《NS运行机制分析》PPT课件.ppt

NS的网络功能实体结构及类结构,Infonet.Lab.Dept.EEISUSTC周晓波20051010,把N门时髦的技术挂在嘴边不如将一门过时的技术记在心里。BBS,Apoorframeworkismuchbetterthannothing.kkzhou,outline,1预修知识2一个最简单的ns仿真的启动过程3Ns的网络实体结构和类结构,1预修知识,C+、Tcl、OTcl的语法,要学透，注意区分类和对象，发现好多问题都是因为OTcl理解不透造成的。,一个仿真例子的操作过程,写场景tcl脚本,temp.tcl运行nstemp.tcl察看仿真过程，是否有错或者是否与预想中的大致相似namtmp.nam分析仿真数据tmp.tr，可以用各种工具,setnsnewSimulatorsettracefdopentmp.trwsetnamfdopentmp.namw$nstrace-all$tracefd$nsnamtrace-all$namfdsetn0$nsnodesetn1$nsnode$nsduplex-link$n0$n11Mb10msDropTailsettcpnewAgent/TCPsetsnknewAgent/TCPSink$nsattach-agent$n0$tcp$nsattach-agent$n1$snksetftpnewApplication/FTP$ftpattach-agent$tcp$nsconnect$tcp$snk$nsat0.1$ftpstart$nsat5.0“exit0$nsrun,注意：仿真的目的。可以认为，对一个协议的改进包括功能和性能两种情况。一般来说是仿真是要分析一个协议的性能。功能性的分析不需要仿真。,例子的仿真结果,+0.2979201tcp1040-00.01.0714-0.2979201tcp1040-00.01.0714+0.2979201tcp1040-00.01.0815r0.3062410ack40-01.00.0411+0.3062401tcp1040-00.01.0916,tmp.tr文件内容节选,V-t*-v1.0a5-a0A-t*-n1-p0-o0 xffffffff-c31-a1A-t*-h1-m2147483647-s0n-t*-a0-s0-SUP-vcircle-cblack-iblackn-t*-a1-s1-SUP-vcircle-cblack-iblackl-t*-s0-d1-SUP-r1000000-D0.029999999999999999-cblack+-t0.1-s0-d1-ptcp-e40-c0-i0-a0-x0.01.00-null-t0.1-s0-d1-ptcp-e40-c0-i0-a0-x0.01.00-nullh-t0.1-s0-d1-ptcp-e40-c0-i0-a0-x0.01.0-1-nullr-t0.13032-s0-d1-ptcp-e40-c0-i0-a0-x0.01.00-null+-t0.13032-s1-d0-pack-e40-c0-i1-a0-x1.00.00-null,tmp.nam文件内容节选,预修知识,C+、Tcl、OTcl的语法,虚拟函数(以c+为例),classApublic:virtualvoidvf()printf(“inA:vf()”);voidf1()printf(“inA:f1()”)voidfA()printf(“inA:fA()”)Private:inta1,a2;classB:publicApublic:virtualvoidvf()printf(“inB:vf”);voidf1()printf(“inB:f1()”)voidfB()printf(“inB:fB()”)private”:intb1,b2;,voidmain()A*pa1=newA;A*pa2;B*pb1=newB;pa1-f1();pa1-fA();pa1-vf();pb1-f1();pb1-fA();pb1-vf();pa2=(A*)pb1;pa2-f1();pa2-fA();pa2-vf();/pa2-fB();,classApublic:virtualvoidvf()printf(“inA:vf()”);voidf1()printf(“inA:f1()”)voidfA()printf(“inA:fA()”)classB:publicApublic:virtualvoidvf()printf(“inB:vf”);voidf1()printf(“inB:f1()”)voidfB()printf(“inB:fB()”),inA:f1(),inA:fA(),inA:vf(),inB:f1(),inA:fA(),inB:vf(),inA:f1(),inA:fA(),inB:vf(),语法出错,类A的实例(对象),Poiter_to_A:vf,Poiter_to_B:vf,A*pa=newA;Pa-xx();,B*pb=newB;Pb-xx();,A*pa=(A*)pb;Pa-xx();,类B的实例(对象),X,预修知识,C+、Tcl、OTcl的语法,要学透，发现好多问题都是因为OTcl理解不透造成的。,动态创建机制(以c+为例),定义：以字符串指定类型(也就是类)，能够创建出对象。例如：已知一个字符串name=“CString”，如何new出一个CString对象用处：很多。是整个复合文档技术的基础，例如word、ppt、pdf等在ns中的用处：在tcl中创建c+对象。例如:setftpnewAgent/UDP创建了OTcl对象Agent/UDP，和c+对象UdpAgent,MFC对动态创建的实现,/B.hclassB:publicADECLARE_DYNCREATE(B);/B.cppIMPLEMENT_DYNCREATE(B,A),#defineDECLARE_DYNCREATE(class_name)DECLARE_DYNAMIC(class_name)staticCObject*PASCALCreateObject();#defineDECLARE_DYNAMIC(class_name)public:staticconstCRuntimeClassclass#class_name;virtualCRuntimeClass*GetRuntimeClass()const;#defineIMPLEMENT_DYNCREATE(class_name,base_class_name)CObject*PASCALclass_name:CreateObject()returnnewclass_name;IMPLEMENT_RUNTIMECLASS(class_name,base_class_name,0 xFFFF,class_name:CreateObject,NULL)#defineIMPLEMENT_RUNTIMECLASS(class_name,base_class_name,wSchema,pfnNew,class_init)AFX_COMDATconstCRuntimeClassclass_name:class#class_name=#class_name,sizeof(classclass_name),wSchema,pfnNew,RUNTIME_CLASS(base_class_name),NULL,class_init;CRuntimeClass*class_name:GetRuntimeClass()constreturnRUNTIME_CLASS(class_name);#defineRUNTIME_CLASS(class_name)_RUNTIME_CLASS(class_name)#define_RUNTIME_CLASS(class_name)(CRuntimeClass*)(virtualCRuntimeClass*GetRuntimeClass()const;staticCObject*PASCALCreateObject();/B.cppIMPLEMENT_DYNCREATE(B,A)CObject*PASCALclass_name:CreateObject()returnnewclass_name;AFX_COMDATconstCRuntimeClassclass_name:class#class_name=#class_name,sizeof(classclass_name),wSchema,pfnNew,(CRuntimeClass*)(,class_name:CreateObject,预设初始值为0 xFFFF,NULL,/B.hclassB:publicApublic:staticconstCRuntimeClassclass#B;virtualCRuntimeClass*GetRuntimeClass()const;staticCObject*PASCALCreateObject();/B.cppCObject*PASCALB:CreateObject()returnnewB;AFX_COMDATconstCRuntimeClassB:class#B=#B,sizeof(classB),0 xFFFF,B:CreateObject,(CRuntimeClass*)(,类A(不是A的对象),？,函数指针,staticCRuntimeClass:pFirstClass,structCRuntimeClassLPCSTRm_lpszClassName;intm_nObjectSize;UINTm_wSchema;CObject*(PASCAL*m_pfnCreateObject)();CRuntimeClass*m_pBaseClass;CRuntimeClass*m_pNextClass;constAFX_CLASSINIT*m_pClassInit;,ns中的动态创建机制,classIdcus:publicAgent;staticclassIdcusClass:TclClasspublic:IdcusClass():TclClass(Agent/Idcus)TclObject*create(int,constchar*const*)return(newIdcus();class_idcus;,classTclClassstaticTclClass*all_;TclClass*next_;OTclClass*class_;constchar*classname_;virtualTclObject*create(intargc,constchar*const*argv);TclClass:TclClass(constchar*classname):class_(0),classname_(classname)if(Tcl:instance().interp()!=NULL)bind();elsenext_=all_;all_=this;,指向队尾,后面会讲详细过程,java中的动态创建呢？,classClass,自己去看看，仔细体会,outline,1预修知识2一个最简单的ns仿真的启动过程3Ns的网络实体结构和类结构,2一个最简单的ns脚本的启动过程,setnsnewSimulatorsetn0$nsnodesetn1$nsnode$nsduplex-link$n0$n11Mb10msDropTailsettcpnewAgent/TCPsetsnknewAgent/TCPSink$nsattach-agent$n0$tcp$nsattach-agent$n1$snksetftpnewApplication/FTP$ftpattach-agent$tcp$nsconnect$tcp$snkprocfinishexit0$nsat0.1$ftpstart$nsat5.0finish$nsrun,一个注意点！,ns的功能实体(完成对数据包的处理)对应一个个c+对象；管理和调度系统由Tcl/OTcl完成。那么数据包是如何从一个对象传递到另一个对象的呢？uptarget_downtarget_就是上面这两个变量(也许名字不同)看代码是要对target_之类的变量多留意例如(下一页)这两个变量是如何被赋值的呢？就是我们要讨论的问题。,Tcl/OTcl是管理者，C+是打工仔！,Ns的类结构,最简单情况下网络实体结构,启动过程0,当命令行运行ns，会创建3个对象_o1,_o2,_o3_o1和_o2是RNG，_o3是Import(tclcl/tcl-import.tcl),simulator:/ins/ns-2.28/idcus$ns%setanewApplication/FTP_o4%_o1infoclassRNG%_o2infoclassRNG%_o3infoclassImport%_o4infoclassApplication/FTP,启动过程1,setnsnewSimulator,#tclcl/tcl-object.tclprocnewclassNameargssetoSplitObjectgetidifcatch$classNamecreate$o$argsmsgifstringmatch_FAILED_SHADOW_OBJECT_$msg#Theshadowobjectfailedtobeallocated.#delete$oreturnglobalerrorInfoerrorclass$className:constructorfailed:$msg$errorInforeturn$o,“Simulatorcreate4”该操作创建一个Simulator对象，并调用它的init函数进行初始化,启动过程1,Simulatorinstprocinitargs,#tcl/lib/ns-lib.tclSimulatorinstprocinitargs$selfcreate_packetformat$selfuse-schedulerCalendar$selfsetnullAgent_newAgent/Null$selfset-address-formatdefiflindex$args0=-multicast$selfmulticast$argseval$selfnext$args,这个还未找到代码位置(找到了)，可以猜想是创建数据包的头标对应的数据结构，创建对象_o5，类型为PacketHeaderManager,创建对象_o6，类型为Scheduler/Calender，一个非常重要的类，单线程的ns能模拟多节点的网络，就是通过它来调度。但是用起来简单，只需要知道“我的一个事件，给定一个时间，交给它，到时候它就会处理”就行了,创建对象_o7，类型为Agent/Null，一个黑洞,#tcl/lib/ns-packet.tclSimulatorinstproccreate_packetformatPacketHeaderManagerinstvartab_setpmnewPacketHeaderManagerforeachclPacketHeaderinfosubclassifinfoexiststab_($cl)setoff$pmallochdr$cl$cloffset$off$selfsetpacketManager_$pm,这一段设置各个头标的offset，这在处理头标的时候会经常用到，例如hdr_ip*hip=hdr_ip:access(p);return(hdr_ip*)p-access(offset_);return(,#tcl/lib/ns-lib.tclSimulatorinstprocuse-schedulertype$selfinstvarscheduler_ifinfoexistsscheduler_if$scheduler_infoclass=Scheduler/$typereturnelsedelete$scheduler_setscheduler_newScheduler/$type$scheduler_now,dbg1.8_o4infoclassSimulatordbg1.9_o5infoclassPacketHeaderManagerdbg1.10_o6infoclassScheduler/Calendardbg1.11_o7infoclassAgent/Nulldbg1.12_o8infoclassAllocAddrBitsdbg1.13_o9infoclassAllocAddrdbg1.14_o10infoclassAddressdbg1.15_o11infoclassinvalidcommandname_o11whileexecuting_o11infoclassdbg1.16dbg1.16,目前为止已经产生了10个对象了,启动过程2,setn0$nsnodesetn1$nsnode,#tcl/lib/ns-lib.tclSimulatorinstprocnodeargs$selfinstvarNode_routingAgent_wiredRouting_satNodeType_#Enable-mcastisnowdoneautomaticallyinsideNode:init#XXXnode_factory_isdeprecated,HOWEVER,sinceitsstillusedby#mobileIP,algorithmicrouting,manualrouting,andbackward#compabilitytestsofhierarchicalrouting,weshouldkeepitaround#beforeallrelatedcodearewipedout.setnodeevalnewSimulatorsetnode_factory_$argssetNode_($nodeid)$node#addtosimulatorsnodelistinC+space$selfadd-node$node$nodeid#setthenodeidinc+Node-ratul$nodenodeid$nodeid$nodesetns_$self$selfcheck-node-numreturn$node,代码没有找到。这一步的所有对象都由这个命令创建(找到了，其实就是newNode),在c+的Simulator对象中加入该node对象,newNode之后，会调用Node类的init函数#tcl/lib/ns-node.tclifllength$args!=0setaddress_lindex$args0elsesetaddress_$id_$selfcmdaddr$address_;$selfmk-default-classifier,显式调用command方法的一个例子。介绍一下command函数,Nodeinstprocmk-default-classifierNodeinstvarmodule_list_#AtminimumweshouldenablebasemoduleforeachmodnameNodesetmodule_list_$selfregister-modulenewRtModule/$modname,Nodeinstprocregister-modulemod$selfinstvarreg_module_$modregister$selfsetreg_module_($modmodule-name)$mod,module_list_是Node的变量！只有Base一个值,RtModule/Baseinstprocregisternode$selfnext$node$selfinstvarclassifier_setclassifier_newClassifier/Hash/Dest32$classifier_setmask_AddrParamsNodeMask1$classifier_setshift_AddrParamsNodeShift1#XXXBaseshouldALWAYSbethefirstmoduletobeinstalled.$nodeinstall-entry$self$classifier_,每一个RtModule/xxx在register函数中都会new一个classifier,Nodeinstprocinstall-entrymoduleclsfrhook$selfinstvarclassifier_mod_assoc_hook_assoc_ifinfoexistsclassifier_ifinfoexistsmod_assoc_($classifier_)$selfunregister-module$mod_assoc_($classifier_)unsetmod_assoc_($classifier_)#Connectthenewclassifiertotheexistingclassifierchain,#ifthereisany.ifinfoexistshook_assoc_($classifier_)if$hook=target$clsfrtarget$hook_assoc($classifier_)elseif$hook!=$clsfrinstall$hook$hook_assoc_($classifier_)sethook_assoc_($clsfr)$hook_assoc_($classifier_)unsethook_assoc_($classifier_)setmod_assoc_($clsfr)$modulesetclassifier_$clsfr,保存最后一次调用时的clsfr,module列表，以classifier为索引,classifier列表，以classifier为索引,Classifierinstprocinstallslotval$selfsetslots_($slot)$val$selfcmdinstall$slot$val,RtModule_3,clfr_3,hook_assoc_(clfr_2),hook_assoc_(clfr_3),mod_assoc_(clfr_3),mod_assoc_(clfr_2),RtModule_2,clfr_2,RtModule_1,clfr_1,hook_assoc_(clfr_1)?,mod_assoc_(clfr_1),Nodeinstprocinsert-entrymoduleclsfrhook$selfinstvarclassifier_mod_assoc_hook_assoc_if$hook!=#Buildaclassifierchainwhenspecifiedsethook_assoc_($clsfr)$classifier_if$hook=target$clsfrtarget$classifier_elseif$hook!=$clsfrinstall$hook$classifier_#Associatethismoduletotheclassifier,soiftheclassifieris#removedlater,wellremovethemoduleaswell.setmod_assoc_($clsfr)$modulesetclassifier_$clsfr,RtModule_3,clfr_3,hook_assoc_(clfr_2),hook_assoc_(clfr_3),mod_assoc_(clfr_3),mod_assoc_(clfr_2),RtModule_2,clfr_2,RtModule_1,clfr_1,hook_assoc_(clfr_1)?,mod_assoc_(clfr_1),RtModuleinstprocregisternode#Attachtonodeandregisterroutingnotifications$selfattach-node$node$noderoute-notify$self$nodeport-notify$self,进入到rtmodule的c+代码中，把该节点的指针交给rtmodule的一个变量,Nodeinstprocroute-notifymodule$selfinstvarrtnotif_if$rtnotif_=setrtnotif_$moduleelse$rtnotif_route-notify$module$modulecmdroute-notify$self,RtModuleinstprocroute-notifymodule$selfinstvarnext_rtm_if$next_rtm_=setnext_rtm_$moduleelse$next_rtm_route-notify$module,把rtmoudule构成链表,Nodeinstprocport-notifymodule$selfinstvarptnotif_lappendptnotif_$module,Node,RtModule/Base,Classifier/Hash/Dest,mod_assoc_(_o13)=_o12,classifier_,entry_,红色是Node的变量,表示对象之间的联系纽带,数据包的传输,dbg1.23setn1$nsnode_o11dbg1.24_o11infoclassNodedbg1.25_o12infoclassRtModule/Basedbg1.26_o13infoclassClassifier/Hash/Destdbg1.28setn2$nsnode_o14dbg1.29_o14infoclassNodedbg1.30_o15infoclassRtModule/Basedbg1.31_o16infoclassClassifier/Hash/Destdbg1.32_o17infoclassinvalidcommandname_o17whileexecuting_o17infoclassdbg1.33,路由模块，如果要加入策略路由的话，或者自己开发路由协议，需要自己开发这个模块。其实该模块的功能是计算路由，而执行路由是由Classifier进行的,路由的执行,插叙：最简单情形下的网络实体,启动过程3,$nsduplex-link$n0$n11Mb10msDropTail,#tcl/lib/ns-lib.tclSimulatorinstprocduplex-linkn1n2bwdelaytypeargs$selfinstvarlink_seti1$n1idseti2$n2idifinfoexistslink_($i1:$i2)$selfremove-nam-linkconfig$i1$i2eval$selfsimplex-link$n1$n2$bw$delay$type$argseval$selfsimplex-link$n2$n1$bw$delay$type$args#ModifiedbyGFRfornix-vectorroutingifSimulatorsetnix-routing#Informnodesofneighbors$n1set-neighbor$n2id$n2set-neighbor$n1id,插叙：单播节点的构造,#tcl/lib/ns-lib.tclSimulatorinstprocsimplex-linkn1n2bwdelayqtypeargsifinfoexistsqueueMap_($qtype)setqtype$queueMap_($qtype)setqnewQueue/$qtypesetlink_($sid:$did)newSimpleLink$n1$n2$bw$delay$q.,这个语句创建Queue/TropTail的一个对象,replacebythefollowing#xxxthisishackyif$qinfoclassinfoheritageErrModule=ErrorModule$head_target$qclassifierelse$head_target$q,Linkinstprocinitsrcdst$selfnext$selfinstvarid_setid_Linksetnl_Linksetnl_expr$id_+1$selfinstvartrace_fromNode_toNode_color_oldColor_setfromNode_$srcsettoNode_$dstsetcolor_blacksetoldColor_blacksettrace_,setqueue_$qsetlink_new$lltype$link_setbandwidth_$bw$link_setdelay_$delay$queue_target$link_$link_target$dstentry$queue_drop-target$drophead_#XXX#putthettlcheckerafterthedelay#sowedonthavetoworryaboutaccounting#forttl-dropswithinthetraceand/ormonitor#fabric#setttl_newTTLChecker$ttl_target$link_target$selfttl-drop-trace$link_target$ttl_,对target_、drop-target_、uptarget_和downtarget_之类的变量要高度注意！因为对它们的赋值决定了数据包的走向。,#Finally,ifrunningamulticastsimulation,#puttheiiffortheneighbornode.if$nsmulticast?$selfenable-mcast$src$dst$nsinstvarsrcRt_ifinfoexistssrcRt_if$srcRt_=1$selfenable-src-rt$src$dst$head_,Queue/DropTail,SimpleLink,DelayLink,TTLCheck,Connector,Connector,target_,target_,target_,target_,Agent/Null,droptarget_,target_,entry_,target_,表示数据包的传输,entry_,fromnode_,tonode_,head_,_o17infoclassQueue/DropTaildbg1.35_o18infoclassSimpleLinkdbg1.36_o19infoclassConnectordbg1.37_o20infoclassConnectordbg1.38_o21infoclassDelayLinkdbg1.39_o22infoclassTTLCheckerdbg1.40_o23infoclassQueue/DropTail,dbg1.41_o24infoclassSimpleLinkdbg1.42_o25infoclassConnectordbg1.43_o26infoclassConnectordbg1.44_o27infoclassDelayLinkdbg1.45_o27infoclassDelayLinkdbg1.46_o28infoclassTTLCheckerdbg1.47_o29infoclassinvalidcommandname_o29whileexecuting_o29infoclassdbg1.48,启动过程4,settcpnewAgent/TCPsetsnknewAgent/TCPSink在tcl/lib/ns-agent.tcl中,Agent/TCPinstprociniteval$selfnextsetnsSimulatorinstance$nscreate-eventtraceEvent$self,ClassAgent/Null-superclassAgentAgent/Nullinstprocinitargseval$selfnext$args,dbg1.55settcpnewAgent/TCP_o29dbg1.56_o29infoclassAgent/TCPdbg1.57_o30infoclassinvalidcommandname_o30whileexecuting_o30infoclassdbg1.58setnulnewAgent/TCPSink_o30dbg1.59_o30infoclassAgent/TCPSinkdbg1.60_o31infoclassinvalidcommandname_o31whileexecuting_o31infoclassdbg1.61,启动过程5,setftpnewApplication/FTP没有相关代码，说明都使用默认情况：简单new一个对象而已,dbg1.61setftpnewApplication/FTP_o31dbg1.62_o31infoclassApplication/FTPdbg1.63_o32infoclassinvalidcommandname_o32whileexecuting_o32infoclassdbg1.64,启动过程6,$nsattach-agent$n0$tcp$nsattach-agent$n1$snk这一步非常重要，也非常复杂。因为这一步完成了路由模块的加载Agent和node的连接,#tcl/lib/ns-lib.tclSimulatorinstprocattach-agentnodeagent$nodeattach$agent,%_o33infoclassClassifier/Port%_o32infoclassClassifier/Port%_o34infoclassinvalidcommandname_o34,这两步创建了两个对象,#tcl/lib/ns-node.tclNodeinstprocattachagentport$selfinstvaragents_address_dmux_lappendagents_$agent$agentsetnode_$self$agentsetagent_addr_AddrParamsaddr2id$address_if$dmux_=“”#会进入这里，因为还没有给dmux赋过值#Usethedefaultmask_andport_valuessetdmux_newClassifier/Port#pointthenodesroutingentrytoitself#attheportdemuxer(ifthereisone)$selfadd-route$address_$dmux_#把到自己的路由加入进去if$port=“”#会进入，因为一般不指定端口setport$dmux_alloc-portSimulatorinstancenullagent$agentsetagent_port_$port$selfadd-target$agent$port,把该agent加到node的agent列表,插叙：Ns的IP地址,/classifier/classifier.ccif(strcmp(argv1,alloc-port)=0)intslot;NsObject*nullagent=(NsObject*)TclObject:lookup(argv2);slot=getnxt(nullagent);tcl.resultf(%u,slot);return(TCL_OK);,就像维护序列号一样，分配的port都是在它的port的基础上加1,不清楚具体操作,Nodeinstprocadd-targetagentport$selfinstvarptnotif_foreachm$selfsetptnotif_$mattach$agent$port,Ptnodif_是路由模块组成的数组。这里通过attach把agent加入到每个路由模块的路由表。是否应该是dmux_的映射表？,RtModuleinstprocattachagentport$agenttarget$selfnodeentry$selfnodedemuxinstall$port$agent,RtModuleinstprocadd-routedsttarget$selfinstvarnext_rtm_$selfsetclassifier_install$dst$targetif$next_rtm_!=$next_rtm_add-route$dst$target,Nodeinstprocadd-routedsttarget$selfinstvarrtnotif_if$rtnotif_!=$rtnotif_add-route$dst$target$selfincr-rtgtable-size,Classifierinstprocinstallslotval$selfsetslots_($slot)$val$selfcmdinstall$slot$val,进入classifier的c+代码,有两个变量要引起注意：rtnotif_和前面提到的ptnotif_；我觉得rtnotif_是路由模块，ptnotif_是端口映射模块。有相关函数(类似route-notify函数)port-notify，但没有看到调用的地方(在RtModule的register函数中调用了，也就是说在路由模块既负责寻路又负责端口的对应，后者只是一个虚名，还是由Classifier/Port自己完成的)。,xxx-notify函数就是把路由模块对象加入到相应的数组中，即ptnotif_和rtnotif_,Node,RtModule/Base,Classifier/Hash/Dest,mod_assoc_(classifier_),classifier_,entry_,红色是Node的变量,表示对象之间的联系纽带,数据包的传输,Classifier/Port,dmux_,Agent,启动过程7,$ftpattach-agent$tcp很简单，不创建对象，直接进入c+代码把ftp和tcp连接起来把c+的tcp对象的app_变量赋为ftp的c+对象把c+的ftp对象的agent_变量赋为tcp的c+对象,启动过程8,$nsconnect$tcp$snk不创建对象,Simulatorinstprocconnectsrcdst$selfsimplex-connect$src$dst$selfsimplex-connect$dst$srcreturn$src,%$nsconnect$tcp$snk_o29%_o29infoclassAgent/TCP,Simulatorinstprocsimplex-connectsrcdst$srcsetdst_addr_$dstsetagent_addr_$srcsetdst_port_$dstsetagent_port_return$src,启动过程9,$nsat0.1$ftpstart“$nsat5.0“exit0“$nsrun,Simulatorinstprocatargs$selfinstvarscheduler_returneval$scheduler_at$args,%$nsat0.1$ftpstart1%$nsat10.0exit02%,进入scheduler.cc,11:Simulatorinstanceget-link-head01dbg11.35n11:Simulatorinstancedbg11.3611:Simulatorinstanceget-link-head10,在启动的过程中，我们没有找到把节点出口和链路的入口连接起来的操作；但是，当运行起来后，即$nsrun之后，会运行下面这样一些tcl代码。,返回SimpleLink的一个变量head_,Node的结构,Simulatorinstprocrun$selfcheck-smac$selfcheck-node-num$selfrtmodel-configure$selfget-routelogicconfigure$selfinstvarscheduler_Node_link_started_setstarted_1foreachnnarraynamesNode_$Node_($nn)resetifSimulatorsetnix-routing$Node_($nn