计网UDP.doc

陕西师范大学计算机网络实验报告年级： 姓名：学号： 实验日期：实验名称：Wireshark Lab: UDP一、 实验目的1. 掌握用Wireshark工具跟踪UDP协议进行抓包分析的方法。2. 通过实验，进一步了解UDP协议。二、 实验器材1. 与因特网连接的PC机电脑一台，主机操作系统为Windows2007或者WindowsXP。2. 下载Wireshark软件(网络封包分析软件)，并安装。三、 实验内容1. 通过使用nslookup查询域名，Wireshark抓包工具抓包并分析这些UDP报文里的内容。四、 实验操作实践与步骤1. 输入命令提示符cmd，并在命令行下输入nslookup www.*.com2. 打开Wireshark，开始抓包。3. 当nslookup程序结束后，停止抓包。如下图-1，图-2所示。图-1图-21. Select one UDP packet from your trace. From this packet, determine how manyfields there are in the UDP header. (You shouldnt look in the textbook! Answerthese questions directly from what you observe in the packet trace.) Name thesefields.答：有4个字段。2. By consulting the displayed information in Wiresharks packet content field forthis packet, determine the length (in bytes) of each of the UDP header fields.答：每个UDP头部字段长度为16 bit，2个字节。3. The value in the Length field is the length of what? (You can consult the text forthis answer). Verify your claim with your captured UDP packet.答：长度是80字节4. What is the maximum number of bytes that can be included in a UDP payload?(Hint: the answer to this question can be determined by your answer to 2. above)答：1500204=1476字节。5.What is the largest possible source port number? (Hint: see the hint in 4.)答：最大源端口号为529036. What is the protocol number for UDP? Give your answer in both hexadecimal anddecimal notation. To answer this question, youll need to look into the Protocolfield of the IP datagram containing this UDP segment (see Figure 4.13 in the text,and the discussion of IP header fields).答：UDP号码十进制为17，十六进制为11。7. Examine a pair of UDP packets in which your host sends the first UDP packet andthe second UDP packet is a reply to this first UDP packet. (Hint: for a secondpacket to be sent in response to a first packet, the sender of the first packet shouldbe the destination of the second packet). Describe the relationship