12081220+金雨鑫+计网报告7

杭州电子科技大学实验报告学生姓名：金雨鑫学号：12081220指导教师：吴端坡实验地点：第1教研楼108实验时间：第10~12节一、实验室名称：计算机通信与网络实验室二、实验项目名称：DNS,DataEncapsulationandFrame三、实验学时：3学时四、实验原理：○1什么是ICMP？答：ICMP是（InternetControlMessageProtocol）Internet控制报文协议。它是TCP/IP协议族的一个子协议，用于在IP主机、路由器之间传递控制消息。控制消息是指网络通不通、主机是否可达、路由是否可用等网络本身的消息。这些控制消息虽然并不传输用户数据，但是对于用户数据的传递起着重要的作用。如下图所示，ICMP包有一个8字节长的包头，其中前4个字节是固定的格式，包含8位类型字段，8位代码字段和16位的校验和；后4个字节根据ICMP包的类型而取不同的值。○2Wireshark（前称Ethereal）是一个网络封包分析软件。网络封包分析软件的功能是撷取网络封包，并尽可能显示出最为详细的网络封包资料。Wireshark使用WinPCAP作为接口，直接与网卡进行数据报文交换。2.TCP的三次握手和四次挥手：○3ICMP是（InternetControlMessageProtocol）Internet控制报文协议。它是TCP/IP协议族的一个子协议，用于在IP主机、路由器之间传递控制消息。控制消息是指网络通不通、主机是否可达、路由是否可用等网络本身的消息。这些控制消息虽然并不传输用户数据，但是对于用户数据的传递起着重要的作用。○4Tracert（跟踪路由）是路由跟踪实用程序，用于确定IP数据包访问目标所采取的路径。Tracert命令用IP生存时间(TTL)字段和ICMP错误消息来确定从一个主机到网络上其他主机的路由。五、实验目的：1.theIPprotocol,IPfragmentationandre-assembly2.UnderstandTCP3-wayhandshakeforconnectionsetupandtermination,aswellasdataexchange3.UnderstandICMPprotocolandhowthepingprogramworks4.Understandhowtracert(traceroute)programworks六、实验内容：1.StudyWindowstracertprogramandhowtofindaroute;2.IPfragmentation;3.TCPoperations.ActiveOpen:CreateTCB,SendSYNWaitForACKtoSYNWaitForServerReceiveSYN+ACK,SendACKESTABLISHEDCLOSEDSYN-SENTClientStateServerStateCLOSEDSYN-RECEIVEDLISTENESTABLISHEDPassiveOpen:CreateTCBWaitForClientReceiveSYN,SendSYN+ACKWaitForACKtoSYNReceiveACK##ACKSYNSYN+ACK#七、实验器材（设备、元器件）：PC,Wireshark八、实验步骤及结果BackgroundYouneedtoreadandanswerthequestionsinthisbackgroundpartbeforethelab.ReadLecturesonIPandICMPprotocols.ReadLecturesonTCPprotocol.Question1:InIPheader,thereisafieldcalled“protocol(type)”.Whatisitusedfor?答：用来规范数据传输方法，使不同电脑之间可以通信Question2:HowanICMPmessageistransported(encapsulation)?答：ICMP信息封装在IP报文当中。Question3:WhichICMPmessagesareusedtoimplementthePingprogram?答：Echorequestandechoresponse。Ping使用type8requests和type0replies。Question4:Useafiguretoshowthe3-wayhandshaketoestablishaconnectionintheTCPprotocol.答：第一次握手：主机A发送位码为syn＝1,随机产生seqnumber=1234567的数据包到服务器，主机B由SYN=1知道，A要求建立联机；第二次握手：主机B收到请求后要确认联机信息，向A发送acknumber=(主机A的seq+1),syn=1,ack=1,随机产生seq=7654321的包第三次握手：主机A收到后检查acknumber是否正确，即第一次发送的seqnumber+1,以及位码ack是否为1，若正确，主机A会再发送acknumber=(主机B的seq+1),ack=1，主机B收到后确认seq值与ack=1则连接建立成功。完成三次握手，主机A与主机B开始传送数据Traceroute(tracert)isanimportantandusefulutilitytoolfornetworktestinganddebugging.Readmoreonitandlearnhowtouseit:MSWindowstracertcommand,=trueTask1StudyWindowstracertprogramandhowtofindarouteInMSWindows,tracertcanbeusedtofindaroutefromthesourcehost,viarouters,todestinationhost.Thistaskisabouthowtracertworksandhowwecanuseitfor.Followthestepstostartuptheprogramsandcapturethepackets.(1)StartupacommandwindowClickStartontheleftcornerofyourdesktop,andchooseRun.ThentypecmdtostartupaDOScommandwindow.Inthiswindow,youcanalsotypecommandtracert/?tolearnmoreonthecommand,orreadmoreviathelinkabove.(2)StartuptheWireSharkprogramActiveOpen:CreateTCB,SendSYNWaitForACKtoSYNWaitForServerReceiveSYN+ACK,SendACKESTABLISHEDCLOSEDSYN-SENTClientStateServerStateCLOSEDSYN-RECEIVEDLISTENESTABLISHEDPassiveOpen:CreateTCBWaitForClientReceiveSYN,SendSYN+ACKWaitForACKtoSYNReceiveACK##ACKSYNSYN+ACK#StartupWiresharkandbeginpacketcapture.(3)RunthetracertprogramTypethefollowingcommandtofindarouteto(4)StoptheWireSharkcapturingWhentracertends,stopthecapturing,andsavethedatatoafile(youcanopenthefiletoanalyzethepacketslater).(5)Copytheoutputoftracerttothelabreportfile.Byanalyzingtheoutput,wecanlearnaroutefromthesourcetothedestination,andhowabouttheresponsetimebetweenthesourceandintermediaterouters.Question5:Howmanyroutersareontheroutefromyourcomputerto答，通过上面的截图我们可以看到一共有8个路由。○110.66.64.2○2210.32.39.250○360.191.32.65○4218.75.123.233○551.164.31.198○6115.233.23.254○7115.239.209.18○8115.239.210.27（百度服务器的地址）Question6:Basedontheoutputfromthetracert,drawthemapofthenetworksbasedontheoutput.ShowtheIPaddressesforthesourcecomputer,destinationcomputer,androuters.Sourcecomputer：10.66.117.27Destinationcomputer：115.239.210.27Routers：○110.66.64.2○2210.32.39.250○360.191.32.65○4218.75.123.233○551.164.31.198○6115.233.23.254○7115.239.209.18Nowlookatthecaptureddata.(6)analyzethefirstICMPmessageSincetracertusesICMPmessagestotracetheroutetothedestinationcomputer,youcanuse“icmpandip.addr==192.168.x.x”asthedisplayfilerinWireSharktoonlydisplayICMPmessages,where192.168.x.xshouldbeyourcomputerIPaddress.ThenselectthefirstICMPEchoRequestmessagesentbyyourcomputer,andexpandtheInternetProtocolandICMPheadersofthepacketinthepacketdetailswindow(asIdidbelow,tooviewbetter,youcanusezooming).Question7:WhatisthevalueintheprotocoltypefieldofIPpacket?Whyitisthisvalue?WhatisthetypevalueinICMPheader?Whatdoesitmean?HowmanybytesarethereintheIPheader?HowmanybytesarethereinthepayloadoftheIPpacket?Explainhowyoudeterminedthenumberofpayloadbytes.答：IP数据包的协议种类是ICMP。ThevalueintheprotocoltypefieldofIPpacketisICMP(1)ThetpyevalueinICMPheaderis1.意味着无法连接到主机Headerlength：20bytes。Payloadlength：64byte