计算机网络原理实验七实验报告

1、实验七、传输层可靠传输协议GBN编程实验报告一、实验目的：1、编程实现简单可靠的数据传输GBN协议，模拟可靠数据传输2、理解TCP协议可靠传输的差错检测、重传、累计确认、定时器的可靠传输策略。二、实验指导：参考教材。三、实验要求：编程实现一个GBN传输协议，采用编程语言不限，要求能将发送一一接收流程以及处理方法 表现出来.附源代码及注释并附上实验结果截图。一、GBN.h#pragma once#include 基础功能模块的数据结构声明#define BIDIRECTIONAL 1/* change to 1 if youre doing extra credit andwrite a rou

2、tine called B_output */如果你想做酷文解码和写一个程序叫B_output就改变值为1/* a msg is the data unit passed from layer 5 (teachers code) to layer 4 (students code). It contains the data (characters) to be delivered to layer 5 via the students transport level protocol entities.*/一个“msg”是从第五层传送到第四层的数据单元.它包含通过传送层协议被传送到 第五层的

3、数据 struct msg char data20;/* a packet is the data unit passed from layer 4 (students code) to layer 3 (teachers code). Note the pre-defined packet structure, which all students must follow. */一个数据包从第四层传送到第三层的数据单元.声明提 前定义的学生必须遵守的数据包结构 struct pkt int seqnum; int acknum; int checksum;char payload20;#de

4、fine WINDOWSIZE 8#define MAXBUFSIZE 50#define RTT 15.0#define NOTUSED 0#define NACK -1 TOC o 1-5 h z #define TRUE1#define FALSE0#define A0#define B1网 络 仿 真 部 分 数 据 结 构声明 * struct event float evtime;/* event time */ 事件时间int evtype;/* event type code */ 事件类型代码int eventity;/* entity where event occurs

5、*/ 所在的实体事件发生时struct pkt *pktptr; /* ptr to packet (if any) assoc w/ this event */ 用指针来显示这个数据包 struct event *prev;struct event *next;/* possible events: */可能发生#define TIMER_INTERRUPT 0 TOC o 1-5 h z #defineFROM_LAYER51#defineFROM_LAYER32#defineOFF0#defineON1 基 础 功 能 模 块 的 函 数 声 明 * void ComputeChecks

6、um(struct pkt *packet);/计算校验和 int CheckCorrupted(struct pkt packet);/检查数据是否出错 void A_output( struct msg message);/A 端向外发送数据 void A_input(struct pkt packet);/A 端接收数据 void A_timerinterrupt();/A 计时器超时 void A_init();/A 端初始化 void B_output(struct msg message);void B_input(struct pkt packet);void B_timerin

7、terrupt();void B_init();网 络 仿 真 部 分 的 函 数 声 明*void init(); 初始化仿真器float jimsrand();/ 随机数发生器0,1/ 处理事件列表部分的 函数声 明*void generate_next_arrival();/产生下一个到达的分组void insertevent(struct event *p);/向事件列表中插入一条新的事件void printevlist();/打印事件列表/* 计时器模块 *void stoptimer(int);/停止计时器void starttimer(int,float);/ 启动计时器 /*

8、/* 网络各层之间传送模块 void tolayer3(int AorB,struct pkt packet);/ 向第 3 层发送信息 void tolayer5(int AorB,char datasent20);/ 向第 5 层发送信息二、GBN.c#include GBN.h#include #include #include extern int TRACE = 1;/* for my debugging */ 为我的调试extern int nsim = 0;/* number of messages from 5 to 4 so far*/目前为止信息的数字是从5到4extern

9、 int nsimmax = 0;/* number of msgs to generate, then stop*/如果信息产生的数字为0，然后就停止extern float time = 0.000;float lossprob;/* probability that a packet is dropped */数据包可能会丢失float corruptprob;/* probability that one bit is packet is flipped*/这一点的数据包可能会被弹出去float lambda;/* arrival rate of messages from layer

10、 5 */ 从第五层到达的信息的次序int ntolayer3;/* number sent into layer 3 */被传送到第三层的数据/* number lost in media */ 在媒介中/* number lost in media */ 在媒介中心r LE AU数据丢失static int ncorrupt = 0;/* number corrupted by media*/被媒介毁坏的数据static int expectedseqnum = 0;/* expected sequence number atreceiver side */在接收者这边接收到预期的序列数据

11、static int nextseqnum;/* next sequence number to use insender side */下一个序列数据使用在发送者这边static int base;/* the head of sender window */发送者的头窗口struct pkt winbufWINDOWSIZE; /* window packets buffer */数据包缓冲区窗口static int winfront,winrear; /* front and rear points of window buffer */ 窗口缓冲区的前方点和后方点static int

12、pktnum;/* packet number of window buffer */窗口缓冲区的数据包个数struct msg bufferMAXBUFSIZE; /* sender message buffer */发送消息缓冲区int buffront,bufrear;/* front and rear pointers of buffer */缓冲区的前指针与后指针static int msgnum;/* message number of buffer */信息数量的缓冲int packet_lost =0;int packet_corrupt=0;int packet_sent =

13、0;extern int packet_correct=0;extern int packet_resent =0;int packet_timeout=0;extern struct event *evlist = NULL; /* the event list */ 事件表计算校验和void ComputeChecksum( struct pkt *packet)int checksum;int i;checksum = packet-seqnum;checksum = checksum + packet-acknum;for ( i=0; ipayloadi);checksum = 0-

14、checksum;packet-checksum = checksum;/检查是否出错int CheckCorrupted(struct pkt packet) int checksum;int i;checksum = packet.seqnum;checksum = checksum + packet.acknum;for ( i=0; i20; i+ )checksum = checksum + (int)(packet.payloadi);if ( (packet.checksum+checksum) = 0 ) return (FALSE);else return (TRUE);/A

15、端向外发送数据/* called from layer 5, passed the data to be sent to other side */ 来自第五层，通过数据派往另一边void A_output(struct msg message)int i;struct pkt sendpkt;/* if window is not full */ 如果窗口没有满 if ( nextseqnum base+WINDOWSIZE )printf(A: New message arrives, send window is not full, send newmessge to layer3!n)

16、;/* create packet */ 创建包 sendpkt.seqnum = nextseqnum; sendpkt.acknum = NOTUSED;for ( i=0; i20 ; i+ )sendpkt.payloadi = message.datai;/* computer checksum */ 计算机校验 ComputeChecksum (&sendpkt);/* send out packet */ 发送数据包 tolayer3 (A, sendpkt);/* copy the packet to window packet buffer */ 复制数据包到窗口 数据缓冲区

17、winrear = (winrear+1)%WINDOWSIZE;pktnum +;winbufwinrear = sendpkt;for (i=0; i20; i+)winbufwinrear.payloadi= sendpkt.payloadi;/* update state variables */ 更新状态变量 nextseqnum = nextseqnum+1;starttimer(A,RTT);B_input(sendpkt);A_input(sendpkt);/* if window is full */ 如果窗口没有满elseprintf(A: New message arri

18、ves, send window is full,);/* if buffer full, give up and exit*/如果缓冲区满了，停止和退出 if ( msgnum = MAXBUFSIZE)printf ( Error: Sender buffer is full! n);exit (1);/* otherwise, buffer the message */ 否则，缓冲信息elseprintf(buffer new message!n);bufrear = (bufrear+1) % MAXBUFSIZE;for (i=0; i20; i+)bufferbufrear.dat

19、ai = message.datai;msgnum +;/B端向外发送数据/* called from layer 5, passed the data to be sent to other side */ 来自第五层，通过数据传送到另一边void B_output(struct msg message) int i;struct pkt sendpkt;/* if window is not full */如果窗口没有满 if ( nextseqnum base+WINDOWSIZE )printf(A: New message arrives, send window is not fu

20、ll, send newmessge to layer3!n);/* create packet */ 创建数据包 sendpkt.seqnum = nextseqnum;sendpkt.acknum = NOTUSED;for ( i=0; i20 ; i+ )sendpkt.payloadi = message.datai;/* computer checksum */计算机校验 ComputeChecksum (&sendpkt);/* send out packet */ 发送数据包 tolayer3 (A, sendpkt);A_input(sendpkt);/* copy the

21、packet to window packet buffer */ 复制数据包到窗口 数据缓冲区winrear = (winrear+1)%WINDOWSIZE;pktnum +;winbufwinrear = sendpkt;for (i=0; i20; i+)winbufwinrear.payloadi= sendpkt.payloadi;/* if it is the first packet in window, start timeout */ 如果第一个数据包在窗口里，开始暂停/if ( base = nextseqnum )/starttimer(A,RTT);/printf(A

22、: start a new timer!n);/ /* update state variables */ 更新状态变量 nextseqnum = nextseqnum+1;/* if window is full */ 如果窗口已经满了elseprintf(A: New message arrives, send window is full,);/* if buffer full, give up and exit*/如果缓冲区满了，停止并退出 if ( msgnum = MAXBUFSIZE)printf ( Error: Sender buffer is full! n);exit (

23、1);/* otherwise, buffer the message */ 否则，缓冲信息elseprintf(buffer new message!n);bufrear = (bufrear+1) % MAXBUFSIZE;for (i=0; i20; i+)bufferbufrear.datai = message.datai;msgnum +;/A端接收数据void A_input(struct pkt packet)struct pkt sendpkt;int i;/* if received packet is not corrupted and ACK is received *

24、/如果接收到的数据包没有被损坏和确认已经被接收了if ( (CheckCorrupted(packet) = FALSE) & (packet.acknum != NACK) printf(A: ACK %d is correctly received,packet.acknum);packet_correct+;/* delete the acked packets from window buffer */删除从窗口缓冲区里的确认数据包winfront = (winfront+(packet.acknum+1-base) % WINDOWSIZE;pktnum = pktnum - (pa

25、cket.acknum+1-base);/* move window base */ 移动窗口底部base = packet.acknum+1;stoptimer(A);if ( base nextseqnum)/starttimer(A,RTT);printf (nnnsend new packets!);/* if buffer is not empty, send new packets */如果缓冲区不空，发送新的数据包while ( (msgnum!=0) & (nextseqnumbase+WINDOWSIZE)/* create packet */ 创建数据包sendpkt.se

26、qnum = nextseqnum;sendpkt.acknum = NOTUSED;buffront = (buffront+1) % MAXBUFSIZE;for ( i=0; i20 ; i+ )sendpkt.payloadi = bufferbuffront.datai;/* computer checksum */ 计算机校验 ComputeChecksum (&sendpkt);/* if it is the first packet in window, start timeout */如果第一个数据包在窗口里，开始暂停if ( base = nextseqnum )/star

27、ttimer(A,RTT);printf (send new packets!n);/* send out packet */ 发送数据包 tolayer3 (A, sendpkt);/* copy the packet to window packet buffer */复制数据包到窗口数据缓冲区winrear = (winrear+1)%WINDOWSIZE;winbufwinrear = sendpkt;pktnum +;/* update state variables */ 更新状态变量 nextseqnum = nextseqnum+1;/* delete message from

28、 buffer */ 删除缓冲区的信息 msgnum -;elseprintf (A: NACK is received, do nothing!n);/B 端接收数据*定 要调用这个/* Note that with simplex transfer from a-to-B, there is no B_output() */* called from layer 3, when a packet arrives for layer 4 at B*/来自第三层，当这个数据包在B中到达第四层时void B_input(struct pkt packet)struct pkt sendpkt;i

29、nt i;/* if not corrupted and received packet is in order */如果没有损坏和接收到的数据包是井然有序的if ( (CheckCorrupted(packet) = FALSE) & (packet.seqnum = expectedseqnum) printf(nB: packet %d is correctly received, sendACK!n”,packet.seqnum);/* send an ACK for the received packet */发送这个接收到的数据包的 确认/* create packet */ 创建

30、数据包sendpkt.seqnum = NOTUSED;sendpkt.acknum = expectedseqnum;for ( i=0; i20 ; i+ )sendpkt.payloadi = 0;/* computer checksum */ 计算机校验 ComputeChecksum (&sendpkt);/* send out packet */发送数据包 /tolayer3 (B, sendpkt);/* update state variables */更新状态变量 expectedseqnum = expectedseqnum+1;printf(B:expectedseqnu

31、m = %dn”,expectedseqnum);/* deliver received packet to layer 5 */ 收到封包传递到第五层 /tolayer5(B,packet.payload);/* otherwise, discard the packet and send a NACK */否则，丢弃这个数 据包和发送否定应答elseprintf(B: packet %d is corrupted or not I expects, sendNACK!n”,packet.seqnum);/* create packet */ 创建数据包 sendpkt.seqnum = N

32、OTUSED;sendpkt.acknum = NACK; for ( i=0; i20 ; i+ ) sendpkt.payloadi = 0;/* computer checksum */ 计算机校验 ComputeChecksum (&sendpkt);/* send out packet */ 发送数据包 tolayer3 (B, sendpkt);/A计时器超时/* called when As timer goes off */ 当 A 时器进行时void A_timerinterrupt() int i;printf(A: time out,resend packets!n);/

33、* start timer */ 开始计时器 starttimer(A,RTT);/* resend all packets not acked */重发没有被确认的所有数据包 for ( i=1; i=pktnum; i+ )packet_resent+;tolayer3(A,winbuf(winfront+i)%WINDOWSIZE);/B计时器超时/* called when Bs timer goes off */ 当 B 时器进行时void B_timerinterrupt()int i;printf(B: time out,resend packets!n);/* start ti

34、mer */ 开始计时器 starttimer(B,RTT);/* resend all packets not acked */重发没有被确认的所有数据包for ( i=1; i0.0：);/fscanf(fp,%f”,&lambda);scanf(%f,&lambda);printf(nEnter TRACE:);/fscanf(fp,%d”,&TRACE);scanf(%d,&TRACE);printf(nn);srand(9999);/* init random number generator */初始化生成器的随机值sum = 0.0;/* test random number g

35、enerator for students */检验学生输入的值for (i=0; i1000; i+)sum=sum+jimsrand(); /* jimsrand() should be uniform in 0,1 */avg = sum/1000.0;/*if(avg 0.75)printf(It is likely that random number generation on your machinen);printf(is different from what this emulator expects. Please taken);printf(a look at the

36、routine jimsrand() in the emulator code. Sorry.n);exit(0);*/printf(%f”,avg);ntolayer3 = 0;nlost = 0;ncorrupt = 0;time=0.0;/* initialize time to 0.0 */generate_next_arrival(); /* initialize event list */随机数发生器float jimsrand()double mmm = 2147483647;/* largest int - MACHINE DEPENDENT!*/最大的中断-与机器相关的flo

37、at x;/* individual students may need to change mmm*/个别学生可能需要改变minmx = rand()/mmm;/* x should be uniform in 0,1 */return(x);/* * /* 事 件 处 理 部 分 * void generate_next_arrival() double x,log(),ceil(); struct event *evptr; char *malloc(); float ttime; int tempint; /if (TRACE2)/printf(GENERATE NEXT ARRIVA

38、L: creating newarrivaln);x = lambda*jimsrand()*2; /* x is uniform on 0,2*lambda */ 要统一值/* having mean of lambda */evptr = (struct event *)malloc(sizeof(struct event); evptr-evtime = time + x; evptr-evtype = FROM_LAYER5;if (jimsrand()eventity = A;elseevptr-eventity = B;insertevent(evptr);向事件列表中插入一条新的

39、事件void insertevent(struct event *p)struct event *q,*qold;if (TRACE2)/printf(INSERTEVENT: time is %lfn”,time);/printf(INSERTEVENT: future time willbe %lfn,p-evtime);q = evlist; /* q points to front of list in which p struct inserted */q指着p结构要插入的列表前面的地方if (q=NULL)/* list is empty */ 列表是空的evlist=p;p-ne

40、xt=NULL;p-prev=NULL;elsefor (qold = q; q !=NULL & p-evtime q-evtime; q=q-next) qold=q;if (q=NULL)/* end of list */ 列表结束qold-next = p;p-prev = qold;p-next = NULL;else if (q=evlist)/* front of list */ 列表前p-next=evlist;p-prev=NULL;p-next-prev=p;evlist = p;else /* middle of list */ 列表中间p-next=q;p-prev=q

41、-prev;q-prev-next=p;q-prev=p;打印事件列表void printevlist()struct event *q; int i;printf(nEvent List Follows:n);for(q = evlist; q!=NULL; q=q-next)printf(Eventtime:%f,type:%dentity: %dn”,q-evtime,q-evtype,q-eventity);printf(n);启动计时器void starttimer(int AorB,float increment)struct event *q;struct event *evpt

42、r;char *malloc();if (TRACE2)printf(nA: START TIMER: starting timer at %fn”,time);/* be nice: check to see if timer is already started, if so, then warn*/最好：检查看看计时器是否已经开始，如果是这样，然后发出警告/* for (q=evlist; q!=NULL & q-next!=NULL; q = q-next) */for (q=evlist; q!=NULL ; q = q-next)if ( (q-evtype=TIMER_INTER

43、RUPT & q-eventity=AorB)/printf(Warning: attempt to start a timer that is already startedn);return;/* create future event for when timer goes off */创建远景即使计时器 停止了evptr = (struct event *)malloc(sizeof(struct event);evptr-evtime = time + increment;evptr-evtype = TIMER_INTERRUPT;evptr-eventity = AorB; in

44、sertevent(evptr);停止计时器/* called by students routine to cancel a previously-started timer */ void stoptimer(int AorB) /* A or B is trying to stop timer */ struct event *q,*qold;if (TRACE2)printf(nA: STOP TIMER: stopping timern);/* for (q=evlist; q!=NULL & q-next!=NULL; q = q-next) */for (q=evlist; q!

45、=NULL ; q = q-next)if ( (q-evtype=TIMER_INTERRUPT & q-eventity=AorB) )/* remove this event */if (q-next=NULL & q-prev=NULL)evlist=NULL;/* remove first and only event on list*/删除第一个和只有一个事件在列表else if (q-next=NULL) /* end of list - there is one in front */ q-prev-next = NULL;else if (q=evlist) /* front

46、 of list - there must be event after */列表有开始就一定会有结束q-next-prev=NULL;evlist = q-next;else /* middle of list */ 列表的中间q-next-prev = q-prev; q-prev-next = q-next;free(q);return;/printf(Warning: unable to cancel your timer. It wasnt running.n);向第三层发送信息/4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*4*

47、 TAT A VT7DQ 4*4*4*4*4*4*4*4*4*4*4*4*4*4*4* / /* TULAYER3 */void tolayer3(int AorB,struct pkt packet)struct pkt *mypktptr;struct event *evptr,*q;char *malloc();float lastime, x, jimsrand();int i;ntolayer3+;/* simulate losses: */ 模拟丢失if (jimsrand() 0)printf(TOLAYER3: packet being lostn);return;/* mak

48、e a copy of the packet student just gave me since he/she may decide*/既然他已经决定，就复制一个学生的数据包给我/* to do something with the packet after we return back to him/her */在我们返回给他后，数据包已经有些改变了mypktptr = (struct pkt *)malloc(sizeof(struct pkt);mypktptr-seqnum = packet.seqnum;mypktptr-acknum = packet.acknum;mypktpt

49、r-checksum = packet.checksum;for (i=0; ipayloadi = packet.payloadi;if (TRACE2)printf(TOLAYER3: seq: %d, ack %d, check: %d ,mypktptr-seqnum,mypktptr-acknum, mypktptr-checksum);for (i=0; ipayloadi);printf();/* create future event for arrival of packet at the other side */创建远景即使数据包到达另一边evptr = (struct

50、event *)malloc(sizeof(struct event);evptr-evtype = FROM_LAYER3; /* packet will pop out from layer3 */ 数据包将会从第三层弹出evptr-eventity = (AorB) % 2; /* event occurs at other entity */事件发生在其他实体evptr-pktptr = mypktptr; /* save ptr to my copy of packet */ 保存指针，该指针指的是我复制的数据包lastime = time;/* for (q=evlist; q!=

51、NULL & q-next!=NULL; q = q-next) */ for (q=evlist; q!=NULL ; q = q-next)if ( (q-evtype=FROM_LAYER3 & q-eventity=evptr-eventity) lastime = q-evtime;evptr-evtime = lastime + 1 + 9*jimsrand();/* simulate corruption: */ 模拟损坏 if (jimsrand() corruptprob) ncorrupt+;if ( (x = jimsrand() payload0=Z; /* corru

52、pt payload */损坏的有效负载else if (x seqnum = 999999;elsemypktptr-acknum = 999999;if (TRACE0) printf(TOLAYER3: packet being corruptedn);/if (TRACE2)/printf(TOLAYER3: scheduling arrival on other siden);insertevent(evptr);向第五层发送信息/* TOLAYER5 */void tolayer5(int AorB,char datasent20) int i;if (TRACE2)printf(

53、TOLAYER5: data received:);for (i=0; i20; i+)printf(%c,datasenti);printf(n);三、GBN-CS.c#include #include GBN.h” extern int TRACE ;extern int nsim ;*/extern int nsimmax;extern float time;extern int packet_correct;extern int packet_resent;extern struct event *evlist;int main()struct event *eventptr;stru

54、ct msg msg2give;struct pkt pkt2give;int i,j;char c;init();A_init();B_init();while (1)eventptr = evlist;/* for my debugging */ 我的调试/* number of messages from 5 to 4 so far/* for my debugging */ 我的调试/* number of messages from 5 to 4 so far至今为止从从第五到第四的数据信息/* number of msgs to generate, then stop */ 将产生

55、大量的信息，然后结束/* get next event to simulate */ 模拟得到的下一个事件evlist = evlist-next; /* remove this event from event list */移动这个事件到事件表中if (evlist!=NULL)evlist-prev=NULL;if (TRACE = 2)printf(nEVENT time: %f,”,eventptr-evtime);printf( type: %d,eventptr-evtype);if (eventptr-evtype=0)printf(, timerinterrupt );els

56、e if (eventptr-evtype=1)printf(, fromlayer5 ”);elseprintf(, fromlayer3 ”);printf( entity: %dn,eventptr-eventity);time = eventptr-evtime;/* update time to next event time*/更新时间到下一次事件时间if (nsim=nsimmax)break; /* all done with simulation */模拟全部做完if (eventptr-evtype = FROM_LAYER5 )generate_next_arrival(

57、); /* set up future arrival */建立远景到来/* fill in msg to give with string of same letter */填写msg给与串字母都相同j = nsim % 26;for (i=0; i2)printf(MAINLOOP: data given to student:);for (i=0; ieventity = A) (A_output(msg2give);else(B_output(msg2give);else if (eventptr-evtype = FROM_LAYER3)pkt2give.seqnum = eventptr-pktptr-seqnum;pkt2give.acknum = eventptr-pktptr-acknum;pkt2give.checksum = eventptr-pktptr-checksum;for