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The Internet is a vast network connecting computers all over the world

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1 The Internet is a vast network connecting computers all over the world
The original plans for the Internet grew out of a series of memos written by J.C.R. Licklider of the Massachusetts Institute of Technology (MIT) in August 1962 discussing his concept of a “Galactic Network” Licklider envisioned a global computer network through which users could access data and programs from any site on the network

2 Accessing cross-referenced documents, known as hypertext linking, is probably the most important aspect of the Web because it allows you to quickly open other Web pages A hypertext link, or hyperlink, contains a reference to a specific Web page that you can click to quickly open that Web page

3 Internet developed in the 1960s by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense to connect the main computer systems of various universities and research institutions that were funded by ARPA In 1990 and 1991, Tim Berners-Lee created what would become the World Wide Web (WWW), or the Web, at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland, as a way to easily access cross-referenced documents that existed on the CERN computer network

4 A document on the Web is called a Web page, identified by a unique address called the Uniform Resource Locator, or URL URL commonly referred to as a Web address A URL is a type of Uniform Resource Identifier (URI), which is a generic term for many types of names and addresses on the World Wide Web A Web site refers to the location on the Internet of the Web pages and related files (such as graphic files) that belong to a company, organization, or individual

5 Internet Protocols TCP/IP Transfer Control Protocol/Internet Protocol
World Wide Web ftp:// File Transfer Protocol telnet: Telnet mailto: address

6 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.

7 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.

8 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.

9 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. (Router)

10 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.

11 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 (28) separated by periods. Each of the four numbers has a value between 0 and 255

12 The IP Address of the Computer Science Department’s Web Server
IP Addresses Example of an IP Address: The IP Address of the Computer Science Department’s Web Server

13 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”.

14 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.

15 Anatomy of a URL file name
domain name sub-sub domain machine name sub domain protocol

16 Top Level Domain Names Assigned Numbers Authority
In the 1980s, seven gTLDs (.com, .edu, .gov, .int, .mil, .net, and .org) were created. Domain names may be registered in three of these (.com, .net, and .org) without restriction; the other four have limited purposes .com Commercial Entity .net Internet Service Provider .org Non-Profit Organization .edu Educational Institution .gov Governmental Agency .mil Military Entity .int Internet Assigned Numbers Authority Assigned Numbers Authority Internet Corporation For Assigned Names and Numbers

17 Country codes .JP Japan .IT Italy .FR France .DK Denmark .AU Australia
.DE Germany .CN China .ES Spain Top Level Domain Names and Country Codes

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