Unit 4:Local area networks Flashcards
purpose of a network
to share hardware and software resources
LAN
networking capabilities of a group of computers which are found near each other.
network hardware includes
nodes
NIC
connecting devices
bounded connection media
cables are known as bounded media. Carry signals between computers and peripheral devices in networks
bounded medium
signals are confined to the medium and do not leave it.
examples of bounded media
twisted pair
fiber optic cable
twisted-pair cable
consists of 2 insulated strands of copper wire twisted around each other.
name the 2 types twisted-pair cables
=shielded twisted pair
=unshielded twisted pair.
unshielded twisted pair cable
easy to install, expand and troubleshoot.
advantages of twisted pair
=the cost of the cabling is low
=it is easy to install with simple computer connections
disadvantages of twisted pair
=the length of the cable cannot be greater than 100m
=Copper cables have inherent weaknesses.
weaknesses of copper cables
=eavesdropping
=attenuation
=crosstalk
=electro-magnetic interference
fiber optic cable
optical fibers carry digital data signals in the form of pulses of light. No electric impulses are carried over the fiber-optic cable. This means that fiber optic cannot be tapped, and its data cannot be stolen.
fibre optic can send signal in Single mode or multimode
true
multimode
has a larger core core and is typically used for for shorter distances.
advantages pf fiber optic cables
=data can be transmitted at very high speeds
=data can be transmitted over long distances securely.
disadvantages of fiber optic cables
=they are more expensive than UTP
=You need the expertise available to properly install and connect to devices.
unbounded media
connect the source and destination devices without any physical connection.
examples of unbounded media
=Bluetooth
=microwave and radio radio waves
wireless technology
allow the transfer of data over both short or long distances
wireless communication consists of the following:
=radio communication
=microwave communication
=light, visible and infrared such as remote controls
Bluetooth
the standard for sending data over short distances, using short-wavelength radio transmissions from 2400-2480 MHz signals are sent from fixed and mobile devices, creating Personal Area Networks with high levels of security.
Bluetooth:
=wireless, inexpensive and automatic
advantage of Bluetooth
can be both data and voice transmissions a the same time.
near field communication
provides a wireless connection between 2 devices within close proximity. Allows for 2-way communication
radio waves
type of electromagnetic wave which is known fr their use in communication technologies and data transfer
examples of radio waves
radio
television
mobile phones
radio waves on the spectrum
ranging from 1mm to more than 100 kilometers
name 2 types of transmission technologies
point to point connection directly connects 2 nodes of a network.
broadcast is a communication channel that is shared by all the devices in the network.
topology
refers to the physical setup of a network-the way in which the network devices are connected
common topologies
star
bus
ring
hybrid technologies
Star topology
the cable that is connected to the NIC in each computer and has its other end in a port on a central device called a switch
advantages of star topology
=easy to setup and maintain
= problem with one computer or cable will not affect the network
=adding and removing nodes does not upset the network.
=it is easy to extend
=it is the most common topology
disadvantages of star topology
=a large amount of cabling is required to connect each node independently to the switch
=the switch adds to the cost
=if the switch fails, the whole system fails
Bus topology
all nodes connect to a single cable which has a terminator at each end to stop the signals bouncing out
Advantages of Bus topology
=requires less cable than star topology ,cost reduction
=no switch is needed wich also reduce costs
=easy to extend the network
disadvantage of bus topology
Faults are difficult to trace because all nodes share the common cable
=the fault in the main cable can shut down the whole network
=can get congested because all signals from all nodes share the common cable.