Fundamentally, the Internet is an extremely large, global computer network connecting millions of host computers (servers) and supporting many millions more, subscribers clients)!
Internet technology originally evolved in the early 1960's, at the instigation of the US defence department, to enable strategic computer networks to remain operational in the event of one or more nodes being out of commission during a nuclear war. The logic was simple; bombing a system based on an individual mainframe computer network would result in only a few nodes being lost, allowing the other nodes to route around the other nodes.
This was achieved by using a methodology known as "packet switching", which worked by breaking up a data file into small "packets" and transmitting them to another location by multiple routes where the packets would be re-assembled back into the original data file and duplicate packets discarded.
In 1969, the first packet-switching network was developed by the Pentagon's Advanced Research Project's Agency. Known as ARPAnet, the original network connected 4 research establishments, and by 1972 the network had expanded to incorporate 40 nodes. ARPAnet soon became a forum for the exchange of information and ideas among scientists and academics, and within a few years the number of computers connected to the network increased to more than 100.
By the mid-1970's, many US government agency networks were linked by ARPAnet and, because the networks were of a disparate nature, a common network protocol called TCP/IP ( Transmission Control Protocol/Internet Protocol ) was developed and became the standard for inter-networking military computers. By 1983, the word "Internet" became the common term for referring to the worldwide network of military, research and academic computers.
However, it is only since 1993 that the Internet has become popular on a global basis and today is universally available to anyone with a computer, a modem and access to a telephone line. Using TCP/IP, computers on the internet operate in an operating system independent environment allowing almost any kind of computer to talk to any other computer, completely transparently.
Computers on the Internet are designated either clients or servers, servers, as the name implies, are configured to perform specific tasks and are usually controlled by high-powered operating systems such as UNIX or windowsNT, while clients are used to access the resources and services provided by the servers and are usually PCs or workstations.
While the technology of the Internet is undoubtedly powerful in its own right, it only becomes useful to the general public when providing services such as Electronic Mail ("E-mail" ), file transfer via File Transfer Protocol ( "FTP" ) and access to WWW, the World Wide Web.
WWW, The World Wide Web
In 1992, a scientist at the European High-Energy Particle Physics Laboratory ( CERN ), Tim Berners-Lee, developed the concept of the World Wide Web ( "WWW", "W3" or simply "the web" ) as we know it today.
The web provides access via the Internet to media-rich documents known as web pages, which may contain formatted text, images and multimedia. each web page has a unique address known as a Uniform Resource Locater or "URL", which allows a page to link to any other page on the Internet via hyperlinks, "clickable" text or images, sometimes known as "hotspots", embedded in the page itself.
A URL is made up of the access method, the name of the server, the directory where the page is stored, and the file name of the page. The URL http://www.microsoft.com/download/index.htm refers to the file index.htm in the directory download on the web server www.microsoft.com using the http ( hypertext transport protocol ) access method.
Web pages are stored on an Internet computer known as a web server and access to its pages is provided by a web browser, a web navigation tool with a user-friendly interface. A single page or a group of related pages are said to occupy a web site, which has a home page or starting point of reference. Web-pages are constructed using a common language known as HTML or Hypertext Mark-up Language and access to the web for the general public is supplied by Internet Service Providers or ISPs, who charge monthly or yearly subscriptions for this service.
The first web browser, known as Mosaic, was developed in 1993 at the National Center for Supercomputer Applications ( NCSA ) in the university of Illinois. The use of Mosaic spread rapidly through the academic community and within a year more than 2 million users were browsing the web. However today the most popular web browsers are Microsoft's Internet Explorer and Netscape's Navigator, and Firefox.
It is predicted thatbefore much longer every person in the world would be connected to the web! But what is the web used for? Increasingly, the web is being utilised for commercial purposes, with cyberspace "shopping malls" being established with increasing regularity. A good example is the "Barclaysquare" web site, which hosts a range of independent businesses offering goods as diverse as flowers clothing and food. Goods are paid for by credit card and delivered the next day or sooner. The web is also extensively used by common interest "News Groups" and for classified advertising, world news, education and many others.
Security On The Internet
Security on the web ( or the lack of it! ) has been the subject of much concern and debate. Commercial transaction processing over the Internet has been inhibited thus far because of justifiable fears concerning the security and privacy of such transactions. In theory, as soon as you connect a corporate system or "Intranet" to the Internet, you create a major security risk.
Internet servers and browsers have long had the capability to restrict access to documents and files by means of user identifiers and passwords. However for secure commerce a higher level of security is required and this has resulted in the development of servers and browsers equipped with sophisticated encryption technology. This technology ensures that all data packets are encrypted so that a packet can only be read by its destination server.
There are a number of ways to solve the problem of unauthorised access to an Internet web server. One is the use of a "packet router" to add data packet filtering by IP address and port; however, this method has several known shortcomings, which allow the more sophisticated hacker to direct a connection that has already been approved by the router.
More sophisticated security is provided by products known as "firewalls", which have been developed to provide a security screen at both the server level and the application level. Firewalls sit between the Internet and corporate Intranets and examine every packet of data passing both in and out of the network.
There are essentially two types of firewall groups: "packet filters" and "proxy servers". Packet filters add filtering capabilities, authentication, audit and alarms to the basic packet router concept. However, proxy servers offer a higher level of security because there is no direct server connection to the Internet. Instead, the connection goes to a firewall where a "proxy session" is established. The lack of a direct connection means that hackers have no way to access to the server.
Firewall products employ "type enforcement" to ensure that the bit pattern of the data packet contents do not violate the protocol rules of the protocol contained in the packet header. If a violation is detected, the packet will not be processed and the connection will be dropped. The latest products in this rapidly expanding market also incorporate "virus control", where all the data packets are scanned by a virus search algorithm against a database of more than 7,000 known viruses.
Most firewalls are completely transparent to the network protocol, the network itself and the application, allowing network managers to secure their networks without disrupting the operating environment. The development of firewall products means that corporations and commercial organisations with multiple locations can now use the Internet at a low cost, secure virtual private network, connecting overseas offices to company-wide applications such as electronic mail.
