A transport layer protocol usually has s

练习题库2022-08-02  76

问题 A transport layer protocol usually has several responsibilities.One is to create a process-to-process communication;UDP uses(  )numbers to accomplish this. Another responsibility is to provide control mechanisms at the transport level. UDP does this task at a very minimal level. There is no flow control mechanism and there is no(  )for received packet. UDP,however, does provide error control to some extent. If UDP detects an error in the received packet, it will silently drop it.The transport layer also provides a connection mechanism for the processes. The (  ) must be able to send streams of data to the transport layer.It is the responsibility of the transport layer at(  )station to make the connection with the receiver, chop the stream into transportable units,number them, and send them one by one. It is the responsibility of the transport layer at the receiving end to wait until all the different units belonging to the same process have arrived, check and pass those that are(  )free, and deliver them to the receiving process as a stream.问题1选项A.hopB.portC.routeD.packet问题2选项A.connectionB.windowC.acknowledgementD.destination问题3选项A.jobsB.processesC.programsD.users问题4选项A.sendingB.routingC.switchingD.receiving问题5选项A.callB.stateC.costD.error

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答案 BCBAD

解析 传输层协议通常有几个功能,其中之一就是生成进程与进程之间的通信。UDP使用端口号来实现这个功能。另外一个责任是在传输级实现控制机制。UDP对于这个任务只做很少的工作。没有流量控制,对于接收的报文也没有应答。然而,UDP在一定程度上还是做了差错控制工作。如果UDP在收到的报文中检测到了错误,就直接丢弃。
传输层也提供进程之间的连接机制。进程应该能够向传输层发送数据流。与接收站建立连接是发送方传输层的责任,同时把数据流划分成可传输的单元,对其进行编号,然后一个接一个地发送他们。接收方传输层的责任就是等待同一个进程的各个传输单元到达,检查其正确性,让没有错误的通过,并将其组织成数据流提交给接受进程。
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