CS 130 Lab #6: Internet basics

Goals

In this lab we will take a look at some of the things that make the Internet run, "peeking under the hood", so to speak, in order to uncover a few of the details which are normally hidden by software. We will also try a few user-visible application techniques.

The idea behind this lab is to give you some concrete experience with some of these concepts, so that you can better follow the lectures, and to build your intuitions about how the internet works.

IP addresses

As we have discussed, computers on the Internet each have a unique "phone number" or address, called an IP address. This comes in two forms, either with "words" or with numbers, but typically written with several parts separated by dots. For example,

158.104.2.87

Follow these steps to find out the (numeric) IP address of the computer you are on:

for Windows: go to the Start menu, then to the Settings menu, then to Net connections. In the dialog box, choose "Local area", then select the "Support" tab.
for Mac OS X: go to the Apple menu, then to the System Preferences menu. Preferences panel select "Network", then then select the "Support" tab.
on WITS lab Windows machines: ... you won't be able to check these settings because you don't have enough privileges. You can use the AntiOnline IP locator link from later in the lab: it will tell you both the domain name (mostly words) and the IP address of your machine.
Question: on a WITS lab machine, what is the relationship between the last part of the Collins part of the domain name (e.g., "XX" in "cln-407-XX.willamette.edu") and the last part of the IP address?

Keep a paper or text file "log" with this information in it for your demo.

FInd at least two other computers you can use (in other Willamette locations, in your dorm or house, or perhaps in your parents house(s). Find out the IP addresses of these computers and jot them down.

Do you see any patterns relating to geographic or organizational relations? (This is an open-ended question: you may not see any patterns based on the specific computers you checked.)

The `ping` and `tracert` commands

You can access some useful internet technical tools from the Windows or Mac OS command line.

for Windows: go to the Start menu, then to the "Run ..." item on the right-hand side (in blue). When the box comes up, type "cmd" (without the quotes) and hit Enter.
for Mac OS X: go to the dock and find the Terminal application (it has a display screen icon). When the applcation opens, if you don't see a window open, use the "New Shell" command.

The ping command allows you to test a connection to another computer, by sending packets to the destination machine repeatedly and measuring how long it takes the packets to come back. Use a command like this:

ping hydra.willamette.edu

Try using this ping command on several different destination computers and compare the results:

try pinging the Hydra machine (as above): this is a local server here at Willamette.
try pinging this machine: occs.cs.oberlin.edu; does it take longer? where is this machine (see below)?
also try this computer: 210.128.152.82 (where is it?)

Having trouble copying and pasting from the command line? Use your right mouse button and choose "Mark", then select a rectangular area that you want to copy, then hit Enter (the key). Now you should be able to paste the text you copied (into your "log file" for example).

You can use either of the following web sites to check the geographic location of a machine based on its IP address:

AntiOnline IP locator
NetWorld map

Another useful command will give you information about the route that your packets took to get to some destination. Use the command

tracert hydra.willamette.edu
(or traceroute hydra.willamette.edu on a Mac)

Using this tool and some of the same addresses above, answer these questions:

How many "hops" does it take to get to the destination?
if you trace a route several times, does the route always look the same? (If you can, try the same route at different times of day.)
try the same destination from a lab machine and from another machine (dorm, house, or different lab, such as Smullin): does the route look the same? For which part and how much of the route?
look up the physical locations of some of the points along the route; do they always move closer geographically to the destination?

Email issues

Email is one of the oldest and most widely-used internet protocols ... but does it respect modern standards such as Unicode?

Try cutting and pasting Unicode text from the Word documents of the last lab into an email message to yourself. Do the Unicode characters arrive intact? Do you need to make any special changes in settings (some email programs might require you to specify a message format that uses Unicode).

Can you paste in styled text with fonts such as those in the WingDings font from the original Microsoft Word document? Do they "survive" the email process intact? (If possible, see what happens when you use a font that doesn't exist on a destination machine where you read your email: this may take a little experimentation.)

Using a wiki

We have looked several times at the Wikipedia web site during lecture. This "collaborative on-line encyclopedia" uses a technology called Wiki to allow people to edit web pages on the fly (i.e., to edit them as they browse them).

Wiki tutorial