英语翻译Inthissectionwecanconsideronlythecaseofunidirectionaldatatransfer,thatis,datatransferfromthesendingtoreceivingside.Thecaseofreliablebidirectional(thatis,fullduplex)datatransferisconceptuallynomoredifficul

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英语翻译
In this section we can consider only the case of unidirectional data transfer,that is,data transfer from the sending to receiving side.The case of reliable bidirectional (that is,full duplex) data transfer is conceptually no more difficult but considerably more tedious to explain.Although we consider only unidirectional data transfer,it is important to note that the sending and receiving sides of our protocol will nonetheless need to transmit packets in both directions,as indicated in Figure 3.8.We will see shortly that,in addition to exchanging packets containing the data to be transferred,the sending and receiving sides of rdt1.0 will also need to exchange control packets back and forth.Both the send and receive sides of rdt1.0 send packets to the other side by a call to udt-send ( ) (where udt stands for unreliable data transfer).
1.Building a Reliable Data-Transfer protocol
We know step through a series of protocols,each one becoming more complex,arriving at a flawless reliable data transfer protocol.
Reliable Data Transfer Over a Perfectly Reliable:rdt1.0
We first consider the simplest case in which the underlying channel is completely reliable.The protocol itself,which we’ll call rdt1.0,is trivial.The finite-state machine (FSM) definitions for the rdt1.0 sender and receiver are shown in Figure 3.9.The sender and receiver FSM s in Figure 3.9 each have just one state.The arrows in the FSM description indicate the transition of the protocol from one state to another.(Since each FSM in Figure 3.9 has just one state diagrams shortly.) The event causing the transition is shown above the horizontal line labeling the transition,and the action(s) taken when the event occurs are shown below the horizontal line.
The sending side of rdt1.0 simply accepts data from the upper layer via the rdt1.0-send (data) event,puts the data into a packets (via the action make_ pkt(packet ,data) and sends the packet into the channel.In practice,the rdt1.0_send (data) event would result from a procedure call (for example,to rdt1.0_send ()) by the upper-layer application.
On the receiving side,simply receives a packet from the underlying channel via the rdt1.0_rcv (packet) event,removes the data from the packet (via the action extract(packet ,data)) and passes the data up to the upper layer.In practice,the rdt1.0_rcv (packet) event would result from a procedure call (for example,to rdt1.0_send ()) from the lower-layer protocol.
In this simple protocol,there is no difference between a unit of data and a packet.Also,all packet flow is from the sender to receiver; with a perfectly reliable channel there is no need for the receiver side to provide any feedback to the sender since nothing can go wrong!Note that we have also assumed that the receiver is able to receive data as fast as the sender happens to send data.Thus,there is no need for the receiver to ask the sender to “slow down!”

Answer 1

在这一节,我们就可以只考虑单向数据传输,数据传输给接收方发送.如果施工可靠(即全部复式)数据传送概念比较困难,但没有解释繁琐得多.虽然我们认为只有单向的数据传送,必须指出的是,我们双方收发议定书仍将需要包双向传送,如380图.我们将很快看到,除了包交换的数据传输,发送和接收方rdt1.0还需要外汇管制包来回.无论收发双方rdt1.0包向对岸发出了号召民盟-送(民)(如主张不可靠数据传送).1.建立可靠的数据传输协议,通过一系列措施,我们知道规矩,每个人变得更加复杂,达成完美的可靠数据传输协议.非常可靠的数据传输,较可靠:rdt1.0我们先考虑最简单的情况,是完全可以信赖的根本途径.议定书本身,请rdt1.0捐,实在是微不足道.有限的国家机器(热线)定义为发送和接收rdt1.0见图3.9.发送和接收的公众人物,每次都只有一个390状态.弓箭的描述说明公众的转变从一个国家对另一个议定书.(因为每一个刚刚接待3.9图图州内).一旦造成过渡段的横线标示出过渡和采取行动时(s)如下事件发生的水平线.发送方只同意rdt1.0数据高层通过rdt1.0-送(资料)活动,把数据包变成(经由行动make_PKT(包、数据)包、发送到管道.实际上,Rdt1.0_send(资料)活动而产生的程序要求(例如,Rdt1.0_send())的上层应用.在接收方 仅获得一包从背后透过管道RDT1.0_RCV事件(包),删除的数据包(经提炼的行动(包、数据))的数据,并通过到上层.实际上,RDT1.0_RCV(包)活动而产生的程序要求(例如,Rdt1.0_send())从低层次的协议.这个简单的议定书 没有区别,一个单位的数据包.同时,所有包发送量从接收; 在一个完全可靠的渠道没有必要向接收方发送任何回音,因为没有什么可以出错.看到我们还以为可以得到接收数据发送情况尽快送资料.因此,没有必要要求接收发送"放慢!"