1. How the Internet Works: What happens when information is sent from your computer?

2. You should know what a protocol is. how TCP/IP works. how IP addresses work. what domain names are. the different protocols available on the Internet.

3. When Computers Communicate When two or more computers communicate, they must have a common way in which to communicate. To do this computers use protocols A protocol is an agreement by which two or more computers can communicate. Transfer Control Protocol/Internet Protocol is the underlying protocol for the Internet. TCP/IP

4. Three Important Concepts: TCP/IP Internet Addresses the Domain Name System

5. How TCP/IP Works 1) Transfer Control Protocol (TCP) breaks data into small pieces of no bigger than 1500 characters each. These “pieces” are called packets. 101010101001 101010011010 011010110101 010101011010 111101010111 011101110110 110000101110 110101010101 001110101001 010111101000 101010101 001101010 011010011

6. How TCP/IP Works 2) Each packet is inserted into different Internet Protocol (IP) “envelopes.” Each contains the address of the intended recipient and has the exact same header as all other envelopes. 101010101 001101010 011010011 131.194.83.47

7. How TCP/IP Works A router receives the packets and then determines the most efficient way to send the packets to the recipient. After traveling along a series of routers, the packets arrive at their destination. There may be more than one route available. When a message is sent, the packets may take different routes or may arrive in the wrong order.

8. How TCP/IP Works Upon arrival at the destination, TCP checks the data for corruption against the header included in each packet. If TCP finds a bad packet, it sends a request that the packet be re- transmitted. You can see examples of packets traveling the Internet by using the tracert command. In Windows, the tracert command can be accessed from the command line (DOS prompt).

9. Using Tracert Start your connection to the Internet Choose Run for the Start menu At the Open prompt, key cmd and click OK. A command prompt will open. At the prompt, key in tracert and the website (e.g., tracert www.trinity.edu)www.trinity.edu

10. IP Addresses Since computers process numbers more efficiently and quickly than characters, each machine directly connected to the Internet is given an IP Address An IP address is a 32-bit address comprised of four 8-bit numbers (2 8 ) separated by periods. Each of the four numbers has a value between 0 and 255

11. IP Addresses Example of an IP Address: http://131.194.83.47/ CLS 344 Instructor Station

12. IP Addresses vs. URLs While numeric IP addresses work very well for computers, most humans find it difficult to remember long patterns of numbers. Instead, humans identify computers using Uniform Resource Locators (URLs), a.k.a. “Web Addresses.”

13. IP Addresses (what machines know) vs. URLs (what humans type in) When a human types a URL into a browser, the request is sent to a Domain Name Server (DNS), which then translates the URL to an IP address understood by computers. The DNS acts like a phonebook. A master database keeps track of what name servers are the authority for each and every domain name. For example, if you register your own domain, part of the registration process requires that you indicate what domain name servers (DNS) will know where to look for your web site. Every time you use a domain name, you use the Internet's domain name servers (DNS) to translate the human-readable domain name into the machine-readable IP address.

14. Anatomy of a URL http://www.cs.iupui.edu/index.html file nameprotocol domain name

15. Top Level Domain Names.eduEducational Institution.govGovernmental Agency.milMilitary Entity.comCommercial Entity.netInternet Service Provider.orgNon-Profit Organization...and some new ones!

16. Internet Protocols http://World Wide Web mailto:E-mail address ftp://File Transfer Protocol telnet:Telnet

17. Terms you should know Backbone Computer network Domain Name Server Internet Internet Protocol (IP) IP address Local Area Network (LAN) Packet-switched network Protocol Router Transmission Control Protocol (TCP)