fall 2005 - introduction to internet computing copyright © 2005 dr. oge marques1 topic 1 -...

Fall 2005 - Introduction to Internet Computing Copyright © 2005 Dr. Oge Marques 1

Topic 1 - Introduction to the Internet, Web, and Web browsers

Outline1 History of the Internet2 The Internet today3 Host Machines and Host Names4 The Client/Server Software Model5 Personal Computing6 The World Wide Web 7 Web Browsers8 Searching the Internet


History of the Internet ARPAnet

Implemented in late 1960’s by ARPA (Advanced Research Projects Agency of DoD)

Networked computer systems of a dozen universities and institutions with 56Kbps communications lines

Grandparent of today’s Internet Intended to allow computers to be shared Became clear that key benefit was allowing

fast communication between researchers – electronic-mail (email)


History of the Internet

ARPA’s goals Allow multiple users to send and receive info

at same time Network operated packet switching

technique Digital data sent in small packages called packets Packets contained data, address info, error-control

info and sequencing info Greatly reduced transmission costs of dedicated

communications lines Network designed to be operated without

centralized control If portion of network fails, remaining portions still

able to route packets



Transmission Control Protocol (TCP) Name of protocols for communicating over

ARPAnet Ensured that messages were properly routed

and that they arrived intact Organizations implemented own networks

Used both for intra-organization and communication



Huge variety of networking hardware and software appeared ARPA achieved inter-communication between all

platforms with development of the IP Internetworking Protocol Current architecture of Internet

Combined set of protocols called TCP/IP The Internet

Limited to universities and research institutions Military became big user Next, government decided to access Internet for

commercial purposes



Internet traffic grew Businesses spent heavily to improve Internet

Better service their clients Fierce competition among communications

carriers and hardware and software suppliers Result

Bandwidth (info carrying capacity) of Internet increased tremendously

Costs plummeted


The Internet is a network of networks that are spread all over the world

Networks that are geographically close are called Local Area Networks (LANs)

Often in the same building The university’s network is a prime example

The Internet is a largely heterarchical network containing many individual LANs

A heterarchical network contains many nodes that are interconnected.

A hierarchical network contains a tree-like structure where some nodes are superior to others.

The Internet today


The Internet today


A characteristic of a heterarchical network is that it is a robust network.

If some nodes are removed, data can still be sent between nodes

Hierarchical networks do not lend themselves to robustness

The Internet also has dynamic routing, where the route of the data is determined at the time of transmission based on current network conditions.

The Internet today


The Internet today

How big is the Internet? Number of networks Number of servers Number of domain hosts Number of (indexed) web pages / web sites Usage statistics Number of countries Amount of stored information

What about the Deep Web?


Each computer on the Internet is a host machine.

Each computer has a unique Internet Protocol (IP) address, such as 124.110.24.1 Some computers have a permanent IP address Some computers borrow an IP address while

they are connected to the Internet An IP address is not human-friendly

Host Machines and Host Names


The IP address for most host machines are mapped to a Domain Name Service (DNS) address in order to be more people-friendly

The DNS address consists of a host name followed by a domain name

Example DNS Address: mail.yahoo.com Host Name is: mail Domain Name is: yahoo.com



Each domain name consists of: Institutional site name Top Level Domain name (TLD)

Example: cse.fau.edu cse.fau is the Dept. of Computer Science and

Engineering at Florida Atlantic University edu refers to an educational site



Examples of TLDs include: .com a commercial organization .edu a US educational site .net a network site .au Australia .fr France .hk Hong Kong .es Spain ... (many others)



New TLDs have been added as the original set became overloaded

While each machine has a unique IP address, it can have multiple DNS addresses (called aliases)

Anyone can register a DNS address When you type in a DNS address, a

domain name server translates it into an IP address.



Clients and servers are host machines A client is the host machine that requests

information from the server The server is a resource that provides a

service for (many) clients The client/server interaction is the

foundation for all Internet communication

The Client/Server Software Model


Some companies use servers that do not need to be installed on the client to supply commercial software to clients

Application Service Providers (ASPs) provide software through subscriptions

The software is “rented” with this arrangement



Personal Computing

IBM 1981, introduced IBM Personal Computer Made personal computing legitimate in

business, industry and government organizations

Computers were “stand-alone” units Info only shared between computers through

exchange of discs Machines could be linked

Over telephone lines Over Local Area Networks (LANs)

Led to distributed computing


Personal Computing

Computers today As powerful as million dollar machines from 20 years

ago Workstations

Most powerful desktops today Provide users with enormous capabilities

Information easily shared over networks Networks controlled by servers

Common programs and data used by client computers Popular operating systems

UNIX, MacOS, Windows XP, Linux Portable devices (PDAs, tablet PCs, cell phones) with

great computing power


The World Wide Web (WWW or Web) has become a popular means of accessing information and services.

The Web allows computer users to easily locate and view multimedia-based documents.

Introduced in 1990 by Tim Berners-Lee The Web and the Internet (Net) are not the

same. A Web browser is the software necessary to view

information. Some browsers are integrated into other

software, such as an email client.

The World Wide Web


Navigating the Web only takes a few commands.

The information in the Web is organized as hypertext, graphics, video, and sound

The text in a Web page may contain hyperlinks that, if clicked, allows you to view related information on other Web pages.

You control where you go and what information you see via these hyperlinks

The World Wide Web


A Web page is a document on the Web that you view through your Web browser

The act of reading Web pages and clicking on hyperlinks is called browsing

Browsing can be seen as a way of exploring

Each Web page has a unique address called a Uniform Resource Locator (URL) that you can use to jump directly to it

The World Wide Web


The World Wide Web

World Wide Web Consortium (W3C) (www.w3.org) Founded in 1994 by Tim Berners-Lee

Devoted to developing non-proprietary and interoperable technologies for the World Wide Web and making the Web universally accessible

Standardization W3C Recommendations: technologies standardized by

W3C include Extensible HyperText Markup Language (XHTML),

Cascading Style Sheets (CSS) and the Extensible Markup Language (XML)

Document must pass through Working Draft, Candidate Recommendation and Proposed Recommendation phases before considered for W3C Recommendation


Web browsers Popular browsers (and market share as of Jan 2005)

(Source: http://www.w3schools.com/browsers/browsers_stats.asp)

Microsoft’s Internet Explorer: 69.9% Firefox: 18.7% Mozilla: 4.1 % Opera: 2.1% Netscape: 1.4 % Others (Safari, Camino, Epiphany, iRider, and several others...):

3.8 % Browser portability

Great challenge Great diversity of client browsers in use Many different platforms also in use

Difficult to Know capabilities and features of all browsers and platforms in

use Find correct mix between absolute portability, complexity and

usability of features


Web browsers Different browsers can be distinguished from each other

by the features they support. Modern browsers and web pages tend to use many features and techniques that did not exist in the early days of the web.

Some of contemporary browsers’ elements and features: ActiveX Ad filtering Autocompletion of URLs and form data Bookmarks for keeping track of frequently accessed

locations Cascading Style Sheets Cookies which enable a website to track a returning user Caching of web content Digital certificates Download management DHTML Embedded images using established graphics file formats

such as GIF, PNG, JPEG, SVG Flash


Web browsers Browser elements and features (cont’d)

Favicons Fonts, size, color Forms for submitting information Frames and IFrames History of recently visited pages HTTPS Integration with other desktop applications Offline browsing of cached content Java applet JavaScript for dynamic content Plug-ins Session management Tabbed browsing Tables XHTML and XML


Searching the Internet Search engines

Web sites that sort through by keywords and categories

Google (www.google.com) The rest

Store information in databases Returns list of sites as hyperlinks

Meta-search engines Do not maintain databases Aggregate results from multiple search

engines Meta Crawler (http://www.metacrawler.com/)


Fun Assignment (FA) # 1 Select a browser of your preference and:

Explore all its menus and options Customize it to your needs and preferences Compare against other browsers Use it to explore Google


Links of the day Blackboard @ FAU:

http://blackboard.fau.edu/ Wikipedia, the free encyclopedia:

http://en.wikipedia.org/wiki/Web_browser Google:

http://www.google.com/

Contribute your own favorite links via Bb’s Discussion Board (“Useful links” forum)

fall 2005 - introduction to internet computing copyright © 2005 dr. oge marques1 topic 1 -...

Documents

internet internet traffic

internet slide

internet arpanet

internet computing copyright

capacity of internet

internet limited

internet arpas goals

internet better service