Internet
From The Ultimate Programming Reference
Revision as of 09:38, 26 March 2006
In the late 1960s, the Advanced Research Projects Agency (ARPA) sponsered a confrence at which several dozen ARPA-funded graaduate students were brought together at the University of Illinois at Urbana-Champaign to meet and share ideas. During this conference, ARPA rolled out the blueprints fir networking the main computer systems of about a dozen ARPA-funded universities and research institutions. They were to be connected with communications lines operating at a then-stunning 56kbps (56,000 bits per second), this at a time when most people (of the few who could be) were connecting over telephone lines to computers at a rate of 110 bits per second. Shortly after this conference, ARPA proceeded to implement what quickly became the ARPAnet, the grandparent of today's Internet.
Things worked out differently from what was originally planned. Rather than the primary benifit being that researchers can share each other's computers, it rapidly became clear that simply enabling the researchers to communicate quickly and easilt among them selves via what became known as e-mail was to be the key benefit of the ARPAnet. This is true even today on the Internet with e-mail facilitating communications of all kinds among millions of people worldwide.
One of ARPA's primary goals for the network was to allow multiple users to send and recieve information at the smae time over the same communications paths. The netwok operated with a technique called packet switching in whcih digital data was sent in small packages called packets. The packets contained data, address information, error-control information and sequencing information. The address information was used to route the packets of data to thir destination. The sequencing information was used to help reassemble the packets (which - because of complex routing mechanisms - actually could arrive out of order) into their original order for presentation to the recipient. Packets of many people were intermixed on the same lines. This packet-switching technique greatly reduced transmission costs compared to the cost of dedicated communications lines.
The network was designed to operate without centralized control. This meant that if a portion of the network should fail, the remaining working portions still would be able to route packets from senders to recievers over alternate paths.
The protocols for communication over the ARPAnet became known as TCP. TCP ensured that messages were routed properly from sender to receiver and that those messages arrived intact.
Im parallel with the early evolution of the Internet, organizations worldwide were implementing their own networks for both intra-organization (i.e., between organizations) communication.
