CMPSC335: Fundamentals of Communication Networks Lab 11 (10 points) Objectives The following concepts and skills are demonstrated through this process: 1. Analyzing network packets with Wireshark. 2. Practicing C/C++ programming by utilizing static library to analyzing binary files. 3. Understand TCP Packet format. Lab Activities Please complete all lab activities (1 2) and submit your Lab report to Canvas per the submission instructions given at the end of this document. Lab Activity 1 (3 points) In this activity, you will use Wireshark to analyze network packets. These packets are captured and stored in a pcapng file (tcp.pcapng). Please analyze this file and answer the following questions. Lab Activity 1 Questions Please include answers to the following questions in your Lab report: 1. How many packets are stored in this file? 2. Lets assume the clients IP address is 192.168.1.140 and the servers IP address is 174.143.213.184. What are the ports used by the client and the server? 3. What is the initial sequence number used by the client and the server (Use the raw number)? 4. When this TCP connection is terminated, what is the last sequence number used by the client and the server (Use the raw number)? Lab Activity 2 (7 points) In this activity, you will complete one function (ParseTCPPackets), which parses the pcapng file (tcp.pcapng) and displays the packet information like the format shown in the figure below. Notice that, you only need to output the details of TCP packet header, such as what is shown for Packet #1. Except the Flags, the Checksum, and the Urgent Pointer, the others use the decimal format. Notice the header length, which uses the byte as the unit. So, you need to multiply four with the number read from the packet. Please use the cpp file (Lab11.cpp) as the start point. It is posted on Canvas. This program uses a static library, which can facilitate our analysis. Download this file (linux.zip) and unzip it. Copy all files into the same directory in Kali Linux. Read the ReadMe.txt file for how to use these files. **Hints - When using the function light_get_next_packet, please notice two variables with the types light_packet_header and uint8_t. This function light_get_next_packet has the following signature: int light_get_next_packet (light_pcapng_t *pcapng, light_packet_header *packet_header, const uint8_t **packet_data); The type light_packet_header has the following detinition: typedef struct _light_packet_header { uint32_t interface_id; struct timeval timestamp; uint32_t captured_length; uint32_t original_length; uint16_t data_link; char* comment; uint16_t comment_length; } light_packet_header; Lab Activity 2 Questions Please include answers to the following questions in your Lab report. 1. Include a screenshot of the console output result of Lab11.cpp, which outputs the information like the figure above. Because there are many packets in this pcapng file, the screenshot only needs to include the last three packets. 2. Include the completed Lab11.cpp file. Lab Activity 3 (Optional) In this activity, you will continue the previous activity and verify the checksum in the TCP packet header. The sample output is: (The added text is highlighted with yellow color.) Notice that, when verifying the checksum in the TCP packet header, recap how the checksum is computed. The pseudo header is: The TCP segment length may be odd. So, the last octet is padded on the right with zeros to form a 16-bit for checksum purposes. The previous class video and labs, discussing checksum verification, can be helpful and some code can be reused. Lab Activity 3 - Questions Please include answers to the following questions in your Lab report. 1. Include a screenshot of the console output result, which contains the checksum verification result. Because there are many packets in this pcapng file, the screenshot only needs to include Packet #1 - #5 and Packet #35 - #40. 2. Rename the Lab11.cpp to Lab11Optional.cpp and upload this file. Submission There is a MS-Word Lab report template on Canvas that you can download as a starting point for your Lab submission. There are two sections for you to fill in. Each section corresponds to the two Lab Activities for this Lab. For each section, please give a brief summary of what you did feel free to include any thoughts / concerns / problems / etc. you encountered during the activities. Also, include your answers to the questions asked in each Lab Activity. Save your report as a PDF and submit it to Canvas before the deadline.

Attachments:

lab-11---anal....pdf