Page 124 - DCAP516_COMPUTER_SECURITY

Computer Security

Notes (e) You can place a CD with pictures on one computer and let other computers access those
pictures.
You can create files and store them in one computer, then access those files from the other
computer(s) connected to it

10.4 Networking Goals

(a) The main goal of networking is Resource sharing, and it is to make all the programs, data
and equipment available to anyone on the network without the regard to the physical
location of the resource and the user.
(b) A second goal is to provide high reliability by having alternative sources of supply.

For example, all files could be replicated on two or three machines, so if one of them is
unavailable, the other copies could be available.
(c) Another goal is saving money. Small computers have a much better price/performance
ratio than larger ones. Mainframes are roughly a factor of ten times faster than the fastest
single chip microprocessors, but they cost thousand times more. This imbalance has caused
many system designers to build systems consisting of powerful personal computers, one
per user, with data kept on one or more shared file server machines. This goal leads to
networks with many computers located in the same building. Such a network is called a
LAN (local area network).
(d) Another closely related goal is to increase the systems performance as the work load
increases by just adding more processors. With central mainframes, when the system is
full, it must be replaced by a larger one, usually at great expense and with even greater
disruption to the users.
(e) Computer networks provide a powerful communication medium. A file that has been
updated/modified on a network can be seen by the other users on the network
immediately.
Self Assessment

Fill in the blanks:
1. The main goal of networking is …………………….
2. In a distributed system, the existence of multiple autonomous computers is …………………
to the user.
3. The computers on a ………………………. may be linked through cables, telephone lines,
radio waves, satellites or infrared light beams.

4. You can create files and store them in one computer, then ………………… those files from
the other computer(s) connected to it.
5. A ………………….. system is a special case of a network, one whose software gives it a
high degree of cohesiveness and transparency.

10.5 Network Hardware

There are two important dimensions for classifying networks — transmission technology and
scale.

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