The Browser

A browser is an application program that provides a way to look at and interact with all the information on the World Wide Web. The word "browser" seems to have originated prior to the Web as a generic term for user interfaces that let you browse (navigate through and read)text files online.

Technically, a Web browser is a client program that uses HTTP (Hypertext Transfer Protocol) to make requests of Web servers throughout theInternet on behalf of the browser user. Most browsers support e-mail and the File Transfer Protocol (FTP) but a Web browser is not required for those Internet protocols and more specialized client programs are more popular.

The first Web browser, called WorldWideWeb, was created in 1990. That browser's name was changed to Nexus to avoid confusion with the developing information space known as the World Wide Web. The first Web browser with a graphical user interface was Mosaic, which appeared in 1993. Many of the user interface features in Mosaic went into Netscape Navigator. Microsoft followed with its Internet Explorer (IE).

As of September 2006, Internet Explorer is the most commonly used browser, having won the so-called browser wars between IE and Netscape. Other browsers include:

Network Backbone

A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks. A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it.

A diagram of a typical nationwide network backbone.

A large corporation that has many locations may have a backbone network that ties all of the locations together, for example, if a server cluster needs to be accessed by different departments of a company that are located at different geographical locations. The pieces of the network connections (for example: ethernet, wireless) that bring these departments together is often mentioned as network backbone. Network congestion is often taken into consideration while designing backbones.

One example of a backbone network is the Internet backbone.

Distributed backbone

A distributed backbone is a backbone network that consists of a number of connectivity devices connected to a series of central connectivity devices, such as hubs, switches, or routers, in a hierarchy.^[6] This kind of topology allows for simple expansion and limited capital outlay for growth, because more layers of devices can be added to existing layers.^[6] In a distributed backbone network, all of the devices that access the backbone share the transmission media, as every device connected to this network is sent all transmissions placed on that network.^[7]

Distributed backbones, in all practicality, are in use by all large-scale networks.^[8] Applications in enterprise-wide scenarios confined to a single building are also practical, as certain connectivity devices can be assigned to certain floors or departments.^[6] Each floor or department possesses a LAN and a wiring closet with that workgroup's main hub or routerconnected to a bus-style network using backbone cabling .^[9] Another advantage of using a distributed backbone is the ability for network administrator to segregate workgroups for ease of management.^[6]

There is the possibility of single points of failure, referring to connectivity devices high in the series hierarchy.^[6] The distributed backbone must be designed to separate network traffic circulating on each individual LAN from the backbone network traffic by using access devices such as routers and bridges.^[10]

Collapsed backbone[edit]

A collapsed backbone (inverted backbone, backbone-in-a-box) is a type of backbone network architecture. The traditional backbone network goes over the globe to provide interconnectivity to the remote hubs. In most cases, the backbones are the links while the switching or routing functions are done by the equipment at each hub. It is a distributed architecture.

In the case of a collapsed or inverted backbone, each hub provides a link back to a central location to be connected to a backbone-in-a-box. That box can be a switch or a router. The topology and architecture of a collapsed backbone is a star or a rooted tree.

The main advantages of the collapsed backbone approach are

1. ease of management since the backbone is in a single location and in a single box, and
2. since the backbone is essentially the back plane or internal switching matrix of the box, proprietary, high performance technology can be used.

However, the draw back of the collapsed backbone is that if the box housing the backbone is down or there are reachabilityproblem to the central location, the entire network will crash. These problems can be minimized by having redundant backbone boxes as well as having secondary/backup backbone locations.

Parallel backbone

There are a few different types of backbones that are used for an enterprise-wide network. When organizations are looking for a very strong and trustworthy backbone they should choose a parallel backbone. This backbone is a variation of a collapsed backbone in that it uses a central node (connection point). Although, with a parallel backbone, it allows for duplicate connections when there is more than one router or switch. Each switch and router are connected by two cables. By having more than one cable connecting each device, it ensures network connectivity to any area of the enterprise-wide network.^[11]

Parallel backbones are more expensive than other backbone networks because they require more cabling than the other , network topologies. Although this can be a major factor when deciding which enterprise-wide topology to use, the expense of it makes up for the efficiency it creates by adding increased performance and fault tolerance. Most organizations use parallel backbones when there are critical devices on the network. For example, if there is important data, such as payroll, that should be accessed at all times by multiple departments, then your organization should choose to implement a Parallel Backbone to make sure that the connectivity is never lost.^[11]

Serial backbone

A serial backbone is the simplest kind of backbone network.^[12] Serial backbones consist of two or more internet working devices connected to each other by a single cable in a daisy-chain fashion. A daisy chain is a group of connectivity devices linked together in a serial fashion. Hubs are often connected in this way to extend a network. However, hubs are not the only device that can be connected in a serial backbone. Gateways, routers, switches and bridges more commonly form part of the backbone.^[13] The serial backbone topology could be used for enterprise-wide networks, though it is rarely implemented for that purpose.

INTERNETWORKING

Internetworking is a term used by Cisco, BBN, and other providers of network products and services as a comprehensive term for all the concepts, technologies, and generic devices that allow people and their computers to communicate across different kinds of networks. For example, someone at a computer on a token ring local area network may want to communicate with someone at a computer on an Ethernet local area network in another country using a wide area network interconnection. The common internetwork protocols, routing tables, and related network devices required to achieve this communication constitute internetworking.

The standard reference model for internetworking is Open Systems Interconnection (OSI), which could also be used as a model for intranetworking as well. OSI enables any technology to be related to another technology because each can be related to the standard communication model. OSI provides a layering approach to the problem of exchanging data across a network or a network of networks so that the problem can be broken down into easier-to-understand components and so that boundaries between components can be more easily determined.

NSFNET

NSFNET was a network for research computing deployed in the mid-1980s that in time also became the first backbone infrastructure for the commercial public Internet. Created as a result of a 1985 National Science Foundation (NSF) initiative, NSFNET established a high-speed connection among the five NSF supercomputer centers and the National Center for Atmospheric Research, and provided external access for scientists, researchers, and engineers who were not located near the computing centers.

Broad access was necessary for a widely dispersed and frequently changing community of users. NSFNET became part of a hierarchical series of networks. Meanwhile, NSF supported the development of regional networks that could carry traffic from individual organizations, such as government agencies and universities, to the national backbone service. NSF commissioned Merit Network, MCI, IBM, and the State of Michigan to manage the NSFNET backbone project.

It was during this critical time that Al Gore entered the picture. Gore was roundly mocked in the press after he claimed that he "took the initiative in creating the Internet" during a 1999 broadcast interview. In fact, during the late 1980s, Gore did give political support to a funding drive aimed at expanding NS NET. Although Gore's "creation" claim was -- to put it mildly -- an exaggeration, the subsequent expansion helped spur the development of the modern-day Internet.

By the early 1990s, as commercial networks began to build their own backbone infrastructures and their own routing mechanisms, the public service furnished by NSFNET's backbone was turned over to the newer backbones and NSFNET was shut down. The scientific and research network continued as vBNS and, more recently, Internet2.

The Arpanet

THE ARPANET

The ARPANET was the first wide area packet switching network, the "Eve" network of what has evolved into the Internet we know and love today.

The ARPANET was originally created by the IPTO under the sponsorship of DARPA, and conceived and planned by Lick Licklider, Lawrence Roberts, and others as described earlier in this section.

The ARPANET went into labor on August 30, 1969, when BBNdelivered the first Interface Message Processor (IMP) to Leonard Kleinrock's Network Measurements Center at UCLA. The IMP was built from a Honeywell DDP 516 computer with 12K of memory, designed to handle the ARPANET network interface. In a famous piece of Internet lore, on the side of the crate, a hardware designer at BBN named Ben Barker had written "Do it to it, Truett", in tribute to the BBN engineer Truett Thach who traveled with the computer to UCLA on the plane.

The UCLA team responsible for installing the IMP and creating the first ARPANET node included graduate students Vinton Cerf,Steve Crocker, Bill Naylor, Jon Postel, and Mike Wingfield. Wingfield had built the hardware interface between the UCLA computer and the IMP, the machines were connected, and within a couple of days of delivery the IMP was communicating with the local NMC host, an SDS Sigma 7 computer running the SEX operating system. Messages were successfully exchanged, and the one computer ARPANET was born. A picture of Leonard Kleinrock with the first ARPANET IMP is shown below (click on the picture to link to a larger image on Kleinrock's home site).

- Leonard Kleinrock with first IMP

The first full ARPANET network connection was next, planned to be with Douglas Engelbart's NLS system at the Stanford Research Institute (SRI), running an SDS-940 computer with the Genie operating system and connected to another IMP. At about 10:30 PM on October 29'th, 1969, the connection was established over a 50 kbps line provided by the AT&T telephone company, and a two node ARPANET was born. As is often the case, the first test didn't work flawlessly, as Kleinrock describes below:

At the UCLA end, they typed in the 'l' and asked SRI if they received it; 'got the l' came the voice reply. UCLA typed in the 'o', asked if they got it, and received 'got the o'. UCLA then typed in the 'g' and the darned system CRASHED! Quite a beginning. On the second attempt, it worked fine! - Leonard Kleinrock, The Birth of the Internet.

The Culler-Fried Interactive Mathematics centre at the University of California at Santa Barbara was the third site added to the ARPANET, running on an IBM 360/75 computer using the OS/MVT operating system. The fourth ARPANET site was added in December 1969 at the University of Utah Graphics Department, running on a DEC PDP-10 computer using the Tenex operating system. These first four sites had been selected by Roberts to constitute the initial ARPANET because they were already DARPA sites, and he believed they had the technical capability required to develop the required custom interface to the IMP.

Over the next several years the ARPANET grew rapidly. In July, 1975, DARPA transferred management and operation of the ARPANET to the Defense Communications Agency, now DISA. The NSFNET then assumed management of the non-military side of the network during its first period of very rapid growth, including connection to networks like the CSNET and EUnet, and the subsequent evolution into the Internet we know today.

Milestones. Some of the milestones in the early history of the ARPANET are summarized below:

• East Coast. In March, 1970, the consulting company Bolt, Beranek & Newman joined the ARPANET, becoming the first ARPANET node on the US east coast.

• Remote Access. In September, 1971, the first Terminal Interface Processor (TIP) was deployed, enabling individual computer terminals to dial directly into the ARPANET, thereby greatly increasing the ease of network connections and leading to significant growth.

• 1972. By the end of 1972 there were 24 sites on the ARPANET, including the Department of Defense, the National Science Foundation, NASA, and the Federal Reserve Board.

• 1973. By the end of 1973 there were 37 sites on the ARPANET, including a satellite link from California to Hawaii. Also in 1973, the University College of London in England and the Royal Radar Establishment in Norway become the first international connections to the ARPANET.

• 1974. In June, 1974, there were 62 computers connected to the ARPANET.

• 1977. In March, 1977, there were 111 computers on the ARPANET.

• 1983. In 1983, an unclassified military only network called MILNET split off from the ARPANET, remaining connected only at a small number of gateways for exchange of electronic mail that could be easily disconnected for security reasons if required. MILNET later become part of the DoD Defense Data Network, or DDN.

• 1985. By the middle of the 80's there were ARPANET gateways to external networks across North America, Europe, and in Australia, and the Internet was global in scope. Marty Lyons has created a map of the existing network gateways from 18 June 1985.

• 1990. The ARPANET was retired in 1990. Most university computers that were connected to it were moved to networks connected to the NSFNET, passing the torch from the old network to the new.

Resources. The following site provides more information about the ARPANET.

• Michael Hauben's History of the ARPANET

Internet

HISTORY OF INTERNET
 - The history of the Internet begins with the development of electronic computers in the 1950s. Initial concepts of packet networking originated in several computer science laboratories in the United States, Great Britain, and France. The US Department of Defense awarded contracts as early as the 1960s for packet network systems, including the development of theARPANET (which would become the first network to use the Internet Protocol.) The first message was sent over the ARPANET from computer science Professor Leonard Kleinrock's laboratory at University of California, Los Angeles (UCLA) to the second network node at Stanford Research Institute(SRI).

Packet switching networks such as ARPANET, NPL network, CYCLADES,Merit Network, Tymnet, and Telenet, were developed in the late 1960s and early 1970s using a variety of communications protocols. Donald Davies was the first to put theory into practice by designing a packet-switched network at the National Physics Laboratory in the UK, the first of its kind in the world and the cornerstone for UK research for almost two decades.^[1][2] Following, ARPANET further led to the development of protocols for internetworking, in which multiple separate networks could be joined into a network of networks.

Access to the ARPANET was expanded in 1981 when the National Science Foundation (NSF) funded the Computer Science Network (CSNET). In 1982, the Internet protocol suite (TCP/IP) was introduced as the standard networking protocol on the ARPANET. In the early 1980s the NSF funded the establishment for national supercomputing centers at several universities, and provided interconnectivity in 1986 with the NSFNET project, which also created network access to the supercomputer sites in the United States from research and education organizations. Commercial Internet service providers (ISPs) began to emerge in the very late 1980s. The ARPANET was decommissioned in 1990. Limited private connections to parts of the Internet by officially commercial entities emerged in several American cities by late 1989 and 1990,^[3] and the NSFNET was decommissioned in 1995, removing the last restrictions on the use of the Internet to carry commercial traffic.

In the 1980s, the work of Tim Berners-Lee in the United Kingdom, on theWorld Wide Web, theorised the fact that protocols link hypertext documents into a working system,^[4] marking the beginning of the modern Internet. Since the mid-1990s, the Internet has had a revolutionary impact on culture and commerce, including the rise of near-instant communication by electronic mail,instant messaging, voice over Internet Protocol (VoIP) telephone calls, two-way interactive video calls, and the World Wide Web with its discussion forums, blogs, social networking, and online shopping sites. The research and education community continues to develop and use advanced networks such as NSF's very high speed Backbone Network Service (vBNS), Internet2, andNational LambdaRail. Increasing amounts of data are transmitted at higher and higher speeds over fiber optic networks operating at 1-Gbit/s, 10-Gbit/s, or more. The Internet's takeover of the global communication landscape was almost instant in historical terms: it only communicated 1% of the information flowing through two-way telecommunications networks in the year 1993, already 51% by 2000, and more than 97% of the telecommunicated information by 2007.^[5] Today the Internet continues to grow, driven by ever greater amounts of online information, commerce, entertainment, and social networking.

Ecommerce

ADVANTAGES OF ECOMMERCE

• Faster buying/selling procedure, as well as easy to find products.
• Buying/selling 24/7.
• More reach to customers, there is no theoretical geographic limitations.
• Low operational costs and better quality of services.
• No need of physical company set-ups.
• Easy to start and manage a business.
• Customers can easily select products from different providers without moving around physically.

DISADVANTAGES OF ECOMMERCE

• Any one, good or bad, can easily start a business. And there are many bad sites which eat up customers’ money.
• There is no guarantee of product quality.
• Mechanical failures can cause unpredictable effects on the total processes.
• As there is minimum chance of direct customer to company interactions, customer loyalty is always on a check.
• There are many hackers who look for opportunities, and thus an ecommerce site, service, payment gateways, all are always prone to attack.