University of Washington CSE 190M

Section 1: Internet, WWW

Except where otherwise noted, the contents of this document are Copyright 2012 Marty Stepp, Jessica Miller, and Victoria Kirst. All rights reserved. Any redistribution, reproduction, transmission, or storage of part or all of the contents in any form is prohibited without the author's expressed written permission.

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Exercise : Ballparking

What do you think are the top 10 most visited sites on the web today? How would you find out what they actually are ?

Exercise : Ballparking 2

What is one of your favorite web sites not listed among those top 10, and why? Do you have a favorite web "meme"?

Exercise : Ballparking 3

What is one of the WORST sites on the web, and why? (Difficulty: no MySpace)

Exercise : Ballparking 4

How many TCP protocols (the http at the beginning of a URL is one) can you name?

Exercise : Ballparking 5

.com, .net, and .edu are examples of Top-Level Domains (TLDs). How many more TLDs can you name? What are the most recent TLDs to be created?

Exercise : Ballparking 6

What are the top 5 web browsers in market share? How many other web browsers are there?

Exercise : History

What was the first email, and when was it sent?

Exercise answer

The first email was sent by Ray Tomlinson in 1971. Ray thinks the message was something like "QWERTYUIOP". More info is available at this website.

Exercise : History 2

What were the first 20 domain names to be registered?

Exercise answer

  1. symbolics.com - 15 March 1985
  2. bbn.com - 24 April 1985
  3. think.com - 24 May 1985
  4. mcc.com - 11 July 1985
  5. dec.com - 30 September 1985
  6. northrop.com - 7 November 1985
  7. xerox.com - 9 January 1986
  8. sri.com - 17 January 1986
  9. hp.com - 7 March 1986
  10. bellcore.com - 5 March 1986
  1. ibm.com - 19 March 1986
  2. sun.com - 19 March 1986
  3. intel.com - 25 March 1986
  4. ti.com - 25 March 1986
  5. att.com - 25 March 1986
  6. gmr.com - 8 May 1986
  7. tex.com - 8 May 1986
  8. fmc.com - 10 July 1986
  9. ub.com - 10 July 1986
  10. bell-ael.com - 5 August 1986

Exercise : History 3

Why are we "running out" of IP addresses? How many are there? What is being done about this?

Exercise answer

We are running out because IP addresses were given 32 bits which means there are only 232 possibile addresses. This seemed like a sufficient number at the time, but we have already run out. IPv6 has been developed with 128 bits for IP addresses, giving 2128 possible addresses. Deployment is slow, but in time we will move over to the new system.

Exercise : History 4

What is one major change that you think will happen to the web within the next 5-10 years?

Exercise : Spelunking

How would you find out the IP address of a website? Does it ever change?

Exercise answer

You can visit what is my ip in your browser. You can also run the nslookup command on the command line.

Internet Service Providers (ISP) offer what static and variable IP addresses, the latter is more expensive, but ensures that your IP address will never change. In practice a variable IP address does not change often, but the ISPs reserve the right to change it.

Exercise : Spelunking 2

How many computers does a piece of data travel through between you and google.com? How can you find out?

Exercise answer

Around 10 is an average measure, though it can be highly variable.

You can run traceroute google.com on the command line (tracert on windows) to find out. It will show you a list of all of the computers that are hit on the way.

Exercise : Spelunking 3

What's the difference between your local IP address and your internet IP address?

Exercise answer

Your local IP address is allocated by your router. It is only valid on your local area network (LAN). Your internet IP address is actually the address of your router, which is the device that communicates to the internet for you.

This technique has helped us cope with the scarcity of IP addresses for quite some time.

Exercise : Spelunking 4

Follow the commands on this lecture slideto simulate being a browser. How is this different from Viewing the Source of a document in your browser?

Exercise answer

Telnet is a text based implementation of HTTP. What you are seeing is the HTML code that the server returns to you when you ask for a given file.

Exercise : Spelunking 5

What type of web server software is our course web server (webster.cs.washington.edu) running? How can you find out?

Exercise answer

We are running Apache. A common technique used to discover what server software is being used on a given computer is to ask for an invalid page (404) and see if the server software identifies itself within the 404 page text.

Exercise : Spelunking 6

Can you find a website whose server software listens on a port other than 80?

Exercise answer

mail.google.com is one example. In fact, anything that uses HTTPS instead of HTTP is not using port 80 and is instead using port 443.

Exercise : Spelunking 7

What internet programs (other than web browsers and email programs) do you use regularly? What TCP port(s) do they communicate on?

Exercise answer

This is a rather exhaustive list.

Exercise : Jargon

Exercise : Slang