1. The Internet Useful Definitions and Concepts About the Internet

2. WWW and Internet The Internet and WWW are separate but related things. The Internet is the vast collection of interconnected networks that all use TCP/IP protocols. WWW refers to the whole constellation of resources that can be accessed using gopher, FTP, HTTP, Telnet, or some other tools. These resources include HTML pages, images, sound files, etc. The WWW is a hypertext-based, distributed information system.

3. Key Terms Domain Name – a unique name that identifies an Internet site. URL: Uniform Resource Locator – standard way to give the address of any resource on the Internet IP Address – a 32-bit number that uniquely identifies each computer on the Internet www.ipchicken.comwww.ipchicken.com DNS: Domain Name System (also Service or Server) – an Internet service that translates domain names to or from IP addresses HTTP: HyperText Transfer Protocol – the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the world wide web HTML: HyperText Markup Language – a tag-based language used for creating hypertext documents for the web

4. Key Terms, cont’d. TCP/IP: Transmission Control Protocol / Internet Protocol – The protocols, or conventions, that computers use to communicate over the Internet. FTP: File Transfer Protocol – a way of exchanging files over the Internet (Download and Upload) SMTP: Simple Mail Transfer Protocol – the protocol used to send email over the Internet. Messages can be retrieved by using email client Email Client: A program that enables you to send, receive, etc. email messages. Mail is sent from many clients to a central server, which re-routes the mail to its intended destination.

5. Key Terms, cont’d. Telnet: The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server. ssh – secure shell sftp – secure ftp

6. IP ADDRESS  Every machine on the Internet has a unique identifying number, called an IP Address  Example: 216.27.61.137  Binary Representation : 11011000.00011011.00111101.10001001  4 Octets, Total 32 Bits. 0 or 1 Value. Possible combination per Octet ( 2 ^ 8 =256)  Total Possible values : 2 ^ 32 = 4,294,967,296  Static and Dynamic IP Address  From Command Prompt > ipconfig

7. Domain Names Web Server usually has a Static IP Address Domain Name is mapped to the web server’s IP address Translation handled via DNS servers From Command Prompt > nslookup www.uconn.eduwww.uconn.edu

8. Domain Names, cont’d.  All of the names in a given domain need to be unique, there has to be a single entity that controls the list and makes sure no duplicates arise  www.networksolutions.com www.networksolutions.com  Who IS Database : http://www.networksolutions.com/en_US/whois/ http://www.networksolutions.com/en_US/whois/

9. World Wide Web

10. DNS Server Requests

11. Internet Connection through ISPs

12. Tracking a Route Strategically positioned multiple servers for Safety, Quality of Service (QoS) such as speed, reliability… From Command Prompt > tracert www.google.comwww.google.com http://www.visualware.com/personal/demo/index.html

13. Web Caching Web caching is the practice of storing frequently requested - but infrequently changed - pages, images and other Web objects on a nearby server or even a user's PC One website resource on the subject: http://www.web-caching.com

14. Web Caching How It Works 1. User requests Web page. 2. Browser checks cache; if in, request is served; no more traffic needed. 3. Not in browser; ask local server. 4. Server checks cache; if in, serves. 5. Not in server cache; request from Internet. 6. Originating server checks location of request; refers request to the closest distribution server. 7. Distribution server delivers request...8. To local server, which sends it to... 9. Original requesting user; browser now caches object