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Network Environments

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Communications Networks
LAN ­ Local Area Network
­ Collection of Computers and peripherals with a
common connection in one building or site.
WAN ­ Wide Area Network
­ Groups of networks connected together over a
larger geographical area.
­ Ultimate WAN ??

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Network topologies
The topology of a network is its physical layout
-- the way in which the computers and other
units (commonly referred to as nodes) are
Common topologies:
­ Star
­ Bus
­ Ring

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LAN - Advantages
­ Shared resources
· Disk storage, printers, modems, scanners etc.
­ Shared Information
­ Efficient Storage
· Programs can be stored on one computer
­ Local Email
­ Easier Set-up procedures
­ Different types of computers can be connected

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LAN - Disadvantages
­ Dependence on a single server machine.
· Large systems will have a back-up server.
­ Hardware/software access depends on network
­ System Manager dependent
· System must be properly organised for efficiency
­ Difficult to make system secure.
· Vulnerable to hackers ­ particularly via modems…

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Types of LAN
Server-based ­ Client-Server Architecture
­ Devices on networks are either clients or servers.
­ Workstations would be clients. They request a service from
servers. For example, retrieve a file from the file server, or
print a document on a printer which is a server device

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Network Maintenance Tasks
Any network requires the management of:
­ Adequate response times
­ Necessary hardware upgrades
­ Software availability
­ Software upgrades
­ Provision of information for users
­ Back-up procedures
­ Network Security

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Server-based Peer-to-peer
Centralised backing storage Distributed storage
Software held centrally and shared. Copies of software held on individual
Server manages distribution of data and machines. Basic network services to
software to clients. Some processing enable sharing of data, software and
may be handled locally but most done printers are…

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Wide Area Networks
LAN is connected by cables.
WAN is spread over a wide geographical
Mode of communication may be:
­ Telephone line, microwave, satellite link
Use of global networks has increased due
­ Telephone networks: analogue to digital
­ Reduced connection and network costs

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Communications links

Possible satellite


Mainframe Mainframe Mainframe
in in in
Norwich London USA

modem modem


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