计网实验data-link-layer-simulation

1、?电脑通信与网络实验?课程实验报告实验二 : 2.data link layer simulation实验名称： 2.data link layer simulation2.Simulation on Performance of Data Link Control ProtocolsUsing the same assumptions that are used for Figure 7.13 in Appendix 7A, plot line utilization as a function of P, the probability that a single frame is in

2、error for the following error-control techniques:a. Stop-and-waitb. Go-back-N with w=7c. Go-back-N with w=127d. Selective reject with w=7e. Selective reject with w=127Do all of the preceding for the following values of a: 0.1, 1, 10, 100. Draw conclusions about which technique is appropriate for var

3、ious ranges oaf.2.实验结果V一一IToLFmNEJb jn£NWJZt沖 Wtw f®MDWM 口 inNr-pui-d=v-IDODiSmp rd iQEMiKi-Hwih i NvKha137 'satedM fei *ii r Saterfcq rapid wti * 可A=100a=0.1时，W=7或者127都是大于2a+1;a=1时，W=7或者127都是大于2a+1;a=10时，那么选择拒绝和返回 N都是一个分段函数. a=100时，那么选择拒绝和返回 N都是一个分段函数。3实验程序a = 0:0.1:1000;W = 1,7,127;f

4、or j = 1:3for i = 1:le ngth(a)if W(j) >= 2*a(i)+1U(i) = 1;elseU(i) = W(j)/(2*a(i)+1);endendif j = 1W1 = U;endif j = 2W7 = U;endif j = 3W10 = U;endend plot(a,W1); hold on;plot(a,W7); plot(a,W10); set(gca,'xscale','log'); axis(0.1 1000 0 1);a = 0:0.1:1000;W = 1,7,127,127;P=10A(-3);f

5、or j = 1:4 for i = 1:length(a)if W(j) =1U(i) = (1-P)/(1+2*a(i);endif W(j)=7if W(2) >= 2*a(i)+1U(i) = 1-P;elseU(i) = W(j)*(1-P)/(2*a(i)+1);endendif W(j)=127 if W(j) >= 2*a(i)+1U(i) = (1-P)/(1+2*a(i)*P); Y(i) = 1-P;elseU(i) = W(j)*(1-P)/(2*a(i)+1)*(1-P+W(j)*P);Y(i) = W(j)*(1-P)/(2*a(i)+1);endend

6、if j = 1W1 = U;endif j = 2 W7 = U;endif j = 3W10 = U;endif j = 4 W = Y;endend end plot(a,W1); hold on; plot(a,W7); plot(a,W10); plot(a,W); set(gca,'xscale','log'); axis(0.1 1000 0 1);2、 Drawfunction U=stopandwait(a,P)U=(1-P)./(1+2*a);endfunction U=selective_reject(a,W,P)U=(1-P).*(W&g

7、t;=2*a+1)+W.*(1-P)./(2.*a+1).*(W<2*a+1);endfunction U=gobackn(a,W,P)U=(1-P)./(1+2.*a.*P).*(W>=2*a+1)+W.*(1-P)./(2.*a+1)./(1-P+W.*P).*(W<2*a+1); endfunction lab2_draw(a)P=0:0.1:1000;U=stopandwait(a,P);semilogx(P,U,'r');hold onU=selective_reject(a,7,P);semilogx(P,U,'g');hold onU=gobackn(a,7,P);semilogx(P,U,'b');hold onU=selective_reject(a,127,P); semilogx(P,U,'k'); hold on U=gobackn(a,127,P); semilogx(P,U,'y'); ylabel('Utilization') ; xlabel('P'); legend('Stop-and-wait','Go-back-N with