计算机网络实验报告-ICMP

PAGE－PAGE1－陕西师范大学计算机网络实验报告实验七ICMP一、实验目的1.熟悉并掌握wireshark的操作。2．分析ICMP协议。二、实验器材1.PC机电脑一台。2．下载wireshark软件并安装三、实验内容及问题回答1.ICMPandPing打开wireshark开始抓包在widows命令下输入ping–n10www.ust.hk待ping程序终止，停止wireshark抓包1.WhatistheIPaddressofyourhost?WhatistheIPaddressofthedestinationhost?源和目的IP地址。源和目的IP地址。我的主机的IP地址为：3目的主机的IP地址为：532.WhyisitthatanICMPpacketdoesnothavesourceanddestinationportNumbers答：从课本可知，ICMP用于主机和路由器彼此交互网络层信息。ICMP报文有一个类型字段和一个编码字段，用来表示特定的消息被接收。因为它能解释所有消息，所以ICMP到应用层不需要端口号。3.Examineoneofthepingrequestpacketssentbyyourhost.WhataretheICMPtypeandcodenumbers?WhatotherfieldsdoesthisICMPpackethave?Howmanybytesarethechecksum,sequencenumberandidentifierfields?类型和编码字段类型和编码字段ICMP类型：8（回显请求）ICMP编码：0ICMP报文其他字段包括：checksum(2字节)、identifier（2字节）、sequencenumber（2字节）、sequencenumber(LE)、datafields.4.Examinethecorrespondingpingreplypacket.WhataretheICMPtypeandcodenumbers?WhatotherfieldsdoesthisICMPpackethave?Howmanybytesarethechecksum,sequencenumberandidentifierfields?类型和编码字段类型和编码字段ICMP类型：0（回显回答）ICMP编码：0ICMP报文其他字段包括：checksum(2字节)、identifier（2字节）、sequencenumber（2字节）、sequencenumber(LE)、datafields.2.ICMPandTraceroute1.打开wireshark开始抓包2.在widows命令下输入tracertwww.inria.fr3.待tracert程序终止，停止wireshark抓包截图如下：5.WhatistheIPaddressofyourhost?WhatistheIPaddressofthetargetdestinationhost?答：我的主机IP地址：3目的地主机IP地址：496.IfICMPsentUDPpacketsinstead(asinUnix/Linux),wouldtheIPprotocolnumberstillbe01fortheprobepackets?Ifnot,whatwoulditbe?答：如果ICMP发送UDP数据报，IP协议号应该为0x11.十进制为17，表明交给UDP。7.ExaminetheICMPechopacketinyourscreenshot.IsthisdifferentfromtheICMPpingquerypacketsinthefirsthalfofthislab?Ifyes,howso?ICMP请求回显报文ICMP请求回显报文答：ICMP回显数据报与ping请求数据报有相同的字段。8.ExaminetheICMPerrorpacketinyourscreenshot.IthasmorefieldsthantheICMPechopacket.Whatisincludedinthosefields?其中的ICMP字段其中的IP字段ICMP错误数据报其中的ICMP字段其中的IP字段ICMP错误数据报答：ICMP错误数据报包括;所有IP字段和原来的ICMP字段。9.ExaminethelastthreeICMPpacketsreceivedbythesourcehost.HowarethesepacketsdifferentfromtheICMPerrorpackets?Whyaretheydifferent?类型码和编码都为0类型码和编码都为0答：最后三个ICMP数据报类型码都为0，是回显回答，而不是11（TTL过期），它不同于错误报文段是引文数据报在TTL过期之前已经全部送往目的地。10.Withinthetracertmeasurements,istherealinkwhosedelayissignificantlylongerthanothers?RefertothescreenshotinFigure4,istherealinkwhosedelayissignificantlylongerthanothers?Onthebasisoftherouternames,canyougu