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.

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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

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Our Internet

NAP-AIP: A.0.0

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NAP-BIP: B.0.0 NAP-C

IP:C.0.0

NAP-EIP:E.0.0

Amazon.com ServerIP: A.AS.0

NAP-DIP:D.0.0

ISP2/POP-1IP:B.1.0

ISP2/POP-6IP:B.6.0

Udel-4IP:C.4.0

Comcast/POP-3IP:D.3.0

Comcast/POP-5IP:D.5.0

ISP1/POP-2IP:E.2.0

PC-aIP:B.1.a

MAC-aIP:B.6.a

MAC-aIP:C.4.a

PC-bIP:C.4.b

PC-bIP:D.5.b

PC-aIP:D.5.a

MAC-aIP:D.3.a

PC-bIP:D.3.b

PC-aIP:E.2.a

MAC-dIP:B.6.d

MAC-bIP:B.6.b MAC-c

IP:B.6.c

PC-dIP:E.2.d

PC-bIP:E.2.b

PC-cIP:E.2.c

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

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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

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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

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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

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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,

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Services Offered by the Internet?

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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

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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

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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

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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

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protocol domain name file name . extensiondirectory

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.

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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

another2-15

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

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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 ?

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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

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Email …

Using email1. Get an , following the

format Joe_Black@earthlink.net.us

2. Type addresses carefully, including capitalization, underscores, and periods

3. Use the to avoid addressing mistakes

4. Use the to store email addresses

5. Sort your email into or use 2-19

User Name Domain name

Email Models

2 for transferring mail from the to the : I

1 for transferring mail from

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Email Models:

– (NOT to be confused with Point of Presence!) How this works:

1. – holds your mail2. – logs on and requests mail3. – downloads all mail to the client (your

computer)4. – removes your mail 5. 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 2-21

Email Models:

How this works:

1. – holds your mail2. – logs on 3. – downloads email

headings (subject) only▪ reads mail on the ▪ chooses which mail to

and ▪ Mail remains on

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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

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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

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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 .

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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

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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

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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 internet2-28

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 2-29