Internet & Networking


Internet is a global network that connect many computers located at different part of the world. It is a public network which is open to all. TCP an IP are the two major protocols on which the whole internet is based. They are the backbone of internet.

The Internet is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide. It is a network of networks that consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, telephony, and file sharing.

  • Global Network
  • International Network
  • Network of Networks
  • Interconnected Networks

History of Internet 

In 1969 , Department of Defence (DOD) of USA started a network called ARPANET (Advanced Research Project Agency Network) to facilitate its research work. Later in 1982, TCP an IP protocol were standardized with the invent of TCP/IP internet has grown. In india, first Internet Service called GIAS (Gateway Internet Access Service) was started in 15th Aug, 1995 by VSNL (Videsh Sanchar Nigam LImited). 

Computer Network

The Network allows computers to connect and communicate with different computers via any medium. LAN, MAN and WAN are the three major types of the network designed to operate over the area they cover. There are some similarities and dissimilarities between them. One of the major differences is the geographical area they cover, i.e. LAN covers the smallest area; MAN covers an area larger than LAN but smaller than WAN; and WAN covers largest area.

There are other types of Computer Networks also, like :

  • PAN (Personal Area Network)
  • SAN (Storage Area Network)
  • EPN (Enterprise Private Network)
  • VPN (Virtual Private Network)

LOCAL  AREA  NETWORK (LAN)

LAN or Local Area Network connects network devices in such a way that personal computer and workstations can share data, tools and programs. The group of computers and devices are connected together by a switch, or stack of switches, using a private addressing scheme as defined by the TCP/IP protocol. Private addresses are unique in relation to other computers on the local network. Routers are found at the boundary of a LAN, connecting them to the larger WAN.

Data transmits at a very fast rate as the number of computers linked are limited. By definition, the connections must be high speed and relatively inexpensive hardware (Such as hubs, network adapters and Ethernet cables). LANs cover smaller geographical area (Size is limited to a few kilometers) and are privately owned. One can use it for an office building, home, hospital, schools, etc. LAN is easy to design and maintain. A Communication medium used for LAN has twisted pair cables and coaxial cables. It covers a short distance, and so the error and noise are minimized. Early LAN’s had data rates in the 4 to 16 Mbps range. Today, speeds are normally 100 or 1000 Mbps.

METROPOLITAN AREA NETWORK (MAN)

MAN or Metropolitan area Network covers a larger area than that of a LAN and smaller area as compared to WAN. It connects two or more computers that are apart but resides in the same or different cities. It covers a large geographical area and may serve as an ISP (Internet Service Provider). MAN is designed for customers who need a high-speed connectivity. Speeds of MAN ranges in terms of Mbps. It’s hard to design and maintain a Metropolitan Area Network.

It is costly and may or may not be owned by a single organization. The data transfer rate and the propagation delay of MAN is moderate. Devices used for transmission of data through MAN are: Modem and Wire/Cable. Examples of a MAN are the part of the telephone company network that can provide a high-speed DSL line to the customer or the cable TV network in a city.

WIDE AREA NETWORK (WAN)

WAN or Wide Area Network is a computer network that extends over a large geographical area, although it might be confined within the bounds of a state or country. A WAN could be a connection of LAN connecting to other LAN’s via telephone lines and radio waves and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high speed and relatively expensive.

There are two types of WAN: Switched WAN and Point-to-Point WAN. WAN is difficult to design and maintain. A Communication medium used for WAN is PSTN or Satellite Link. Due to long distance transmission, the noise and error tend to be more in WAN.

WAN’s data rate is slow about a 10th LAN’s speed, since it involves increased distance and increased number of servers and terminals etc. Speeds of WAN ranges from few kilobits per second (Kbps) to megabits per second (Mbps). Propagation delay is one of the biggest problems faced here. Devices used for transmission of data through WAN are: Optic wires, Microwaves and Satellites. Example of a Switched WAN is the asynchronous transfer mode (ATM) network and Point-to-Point WAN is dial-up line that connects a home computer to the Internet.

ISP (Internet Service Provider) : The organization that provides internet service to companies and users is known as an ISP. Some of the inidan ISPs are BSNL, MTNL, Reliance, TATA, etc.              

Internet Services

Internet Services allows us to access huge amount of information such as text, graphics, sound and software over the internet. Following diagram shows the four different categories of Internet Services.

WWW (World Wide Web) : WWW is a storehouse of information. It is a collection of all the web services located at different part of the world. WWW stands for World Wide Web. WWW is also known as W3. It offers a way to access documents spread over the several servers over the internet. These documents may contain texts, graphics, audio, video, hyperlinks. The hyperlinks allow the users to navigate between the documents.

A technical definition of the World Wide Web is : all the resources and users on the Internet that are using the Hypertext Transfer Protocol (HTTP). A broader definition comes from the organization that Web inventor Tim Berners-Lee helped found, the World Wide Web Consortium (W3C). The World Wide Web is the universe of network-accessible information, an embodiment of human knowledge.

Evolution

World Wide Web was created by Timothy Berners Lee in 1989 at CERN in Geneva. World Wide Web came into existence as a proposal by him, to allow researchers to work together effectively and efficiently at CERN. Eventually it became World Wide Web.

In simple terms, The World Wide Web is a way of exchanging information between computers on the Internet, tying them together into a vast collection of interactive multimedia resources.

Internet and Web is not the same thing: Web uses internet to pass over the information.

WWW Operation

WWW works on client- server approach. Following steps explains how the web works:

1. User enters the URL (say, http://www.pcieduhub.com) of the web page in the address bar of web browser.

2. Then browser requests the Domain Name Server for the IP address corresponding to www.pcieduhub.com.

3. After receiving IP address, browser sends the request for web page to the web server using HTTP protocol which specifies the            way the browser and web server communicates.

4. Then web server receives request using HTTP protocol and checks its search for the requested web page. If found it returns it            back to the web browser and close the HTTP connection.

5. Now the web browser receives the web page, It interprets it and display the contents of web page in web browser’s window.

E-mail (Electronic Mail) : It is a private letter written and send by one internet user to another internet user. For sending and receiving e-mail we need a valid e-mail ID. Email is an important communications service available on the Internet. Pictures, documents, and other files are sent as email attachments

FTP (File Transfer Protocol) : Allows to transfer files (download and upload) between server and client. File sharing is an example of transferring large amounts of data across the Internet. A computer file can be emailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or File Transfer Protocol (FTP) server for easy download by others.

Newsgroup : These are electronic discussion groups where user can join and share their ideas, view, etc with the other members of that group. Newsgroups Offers a forum for people to discuss topics of common interests.

IRC (Internet Relay Chat) : Chatting with someone we need to connect with a chat server that conducts the chat. IRC allows the people from all over the world to communicate in real time.

Telnet : It is an internet service that allows to remote login on any other computer available on internet and use its resources. Telnet used to log on to a remote computer that is attached to internet.

Instant Messaging : It offers real time chat between individuals and group of people. Eg. Yahoo messenger, MSN messenger.

WEBSITE : Website is a collection of webpages. The first page of a website is known as Home page. The first page of the website is like an Index page that contains links to other pages on the site. Web pages are created using different technologies like HTML, ASP, JSP, PHP,etc. Website is a location on web and is hosted on a web server. It is a set of related web pages. It is accessed using Internet address known as Uniform Resource Locator

Categories of Web pages :        

a) Static Web Pages b) Dynamic Web Pages

a) Static Web Pages : HTML is used to create webpages. Static websites are also known as flat or stationary websites. They are loaded on the client’s browser as exactly they are stored on the web server. Such websites contain only static information. User can only read the information but can’t do any modification or interact with the information. Static websites are created using only HTML. Static websites are only used when the information is no more required to be modified.

b) Dynamic Web Pages : These pages show information that change frequently like a page that shows score of a live match, weather report or stock information. These pages are designed using technologies like ASP(Active Server Page), JSP (Java Script Page), CGI (Common Gateway Interface), PHP (Personal Home Page), etc.

Server-side dynamic web page

It is created by using server-side scripting. There are server-side scripting parameters that determine how to assemble a new web page which also include setting up of more client-side processing.

Client-side dynamic web page

It is processed using client side scripting such as javascript. And then passed in to Document Object Model (DOM).

Web Server

Web servers are also called HTTP servers. These are the computers that store web pages. After creating website, we need to host or publish it. For web hosting we need space on web server. Web server  receives request from web clients, process the request and returns requested page to the client system. Web server is a computer where the web content is stored. Basically web server is used to host the web sites but there exists other web servers also such as gaming, storage, FTP, email etc. Web site is collection of web pages while web server is a software that respond to the request for web resources.

Web Server Working

Web server respond to the client request in either of the following two ways:

• Sending the file to the client associated with the requested URL.

• Generating response by invoking a script and communicating with database

Web Browser

Web Browser is an application software that allows us to view and explore information on the web. User can request for any web page by just entering a URL into address bar. Web browser can show text, audio, video, animation and more. It is the responsibility of a web browser to interpret text and commands contained in the web page. Earlier the web browsers were text-based while now a days graphical-based or voice-based web browsers are also available. Following are the most common web browser available today:

        Browser                                   Vendor

  • Internet Explorer                      Microsoft
  • Google Chrome                               Google
  • Mozilla Firefox                                 Mozilla                
  • Netscape Navigator               Netscape Communications Corp.
  • Opera                                           Opera Software
  • Safari                                           Apple

Architecture

There are a lot of web browser available in the market. All of them interpret and display information on the screen however their capabilities and structure varies depending upon implementation. But the most basic component that all web browser must exhibit are listed below:

• Controller/Dispatcher

• Interpreter

• Client Programs

Controller works as a control unit in CPU. It takes input from the keyboard or mouse, interpret it and make other services to work on the basis of input it receives.

Interpreter receives the information from the controller and execute the instruction line by line. Some interpreter are mandatory while some are optional For example, HTML interpreter program is mandatory and java interpreter is optional.

Client Program describes the specific protocol that will be used to access a particular service. Following are the client programs that are commonly used:

• HTTP

• SMTP

• FTP

• POP

HTTP (Hypertext Transfer Protocol) : HTTP (Hypertext Transfer Protocol) is the set of rules for transferring files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. As soon as a Web user opens their Web browser, the user is indirectly making use of HTTP. HTTP is an application protocol that runs on top of the TCP/IP suite of protocols (the foundation protocols for the Internet).

URL(Uniform Resource Locator)

A URL (Uniform Resource Locator) is a form of URI and is a standardized naming convention for addressing documents accessible over the Internet and Intranet. An example of a URL is https://www.computerhope.com/, which is the URL for the Computer Hope website.

URL has for parts 

1) Protocol

2) Domain name of server or IP Address

3) Directory (Optional)

4) File Name (Optional)

Eg. :       http://www.google.com

                http://www.kanpuruniversity.org/result/aspx

                http://www.yahoo.com/images/mail.gif