Networks

clashjudiciousElectronics - Devices

Nov 8, 2013 (4 years ago)

93 views

Networks

A network is two or more computers linked together in such a
way that documents and peripherals may be shared.

LANS

A local area network covers a small
area such as a room or building and is
controlled by an individual or an
organisation such as a school.

A network interface card is fitted inside a
computer to allow network access and
communication. Laptops often have wireless
network cards installed. If this is the case
wireless hotspots will be accessed for
network usage (often internet).

Advantages of LANS over standalone PCs


Share data


Share peripherals


Internal mail

Peer to Peer Networks and Client

Server
Networks

A peer to peer network has work
stations each with a similar status
to each other. It is possible for a
station to act as file server but it
can still be used as a workstation.



Advantages of peer to peer network


Each station has similar status with own local storage devices


Cheaper to install than client
-
server. No network OS


Easy to set up


Disadvantages of peer to peer network


No central file storage


Individual back ups required


Less secure than client
-
server


Problems may occur if one station is switched off

A client server network has at least one server and client
workstations are connected. Resources are stored on the server.


Advantages of client
-
server network



Increased security
-

Usernames and passwords


Different access levels


Resources are controlled through the server


Workgroup computing


Flexible use of stations


Central backup system


Disadvantages of client
-
server



File server problems affect all users


Cost of setting up
-

Server and software cost


May require network manager



Network Terms

Internet

A network of WANs spreading all over the world.
It allows communication
by electronic mail (email) and video conferencing, the sharing of data files
and access to web pages. The transmission media are wired and wireless
channels that belong to telecommunications companies. Bandwidth can
range from only a few kilobits per second (Kbps) to dozens of megabits per
second (Mbps).

Intranet

An Intranet is a private network that spans short or long distances.
It has an Internet
-
style interface and is accessed through a
browser. It allows communication by electronic mail (email) and
video conferencing, the sharing of data files and access to web
pages. Depending on the size of the intranet, the transmission
media are wired and wireless channels that belong either to the
organisation or telecommunications companies. Bandwidth can
range from only a few kilobits per second (Kbps) to dozens of
megabits per second (Mbps).

Internetwork

One or more local or wide area networks joined by devices such as
routers and switches. Depending on its geographical spread, it
allows the sharing of programs, data files and peripherals,
communication by electronic mail (email) and video conferencing and
access to web pages. Depending on the size of the Internetwork, the
transmission media are wired and wireless channels that belong
either to the organisation or telecommunications companies.
Bandwidth can range from several megabits per second (Mbps) in
wide area networks (WAN) to over 100 gigabits per second (Gbps) in
a fibre
-
optic local area network (LAN).


Mainframe Computers

A mainframe computer is a large computer system
which can process a very large amount of data at high
speed. It may occupy a whole room and have hundreds
of user terminals. A mainframe may have many users
simultaneously. This is multi
-
user or multi access.

Mainframes may
have many
processors to
allow for dumb
terminals.

Nodes and Channels

A workstation on a network may be described as a node or
terminal.

The way in which a node is connected to another node is
described as a channel. A channel may be wire, fibre optic cable
or wireless.

Node

Channel

Task 2

Draw the following network topologies in your jotter:


Star


Bus


Ring


Mesh



Task 1

Use the internet to find out the definition of
“topology” in terms of computing then name five
different network topologies

Write a short paragraph on each topology
describing what the effect on the system
will be if there is a node or channel failure

Whatever type of topology or transmission medium is
chosen for a network there must be some way of
connecting workstations. The following may be used.


Hub


Router


Switch

Hub

A hub connects all work stations
on a network.

A hub amplifies the signal across
the network to connected
workstations

When a signal is received from
one node it is broadcast to
all

connected nodes



The main disadvantage of a hub is that signal collisions may slow
the network down

The main advantage of a hub is that a port with problems may
be shut down so the rest of the network is unaffected

Router

A router is a device which links two or more networks. It
receives packets of data and forwards them to their correct
destination over the most efficient available route.

A router has its
own processing and
memory capabilities
to allow it to work
out the best routes
for packets of data

Routers are used to
divide larger
networks into
smaller units to
make them perform
more efficiently

Routers are used to direct traffic
across the internet

Switch

A switch is similar to a hub but
has the advantages that it divide
a network into segments allowing



More than one machine to
speak at once



Only intended data recipients
receive the data (not broadcast
to all)



A switch will operate well as there will be no signal
collisions slowing the network down

Task


Servers

Write a short paragraph describing the
following servers and their uses:


File


Print


Web


Mail

Bandwidth

Bandwidth is a measure of quantity of data which may be
carried by a communications channel at any one time.

Demands of networks are increasing all the time with the
expectancy of:


Running complex software (games with 3d images and sound)


Transmission of large data files (multimedia documents)


Video conferencing


To support these demands high
-
bandwidth telecommunications
technology is used

Bandwidth is measured in megabits per second

Wireless Communication

It is possible to have a wireless communication between the CPU and
peripherals. The two most common standards are:



Bluetooth


WiFi

Both use radio waves to transmit data.

Bluetooth can make short range links between personal devices, such as mobile
phones and headsets, keyboards and mice with the CPU.

Most Bluetooth devices have a range of about 10 metres.

WiFi is used in wireless networking as it has a range of up to 50 metres.
Often used with a router to produce a wireless LAN with broadband
Internet access in the home or office.