wireshark抓包实验之UDP(陕师大).doc

实验五 Wireshark Lab: UDP 一、实验目的 1.通过wireshark抓包理解应用层UDP协议。 二、实验器材 1.PC机电脑一台。 2.Wireshark软件。 三、实验内容 1．依照Wireshark Lab 提供的实验步骤完成实验。 2．回答实验中的问题。 四、实验操作实践与步骤 The Assignment 1. Select one packet. From this packet, determine how many fields there are in the UDP header. (Do not look in the textbook! Answer these questions directly from what you observe in the packet trace.) Name these fields. There are 4 fields in the UDP header. They are source port, destination port, length and checksum. 2. From the packet content field, determine the length (in bytes) of each of the UDP header fields. Every length of each of the UDP header fields is (4*4)bits. It is equal to 2B. So the length of each of the UDP header fields is 2B. 3. The value in the Length field is the length of what? Verify your claim with your captured UDP packet. 55=8+47 The value in the Length field is 8 bytes of the UDP header fields and 47 bytes of data fields. 4. What is the maximum number of bytes that can be included in a UDP payload? The maximum number of bytes that can be included in a UDP payload is (2^16-1-8)=65527. 5. What is the largest possible source port number? The largest possible source port number is (2^16-1)=65535. 6. What is the protocol number for UDP? Give your answer in both hexadecimal and decimal notation. (To answer this question, you’ll need to look into the IP header.) 7. Search “UDP” in Google and determine the fields over which the UDP checksum is calculated. The following passage is from the RFC 768. 8. Examine a pair of UDP packets in which the first packet is sent by your host and the second packet is a reply to the first packet. Describe the relationship between the port numbers in the two packets. UDP sent by my host UDP reply to my host The relationship between the port numbers in the two packets is that:the soure port of the UDP packet sent by my host is the same as the destination port of the reply packet to my host; and the dest