For each blank,choose the best answer from the four choices and write down on the answer sheet.(1) is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group.(2) is an error detection code that most data communication networks use.(3) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.(4) is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non -periodic basis over a range of media.(5) is an identifier of a web page. 5()
A. HTTP
B. URL
C. HTML
D. TAG
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RSA是一种基于 (1) 原理的公钥加密算法。网络上广泛使用的PGP协议采用 RSA和IDEA两种加密算法组成链式加密体系,这种方案的优点是 (2) 。POP还可以对电子邮件进行认证,认证机制是用MD5算法产生 (3) 位的报文摘要,发送方用自己的 RSA私钥对 (4) 进行加密,附加在邮件中进行传送。如果发送方要向一个陌生人发送保密信息,又没有对方的公钥,那么他可以 (5) 。 4()
A. 邮件明文
B. IDEA密钥
C. 邮件明文和报文摘要
D. 报文摘要
For each blank,choose the best answer from the four choices and write down on the answer sheet.(1) is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group.(2) is an error detection code that most data communication networks use.(3) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.(4) is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non -periodic basis over a range of media.(5) is an identifier of a web page. 2()
A. 4B/SB
B. CRC
C. Manchester Code
D. Huffman Code
RS-232C是 (1) 之间的接口标准,其规定的电平表示方式为 (2) 。当使用 RS232C连接相关设备时,电缆的长度不应超过 (3) m。当用RS232C直接连接两台计算机时,采用零调制解调器方式,其连接方式为 (4) 。当计算机需要通过相连的MO- DEM发送数据时,依次设置的信号是 (5) 。 4()
A. 用25针插座及电缆连接
B. 用9针插座及电缆连接
C. 信号地对接,一台计算机的发送(接收)数据线与对方的接收(发送)数据线相连
D. 不能采用这种连接方式
对一路信号进行频移键控(FSK)调制时,若载波频率为fc,调制后的信号频率分别为 f1和f2(f1<f2),则三者的关系是 (1) 。当对多路信号进行调制时,调制后各信号的频谱(2) 。信号到达接收端后通过 (3) 分离各路信号。WDM与FDM工作方式很相似,但WDM调制的是 (4) 。ILD是 (5) 使用的设备。 3()
A. 解调器
B. 带通滤波器
C. 载波发生器
D. 终端软件