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Assignment & Lab #3 ITM301 - IT Infrastructure Instructor: Mehdi Shajari


Assignment: Understanding encapsulation and de-encapsulation, addressing, and routing in TCP/IP layers


1.     In this assignment, we will practice the concepts of encapsulation and de-encapsulation, addressing, and routing when data (or payload) travels through TCP/IP layers in the source computer and the different layers of the protocol in routers and eventually arrives at its destination.

The following figure from the shows an example internetwork based on TCP/IP protocol family. I have added some more details to the figure.

In this scenario, a web browser application on Computer B using the HTTP protocol sends a request to a web server running on Computer A.

a.     Draw a figure that shows how data (or payload) is transferred from Computer B to Computer A. The figure will look like Figure 4.1 of the textbook which is also available in slide 10 of the week 3 lecture slides, but you should depict the routers in the path as well. It also should include MAC address, IP address, and port numbers in each layer. Please note that data traverses all of the protocol layers in the source computer (Computer B), arrives at the first router, goes up through existing protocol layers in one interface of the router, and comes down to be transmitted through another interface to the next router, and continues to get to the destination computer (Computer A).

Your drawing will look like the figure 20 of the Week 2 slides, but you need to specify routers that the data will traverse based on the routing tables. In all layers of the TCP/IP protocol in all computers and routers in the route, you should specify all of the above-mentioned addresses if they appear in the headers of each encapsulated protocol.

The following table shows the IP addresses and MAC addresses of each interface of the routers depicted in the network. MAC addresses are hardware addresses of data link layer networking technologies used to interconnect different networks, for example, ethernet uses a 48-bit MAC address.


Router & Interface

IP Address

MAC Address

























b.     Explain the functionality of the Layer 2 switches in LANs. Do they add any header to the data?

It is for multiple computers/devices to connect to the router using an ethernet. A layer 2 switch is like a power bar. Layer 2 is efficient because there is no modification to the data packet, only the frame encapsulation of the packet. The header is part of the data packet, which means it is unaffected.



Assignment: Network diagrams


2.     Network Diagrams are explained in pages 71 to 79 of your textbook. In your previous lab activities, you used Zenmap to perform network mapping. Network mapping is the process of discovering and identifying the devices on a network. In this assignment, you will sketch a map of the network devices you discovered in your previous lab activities. Use the instruction on page 75 to create a network diagram in the You can also use other diagramming tools such as Visio if you are more comfortable with them.

Lab activity: Netstat and arp commands


1.     In this lab, you will use the netstat command-line utility to identify your default gateway and arp command-line utility to see the cache used by the ARP protocol on your computer. netstat and arp commands are available on Windows, Linux, and Mac computers, but they use different arguments and output formats.

a.     Use netstat -r in a command prompt (Windows) or terminal (Mac) to identify your default gateway. In Windows the output will look like the following screenshot:

b.     Use the arp -a command to see the arp cache on your computer. This table shows the IP addresses and their corresponding MAC addresses obtained by the arp protocol. Find the MAC address of your default gateway, and include a screenshot to show the output of the command.

4.     Repeat the activity from the previous assignment. If you still cannot complete the activity use other similar sites such as Wikiful.

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