FTP是基于_(1)_實現的文件傳輸協議，使用此協議進行文件傳輸時，FTP客戶和服務器之間建立的連接是_(2)_，用于傳輸文件的是_(3)_連接。TFTP是基于UDP實現的簡單文件傳輸協議，它共有五種協議數據單元PDU，其中數據PDU一次可以攜帶的數據最多是_(4)_，當傳輸的文件長度恰好是其整數倍時，則文件傳輸完畢后，還必須在最后發送一個_(5)_。

　　⑴A.IP B.TCP C.UDP D.ICMP

　　⑵A.數據連接 B.控制連接和指令連接

　　C.控制連接和數據連接 D.數據連接和指令連接

　　⑶A.數據 B.指令 C.控制 D.UDP

　　⑷A.384 B.512 C.1024 D.1500

　　⑸A.確認PDU B.應答PDU C.請求PDU D.無數據的數據PDU

　　答案：BCABD

　　Flow control is a function that prevents network congestion by ensuring that _(1)_ do not overwhelm_(2)_ with data.

　　There are three commonly used methods for handling network congestion . _(3)_is used by network devices to temporarily store bursts of excess data in memory until they can be processed. _(4)_ are used by receiving devices to help prevent their buffers from overflowing . _(5)_ is a flow-control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted.

　　⑴⑵A.transmitting devices B.transmitted devices

　　C.receiving devices D.received devices

　　⑶⑷⑸A.Buffer B.Source-quench messages

　　C.window D.Windowing E.Buffering Answer：ACEBD