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LANs - Local Area Networks &
WAN - Wide Area Network


A local area network is connected by cable to allow a group of users in a small or limited area, usually
within one building or several buildings in close proximity. This is done in order to share data,
programs…

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network is distributed nationally or transmission uses telecommunications
internationally network or even satellite links




WAN Wide Area Network



A type of private network that uses a series of technologies including phone lines, modems,
microwave relaying stations, satellites to connect computers over a wide geographical area
Digital communication systems will greatly…

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Bus topology: All devices are connected to a central cable, called the bus or backbone. Bus
networks are relatively inexpensive and easy to install for small networks. Ethernet systems use a
bus topology. Advantages are that less cable is needed than token ring, network can be easily
extended and that…

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Baseband transmission allows for very fast data transmission but it has one major disadvantage.
Electrical pulses flatten out when they travel through a long wire. This, together with other electrical
and factors impose a maximum length restriction on LAN's. The maximum length will depend on the
type of cable used…

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In enterprises, the gateway node often acts as a proxy server and a firewall. The gateway is also
associated with both a router, which use headers and forwarding tables to determine where packets
are sent, and a switch, which provides the actual path for the packet in and out of…

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A company that provides Internet access to ISPs. Sometimes called backbone providers,
NSPs offer direct access to the Internet backbone and the Network Access Points
(NAPs). What does a browser do?



Web Browser
A software application used to locate and display Web pages. The two most popular
browsers are Netscape…

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Distributed Databases


Distributed systems may contain a number of separate but connected processors, although
some centralised processing is possible. Read Heathcote and be able to explain the
difference between centralised and distributed computing.
Files and programs need not be held centrally in a distributed system functions can be
passed onto…

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System is dependent on high quality telecommunication lines, which may be vulnerable.
Need to maintain and enforce consistent standards and data definitions over a wide area.
Increased security problems need to enforce security procedures over wider area plus
increased problems over data transmission.










With a replicated database a central database…

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A partitioned database is subdivided so that each location has only the portion that serves its local
needs. Partition. The database is partitioned with each node on the network containing that section of
the database that relates to it.

For example the section of the database that relates to customers…

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ClientServer networks

Networks with powerful servers in which different pieces of hardware work on the same
processing problem. The network tries to use the full processing power of each computer in the
network, including the fileserver and the user workstations or clients.
Servers are required to:

Manage the activities of…

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