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History of Internet
Late 1960s, Internet is called ARPANET Consisted of two network nodes (hosts)
located at Univ. of Calif., Los Angeles and Stanford Univ. – connected by phone lines
Today, the Internet has grown into interconnection of mobile phones, PDAs, televisions, networks
Connections now consist of fiber optics cables, satellites, phone lines, other media
The World Wide Web
Foundations for WWW (triple W or Web) were laid in 1989 by Timothy Berners-Lee and other researchers at CERN nuclear research facility near Geneva, Switzerland
Rather than using some crazy arrays of terms, acronyms and commands, a simpler interface was created: the WWW
ISP
An Internet service provider is a company or business that provides access to the Internet and related services.
In the past, most ISPs were run by the phone companies.
Now, ISPs can be started by just about any individual or group with sufficient money and expertise.
In addition to Internet access via various technologies such as dial-up and DSL, they may provide a combination of services including Internet transit, domain name registration and hosting, web hosting, and collocation.
IP IP is a network layer protocol in the Internet
protocol suite and is encapsulated in a data link layer protocol (e.g., Ethernet).
As a lower layer protocol, IP provides the service of communicable unique global addressing amongst computers.
An IP address (or Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address.
IP IP addresses are managed and created by
the Internet Assigned Numbers Authority (IANA). The IANA generally allocates super-blocks to Regional Internet Registries.
Figure 1b : An illustration of an IP address (version 4), in both dot-decimal notation and binary.
Hypertext
Method of organizing information that gives readers control over the order that information is presented
Gives quicker and simpler access to diverse pieces of information
Unlike reading a book, where a linear progression is used (reading page by page), hypertext allows a myriad of ways where readers can straight away go to where they desire
… contd.
Key to hypertext is hyperlinks (links)› Allows users to jump from one document
to another Individual web page may includes the
elements of multimedia› Texts, animation, graphics, audio, video
and other programs
Web Server & Web Browser
Web Server› This is where web pages are stored, which
made available to the network Web Browser
› A client runs this to view a Web page
URL
Uniform Resource Locator (URL) is comprised of the protocol, followed by the domain name
Hypertext Transfer Protocol Domain name can be an IP address or
a text version of this address
http://pucinfo.calumet.purdue.edu http://205.216.71.230
protocol IP
address
protocol domain name
dns Domain Name System (DNS) is to
translate hostnames to IP addresses. DNS distributes the responsibility for assigning domain names and mapping them to IP networks by allowing an authoritative name server
Search Engine
A search engine is an information retrieval system designed to help find information stored on a computer system.
A Web search engine is a search engine designed to search for information on the World Wide Web. Information may consist of web pages, images and other types of files.
Other Internet Services a. FTP
› File Transfer Protocol (FTP) is a network protocol used to transfer data from one computer to another through a network, such as over the Internet. While transferring data over the network, several data representations can be used. ASCII mode Binary mode: In "Binary mode", the sending machine sends each file byte for byte and
as such the recipient stores the bytestream as it receives it. (The FTP standard calls this "IMAGE" or "I" mode)
› e.g. ftp://ftp.centre2u.com/ b. Email
› Electronic Mail (e-mail) is a store and forward method of composing, sending, receiving and storing messages over electronic communication systems
c. Newsgroups
› Newsgroup is a web application for holding discussions and posting user-generated content. its also commonly referred to as Web forums, message boards, discussion boards, (electronic) discussion groups, discussion forums, bulletin boards or forums.
d. Mailing Lists
› A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients.
cont,.. f. Chat Rooms
› A chat room is a term used primarily by mass media to describe any form of synchronous conferencing, occasionally even asynchronous conferencing
› The term can thus mean any technology ranging from real-time online chat over instant messaging and online forums to fully immersive graphical social environments.
g. Web Portals
› Web portal is site that provides a single function via a web page or site. Portals provide a way for enterprises to provide a consistent look and feel with access control and procedures for multiple applications, which otherwise would have been different entities altogether.
› Two broad categorization of portals are a. Horizontal portals (e.g. Yahoo) b. Vertical portals (focused on one functional area. e.g., salesforce.com)
h. telnet
› A terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on computer and connects PC to a server on the network. User can enter commands through the Telnet program and they will be executed directly on the server console. This enables user to control the server and communicate with other servers on the network.
Impact of the Internet and the Web
Communication› worldwide communication medium that lends itself to the
peculiar needs of international dialogue› Email, video conferencing, chat etc.
Education› Formal and informal teaching and learning› Learning and Teaching Style› Enhances traditional teaching methods› Online education or web base environment (course, material
etc.)
Entertainment
› Entertainment web sites include music, videos, sports, games, and Online gambling.
Cont.. Business
› Electronic commerce (e-commerce) is the practice of conducting business activities online, such as shopping
› Opportunity to change its relationships with the organizations and individuals with which it does business--from trading partners to suppliers, from internal customers to end customers
› Business-to-consumer (B2C), Business-to-business (B2B, Consumer-to-consumer (C2C).
› Internet marketing, advertising.› operation efficiencies and reduced costs.
Medical› informational web-based tools for physicians, patients, and their
families for best practices in clinical care, research, and education.
› Share online medical resources.
Client-Server Definition
A client is defined as a requester of services and a server is defined as the provider of services.
Two tier architectures consist of three components distributed in two layers: client (requester of services) and server (provider of services).
The three components are :› User System Interface (such as session, text input,
dialog, and display management services) › Processing Management (such as process
development, process enactment, process monitoring, and process resource services)
› Database Management (such as data and file services)
Cont.. The three tier architecture (also referred to as the multi-tier architecture)
emerged to overcome the limitations of the two tier architecture. In the three tier architecture, a middle tier was added between the user
system interface client environment and the database management server environment.
There are a variety of ways of implementing this middle tier, such as transaction processing monitors, message servers, or application servers. The middle tier can perform queuing, application execution, and database staging.
Characteristics
Characteristics of a client :› Request sender is known as client› Initiates requests› Waits for and receives replies.› Usually connects to a small number of
servers at one time› Typically interacts directly with end-users
using a graphical user interface
Cont..
Characteristics of a Server :› Receiver of request which is sent by client is
known as server› Passive (slave)› Waits for requests from clients› Upon receipt of requests, processes them
and then serves replies› Usually accepts connections from a large
number of clients› Typically does not interact directly with end-
users
advantages Greater ease of maintenance. For example, it is possible to
replace, repair, upgrade, or even relocate a server while its clients remain both unaware and unaffected by that change. This independence from change is also referred to as encapsulation.
All the data is stored on the servers, which generally have far greater security controls than most clients. Servers can better control access and resources, to guarantee that only those clients with the appropriate permissions may access and change data.
Since data storage is centralized, updates to those data are far easier to administer than would be possible under a P2P paradigm.
Many mature client-server technologies are already available which were designed to ensure security, 'friendliness' of the user interface, and ease of use.
It functions with multiple different clients of different capabilities.
Web server
The term web server can mean one of two things:› i) A computer program that is responsible
for accepting HTTP requests from clients, which are known as web browsers, and serving them HTTP responses along with optional data contents, which usually are web pages such as HTML documents and linked objects (images, etc.).
› ii) A computer that runs a computer program as described above.
Application server An application server is a software engine that delivers
applications to client computers or devices, typically through the Internet and using the HyperText Transfer Protocol(HTTP). Application servers are distinguished from web servers by the extensive use of server-side dynamic content and frequent integration with database engines.
Example :Wiki is an application server that allows users to build dynamic content assembled from articles. Moreover, Wikipedia is an assembled Wiki that delivers an encyclopedia stored in a files ystem, with changes to the encyclopedia stored in a database.
The term is used to refer to servers of web-based applications, such as integrated platforms for e-commerce, content management systems, and web-site builders. Alternatively, the term is used as a synonym for web application framework.
DATABASE SERVER
A database server is a computer program that provides database services to other computer programs or computers, as defined by the client-server model. The term may also refer to a computer dedicated to running such a program. Database management systems frequently provide database server functionality, and some DBMS's (e.g., MySQL) rely exclusively on the client-server model for database access.
BENEFIT OF USING DATABASE SERVER
A database server allows users to store data in one central location.
It performs complex functions such as searching, sorting, and indexing on the server itself. This reduces network traffic because fewer items need to be transferred between the client and the server.
Because data is stored centrally, there is enhanced security.
A database server uses its own processing power to find requested data, rather than sending the complete data to the client so that the client searches for the data, as is done in a file server.
A database server allows concurrent access to data.
STATIC WEB PAGES A static Web page is a Web page that always comprises the same
information in response to all download requests from all users. Contrast with Dynamic web page.
It displays the same information for all users, from all contexts,
providing the classical hypertext, where navigation is performed through "static" documents.
Advantages
› Quick and easy to put together, even by someone who doesn't have much experience.
› Ideal for demonstrating how a site will look.› Cache friendly, one copy can be shown to many people.
Disadvantages
› Difficult to maintain when a site gets large.› Difficult to keep consistent and up to date.› Offers little visitor personalization (all would have to be client side).
DYNAMIC WEB PAGES
Web navigation can also provide an interactive experience that is termed "dynamic".
Content (text, images, form fields, etc.) on a web page can change, in response to different contexts or conditions.
Dynamic HTML or DHTML is a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (Cascading Style Sheets, CSS), and the Document Object Model.
Cont.. There are two ways to create this kind of interactivity: a) Client-side :
› The Client-side dynamic content is generated on the client's computer. The web server retrieves the page and sends it as is. The web browser then processes the code embedded in the page (typically written in JavaScript) and displays the page to the user. 1. ActionScript 2. JavaScript
The problems with client-side dynamic pages are:› - Some browsers do not support the language or they do not
support all aspects (like write command and innerHTML property) of the language.
› - The information cannot be stored anywhere but the user's computer, so it cannot really be used for statistics gathering.
› - Search engines are not able to run client-side languages and cannot crawl links generated by them.
› - Some users have scripting languages disabled in their browsers due to possible security threats.
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