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Intro to the Internet

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. Brief History. Internet History Began with 1969’s ARPANET for US Dept. of Defense 62 computers in 1974

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Intro to the Internet

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  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

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