问题 单项选择题

TCP是一个面向连接的协议,它提供连接的功能是______的,采用______技术来实现可靠数据流的传送。

A.超时重传

B.肯定确认(捎带一个分组显的序号)

C.超时重传和肯定确认(捎带一个分组显的序号)

D.丢失重传和重复确认

答案

参考答案:C

解析:

[分析]: TCP协议的主要功能是在一对ULP(upper level protocol)之间提供面向连接的传输服务,连接管理可以分为建立连接、数据传输和终止连接3个阶段。TCP连接使用3次握手协议来建立连接,通常在一台计算机上的TCP软件被动地等待握手,而另一台计算机上的TCP软件则主动发起连接请求。握手协议允许双方同时试图建立连接,即连接可由任何一方或双方发起。一旦连接建立,就可以双向对等地数据流动,无主从关系。当传送结束后,连接双方都要终止各自的连接。TCP提供的连接功能是双向的,即全双工连接。全双工连接包括两个独立的、流向相反的数据流,而且这两个数据流之间不进行显式的交互。如果在主机A和主机B之间有连接,A可向B传送数据,而B也可以向A传送数据。TCP采用超时重传和肯定确认技术来实现可靠数据流的传送。在每条TCP通信连接上传送的数据段都有一个与之相对应的序号,主要用于数据排序、重复检测、带重传的正向确认及流量控制窗口等TCP机制。这种序号机制使得请求建立连接和拆除连接的可靠性得到保证。

完形填空
Richard found a job in a big office after he finished college. He liked to use his (1)_______ and was good at his job. So he was often paid more than (得到的报酬多于) his workmates and he worked (2) __________. But something was wrong with the young man a month ago. He couldn't fall (3) _________ at night. So he was always (4) _________ in the daytime and often made mistakes. He had to go to a hospital. The doctor (5) _________ and told him to buy some sleeping pills. He took them (6) _________ he went to bed. Soon after that he went to sleep. Richard  (7) _________ in the morning. He had a look at the clock on the wall. It was a quarter to seven. He got up and went to work after (8) _________ . As soon as he went into the office, he said to the head of the office, "Good morning, Mr Clarke! I've (9) _________ had a good sleep like last night's and I'm feeling much better now!" "Skunk (混蛋)!" the head (10) _________ loudly. "We've looked for you for two days! I wanted you to do something important, but it's too late now!"
小题1:
A.handB.headC.eyesD.feet
小题2:
A.hardB.fastC.harderD.faster
小题3:
A.asleepB.aloneC.afraidD.awake
小题4:
A.wellB.hungryC.thirstyD.tired
小题5:
A.looked for himB.looked at himC.looked after himD.looked him over
小题6:
A.afterB.becauseC.beforeD.if
小题7:
A.stood upB.woke upC.sat downD.lay down
小题8:
A.lunchB.dinnerC.supperD.breakfast
小题9:
A.alwaysB.usuallyC.neverD.often
小题10:
A.laughedB.shoutedC.smiledD.asked
材料分析题