Page 289 - DCAP101_BASIC_COMPUTER_SKILLS

Basic Computer Skills

Notes ISPs requiring no upstream and having only customers (end customers and/or peer ISPs) are
called Tier 1 ISPs.
Network hardware, software and specifications, as well as the expertise of network
management personnel are important in ensuring that data follows the most efficient
route, and upstream connections work reliably. A tradeoff between cost and efficiency is
possible.
13.7.6 Derivatives

The following are not a different type of the above ISPs, rather they are derivatives of the
3 core ISP types. A VISP is reselling either access or hosting services. Free ISPs are similar,
but they just have a different revenue model.

Virtual ISP

A Virtual ISP (VISP) is an operation which purchases services from another ISP (sometimes

called a “wholesale ISP” in this context which allow the VISP’s customers to access the
Internet using services and infrastructure owned and operated by the wholesale ISP.

Free ISP
Free ISPs are Internet Service Providers (ISPs) which provide service free of charge. Many
free ISPs display advertisements while the user is connected; like commercial television, in
a sense they are selling the users’ attention to the advertiser. Other free ISPs, often called
freenets, are run on a nonprofit basis, usually with volunteer staff.

History of the Internet

he History of the Internet has precursors that date back to the 19th century,
especially the telegraph system, more than a century before the digital Internet
Tbecame widely used in the second half of the 1990s. The concept of data
communication - transmitting data between two different places, connected via some
kind of electromagnetic medium, such as radio or an electrical wire - actually predates
the introduction of the first computers. Such communication systems were typically
limited to point to point communication between two end devices. Telegraph systems
and telex machines can be considered early precursors of this kind of communication.
Early computers used the technology available at the time to allow communication between
the central processing unit and remote terminals. As the technology evolved, new systems
were devised to allow communication over longer distances (for terminals) or with higher
speed (for interconnection of local devices) that were necessary for the mainframe computer
model. Using these technologies it was possible to exchange data (such as files) between
remote computers. However, the point to point communication model was limited, as it
did not allow for direct communication between any two arbitrary systems; a physical link
was necessary. The technology was also deemed as inherently unsafe for strategic and
military use, because there were no alternative paths for the communication in case of an
enemy attack.
As a response, several research programs started to explore and articulate principles of
communications between physically separate systems, leading to the development of the
packet switching model of digital networking. These research efforts included those of

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