1. CS101
How the Internet Works

2. When did the Internet start?
The Internet was born in 1969 with the invention of ARPANET
ARPANET was a research project funded by the Defense Department
The network had to be able to operate even if part of it was destroyed

3. The Internet is a Client/Server Network
Computers on a network fall into two categories:
Client (Workstation) = Computers that are part of the network that are not servers. These computers are using the network.
Server = Computers on the network dedicated to running some part of the network.

4. Types of clients (or workstations)
Dumb Client = Just a screen and a keyboard. All functions done by a computer somewhere else on the network
Thin Client = Has some computer parts such as processor and RAM but is missing others such as a hard drive. Cannot function without using the network.
Fat Client = Fully equipped computer that can function without the network

5. Types of Servers
File server = serves files to other computers on the network
Web server = serves web pages to other computers on the network
Print server = controls print jobs from the network heading to networked printers
server = handles accounts and s on a network
Game server = hosts online games
Application sever = run apps off other comptuers
Lots of different kinds of servers on the Internet

6. When did the WWW start?
The Internet is the hardware of the worlds largest network of computers.
The WWW is one of the functions invented to use the hardware of the largest computer network in the world.
This means the Internet is older then the WWW
WWW was not invented until 1991
On August 6, 1991, Tim Berners-Lee posted a short summary of the World Wide Web project on the alt.hypertext newsgroup. This date also marked the debut of the Web as a publicly available service on the Internet.

7. How does information move about on a network? Packet Switching!
Information represented as zeros and ones ( , web pages, IM, files, video, sound, etc) is broken into packets.
Each packet has a send address, return address, and an order number
Each packet then moves across the network finding the best way to its send address (routers and switches help out).
Not all packets have to go the same route
Once they get to their destination the packets put themselves back in order
This system allows the network to keep functioning even if part of it is not working

8. How do the packets know where to go?
When your computer (or network) becomes part of the Internet it has to agree to the TCP/IP protocols
The TCP/IP protocols tell the packets what form they should be in so all computers on the network will understand the information
The TCP/IP protocols makes sure that every computer has a unique IP (Internet Protocol) address
The packets move from one IP address to the destination IP address

9. What is an IP address? There are two types of IP addresses
IP version 4 (Ipv4) = the older system that is still the most widely used
Ipv4address = 4 numbers between 0 and 255 separated by periods (for example )
A 32 bit number
IP version 6 (Ipv6) = the new system created because we are running out of numbers
Ipv6 address = are 128-bit numbers and are conventionally expressed using hexadecimal strings (for example 1080:0:0:0:8:800:200C:417A)
You can find your IP address in System Information (Win) or System Profiler (Mac)

10. Who is in charge of IP addresses?
On October, 1st ,2016, IANA (Internet Assigned Number Authority) handed over control of the Internet to ICANN (Internet Corporation for Assigned Names and Numbers)
The ICANN delegates the responsibility for this part of the world to ARIN (American Registry for Internet Numbers)
ARIN delegates the responsibility to accredited companies who register with InterNIC

11. How do you get an IP address?
Two ways to get an IP address
1) From your ISP (Internet Service Provider)
2) From the DNS (Domain Name System)

12. IP address from your ISP
Your ISP will assign your computer an IP address when you contact their computer to gain access to the Internet
Most of the time you will get a dynamic IP address
Different address each time you access the Internet
You can pay more and get a IP static address
Same IP address each time you access the Internet

13. How do I get an IP address all by myself?
You use an accredited registrar for the Domain Name System to first find some text that no else has used for their domain on the Internet
Once you find your unique text you then register that unique text with the domain name system which assigns a unique IP address to the text
The text and IP address that it is paired with are then stored in the Domain Name System database so that no one else can use it

14. How do computers find each other using IP addresses?
Computers use the Domain Name System (DNS) to find each other.
The DNS is managed by IANA.
The DNS breaks all the computers on the Internet into top level domains
.com, .edu, .net, .org, .uk, .net, etc
Each computer in a domain has a unique IP address attached to a unique string of text
sonoma.edu is attached to
You can lookup an IP address at this website:

15. So how does the Domain Name System work?
When you enter an address such as
into your browser the DNS helps your computer contact the other computer by using the following method:
(Explanation given in class using the whiteboard.)
If you missed the lecture then read about a web address on the following web page