Question 1: LINK AND NETWORK LAYER UNDERSTANDING VIA COMMAND PROMPT 

Command Prompt/PowerShell is a command-line interpreter application available in Windows and Mac OS. It is used to execute entered commands. These are some common Microsoft Windows or Mac network commands are listed as follow:

• ipconfig
•  ifconfig
•  netstat
•  tracert
• traceroute
• ping
• telnet
• ftp
• route
• arp
• nslookup
• nbtstat
• netsh
• getmac

For Windows OS:

Type “command prompt” into the Start Menu to search for it and open it.

For Mac OS:

Type “terminal” at the spotlight search and open it

Debate the usage of the suitable network commands in the following cases:

• Use the correct network command to get the 48-bits hardware address of your computer. Provide the screenshots to show how to get this information.
• Use the correct network command to find the IP addresses of your computer. Hence, show all active IP addresses on your network. Provide the screenshots to show how to get this information.
• Use the correct network command to differentiate and find the IP addresses of “wireshark.org” and “suss.edu.sg”. Provide the screenshots to show how to get this information.
• Use the correct network command to determine whether the computer can send information out and receive the information back from itself. State overall received time. Provide the screenshots to show how to get this information. Hint: Loopback.
• With your mobile phone connect to the same Wi-Fi network as your computer, use the appropriate network command to create an ICMP ping packet to your mobile phone. Provide the screenshots to show how to get this information, including evidence on the IP address on the mobile phone.

Question 2: TRANSPORT LAYER UNDERSTANDING VIA WIRESHARK

Both TCP and UDP are simple connection-oriented and connectionless-oriented communication protocol mechanisms. TCP is suitable for highly reliable data transfer such as bank transfer applications while UDP is suitable for real-time video transmission where error checking and correction are not necessary. Use Wireshark software to conduct the following experiment. Start capturing packets in Wireshark and then do something that will cause your host to send and receive several TCP and UDP segments. After stopping segment capture, set your filter so that Wireshark only displays the TCP and
UDP segments are sent and received at your host. Pick one of these TCP/UDP segments and expand the TCP and UDP fields in the details window. Answer the following questions to appraise the importance of TCP and UDP.

• Select one TCP segment from your trace. From this segment, determine how many fields there are in the TCP header. Name these fields and highlight them in the screenshot.
• Select one UDP segment from your trace. From this segment, determine how many fields there are in the UDP header. Name these fields and highlight them in the screenshot.
• What is the maximum number of bytes that can be included in a TCP payload excluding the header?
• What is the maximum number of bytes that can be included in a UDP payload excluding the header?
• Can the TCP and UDP maximum payload be achievable?
• What are the largest possible source and destination TCP and UDP port numbers?

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