Each machine supporting TCP has a TCP transport entity, either a library procedure, a user process, or part of the kernel. In al

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问题 Each machine supporting TCP has a TCP transport entity, either a library procedure, a user process, or part of the kernel. In all case, it manages TCP streams and (71) to the IP layer. A TCP (72) accepts user data streams from local process, breaks them into pieces not exceeding 64KB, and sends each piece as a separate IP (73). When datagrams containing TCP data arrive at a machine, they are given to the TCP entity, which reconstructs the original byte streams.The IP layer gives no guarantee that datagrams will be delivered properly, so it is up to TCP to time out and (74)  them as need be. Datagmms do arrive may well do so in the wrong order, it is also up to TCP to  (75) them into messages in the proper sequence.

选项 A、reassemble
B、reduce
C、re-create
D、retransmit

答案A

解析 每一个支持TCP的机器都有一个TCP实体,或者是一个库过程,或者是一个用户进程,或者是内核的一部分。在所有情况下,它都管理着TCP流和通向IP层的接口。 TCP实体从本地进程中接收用户的数据流,将其划分为不超过64KB的段,把每一段作为IP数据报进行发送。当包含TCP数据的数据报到达一个机器时,它们被交给TCP实体,重新构造成原来的字节流。IP层不保证数据报完整地提交,所以TCP必须利用超时机制在必要时进行重传。数据报也许不会按顺序到达,还需由TCP把它们按照正确的顺序重新组装成报文。
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