How to Tackle Network Administration Assignments with Ease

Step 1: Understanding the Assignment Requirements

The first step in solving a computer network assignment is to thoroughly review the requirements and guidelines provided by the instructor. This includes identifying the necessary software tools, such as Wireshark, ping, or traceroute, that will be used in the assignment. Students should also focus on understanding the specific tasks, such as packet analysis, network diagram creation, and TCP flow interpretation. It is essential to note the expected outputs (e.g., tables, diagrams, numerical calculations) and follow any formatting instructions, such as including screenshots or written explanations. Understanding these requirements ensures a focused approach to the assignment and prevents overlooking any critical aspects of the task. Key areas to focus on include:

• Required software (e.g., Wireshark, traceroute, ping)
• Expected outputs (e.g., network diagrams, tables, numerical calculations)
• Specific network components to analyze (e.g., MAC addresses, IP addresses, ports, RTT values)
• Formatting requirements for responses (e.g., screenshots, tables, written explanations)

Step 2: Capturing and Analyzing Packets in Wireshark

Once the assignment requirements are clear, the next step is capturing and analyzing network packets using Wireshark. To do this, students should first open the provided packet capture file (.pcap) in Wireshark and apply relevant filters (e.g., IP or TCP). Analyzing MAC and IP addresses helps identify the source and destination of network traffic, which is crucial for building a network topology. Additionally, students should examine the packet headers to understand the structure and flow of data across the network, allowing them to map out the communication paths between devices such as routers, servers, and clients. Network assignments often involve analyzing packet captures (.pcap or .pcapng files). Follow these steps:

• Open the Provided Packet Capture File
• Use Wireshark to load the .pcap file.
• Apply necessary filters (e.g., tcp, ip.addr==X.X.X.X) to focus on relevant traffic.
• Examine MAC and IP Addresses
• Identify source and destination MAC addresses for each packet.
• Identify IP addresses and categorize them as client, server, or router.
• Cross-reference IP addresses with known hostnames using nslookup if required.
• Create a Network Diagram
• Represent network elements (routers, switches, PCs, servers) based on observed addresses.
• Indicate interconnections and label addresses accordingly.

Step 3: Interpreting TCP Flow Data

Interpreting TCP flow data is an essential step in many network assignments, as it reveals how communication is established and maintained between devices. To do this, students can use Wireshark’s “Follow TCP Stream” feature to isolate individual conversations between devices. By documenting key details like source and destination IP addresses, port numbers, and sequence numbers, students can track the behavior of each TCP connection. A key part of the analysis is evaluating the three-way handshake process (SYN, SYN-ACK, ACK) and calculating the duration of the handshake, which provides insights into network latency and performance. Many assignments require analysis of TCP sessions. Follow these steps:

• Identify TCP Streams
• Use the Follow TCP Stream feature in Wireshark to isolate conversations.
• Record key details like source and destination addresses, port numbers, and sequence numbers.
• Build a TCP Flow Table
• Document the number of TCP flows.
• Record attributes such as packet number, source and destination addresses, ports, and options (Window Size, MSS, WS, SACK).
• Measure TCP Handshake Duration
• Locate the three-way handshake packets (SYN, SYN-ACK, ACK) and calculate the time difference between the first and last handshake packets.

Step 4: Analyzing DNS Resolution and HTTP Performance

Another important task in network assignments is analyzing DNS resolution and HTTP performance. Students should identify DNS request and response packets to evaluate domain name resolution times. By calculating the delay between the query and the response, they can assess DNS performance. Similarly, students should examine HTTP packets, particularly the GET and OK responses, to calculate round-trip time (RTT) and download performance. By measuring the RTT and transfer rates, students can identify bottlenecks in web traffic, helping to evaluate network efficiency and optimize communication paths for better performance.

• Extract DNS Query and Response Details
• Identify the DNS request packet and its corresponding response.
• Note the queried domain name and the returned IP address.
• Calculate the DNS lookup delay (difference between query timestamp and response timestamp).
• Measure HTTP RTT and Download Performance
• Locate HTTP GET and HTTP OK packets.
• Compute the RTT as the time difference between these packets.
• Determine the total file download time and estimate the transfer rate (bytes per second, bits per second).

Step 5: Using Traceroute to Analyze Network Paths

Traceroute is a valuable tool for analyzing the path data takes through a network. By using the “tracert” command on Windows or “traceroute” on Linux/macOS, students can trace the route packets take to reach a specific server or domain. This helps identify network hops, which are intermediate routers or switches, and the round-trip times (RTT) for each hop. Analyzing RTT values can highlight delays at specific points in the network, helping students troubleshoot performance issues and understand the efficiency of long-distance connections, such as trans-oceanic routes.

• Run Traceroute to a Target Server
• Use tracert (Windows) or traceroute (Linux/macOS) to track the path to a given domain.
• Increase the maximum hop limit if necessary (-h flag in Windows).
• Analyze Per-Hop RTT Delays
• Identify routers along the path and their corresponding RTT values.
• Focus on hops with RTT > 10ms for deeper analysis.
• Estimate the one-way propagation delay for long-distance links (e.g., trans-oceanic connections).

Step 6: Computing Frame Transmission Rates

Computing frame transmission rates involves calculating how quickly data can be transmitted across a network. Given the link speed and frame size, students can compute the maximum frames per second (fps) that can be sent over different link speeds (100 Mbps, 1 Gbps, 10 Gbps) and for different frame sizes. This helps assess the efficiency of a network link under various conditions. Additionally, students should estimate the total number of frames required for file transfers by considering factors like data frames and acknowledgment frames. This analysis is vital for understanding how network capacity impacts file transfer speeds and overall network performance.

• Calculate Maximum Frames per Second (fps)
• Given the link speed and frame size, use the formula



• Compute values for different link speeds (100 Mbps, 1 Gbps, 10 Gbps) and frame sizes (standard, jumbo).
• Estimate Frame Counts for File Transfers
• Assume 1 TCP ACK for every 2 data frames.
• Compute total frames required for file transfers of 1MB and 10MB using:



• Compare results for standard and jumbo frames.

Conclusion

In conclusion, effectively solving computer network assignments requires a systematic approach that includes understanding assignment requirements, capturing and analyzing packets, interpreting TCP flows, and evaluating network performance using tools like Wireshark, traceroute, and ping. Students must also be able to calculate key metrics such as frame transmission rates and analyze DNS and HTTP performance to gain insights into network behavior. By following these structured steps, students can develop a comprehensive understanding of networking principles, which not only helps them complete assignments efficiently but also enhances their practical knowledge of real-world networking tasks.