Internet and World Wide Web

The Internet Today

Internet has come a long way since 1960s. The Internet today is not a simple hierarchical structure. It is made up of very local and wide area networks joined by connecting devices and switching stations. Today Internet is run by private companies and not government.

 

Most people know the Internet through its applications: the World Wide Web, email, streaming audio and video, chat rooms, and music (file) sharing. TheWeb, for example, presents an intuitively simple interface. Users view pages full of textual and graphical objects, click on objects that they want to learn more about, and a corresponding new page appears. Most people are also aware that just under the covers, each selectable object on a page is bound to an identifier for the next page to be viewed. This identifier, called a uniform resource locator (URL), uniquely names every possible page that can be viewed from your Web browser. For example,

http://www.google.com/index.html

is the URL for a page representing google.com: The string http indicates that the HyperText Transfer Protocol (HTTP) should be used to download the page, www.google.com is the name of the machine that serves the page, and index.html uniquely identifies the page at the site.

In this situation, a set of independent networks (clouds) are interconnected to form an internetwork, or internet for short. We adopt the Internet’s convention of referring to a generic internetwork of networks as a lowercase i internet, and the currently operational TCP/IP Internet as the capital I Internet. A node that is connected to two or more networks is commonly called a router or gateway, and it plays much the same role as a switch—it forwards messages from one network to another. Note that an internet can itself be viewed as another kind of network, which means that an internet can be built from an interconnection of internets. Thus, we can recursively build arbitrarily large networks by interconnecting clouds to form larger clouds.

Internet Today

What Is an Internetwork?

We use the term “internetwork,” or sometimes just “internet” with a lowercase i, to refer to an arbitrary collection of networks interconnected to provide some sort of host-to-host packet delivery service. For example, a corporation with many sites might construct a private internetwork by interconnecting the LANs at their different sites with point-to-point links leased from the phone company. When we are talking about the widely used, global internetwork to which a large percentage of networks are now connected, we call it the “Internet” with a capital I. In keeping with the first-principles approach of this book, we mainly want you to learn about the principles of “lowercase i” internetworking, but we illustrate these ideas with real-world examples from the “big I” Internet.

An internetwork is an interconnected collection of such networks. Sometimes, to avoid ambiguity, we

refer to the underlying networks that we are interconnecting as physical networks.

An internet is a logical network built out of a collection of physical networks. In this context, a collection of Ethernets connected by bridges or switches would still be viewed as a single network.

Types of Networks

Parameter	Local Area Network(LAN)	Metropolitan Area Network(MAN)	Wide Area Network(WAN)
Definition	Covers a small geographical area like office, building, campus	Its size is between a LAN and WAN and covers area inside a town or city	Covers a large geographical area
	Privately owned	Both privately owned and publically owned	Multiownership
Diameter	Size limited to few kilometres. Maximum distance=1.3km	Covers hundreds of kilometres. Maximum distance is less than 30-50km	Diameter more than 100km. Maximum distance=30-50km
Topology	Commonly used symmetric topologies are bus, ring and star	It has irregular topologies.	It has irregular topologies.
Data Rate	Data rate is typically 4-16Mbps in range. Speed is normally 100 or 1000Mbps	Data rate is in Mbps but less than that of LAN	Data rate below Mbps
Channel links	They are multi access links	They use broadcast channel	They use point to point link
Error	Error rate is less.	Error rate is higher than LAN but less than WAN	Error rate is thousand times that of LAN
Reliability	LAN cables are reliable	MAN cables are moderately reliable	WAN cables are less reliable
Protocols	Simple	Simple	Complex eg:TCP/IP

 

Internet Servers

A prerequisite for the commercialization of the internet was its ability to provide data in a user friendly manner and to store large volumes of data. It was essential that the contents of a file be displayed directly on the user’s terminal instead of him having to download the file onto his computer nd then view it. This was successfully achieved by servers that re applications running on the host computer and primarily wait for the users requests for providing data stored on it.

The three path breaking developments in the early 1990s that played a significant role in shaping of the Net today are: 
WAIS Wide Area Information Server : It was invented by Brewster Kahle and released by Thinking Machine Corporation. It is distributed information system that allows simple natural language input, indexed searching and relevance feedback. 

    Gopher: Gopher was invented by Paul Linder and Marc McCahill of the University of Minnesota. It is a distributed information system that presents information to the user in the form of hierarchal menus. Co-operation between the many gophers on the Internet allows users to search information on different host computers using the same interface.

    WWW World Wide Web: it was developed by Tim Berners  Lee of Massachusetts’s Institute of Technology and released by the Centre for European Nuclear Research (CERN), Switzerland. The servers are interconnected in the formation of a web an since the network spreads over the globe, it is aptly called the World Wide Web. These servers are called web servers. Each distinct file on a web server that can be downloaded is called a web page. A set of related web pages constitute a web site. The first page of a web site is called its home page. Generally, the domain name of the World Wide Web servers begins with ‘www’ for example www.yahoo.com.

WAIS, Gopher and WWW were the pioneering servers and they registered phenomenal growth.

Hyperlinks

The World Wide Web gradually pushed WAIS and Gopher into oblivion as it offered links to related Web pages called Hyperlinks. The WWW experienced exponential growth and the key underlying technical idea behind this technology was the Hyper Text Markup Language (HTML).

The protocol used by the WWW is the Hyper Text Transfer Protocol (HTTP). Hence, all addresses on the world Wide Web begin with http:// These addresses are called Uniform Resource Locater (URLs) and they aid the browsers to find the documents as well as getting the information.

The links between resources started a new chapter in the evolution of the Internet. A user could hop from one link to another on the Internet commonly known as ‘surfing the net’. Internet had become interactive and this added tremendous value to it as a media.

It is important to emphasise that the Internet and WWW are two separate entities. The internet is a connection of computers networked, so that each individual network can transmit data among themselves. The WWW is software created to  make communication of information among networks simpler.

Browsers

In 1993, traffic on the Internet was growing at the rate of 341,634 per cent per annum and the number of hosts had grown to over 1500000. The stage was set for the software that could facilitate surfing on the net, also called browsing. Mosaic jumped on the opportunity, occupied the centre stage and took the world by storm. It was the first Windows based front –end to the WWW released by the National Centre for upper Computing Applications (NCSA). Its graphical user-interface made it instantly popular amongst users. Close on the heels of Mosaic was Netscape Navigator, the most popular browser today. Other browsers like Microsoft Internet Explorer came in later.

As the wars between the browsers for market share steamed up, the technologies supporting Internet rapidly developed and many new technologies were also born.

Hyper Text Markup Language (HTML)

In essence, HTML is text enclosed in tags that describe it. For example<b> Today is Sunday </b> has the text ‘Today is Sunday’ enclosed between the tags <b> and </b> that result in the text being presented in bold letters. The hyperlinks to related resources are similarly enclosed in tags.

HTML 1.0 supported simple text and graphics only. Rival browser manufacturers incorporated special features in their browsers to spur sales and many of these features became a part of the HTML standard. Later versions included tables for page layouts, background images, advanced text alignments, frames and a host of such features. These features added significantly to the aesthetics of the web pages.

The mid 90s saw a transition in the usage of the Internet. Whereas, initially, the internet was primarily used for information dissemination, the proliferation of Internet users and web sites of commercial setups added anew flavour to surfing. Web sites wanted to attract as many surfers as possible and get them hooked on to their site so that they would revisit it.

New Technologies and Innovations

There was a strong need to replace static pages with interactive dynamic pages to attract the visitor and to keep him glued to the web site. As HTML is essentially text and graphics with some minor adornments, something different was required. Thus, new technologies that could do computing at client-end like JavaScript came into being. Technologies that could do processing at the server-end like CGI-Perl, Active Server Pages (ASP’s) and Cold Fusion could query and update large databases.

The fundamental problem with scripting languages is that they are exposed to the user and cannot be trusted for confidential information. Java, with a repertoire of secure, robust and platform independent features, has become important for handling secure transactions and is poised to make a difference to commerce on the internet.

HTML itself has gone through a revolution and Dynamic HTML (DHTML) and Extensible Markup Language (XML) have found their own place in the market.

Tools for developing web pages and sites have done their rounds of the market-place. Some of the more popular tools are Microsoft Front Page, Netscape Composer and Hotdog.

One can listen to music on the Net, courtesy RealAudio and watch movies too with Quick Time Movie. A standard for Virtual Reality models, VRML is also in page.

Restricted usage of the web is possible through 'firewalls' that allow only specific IP addresses to have access to specific web pages giving rise to Intranets- a LAN on the Internet.

The innovations have been far too many limited time frame. This has been the hallmark of Internet technologies since its onset and the trend will probably continue.

Search Engine

Principally, traffic on a web site can be generated by propagating it through the print media. As traditional media is quite expensive, the Internet itself came to the rescue by providing a zero cost innovation- search engine.

Search engines are web sites maintaining gargantuan databases of web sites and their contents. If you want to locate companies manufacturing piston rings, all you need to do is to specify the search string ‘Piston ring’ in the search and you get the list of related web sites. Registering a web site on a search engine became the fastest, inexpensive and convenient manner to increase traffic to the web site. Some of the more popular search engines are www.yahoo.com, www.excite.com and www.altavista.com. It is interesting to note that innovation and its rapid adoption by net surfers is an important attitudinal aspect leading to the success of the net.