannot (27) with the curvature of the earth, they can be (28) only over short distance. Thus, microwave is a good (29) for sendingdata between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of "dishes" or (30) . These can be installed on towers, high buildings, and mountain tops.
A. optical
B. radio
C. electrical
D. magnetic
In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet.Open Shortest Path First (OSPF) is a (1) routing algorithm that (2) work done on the OSI IS-IS intradomain routing protocol. This routing, as compared to distance-vector routing, requires (3) processing power. The (4) algorithm is used to calculate routes. OSPF routing table updates only take place when necessary, (5) at regular intervals. 5()
A. but rather
B. rather too
C. rather than
D. rather that
A向B发送消息P,并使用公钥体制进行数字签名。设E表示公钥,D表示私钥,则 B要保留的证据是 (1) 。基于数论原理的RSA算法的安全性建立在 (2) 的基础上。 Kerberos是MIT为校园网设计的身份认证系统,该系统利用智能卡产生 (3) 密钥,可以防止窃听者捕获认证信息。为了防止会话劫持,Kerberos提供了 (4) 机制,另外报文中还加入了 (5) ,用于防止重发攻击(Replay Attack)。 5()
A. 伪随机数
B. 时间标记
C. 私有密钥
D. 数字签名