计算机网络实验报告 ICMP

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. ICMP and Ping

1. 打开wireshark开始抓包

2. 在widows命令下输入ping –n 10

3. 待ping程序终止，停止wireshark抓包

1. What is the IP address of your host? What is the IP address of the destination

host?

我的主机的IP地址为：10.2.136.33 目的主机的IP地址为：202.117.145.153

2. Why is it that an ICMP packet does not have source and destination port Numbers

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. Examine one of the ping request packets sent by your host. What are the ICMP type and code numbers? What other fields does this ICMP packet have? How many bytes are the checksum, sequence number and identifier fields?

ICMP类型：8（回显请求） ICMP编码：0

ICMP报文其他字段包括：checksum(2字节)、identifier（2字节）、sequence number（2字节）、sequence number (LE)、data fields.

4. Examine the corresponding ping reply packet. What are the ICMP type and code numbers? What other fields does this ICMP packet have? How many bytes are the

checksum, sequence number and identifier fields?

ICMP类型：0（回显回答） ICMP编码：0

ICMP报文其他字段包括：checksum(2字节)、identifier（2字节）、sequence number（2字节）、sequence number (LE)、data fields.

2. ICMP and Traceroute

1.打开wireshark开始抓包

2.在widows命令下输入tracert www.inria.fr 3.待tracert程序终止，停止wireshark抓包 截图如下：

5. What is the IP address of your host? What is the IP address of the target destination host?

答：我的主机IP地址：10.2.136.33

目的地主机IP地址：193.51.193.149

6. If ICMP sent UDP packets instead (as in Unix/Linux), would the IP protocol number still be 01 for the probe packets? If not, what would it be? 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. Examine the ICMP echo packet in your screenshot. Is this different from the

ICMP ping query packets in the first half of this lab? If yes, how so?

答：ICMP回显数据报与ping 请求数据报有相同的字段。

8. Examine the ICMP error packet in your screenshot. It has more fields than the

ICMP echo packet. What is included in those fields?

答：ICMP错误数据报包括;所有IP字段和原来的ICMP字段。

9. Examine the last three ICMP packets received by the source host. How are these

packets different from the ICMP error packets? Why are they different?

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. Within the tracert measurements, is there a link whose delay is signific

antlylonger than others? Refer to the screenshot in Figure 4, is there a link whose delay is significantly longer than others? On the basis of the router names, can you guess the location of the two routers on the end of this link?

答：从上面截图可以看到，在第12和13步间的延时比较大，这个链接是位于中国和荷兰的路由器上。