计算机网络原理GBN协议代码

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1、、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 and write a routine called B_output */* a msg is the data unit passed from layer 5 (teachers code) to layer4 (students code). It contains the data (characters) to be delivered to layer 5 via t

2、he students transport level protocol entities. */ struct msg char data20;/* a packet is the data unit passed from layer 4 (students code) to layer3 (teachers code). Note the pre-defined packet structure, which all students must follow. */struct pktint seqnum;int acknum;int checksum;char payload20;#d

3、efine WINDOWSIZE 8 #define MAXBUFSIZE 50 #define RTT 15.0 #define NOTUSED 0 #define NACK -1 #define TRUE 1 #define FALSE 0 #define A 0 #define B 1/ 网络仿真部分数据结构声明* struct eventfloat evtime;int evtype;int eventity; struct pkt *pktptr; struct event *prev;/* event time */* event type code */* entity wher

4、e event occurs */* ptr to packet (if any) assoc w/ this event */struct event *next; ;/* possible events: */#define TIMER_INTERRUPT 0#defineFROM_LAYER51#defineFROM_LAYER32#defineOFF0#defineON1/ 基 础 功能模块的函数声void ComputeChecksum(struct pkt *packet); 计算校验和 int CheckCorrup ted(s truct pkt packe t); 检査数据是

5、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_timerinterrupt();void B_init();/ 网 络 仿 真 部 分 的 函 数 声 明*void init(); /初始化仿真器float ji

6、msrand(); 随机数发生器0,1/ 处 理 事 件 列 表 部 分 的 函 数 声 明*void genera te_next_arrival(); 产生下一个到达的分组void inser tevent(s truct event *p);向事件列表中插入一条新的事件void printevlis t(); 打印事件列表void st op timer(int);/停止计时器void st ar tt imer(int,floa t); 启动计时器/*/* 网 络 各 层 之 间 传 送 模 块void tolayer3(int AorB,struct pkt packet) ; /向

7、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 /* for my debugging */*numberofmessagesfrom5to4sofar/* number of msgs to generate, then stopextern int TRACE = 1;extern int nsim = 0;*/extern int nsimmax = 0;*/extern float time = 0.000;float los

8、sprob; float corruptprob;*/* probability that a packet is dropped */ /*probabilitythatonebitispacketisflippedfloat lambda;int ntolayer3;static int nlost = 0;static int ncorrupt = 0;/* arrival rate of messages from layer 5 */* number sent into layer 3 */* number lost in media */* number corrupted by

9、media*/static int expectedseqnum = 0; /* expected sequence number at receiver side */static int nextseqnum; /* next sequence number to use in sender side */static int base; /* the head of sender window */struct pkt winbufWINDOWSIZE; /* window packets buffer */static int winfront,winrear; /* front an

10、d rear points of window buffer */static int pktnum; /* packet number of window buffer */struct msg bufferMAXBUFSIZE; /* sender message buffer */int buffront,bufrear; /* front and rear pointers of buffer */ static int msgnum; /* message number of buffer */int packet_lost =0;int packet_corrupt=0;int p

11、acket_sent =0;extern int packet_correct=0;extern int packet_resent =0;int packet_timeout=0;extern struct event *evlist = NULL; /* the event list */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);check

12、sum = 0-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);elsereturn (

13、TRUE);/A端向外发送数据/* called from layer 5, passed the data to be sent to other side */ void A_output(struct msg message)int i;struct pkt sendpkt;/* if window is not full */if ( nextseqnum base+WINDOWSIZE )printf(A: New message arrives, send window is not full, send newmessge to layer3!n);/* create packe

14、t */ sendpkt.seqnum = nextseqnum; sendpkt.acknum = NOTUSED;for ( i=0; i20 ; i+ )sendpkt.payloadi = message.datai;/* computer checksum */ ComputeChecksum (&sendpkt);/* send out packet */ tolayer3 (A, sendpkt);/* copy the packet to window packet buffer */ winrear = (winrear+1)%WINDOWSIZE;pktnum +; win

15、bufwinrear = sendpkt;for (i=0; i20; i+) winbufwinrear.payloadi= sendpkt.payloadi;/* update state variables */ nextseqnum = nextseqnum+1; starttimer(A,RTT);B_input(sendpkt);A_input(sendpkt);/* if window is full */elseprintf(A: New message arrives, send window is full,);/* if buffer full, give up and

16、exit*/ if ( msgnum = MAXBUFSIZE)printf ( Error: Sender buffer is full! n); exit (1);/* otherwise, buffer the message */ else printf(buffer new message!n); bufrear = (bufrear+1) % MAXBUFSIZE;for (i=0; i20; i+)bufferbufrear.datai = message.datai;msgnum +;/B端向外发送数据/* called from layer 5, passed the dat

17、a to be sent to other side */ void B_output(struct msg message)int i;struct pkt sendpkt;/* if window is not full */if ( nextseqnum base+WINDOWSIZE )printf(A: New message arrives, send window is not full, send newmessge to layer3!n);/* create packet */ sendpkt.seqnum = nextseqnum; sendpkt.acknum = NO

18、TUSED;for ( i=0; i20 ; i+ ) sendpkt.payloadi = message.datai;/* computer checksum */ ComputeChecksum (&sendpkt);/* send out packet */ tolayer3 (A, sendpkt);A_input(sendpkt);/* copy the packet to window packet buffer */ winrear = (winrear+1)%WINDOWSIZE;pktnum +; winbufwinrear = sendpkt;for (i=0; i20;

19、 i+) winbufwinrear.payloadi= sendpkt.payloadi;/* if it is the first packet in window, start timeout */ /if ( base = nextseqnum )/starttimer(A,RTT);/printf(A: start a new timer!n);/ /* update state variables */ nextseqnum = nextseqnum+1;/* if window is full */elseprintf(A: New message arrives, send w

20、indow is full,);/* if buffer full, give up and exit*/if ( msgnum = MAXBUFSIZE)printf ( Error: Sender buffer is full! n); exit (1);/* otherwise, buffer the message */ else printf(buffer new message!n); bufrear = (bufrear+1) % MAXBUFSIZE;for (i=0; i20; i+)bufferbufrear.datai = message.datai; msgnum +;

21、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 */ if ( (CheckCorrupted(packet) = FALSE) & (packet.acknum != NACK) ) printf(A: ACK %d is correctly received,packet.acknum);packet_correct+;/* delete the acked packets from window

22、buffer */winfront = (winfront+(packet.acknum+1-base) % WINDOWSIZE;pktnum = pktnum - (packet.acknum+1-base);/* move window base */base = packet.acknum+1;stoptimer(A);if ( base nextseqnum)/starttimer(A,RTT);printf (nnnsend new packets!);/* if buffer is not empty, send new packets */while ( (msgnum!=0)

23、 & (nextseqnumbase+WINDOWSIZE) )/* create packet */sendpkt.seqnum = nextseqnum;sendpkt.acknum = NOTUSED;buffront = (buffront+1) % MAXBUFSIZE;for ( i=0; i20 ; i+ )sendpkt.payloadi = bufferbuffront.datai;/* computer checksum */ComputeChecksum (&sendpkt);/* if it is the first packet in window, start ti

24、meout */ if ( base = nextseqnum )/starttimer(A,RTT);printf (send new packets!n);/* send out packet */ tolayer3 (A, sendpkt);/* copy the packet to window packet buffer */ winrear = (winrear+1)%WINDOWSIZE; winbufwinrear = sendpkt;pktnum +;/* update state variables */ nextseqnum = nextseqnum+1;/* delet

25、e message from buffer */ msgnum -;elseprintf (A: NACK is received, do nothing!n);/B 端接收数据*一定 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*/ void B_input(struct pkt packet)struct pkt sendpkt;int i;/* if n

26、ot corrupted and received packet is in order */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 */* create packet */ sendpkt.seqnum = NOTUSED;sendpkt.acknum = expectedse

27、qnum; for ( i=0; i20 ; i+ )sendpkt.payloadi = 0;/* computer checksum */ComputeChecksum (&sendpkt);/* send out packet */tolayer3 (B, sendpkt);/* update state variables */expectedseqnum = expectedseqnum+1;printf(B:expectedseqnum = %dn,expectedseqnum);/* deliver received packet to layer 5 */ /tolayer5(

28、B,packet.payload);/* otherwise, discard the packet and send a NACK */elsesendprintf(B: packet %d is corrupted or not I expects,NACK!n,packet.seqnum);/* create packet */sendpkt.seqnum = NOTUSED;sendpkt.acknum = NACK;for ( i=0; i20 ; i+ ) sendpkt.payloadi = 0;/* computer checksum */ComputeChecksum (&s

29、endpkt);/* send out packet */tolayer3 (B, sendpkt);/A计时器超时/* called when As timer goes off */void A_timerinterrupt()int i;printf(A: time out,resend packets!n);/* start timer */starttimer(A,RTT);/* resend all packets not acked */ for ( i=1; i=pktnum; i+ ) packet_resent+;tolayer3(A,winbuf(winfront+i)%

30、WINDOWSIZE); /B 计时器超时/* called when Bs timer goes off */ void B_timerinterrupt()int i;printf(B: time out,resend packets!n);/* start timer */ starttimer(B,RTT);/* resend all packets not acked */ for ( i=1; i0.0: );/fscanf(fp,%f,&lambda);scanf(%f,&lambda);printf(nEnter TRACE: ); /fscanf(fp,%d,&TRACE);

31、 scanf(%d,&TRACE);printf(nn);srand(9999); /* init random number generator */ sum = 0.0; /* test random number generator for students */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

32、 your machinen ); printf(is different from what this emulator expects. Please taken); printf(a look at the 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

33、 event list */随机数发生器float jimsrand()double mmm = 2147483647; /* largest int - MACHINE DEPENDENT! */float x;*/x = rand()/mmm;/* individual students may need to change 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;ch

34、ar *malloc();float ttime;int tempint;/if (TRACE2)/printf(GENERATE NEXT ARRIVAL: creating newarrivaln);x = lambda*jimsrand()*2; /* x is uniform on 0,2*lambda */* having mean of lambda */evptr = (struct event *)malloc(sizeof(struct event); evptr-evtime = time + x;evptr-evtype = FROM_LAYER5;if (jimsran

35、d()eventity = A;else evptr-eventity = B;insertevent(evptr);/向事件列表中插入一条新的事件 void insertevent(struct event *p) struct event *q,*qold;if (TRACE2)/printf( INSERTEVENT: time is %lfn,time);/printf( INSERTEVENT: future time will be %lfn,p-evtime);q = evlist; */* q points to front of list in which p struct

36、inserted if (q=NULL)/* list is empty */evlist=p;p-next=NULL;p-prev=NULL;elsefor (qold = q; q !=NULL & p-evtime q-evtime; q=q-next) qold=q;if (q=NULL)/* end of list */qold-next = p;p-prev = qold;p-next = NULL;else if (q=evlist)/* front of list */ p-next=evlist; p-prev=NULL; p-next-prev=p; evlist = p;

37、else /* middle of list */p-next=q;p-prev=q-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(Event time: %f, type: entity: %dn,q-evtime,q-evtype,q-eventity);printf(n);/启动计时器void starttimer(int AorB,floa

38、t increment)struct event *q;struct event *evptr;char *malloc();if (TRACE2)printf(nA: START TIMER: starting timer at %fn,time);%dwarn/* be nice: check to see if timer is already started, if so, then */* for (q=evlist; q!=NULL & q-next!=NULL; q = q-next) */ for (q=evlist; q!=NULL ; q = q-next)if ( (q-

39、evtype=TIMER_INTERRUPT & q-eventity=AorB) )/printf(Warning: attempt to start a timer that is already startedn);return;/* create future event for when timer goes off */ evptr = (struct event *)malloc(sizeof(struct event); evptr-evtime = time + increment;evptr-evtype = TIMER_INTERRUPT;evptr-eventity =

40、 AorB; insertevent(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=e

41、vlist; q!=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*/else if (q-next=NULL) /* end of list - there is one in front */ q-prev-next = NULL;else if (q=evlist) /* front of

42、list - there must be event after*/q-next-prev=NULL; evlist = q-next;else /* middle of list */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/aaaaaaaaaaaaaaaaaaaaaaaaaa TCT A VT7D Q aaaaaaaaaaaaaaa /* TOLAYER3 */voi

43、d tolayer3(int AorB,struct pkt packet)struct pkt *mypktptr;struct event *evptr,*q;char *malloc();float lastime, x, jimsrand();int i;ntolayer3+;/* simulate losses: */if (jimsrand() 0)printf( TOLAYER3: packet being lostn);return;/* make a copy of the packet student just gave me since he/she may decide

44、 */* to do something with the packet after we return back to him/her */ mypktptr = (struct pkt *)malloc(sizeof(struct pkt);mypktptr-seqnum = packet.seqnum;mypktptr-acknum = packet.acknum; mypktptr-checksum = packet.checksum;for (i=0; ipayloadi = packet.payloadi;if (TRACE2)printf( TOLAYER3: seq: %d,

45、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 */ evptr = (struct event *)malloc(sizeof(struct event);evptr-evtype = FROM_LAYER3; /* packet will pop out from layer3 */ evptr-eventity =

46、 (AorB) % 2; /* event occurs at other entity */ evptr-pktptr = mypktptr; /* save ptr to my copy of packet */ /* finally, compute the arrival time of packet at the other end. medium can not reorder, so make sure packet arrives between 1 and 10 time units after the latest arrival time of packets curre

47、ntly in the medium on their way to the destination */lastime = time;/* for (q=evlist; q!=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 corruptio

48、n: */if (jimsrand() corruptprob)ncorrupt+;if ( (x = jimsrand() payload0=Z; /* corrupt payload */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

49、息/* TOLAYER5 */void tolayer5(int AorB,char datasent20)int i;if (TRACE2)printf( TOLAYER5: data received: );for (i=0; i20; i+)printf(%c,datasenti);printf(n);三、GBN-CS.c#include extern int TRACE ;/* for my debugging */* number of messages from 5 to 4 so far/* number of msgs to generate, then stop */#inc

50、lude GBN.hextern 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;struct msg msg2give;struct pkt pkt2give;int i,j;char c;init();A_init();B_init();while (1)eventptr = evlist; /* get next e

51、vent to simulate */ if (eventptr=NULL)goto terminate;evlist = evlist-next; /* remove this event from event list */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 );else if (even

52、tptr-evtype=1) printf(, fromlayer5 );elseprintf(, fromlayer3 );printf( entity: %dn,eventptr-eventity);time = eventptr-evtime; /* update time to next event time */if (nsim=nsimmax)break; /* all done with simulation */if (eventptr-evtype = FROM_LAYER5 ) generate_next_arrival(); /* set up future arriva

53、l */* fill in msg to give with string of same letter */ j = nsim % 26;for (i=0; i2)printf( MAINLOOP: data given to student: ); for (i=0; ieventity = A)A_output(msg2give);elseB_output(msg2give);else if (eventptr-evtype = FROM_LAYER3)pkt2give.seqnum = eventptr-pktptr-seqnum; pkt2give.acknum = eventptr-pktptr-acknum; pkt2give.checksum = eventptr-pktptr-checksum; for (i=0; ipktptr-payloadi;if (eventptr-eventity = A)A_input(pkt2give);elseB_input(pkt2give);free(eventptr-pktptr);else if (eventptr-evtype = TIMER_INTERRUPT) if