TCP协议通过建立连接为用户提供可靠传输，与数据链路层的连接建立不同，　TCP要经过(11)才能确定一个连接，这是因为(12)。TCP采用的差错控制也是超时重发技术，超时时间的设置采用(13)策略，以便适应互联网的特性。超时时间设置的根据是(14)。TCP的拥塞控制采用慢启动、加速递减和拥塞避免策略。慢启动是指(15)。

(143)

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(138)

In the following essay, each blank has four choices. Choose the best answer and write down on the answer sheet.

 Spread spectrum simply means that data is sent in small pieces over a number of the(71)frequencies available for use at any time in the specified range. Devices using(72)spread spectrum(DSSS)communicate by(73)each byte of data into several parts and sending them concurrently on different(74). DSSS uses a lot of the available(75), about 22 megahertz(MHz).

(137)

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For each blank, choose the best answer from the four choices and write down on the answer sheet.

(66)is a protocol that a host uses to inform. a router when it joins or leaves an Internet multicast group.

(67)is an error detection code that most data communication networks use.

(68)is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.

(69)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.

(70)is an identifier of a web page.