Lab 5 in my Netwoking class was all about data encapsulation and the process of communication between the 7 layers of the OSI model.
My objective in completing this lab was to develop an understanding of data encapsulation, the process by which data is Protocol Data Unit (PDU) for one layer of the OSI model becomes the data for the next layer by performing a simulation using paper, markers, and yarn wires.
- laminated paper
- dry erase markers
Notes and Observations:
The blue strands of yarn represent Ethernet cables. They are being taped to a laminated sheet of paper that represents a switch. All devices that users interact with are connected to the switch. To simulate how a switch learns the MAC addresses of all the devices attached to it, the person playing as the switch had to keep a table of users and their MAC addresses. The switch also creates collision domains so multiple users can communicate on the same network at the same time without data collisions occurring.
I was a computer for most of this exercise. “Sweetrelish” was the name of the imaginary network I was connected to, so my network address is “Sweetrelish.Reagan.” I just used my name as my MAC Address.
I sent this message to another participant who was on the “Bun” network.
It had to be encapsulated into this packet, addressed from me to the other computer, and then sent to the switch. It was then encapsulated further and sent to the router. The router sent it through the “Dijon” network and to the “Bun” network. My message got intercepted and read out loud and the entire class groaned and face-palmed. I guess that is just what happens when I try to be funny.
I then switched roles and had to be the router. It is pretty difficult to read anything on this routing table, but my main job was to communicate across networks. I sent messages through the Dijon network and to the Bun Network. I also received messages from the Dijon Network and sent them to the switch.
Here is a map of all three networks that were created in this simulation. As you can see, participants are on two separate networks, the “Bun” network and the “Sweetrelish” network. These two networks communicate across the “Dijon” network.
The instruction sheet for the lab contained several questions that I will answer in this section.
What is the switch’s Mac address? What should the switch do with a frame once it is received?
The switch’s MAC address is Sweetrelish.Mike. The switch should look for the MAC address the frame is to be sent to.
What is the purpose or benefit of sending the frame on only one port?
The frame has less chance of colliding with other data.
Why does the router use the MAC address of the next router, rather than the MAC address of the destination device on the IP packet?
The router is only concerned with communication across networks. The router will send the IP packet to the switch and the switch will get the packet to the destination device.
This was a valuable exercise. Computers and network devices are complex and abstract machines, so building a network isn’t necessarily enough to understand how one works. I was pretty confused by last week’s lab where we actually created a TCP/IP network. Focusing on the functions of the networking devices helped me to understand them a lot better than focusing on the nitty gritty of how they work.