1. Tools of Web Development 1: Internet Protocols

2. Goals Understand what a protocol is. Understand how TCP/IP works. Understand how IP addresses work. Understand what domain names are. Understand 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.

4. 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 011010210101 010101011010 111101010111 011101110110 110000101110 110101010101 001110101001 010111101000 101010101 001101010 011010011

5. 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

6. 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.

7. How TCP/IP Works Upon arrival at their 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.

8. 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

9. IP Addresses Example of an IP Address: http://134.68.140.1/ The IP Address of the Computer Science Department’s Web Server

10. 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”.

11. IP Addresses vs. URLs 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.

12. Anatomy of a URL http://www.cs.iupui.edu/index.html file name domain name sub-sub domain machine name sub domain protocol

13. What about Email Addresses? jstudent@cs.iupui.edu usernamesub-domain domain name sub-sub domain

14. Top Level Domain Names.eduEducational Institution.govGovernmental Agency.milMilitary Entity.comCommercial Entity.netInternet Service Provider.orgNon-Profit Organization

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