Behind the Plug

An Introduction to Computer Networks

This class is designed to provide an overview of how the Internet at large works to middle and high school students. The information presented here isn’t highly detailed, but it is enough for a learner to use computer networks more intelligently, or provide the basis for more in depth work in the area of network engineering. The exercises provided for each class may be used as a way to assess student achievement, they may be used to provide some hands-on experience with some of the concepts covered, they may be used as classroom examples, or they may simply be ignored.

A reading list is provided at the end of the course for those students who wish to go more deeply into the concepts covered here.

Note this class was originally designed for a homeschool co-op; the level of material may need to be adjusted for other audiences.

0001: How Computers Work

Slides & Media

  • The two forms of memory most computers have are RAM, or “random access memory,” and the hard drive. Can you explain the difference between these two? This article might help.
  • Can you find out how much memory the computer you’re using has without looking inside the case? There’s almost always a control panel or system information application built into the operating system of the computer that can tell you this information. Or, you can download a specialized application like this one to find out.
  • Video cards also have memory on them; can you find out how much memory the video card in the computer you’re using has on it?
  • If you’re interested in how memory is designed and manufactured, try this web page from Kingston. They have a series of videos explaining the process.

0010: The Domain Name System

Slides & Media

  • Use whois.org to look up the domain names of several web sites you regularly go to. Is there anything interesting in the whois records for these sites?
  • Use whois.org to look up thinkinginchrist.com. Do you see anything different about this whois record? What information appears to be missing from this record? Can you think of any reason why this information would be missing?
  • network-tools.com, as well as other sites, provide tools on line to convert a domain name into an address. The local tools you can use to do resolve a domain name to an address are nslookup and ping; can you figure out how to use these tools to find the ip address for some domain names?
  • There are a number of different types of DNS records. The one you use most often is called an “A record,” which means it is an authoritative records that tells you the address of a domain name. Can you figure out what an “MX record” is used for?

0011: IP Addresses

Slides & Media

0100: A Plethora of Packets

Slides & Media

  • What are the different fields in the header of an IP packet?
  • How are the type of service fields used in IP?
  • What protocol would be used to provide security for IP packets?
  • UDP adds very little to the services IP offers; can you explain why an application might choose to use UDP instead of TCP?
  • How do you think your computer knows what IP address to use? You probably didn’t configure it, so there must be some magic involved someplace, but what is it? Look up a protocol called the Dynamic Host Configuration Protocol (DHCP) to find out.
  • Computers actually can have multiple addresses —almost all of them have a physical address (called a MAC address) and an IP address. If DNS is used to map between names and IP addresses, then what protocol is used to map between MAC addresses and IP addresses? Hint: Look for information on the Address Resolution Protocol (ARP).

0101: How Do I Get There?

Slides & Media

  • For a demonstration of Dijkstra’s SPF algorithm, check out this link. It allows you to draw complex networks and run the algorithm step by step over the network you’ve drawn.
  • Try running the Bellman-Ford algorithm over one of the networks you’ve drawn with the tool above by hand.
  • Try this worksheet on routing protocols.
  • Can you figure out how an automotive GPS or a program like Mapquest figures out the best path between two locations?

0110: In the Dirt, Under the Sea

Slides & Media

  • Explain the difference between Unicode and ASCII, and the reasoning behind the change from one to the other.
  • See if you can find a map of all the cables that run under the Atlantic Ocean. Are you surprised at the number of cables?
  • Look up a type of data construction called a type length vector (TLV). What role do you think these might play in the construction of network packets?
  • Try this ASCII worksheet.

0111: Geek Politics

Slides & Media

  • Many of these standards organizations have overlapping areas of standards. Can you find out how two of them, for instance the IETF and the ISO, handle their overlapping standards? (hint: look at the standard for the IS-IS routing protocol as an example).
  • Can you find any other standards bodies that work in the space of internet protocols? What do they standardize, and why do you think their work is interesting?
  • Why do you think a network equipment vendor would pay to have people work in these standards bodies? Can you find any information on the Internet about why they might?
  • What role might a college or university play in any of these standards bodies?

1000: Search Engines

Slides & Media

1001: Data & Metadata

Slides & Media

  • Read the Wikipedia article on metadata. What do you think is the most interesting point about metadata covered in this article?
  • Do a web search for search engine optimization companies and tools. Pick two sites and see what you can find out about the way companies work to improve a web site’s search engine page ranking. What methods do they appear to share?
  • Can you think of any strategies, other than simply not placing any information on line at all, to control the leakage of data and metadata from your life?

1010: Viruses, Phishes, & Firewalls

Slides & Media

  • Take a look through the Top Ten Scams page over at About.com. Which of these scams do you think is the most believable and why?
  • Is there one specific thing other than what is covered in the slides that always appears to be true of scam or phishing emails?
  • Can you explain how reading email in plain text would help protect you from scams and phishing?

1011: Careers in Computing

Slides & Media