The Internet

You can think of the Internet as a network of computer networks. The origins of the Internet go back to the 1960's, when officials at the U.S. Defense Department's Advanced Research Projects Agency (ARPA) became frustrated that they were always having to switch back and forth between different computer networks in order to communicate with their research projects at universities around the country. The idea of the internet was to somehow connect the dissimilar computer networks together in such a way that the user would only have to deal with a generic set of log-in and operating procedures.

How is something sent from one computer to another?

The Internet does not have a central hub, rather it is a distributed network.

Numerous connectors, or routers are like the traffic cops of the Internet. These special-purpose computers are in charge of directing and routing the network's traffic.

The traffic is made up of packets. When you send a file over the network from one computer to another, the file is broken up into packets. Packet sizes range from 100 to 1,500 bytes. Each packet includes "header" information that lists:

the filename
the origin
the destination
the order number of the packet

Packets are sent out over the network. The nearest router receives them, checks their destination, and sends them on to another router that is closer to the final destination. An individual packet typically goes through a number of routers before it arrives at its destination. Once all the packets arrive, the file is put back together by reassembling the packets in the proper order.
This process is called packet-switching.

The routers on the network are constantly communicating with each other in order to have up-to-the-second "traffic reports." If one of the routers is experiencing heavy traffic loads or goes offline, the other routers will send packets around it until the traffic subsides or the router is back online.

TCP/IP and Domain Names

IP stands for Internet Protocol, which is the software that runs the routers, performing the basic task of moving packets as quickly as possible from router to router.

TCP stands for Transmission Control Protocol and is the software that breaks messages into packets at the sending end, and recombines the packets on the receiving end. TCP also provides error-checking in order to take care of packets that are lost or delayed in transit. If the packet is not at the receiving end, TCP sends a message to the origin and requests that the missing packet be resent.

Routing packets to the correct destination requires some addressing scheme. Every host computer on the Internet is given a unique IP address, made up of four numbers each between 0 and 255:

192.56.215.131

In the mid 1990's the Internet Engineering Task Force proposed IPv6, an updated version of IP that allows for 64 billion billion billion addresses.

To help people use the IP system, An Internet domain name system (DNS) is laid on top of the addressing system.

The Internet is divided into different country domains, then within each country, the hosts are grouped according to organizations:

hostname.organizationname.countryname

The codes for the major types are:
.edu—education
.com—commercial
.gov—government
.mil—military
.org—non-profit organizations
.net—networking companies and organizations

Basic Services from FTP to the WWW

In addition to TCP/IP, the Internet uses other software protocols:

FTP stands for file transfer protocol. It allows Internet users to transfer or download files from another computer on the network to their own.
telnet allows the user to connect and log in to a remote computer on the network in order to access its resources.

The basic protocol for the Web was created between 1989 and 1991 by Tim Berners-Lee, who was looking for a way to access and share documents across all the different research groups at CERN (the European high energy lab). He built on the idea of hypertext, which makes it possible to have a random, non sequential reading experience.

To create hypertext documents, Berners-Lee invented a special kind of document formatting or "markup" language, called hypertext markup language (HTML), as well as a transmission protocol called hypertext transfer protocol (HTTP) to make it possible to send and receive HTML documents over a network. He also created browser software that could read the HTML.

The first PC version of HTML and HTTP worked with software that used a text based user interface (no icons, images, buttons, etc.). In 1993 a group of graduate students at the University of Illinois, led by Marc Andreesen, created the first GUI browser called Mosaic. After the students left school in 1994, they founded their own company and renamed their browser Netscape Navigator. In 1995, Microsoft released their browser called Internet Explorer.

Netscape? Never heard of it.

By 1996, 75% of Web users used Netscape. Now Netscape is just a subsidiary of America Online and has only a third of the Web's users. Microsoft Internet Explorer has replaced Netscape as browser number one. What happened? Over time, Internet Explorer became the more reliable browser with better features. Netscape continued to charge for its product and its pricing structure continually changed and was inconsistent with the free internet. By 1999, Netscape was battle-weary and America Online bought it for $10 billion in stock. America Online was more interested in converting the remaining Netscape audience into its own than in using the software.

Currently Andreessen is an investor in social news website Digg and several other early-stage technology startups, like Plazes. His latest project is Ning, which launched in October 2005. He serves on the board of Open Media Network.

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