Section 2.6

Learning Goals

• CSN-1.A: Students will explain how computing devices work together in a network.

• Students will define a computer network as a group of interconnected computing devices capable of sending or receiving data. 

• Students will define a path between two computing devices on a computer network as a sequence of directly connected computing devices that begins at the sender and ends at the receiver. 

• Students will demonstrate different types of configurations for a computer network. 

• Students will evaluate Ring, Star and Bus topologies. 

• CSN-1.A.3: A computer network is a group of interconnected computing devices capable of sending or receiving data. 

• CSN-1.A.5: A path between two computing devices on a computer network (a sender and a receiver) is a sequence of directly connected computing devices that begins at the sender and ends at the receiver. 

Important Vocabulary:  Bit, byte, latency, binary, bandwidth, bitrate,  ethernet, fiber optic cables, Wi-Fi, ring topology, star topology, bus topology, LAN, MAN, WAN

Objectives and General Description

Now that the students have an understanding of what the internet is and its impact, the students will learn how the physical infrastructure of the Internet moves data.  The objective of this section is to have the students understand what a network is, what a path on a network is and how paths are formed and evaluate different configurations of networks.

The lesson starts with a video and guided notes.  This can be flipped and done at home or it can be completed at the beginning of class.  The video summarizes the types of connections (electricity (ethernet),  radio (Wi-Fi) and light (fiberoptics).  The video also explains the measurement of data transfer (bit, bitrate, bandwidth).  After a discussion of the video & concepts, the students will participate in hands on simulations of three different types of topology (ring, star and bus).  Reflection discussions will evaluate the efficiency of each.

Activities

Activity 2.6.1 (Budget 10 minutes)

1.  Have students watch “Wires, Cables & Wi-Fi” .  The video is 6 minutes, 41 seconds.  It can be watched as a warm up in class or as homework the night before.

2. Students complete The Internet: Wires, Cables, & Wi-Fi Video Guided Notes.

3. Discuss concepts and assess understanding, especially vocab (Bit, byte, binary, bandwidth, bitrate, latency) and the pros and cons of Ethernet, fiber optics and Wi-Fi.

Activity 2.6.2  (Budget 30 minutes)

1. Topology group activity:  This activity illustrates three types of topology (ring, star and bus) and gives the students experience with limitations of each.  Divide class into teams of 6 - 8 students.  Each team is given a set of index cards.  Each student has two cards with the same letter on each (2 A’s, 2 B’s etc.) except for the last student only has one letter.

2. Each student represents a computer.  Refer to them with corresponding letters (Computer A, Computer B, etc.)

3. The cards represent pieces of data that need to travel to their matching computer.

4. Ring Topology:  

   1. Each team sits in a circle.  The cards are shuffled and distributed face down.  Each “computer” should have two pieces of unknown data except the last computer will only have one piece.  The goal is to pass the data around the ring until each computer has the correct data.  Data can only travel in one direction.  

   2. Discussion:  What made this transfer of data challenging?  What are the limitations of a ring topology?  What are the benefits?  How would outside/new data make its way into a ring topology?

5. Star Topology:  

   1. For this simulation, the students change their seating arrangement.  One student is sitting in the center of the circle.  The cards should be gathered, shuffled and redistributed.  The goal is the same….data must be returned to the destination computer.  However, the movement of this topology is different.  All data movement must go through the center; there is no side to side movement. The center computer can only hold two pieces of data at a time (one in each hand).  Time the teams to see which one finishes first.  

   2. Combine two teams together.  There is still only one central computer.  Shuffle and redistribute cards.  Does it take longer to get the data moved to the correct destination?

   3. If desired, combine teams again to make a very large network.  Still only have one central computer.  Time the distribution again.  Did it take longer?

   4. Discussion questions:  Was this easier that than the ring topology?  Why?  What are the limitations?  Benefits?  What happens to the central computer as the network grows larger?  What happens to the transfer of data if the central computer goes down?

   5. Notes to emphasize:  Star topology puts a huge burden on the central computer (node).  If it is not working, network communication halts.

6. Bus topology:

   1. Have a new set of index cards, one per student.  Each card will have a corresponding number on it.  Add one extra card with a big number on it (100).

   2. Have the students sit/stand in one long row. Have the students number off so that they each are assigned a different number.

   3. Shuffle the cards.

   4. To simulate the bus topology, distribute the cards one at a time to the first person in line.  Students should check the card number.  If it belongs to them, they keep it.  Otherwise they pass it to the next person.  Keep feeding cards quickly to the first person in line to get the data flowing.

   5. By the time all data has flowed through the network, each “computer” has its designated data.  There should be one piece of data that didn’t find a home (the 100 card).  

   6. Discussion questions:  Was this topology easier or more difficult for distributing data?  Why was there unclaimed data? What happens to the unclaimed data?  Does the sender know that the data didn’t arrive at its location?  What happens if a computer goes down or has gotten it’s data?  What happens if the line gets broken?

   7. Notes to emphasize:  

      1. Data can travel in both directions in bus topology.  You can simulate this if you wish.

      2. If a node isn’t working in a bus topology, the data continues to flow.

      3. Data is ignored if it doesn’t “belong” to a node.  It just keeps flowing.  

      4. Ethernet is a commonly used type of bus topology and is the industry standard for local-area networks.

7. Concluding questions:  

   1. How do the structural characteristics of the internet offset the limitations of bus topology?

   2. Evaluate the topologies:

      1. Which is the simplistic to set up?

      2. Which is better for a small network?  A large network?

8. Optional:  Have each student write a summary/reflection of the topologies for their notes.

Supplies needed for lesson:

• Index cards

Activity 2.6.3 (Budget 10 minutes)

1. Remind students that they now know what a network is, different ways of connecting devices and networks and that there are multiple paths from a sender to a receiver.

2. Introduce the concepts of PING and TRACEROUTE.  

   • A ping is a program that allows you to test the availability of a receiving destination.  Is it available and ready to receive data?

   • A traceroute is a program that allows you to see the path that a data packet travels on from sender to receiver.  It lists the IP address of the sender, the time it takes to get to it's next stop or hop, the IP address of the hop and the ultimately the IP address of the receiving device.

3. If possible, have your students run a PING and a traceroute from their command prompt.  (Many school IT departments do not allow this so the teacher may need to demonstrate).

4. To run a PING:

   • Open the command prompt

   • type in the word ping and a web destination.  Then hit enter.  For example, type:  ping www.cnn.com

   • The ping will send four packets of data.  The statistics will show how many packets were sent and how many were received and the approximate amount of time for the round trip.

5. To run a traceroute

   • Open the command prompt

   • Type in tracert and the web destination.  Example:  tracert www.cnn.com

   • The result will be  table that shows each hop a packet takes on its path to the destination.  There is a maximum of 30 hops on a tracert call.  The table gives the amount of time from one hop to the next.  It also shows the IP address of where the hop landed.  These landing spots could be routers, servers, etc.  If a landing spot is busy, you will see a timeout message the the packet moves on to another location.

6.   If you can't successfully run a ping or traceroute in your classroom environment, you could try these options...

   • Use an online program.  

     • https://network-tools.com/ 

     • https://www.monitis.com/traceroute/

   • Run the tests at home and make a screencast video.  Show the video to the students.

   • Have students run the tests at home and take screenshots of the results.

7.  Thought question:  I typed in a web address (www.cnn.com).  How did the ping and traceroute know the IP address for the destination?

8. Have students watch IP Addresses and DNS for homework.  No guided notes.  Tell them to come to class the next day with the answer to the thought question.

Resources

• 2.6.1: The Internet: Wires, Cables, & Wi-Fi Video Guided Notes (student worksheet)

• 2.6.1: The Internet: Wires, Cables, & Wi-Fi Video Guided Notes KEY (teacher resource)