This activity can be made as long or as short as you wish; whilst you can make it a short learning hook, there is potential to revisit this activity as the hook to Computer chatter 2: Network performance.
In both networks there are multiple ways to get from one station to the other. For this activity, the Sydney network will be used in the examples given. (Here are some useful links: Sydney Train Network, Transport Sydney Trains)
Ideally, localise the context by using a transportation network in your local city, but if you choose to do this make sure the network provides alternative routes to most destinations.
Additional scaffolding: For students who find this task/concept challenging, you could adapt this task with a map of your school. You could print out a basic map of your school grounds and choose two familiar places that have more than one possible route.
It is up to you how many different routes you want to distribute throughout the class, but have about four students working on each route (so, in a class of 24, you would have six different routes shared between the students).
Have them answer the following questions:
Have students answer the following questions:
Once students have shared their findings with the rest of the class, share the learning intentions for the lesson.
For example, in this activity we will:
Have students access the HowStuffWorks Tech: How Internet Infrastructure Works resource. (A printable, single-page version of the resource is also available by selecting the ‘Print’ link towards the bottom of the page.) The above example still makes reference to 'dialling in' to the Internet, which is no longer how most people connect. You can use this as an opportunity to talk about how technology has improved over time, and return to this when we explore network performance in the next activity.
Additional scaffolding: For students who find this task/concept challening, you could first roleplay how messages get from the classroom to the office. You would first relate computer terms to concrete objects:
For example, if a student wanted to bring a note (DATA) to the Prinicpal, they would look at the school map (DNS) and likely first go to the office (ROUTER) who would redirect the student to the Principal's office. The Principal could then send a message or document back, minimicing an Internet request.
There are lots of opportunities to try out some different formative assessment techniques here to gauge the understanding of learners. Try some think, pair, share or one of the other thinking routines found on the formative assessment page.
As is always the case with analogies, it is difficult to come up with a perfect mapping between a transportation and computer network, so students may come up with different answers. To determine the ‘correctness’ of the answer, consider whether the student’s answer demonstrates:
Have them explain the similarities between the component in the computer network and the transportation network, and use this to assess their learning.
Students should very quickly identify that one of the ways we prevent people from accessing the data on our computers is to keep them off our network entirely, and we often do that using some kind of password or other security mechanism.
Students should come up with some of the following:
Examples of security measures that can protect computer networks include: passwords, security settings on routers, firewalls, security certificates, and anti-virus and anti-malware tools.
Students will now complete the CS Unplugged Tablets of Stone activity
Note that this activity does not require computer access, and should be done in a large space where students can easily move around.
Some notes about the activity:
Stop the game and discuss the issues mentioned in the activity so that students stay engaged and thinking about the implications of any changes they make to the ‘rules’ of the game.
Some stimulus questions you could use with students include:
You can add a security layer to the game if your students are up for it (it generates some interesting discussion and isn't much more complicated). To do this, read the tablets of stone extension and incorporate the suggestions into the rules.
Stimulus questions for the extension might include:
The addition of the security checks to the game brings it closer to what occurs in real network communication – computers don’t just accept any communication that is addressed to them, and will often have some mechanism in place to check that the content of the message is accurate and safe.It is also important to reiterate that computers do not have control over all stages of transmission of data, so the message can easily be intercepted by other computers (our messengers) and potentially read or tampered with.
What implications do students identify from this? Some students will notice that the ‘security’ measures we have put in place for this activity wouldn't be adequate in the real world; this is a simplified version of the techniques used.
At the end of the game, have students record their learning through a quick reflection activity (such as the one described in ‘Learning demo’ below).
Another way of presenting the communication of messages around a network would be to use the analogy of postcards being sent through the mail system. A good explanation of this was presented by Vinton Cerf and can be found here.
Whole class activity
Encourage students to share their reflection with others, and to explain why they feel that it is important to understand that aspect of network communication.
Note that the reflection here should focus on the lesson content. Questions that might assist with the reflection could include:
Have students complete a Plus, Minus, Interesting (PMI) chart on the activity itself, with the focus this time on the way that other students in the class behaved, or on the activity itself (rather than what was being taught).
Note that the examples don’t talk about the content that was learned, but the process of learning that took place.