Internet Explained

The Internet

History

The Internet

J.C.R. Licklider of MIT conceptually originated in 1962.

Globally interconnected set of computers through which everyone could quickly access data and programs from any site.

First head of the computer research program at DARPA.

The Defense Advanced Research Projects Agency is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military.

https://www.darpa.mil/

Leonard Kleinrock at MIT published the first paper on packet switching theory in July 1961.

1966 Roberts went to DARPA to develop the computer network concept and quickly put together his plan for the “ARPANET”.

The Advanced Research Projects Agency Network was the first wide-area packet-switched network with distributed control and one of the first computer networks to implement the TCP/IP protocol suite. Both technologies became the technical foundation of the Internet.

Communications using packets rather than circuits.

In September 1969 when BBN installed the first IMP at UCLA and the first host computer was connected.

By the end of 1969, four host computers were connected together into the initial ARPANET, 

The initial ARPANET Host-to-Host protocol, called the Network Control Protocol (NCP).

 As the ARPANET sites completed implementing NCP during the period 1971-1972, the network users finally could begin to develop applications.

In 1972 the initial “hot” application, electronic mail, was introduced. 

ARPANET as the pioneering packet switching network

Communications would be on a best effort basis. If a packet didn’t make it to the final destination, it would shortly be retransmitted from the source.

The need for global addressing.

Communication between two processes would logically consist of a very long stream of bytes (they called them octets). The position of any octet in the stream would be used to identify it.

The destination could select when to acknowledge and each ack returned would be cumulative for all packets received to that point.

Ethernet was under development at Xerox PARC 

Thus a 32 bit IP address was used of which the first 8 bits signified the network and the remaining 24 bits designated the host on that network

The TCP protocol supports a range of transport services, from the totally reliable sequenced delivery of data (virtual circuit model) to a datagram service in which the application made direct use of the underlying network service, which might imply occasional lost, corrupted or reordered packets.

Widespread development of LANS, PCs and workstations in the 1980s allowed the Internet to flourish.

 Ethernet technology, developed by Bob Metcalfe at Xerox PARC in 1973, is  the dominant network technology in the Internet.

The World Wide Web

Tim Berners-Lee, a British scientist, invented the World Wide Web (WWW) in 1989, while working at CERN. 

The European Organization for Nuclear Research is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954,

The Web was originally conceived and developed to meet the demand for automated information-sharing between scientists in universities and institutes around the world.

The idea of the WWW was to merge the evolving technologies of computers, data networks and hypertext into a powerful and easy to use global information system.

The "hypertext project" called "WorldWideWeb" in which a "web" of "hypertext documents" could be viewed by “browsers”.

 By the end of 1990, Tim Berners-Lee had the first Web server.

The WWW design allowed easy access to existing information and an early web page linked to information useful to CERN scientists.

Early in 1993, the National Center for Supercomputing Applications (NCSA) at the University of Illinois released the first version of its Mosaic browser. 

The existence of reliable user-friendly browsers on these popular computers had an immediate impact on the spread of the WWW.

 

What is a Web Server?

A web server is a program that serves content to the Internet(WWW). 

The primary function of a web server is to store, process and deliver web pages to clients.

 The client and server communicate using the Hypertext Transfer Protocol (HTTP). HTTP means HyperText Transfer Protocol. HTTP is used by the World Wide Web and this protocol defines how messages are formatted and transmitted. Content being transferred is most frequently HTML documents.

 

The Browser

The browser is a software application used to locate, retrieve and display content It interprets code and displays it as a web page.

The user needs to tell the browser what website or specific web page they want.

The DNS

The DNS (Domain Name server) helps locate servers by keeping a list of ip addresses. An IP address is a unique number, like a phone number, that enables the user to locate a website on the Internet. Each website has an ip address. Web servers don't know what google.com is and require the ip address of the website in order to return the desired html page.

 

If you wanted to get a domain for your website for example myfirstwebsite.com you would have to buy the domain and link the ip address to it. The ip address would be assigned to the server that hosts your site.

Working Together

To access a website, enter a URL(Universal Resource Locator) in the browser's  address bar. The browser takes the URL and goes to the DNS to find the ip address The browser makes a request to the web server via HTTP.

The document is returned to the browser.

Apache

Apache is the most widely used web server software. It runs mostly on UNIX-based operating systems with 92% of server copies running on linux distributions. 60% of all Web sites on the Internet are using Apache making it the most widely used web server.