The Internet Useful Definitions and Concepts About the Internet

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.

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 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

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 over the Internet. Messages can be retrieved by using client Client: A program that enables you to send, receive, etc. messages. Mail is sent from many clients to a central server, which re-routes the mail to its intended destination.

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

IP ADDRESS  Every machine on the Internet has a unique identifying number, called an IP Address  Example:  Binary Representation :  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

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

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   Who IS Database :

World Wide Web

DNS Server Requests

Internet Connection through ISPs

Tracking a Route Strategically positioned multiple servers for Safety, Quality of Service (QoS) such as speed, reliability… From Command Prompt > tracert

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:

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 Original requesting user; browser now caches object