Intro to the Internet

1. Intro to the Internet • Internet: a network of network • The internet consists of thousands of smaller networks • They may be educational, commercial, nonprofit, military organizations, etc.

2. Brief History • Internet History • Began with 1969’s ARPANET for US Dept. of Defense • 62 computers in 1974 • 500 computers in 1983 • 28,000 computers in 1987 • Early 1990s, multimedia (www) became available on internet

3. Our Internet MAC-b IP:B.6.b MAC-c IP:B.6.c MAC-a IP:B.6.a MAC-d IP:B.6.d PC-a IP:B.1.a MAC-a IP:C.4.a NAP-A IP: A.0.0 ISP2/POP-6 IP:B.6.0 ISP2/POP-1 IP:B.1.0 Udel-4 IP:C.4.0 PC-b IP:C.4.b Amazon.com Server IP: A.AS.0 NAP-B IP: B.0.0 NAP-C IP:C.0.0 PC-b IP:D.3.b Comcast/POP-3 IP:D.3.0 NAP-D IP:D.0.0 NAP-E IP:E.0.0 MAC-a IP:D.3.a ISP1/POP-2 IP:E.2.0 Comcast/POP-5 IP:D.5.0 PC-a IP:E.2.a PC-b IP:E.2.b PC-d IP:E.2.d PC-b IP:D.5.b PC-a IP:D.5.a PC-c IP:E.2.c

4. Internet Terms: • NAP (Network Access Point): A routing computer at a point on the internet where several connections come together • Connects to the Internet Backbone (fast, expensive connection) • Router: A device that forwards data from one network to another based on internal routing tables • Routers read each packet’s destination IP address and decide how to forward it. • IP Address: Internet Protocol Address – a unique address that identifies every computer and device connected to the internet • POP – Point of Presence – A local access point to the internet • ISP:Internet Service Provider – A local, regional, or national organization/company that provides access to the internet • LAN – Local Area Network – a computer network that spans a relatively small area

5. How Does the Internet Work? • Protocols • set of rules and encoding specifications for sending data • Internet uses TCP/IP (Transfer Control Protocol/Internet Protocol • Used for all internet transactions • TCP – Deals with Transfer of Data – how it is broken up and reassembled to be sent across the internet • Packets • Fixed-length blocks of data for transmission • Data transmissions (files) are broken up into packets • Not all packets from the same file will follow the same pathway • Data must be reassembled at the other end

6. How Does the Internet Work? • IP – Deals with the addressing and pathways the data travels over the internet • IP Addresses • Every device connected to the internet has an address • Each IP address uniquely identifies that device • The address is four sets of 3-digit numbers separated by periods • Example: 95.160.10.240

7. Central Concept: • The Internet is Distributed • No centralized control of the internet • If any one computer goes down, the internet can continue to function • Allows for expansion of the internet as well • Can easily add new computers and networks to the internet. • Must assign unique IP addresses to computers connecting to the internet and • Must update Router Tables

8. Key Model: • Client/Server Model • Client: a computer requesting data or services • Server: a host computer, a central computer supplying data or services requested of it • Services can be requested over the internet • E.g., Check your bank account • A client program on your computer forwards your request to a server program at your bank. The bank server sends the info back to your client program • Often multiple clients share the services of one server • Or Services can be local requests • Maybe one computer on a local network has extra disk space and can hold a large database • Clients on the network make requests from the local server and the server sends only the data the client requests • Peer to Peer (P2P) Model • Computers that both provide services to and receive services from each other • Services execute on a temporary basis • E.g., Instant Messaging,

9. Services Offered by the Internet?

10. Services Offered by the Internet:WWW • The World Wide Web: • Browsers • Software for web-surfing • Examples: Internet Explorer, Netscape Navigator, Mozilla FireFox, Opera, Apple Macintosh browser, Safari • Browsers do 2 key things: • Locate web sites via unique addresses • Read web pages and display them

11. World Wide Web • Website • A location on the web that has a unique address and a set of interconnected web pages, usually on the same server • Example: www.barnesandnoble.com, www.eecis.udel.edu • The website could be anywhere • not necessarily at company headquarters

12. The World Wide Web • Web Pages • The documents and files on a website • Can include text, pictures, sound, and video • Home page • The main entry point for the website • Contains links to other pages on the website

13. The World Wide Web • (URL) • A string of that points to a specific (unique) on the web • URL = • It consists of • The web protocol- • The of the web server • The directory or on that server • The file within the directory, including optional extension • http://www.imageek.com/girlgeek/java.htm file name . extension directory domain name protocol

14. The World Wide Web • Must be unique • Identify the , and the type of it is • www.whitehouse.is NOT the same as www.whitehouse. • .gov ,.org, .edu, etc.

15. The World Wide Web • The used to access the World Wide Web • Stands for • The version of • The language used in writing and publishing • The set of tags used to specify document structure, formatting, and links to other documents on the web • NOT a programming language (but it can contain programming code) • connect one web document to another

16. The World Wide Web • Organizations that maintain accessible through websites to help you find on the internet • Users can ask questions or use to locate information • Examples: Google, Ask Jeeves, and Gigablast • are compiled using software programs called • crawl through the World Wide Web • Follow links from one page to another • the words on that site

17. The World Wide Web • There is no that verifies all internet sites • Should you information you find online? • Guidelines to evaluate Web Resources • Does the information appear on a maintained by a ? • Does the website appear to be legitimate? • Is the website , , and ?

18. Email & Other Ways of Communicating over the Net • Email Program • Examples: Microsoft’s Outlook Express, Mozilla’s Thunderbird, Apple’s Apple Mail • Enables you to send email by running email software on your computer that interacts with an email (usually at your ) • mail is stored on the in an electronic mailbox • Upon , mail is sent to your

19. Email … • Using email • Get an , following the format Joe_Black@earthlink.net.us • Type addresses carefully, including capitalization, underscores, and periods • Use the to avoid addressing mistakes • Use the to store email addresses • Sort your email into or use Domain name User Name

20. Email Models • 2 for transferring mail from the to the : • I • 1 for transferring mail from

21. Email Models: • – (NOT to be confused with Point of Presence!) • How this works: • – holds your mail • – logs on and requests mail • – downloads all mail to the client (your computer) • – removes your mail • can disconnect – you’ve got all your mail now! • Advantages: • Don’t need to stay to the for long • are used minimally • More software is currently available for

22. Email Models: • How this works: • – holds your mail • – logs on • – downloads email headings (subject) only • reads mail on the • chooses which mail to and • Mail remains on

23. Email Models: (cont.) • Advantages: • You can your anywhere, from any computer • Faster time (not all your email files) • Good for • Ability to handle (e.g., MIME messages) • can act like – functionally is a superset of

24. Which model is right for you? • : • Your limits your • You use and only to read your email • You can only stay to the for a limited amount of time • Your server has • : • You travel or check your from more than one • You get a lot of and don’t want to it all to your computer • You want to your messages • You can maintain a to your • You have a lot of on your

25. Email Model: • used to transfer data from one to another • Uses • Think of it this way: When you send an email message out, it uses to travel to . When you want to read an email, you use or to get the email message from the .

26. Other Ways of Communicating over the Net • Any user on a given email system can send a message and have it pop up instantly on the screen of anyone logged into that system • Participants have a typed discussion while online at the same time • is one-on-one, but has a list of participants

27. Other Ways of Communicating over the Net • A software standard for transferring between computers with different Operating Systems • A giant electronic discussion board • Usenet is the of servers on the internet www.usenet.com • To participate you need a • An email-based • Uses an automatic that sends to subscribers on selected topics

28. Telephony, Webcasting, Blogs, E-Commerce • Internet Telephony • Uses the internet to make • Long-distance calls are either very inexpensive or free • Currently to normal phone connections • Programs that scour the web and pull together from several to one place • Short for , a diary-style web page • Have become popular, both privately and in politics • Recording internet radio or similar internet audio programs • Some radio stations their audio programs over the internet

29. Telephony, Webcasting, Blogs, E-Commerce • Conducting business activities online • is business-to-business e-commerce • now involves online banking, stock trading online, and e-money such as PayPal • Online link buyers with sellers • is the most well-known example of person-to-person